HomeMy WebLinkAboutSUS455DRAFT
ALASKA POWER Al.Tl'HORITY
SUSITNA HYDROELECTRIC PROJECT
Federal Energy Regulatory Commission
Project No. 7114
WORKING DRAFT
SETTLEMENT PROCESS
INSTREAM FLOW RELATIONSHIPS REPORT
VOLUME NO. 1
FEBRUARY 1985
Prepared for:
HARZA-EBASCO SUSITNA JOINT VENTURE
E. WOODY TRIHEY AND ASSOCIATES
AND
WOODWARD-CLYDE CONSULTANTS
-. :.;
DRAFT
E. Woody Trihey
Jean E. Ba 1 dri ge
Greg Reub
Bob Aaserude
~lizabeth Bradley
Steve Bredthauer
Steve Crumley
Linda Perry Dwight
Diane Hilliard
Tim Jennings
Carol Kerkvnet
Sharon Klinger
Joe LaBelle
Paul Meyer-
Larry Moulton
Larry Rundquist
Carl Schoch
Cleve Steward
Rhonda Steward
Erwin Van Nieuwenhuyse
Curt Wilkinson
This Report was Prepared by
the Following Project Staff
E. Woody Trihey & Associates
Woodward-Clyde Consultants
E. Woody Trihey & Associates
E. Woody Trihey & Associates
Woodward-Clyde Consultants
R&M Consultants
Woodward-Clyde Consultants
E. W~ody Trihey & Associates
E. Woody Trihey & Associates
Woodward-Clyde Consultants
Woodward-Clyde Consultants
E. Woody Trihey & Associates
Arctic Environmental Information &
Data Center
Arctic Environmental Information &
Data Center
Woodward-Clyde Consultants
Woodward-Clyde Consultants
R&M Consultants
E. Woody Trihey & Associates
Woodward-Clyde Consultants
E. Woody Trihey & Associates
E. Woody Trihey & Associates
i
ACKNOWLEDGMENTS
The Instream Flow Relationship Report (IFRR) and its associated
technical report series were funded by the Alaska Power Authority
{APA) as part of the engineering feasibility and licensing studies for
the proposed Susitna Hydroelectric Project. Much of the IFRR is based
on engineering and environmental studies which were initiated by Acres
American, Inc. and continued by Harza-Ebasco Susitna Joint Venture.
Except for the stream temperature modeling, Harza-Ebasco has conducted
all physical process modeling directly or indirectly referenced in
this document. Of particular value is their reservoir temperature and
ice processes modeling.
Field studies and analyses completed by other members of the Aquatic
Study Team are also cited within this report . Most visible are
numerous references to the Alaska Department of Fish and Game Susitna
Hydroelectric Aquatic Study Team {AOF&G). The ADF&G SuHydro Study
Team conducted field studies to determine the seasonal distribution,
relative abundance , and habitat requirements of anadromous and
selected resident fish populations in the Susitna River.
The University of Alaska, Arctic Environmental Information and Data
Center {AEIDC) conducted the instream temperature modeling studies, a
key element in this evaluation. Mr. Paul Meyer and Mr. Joe Labelle
are recognized for assembling the supporting technical information and
drafting portions of the Instream Tem;1erature and Ice Processes
section of this report.
R&M Consultants has conducted the hydrologic and climatologic field
studies . Of most value in preparing this report has been their
assistance in providing data, analytical results, and technical
revif>'AS pertaining to basin hydrology and climatology, slough
geohydrology (upwelling), and ice processes. Recognition is given
Mr. Steve Bredthauer for drafting portions of the Basin Hydrology and
iii
Streamflow Variability section of this report. Mr. Carl Schoch
proviaed technicaT information and -drafted portions of the Instream
Temperature and Ice Processes section of this report.
Finally special recognition is given to Milo C. Bell for the flawless
insights he provided at the onset of the feasibility studies regarding
the issues that would arise as being central to project licensing and
his wise counsel concerning their implications to the maintenance and
enhancement of salmon resources in the Susitna River Basin.
iv
TABLE OF CONTENTS
DECEMBER DRAFT
INSTREAM FLOW RELATIONSHIPS REPORT
ACKNOWLEDGMENTS
PREFACE
I INTRODUCTION
Instream Flow Relationships Report
Project Setting
II APPLICATION OF AQUATIC HABITAT MODELING TO THE
MIDDLE SUSITNA RIVER
Approach
Framework for Analysis
The IFR Model
III FISH RESOURCES AND HABITAT TYPES
Overview of Susitna River Fish Resources
Relative Abundance of Adult Salmon
Distribution and Timing of Juvenile
Salmon and Resident Species
Identification and Utilization of Habitat Types
Selection of Evaluation Species
IV WATERSHED CHARACTERISTICS AND PHYSICAL PROCESSES
INFLUENCING MIDDLE RIVER HABITATS
Watershed Characteristics
Sediment Transport Processes
lnstream Water Quality and Limnology
Instream Temperature and Ice Processes
V INFLUENCE OF STREAMF LOW AND INSTREAM HYDRAULICS ON
MIDDLE SUSITNA RIVER HABITATS
Habitat Types and Categories
Passage
Microhabitat Response to Instream Hydraulics
VI EVALUATION OF HABITAT COMPONENTS WITHIN THE IFR
FRAMEWORK
Watershed and Climatologic Influences on
Physica1 Habitat Components
Seasonal Utilization of Middle River Habitats
Evaluation Periods and Sepcies
Relative Rankirtg of Existing Phys ·ical Habitat
Components
Inherent P~ject Influences on Existing
Pnysical Processes
Control Over With-Project Relationships
VII REFERENCES
v
1-1
1-1
1-3
11-1
11-3
11-9
111-1
111-1
111-8
II 1-13
I 11-14
111-22
IV-1
IV-1
IV-18
IV-28
IV-39
V-1
V-1
V-11
V-24
VI-1
VI-1
VI-3
VI-4
VI-6
VI-12
VI-15
VI 1-1
LIST OF TABLES
Page
Table III-1. Common and scientific names of fish species
recorded from the Susitna Basin. III-2
Table I II -2. Commercial catch of upper Cook Inlet salmon
in numbers of fish by species, 1954-1984. I II-3
Table II I -3. Summary of commercial and sport harvest on
Susitna River basin adult salmon returns . III-6
Table III-4 . Sport fish harvest for Southcentral Alaska
and Susitna Basin in numbers of fish by species,
1978-1983. III-7
Table I II-5. Susitna River average annual salmon escapement
by sub-basin and spec i es. III-9
Table IV-1. Summary of monthly streamflow statistics for
the Sus i tna Ri ver at Gold Creek {Scully et al .
1978). IV-5
Table IV-2. Percent distri bution and duration of annual
peak flow evP.nts for the Susitna River at
Gold Creek 1950-1982 (R&M Consultants 1981). IV-6
Table IV-3. Number of times breached for duration
indicated based on analysis of Go l d Creek
record 1950-1984. IV-11
Table IV-4. Sediment transport processes and co mponents
and the i r relati ve importa nce in the formation
and maintenance of habitat. IV-19
Table IV-5. With-project influence on sediment transfer
processes and sediment loading. IV-25
Table IV-6. Mean baselinP. water quality characte ~i stics
for middle Susitna River at Gold Creek under
(a) turb i d summer (June -August) conditi ons
and (b) clear, winter (November-April)
condit i ons. IV-30
Table IV-7. Preliminary stream temperature cri teria for
Pacific salmon developed from l i terature sources
for application to the Susit~a River. IV-40
vii
LIST OF TABLES (Continued)
Table IV-8. Comparison of accumulated centigrade temperature
units (CTU 1 s) needed to produce 50 percent
hatching of chum salmon eggs and 50 percent
emergence of chum salmon alevins at selected
sites on the Susitna River with those required
under controlled incubating environments
elsewhere in Alaska. IV-42
Table IV-9. Comparison between measured surfact water
temperatures (°C) in side sloughs and
simulated mainstem temperatures IV-47
Table IV-10. Simulated middle Susitna River mean summer
mainstem temperatures for natural, Watana
only, and Watana/Devil Canyon conditions. IV-49
Table IV-11. Downstream temperatures (°C) resulting from
differences in summer reservoir release flows
and temperatures. IV-50
Table IV-12. Comparison between simulated downstream water
temperatures for constant reservoir outflow
conditions and different air temperatures. IV-53
Table IV-13. Downstream temperatures (°C) resulting from
differences in winter reservoir release flows
and temperatures. IV-54
Table IV-14. Summary of freeze up observations for several
locations within the Talkeetna-to-Devil Canyon
reach of the Susitna River. Source: R&M
Consultants 1980-81, 1982, 1983, 1984. IV-59
Table IV-15. !CECAL simulated ice front progression and
meltout dates (Harza-Ebasco Susitna Joint
Venture, 1984c). IV-66
Table IV-16. Occurrences where with-project maximum river
stages are higher than natural conditions. IV-68
Table V-1. Descripti~n of habitat categories. V-5
iable V-2. Numher of specific areas classified in each
habitat category for seven mainstem discharges. V-8
Table V-3. Frequency of breaching flows at selected
sloughs and side channels. V-20
viii
LIST OF TABLES (Continued)
Table V-4. Calculation of turbidity factors for
determination of the infleunce of turbidity
on clear water cover criteria for juvenile
chinook salmon. V-46
Table V-5. Habitat suitability criteria used in revised
model to forecast WUA for juvenile chinook
salmon under low and high turbidities. V-51
Table VI-1. Simplified periodicity chart. VI-4
Table VI-2. Evaluation of the relative degree of influence
physical habitat components exert on the
suitability of middle Susitna River habitat
types. VI-7
Table VI-3. Tabulation of habitat and evaluation period
indices for the middle Susitna River. VI-11
ix
LIST OF FIGURES
Page
Figure I-1. Project area. I-6
Figure II-1. Primary l i nkages among habitat components and
their relationship to freshwater life phases
of salmon within the Talkeetna-to-Devil Canyon
reach of the Susitna River . II-4
Figure II-2 . Hierarchical structure of the relationship
analys i s. II-7
Figure II-3. A schematic diagram of the structural and
functional components of the r elationship
analysis. II-10
Figure II-4. Schematic diagram showing the integration
of physical processes and the habitat
response components of the Relationships
Model. II-12
Figure II I-1. General habitat types of the Susitna River II I-15
Figure I II -2. Relat i ve distribution of salmon spawning
within different habitat t)pes of the middle
Susitna River (ADF&G 1984c • III-23
Figure III-3. Relat i ve abundance and distribution of
juvenile salmon wi t hin different habitat
types of the middle Susitna River (ADF&G
1984c). I II-26
Figure IV-1. Stream network within the Susitna River Basin. IV-2
Figure IV-2. Estimated percent co ntribution to flow at
Gold Creek. IV-4
Figure IV-3 . Comparison between natural and anti cipated
with-project annual flood frequency curves
for the mi ddle Susitna River (Source: Alaska
Power Authority 1983}. IV-8
Figure IV-4 . Upwelling, downwelling and intergravel flow. IV-12
Figure IV-5. Chum salmon spawning time versus mean incubation
tempertaure nomograph (Source: AEIDC 1984b). IV-43
Figure IV-6. Comparision between average weekly stream
temperatures for the Susitna Ri ver and its
tributaries (Adapted from AEIDC 1984b). IV-46
xi
LIST OF FIGURES {Continued)
Figure IV-7. Comparison of simulated natural and with-
project monthly temperatures of the Susitna
River at RM 130 for the one and two dam
scenarios {Source: AEIDC 1984b). IV-52
Figure IV-8. Flowchart of general ice forming processes
on the middle reach of the Susitna River. IV-56
Figure V-1. Surface area responses to mainstem discharge
in the Talkeetna-to-Devil Canyon reach of the
Susitna River {RM 101 to 14g). V-2
Figure V-2. Flowchart describing possible habitat
transformation that may occur with
decreases in mainstem discharge. V-6
Figure V-3. Number of specific areas classified in each
habitat category for various Gold Creek
mains tem d_i s charges. V-9
Figure V-4. Typical passage reach configuration. V-13
Figure V-5. Breaching flow occurrence during 12 August
to 8 September based on Susitna River
discharge period 1950-1984. V-21
Figure V-6. Thalweg profile of Slough 8A. V-22
Figure V-7. Habitat suita~ility criteria for slough
spawning chum and sockeye salmon. V-26
Figure V-8. Comparison of WUA responses to site flow
for spawning chum and sockeye salmon at four
middle Susitna River study sites {Ad~pted from
ADF&G 1984d) • V-29
Figure V-9. Total surface area and WUA index for spawning
chum salmon at Habitat Category I, II, and III
study sites {Adapted from ADF&G 1984d). V-31
Figure V-10. Simulated influence of increased upwelling on
WUA for spawning chum salmon at Slough 21 and
Upper Side Channel 11. V-33
Figure V-11. Surface area and WUA responses to mainsten
discharge Habitat Category I, II, and III
spawning sites {Adapted from ADF&G 1984c ). V-34
Figure. V-12. Frequency distribution Df cell depth over
upwelling areas in Upper Side Channel 11 at
site flows of 5 and 50 cfs. V-35
xH
LIST OF FIGURES (Cont 1nued)
Figure V-13. Frequency distribution of cell veloc i ty
over upwelling areas in Upper Side Channel
11 at site flows of 5 and 50 cfs. V-36
Figure V-14. Flow and habitat duration curves for spawning
chum salmon by habitat categories V-38
Figure V-15 . Velocity criteria for juvenile .chinook in
clear and turbid water. V-42
Figure V-16. ADF&G cover criteria for juvenile chinoo k in
clear and turbid water. V-43
Figure V-17. Velocity suitability criteria for juvenile
chinook in the Kenai and Chakachamna rivers,
Alaska (Source : Burger et al. 1982 and Bechtel
1983). V-44
Figure V-18. Revis~d cover criteri a for juvenile chinook
i n clear and t urbid water. V-49
Figure V-19. Comparison between WUA forecasts using ADF&G
low turbidity velocity criteria and modified
low turbidity velocity criteria. V-51
Figure V-20 . Comparison between WUA forecasts usir.g ADF&G
and modified cover criteria for juvenile chinook. V-52
Figure V-21. Simulateu effect of reducing fine sedi~~nt
deposition at two study sites. V-54
Figu r e V-22 . Comparison between WUA forecasts using ADF&G
and revised rearing habitat model. V-55
Figure V-23. Percent ~f total wetted surface area provid i ng
WUA for rearing chinook at Side Channel 21
and Upper Side Channel 11. V-57
Figure VI-1. Phenology and habitat utilization of middle
Susitna River salmon in mainstem, tributary,
and slough habitats. VI-5
Figu !"e VI-2. Comparison of natural and with-project habitat
components. Vl-13
Figu r e VI-3 . Ranking of habitat component in accord with
the degree of control project design and
operation might provide them. VI-16
xi ii
Preface
The Alaska Power Authority submitted a ·license application to the
Federal Energy Regulatory Commission (FERC) for the proposed Susitna
Hydroelectric Project on February 18, 1983. Following submission of
supplemental information and responses to FERC comments, the applica-
tion was accepted on July 19, 1983 for review by the FERC. The appli-
cation was then sent by the FERC to resource agencies for review and
comment. This review is now complete, and the FERC is proceeding with
preparation of the final environmental impact statement (FEIS). The
decision to issue the license is tentatively scheduled to be made by
the FERC in 1987, assuming no substantial delays in the licensing
process prior to that date. Even though the license application has
been accepted by the FERC for review, and preparation of the FEIS has
begun, various aquatic or aquatic-related studies are still in pro-
gress to assure that the licensing process proceeds on schedule .
In 1982, following two years of preliminary baseline studies, a multi-
disciplinary approach to quantify effects of the proposed Susitna
Hydroelectric Project on existing fish habitats and identify mitiga-
tion options was initiated. As part of this multi-disciplinary
effort, a technical report series was planned that would (1) describe
the existing fish resources of the Susitna River and identify the
seasonal habitat requirements of selected species, and (2) evaluate
the effects of alternative project designs and operating scenarios on
naturally occurring physical processes which most influence the
seasonal availability of fish habitat in the middle Susitna River.
In addition, a summary report, the Instream Flow Relationships Report
(IFRR), would (1) identify the relative importance of the physical
processes evaluated in the technical report series, (2) integrate the
findings of the technical r!port series, and (3) provide quantitative
relationships (where possible) and discussions regarding the influ-
ences of incremental changes in streamflow, stream temperature, and
water quality on fish habitats in the Talkeetna to Devil Canyon reach
of the Susitna River (Middle River) on a seasonal basis.
xiv
Midway in preparing ~h is draft of the IFRR it became apparent a final
report that would adequately me et all three of these objectives could
not be prepared by March 1985. However, it was also apparent that
many reliable interim statements could be based on existing informa-
tion. Hence it would be possible to apply a large amount of technical
information and identify the relative importance of various inter-
actions among physical processes with regard to providing fish habitat
in the middle river on a seasonal basis.
The IFRR will consist of two volumes. Volume I uses project reports,
data and professional judgement to develop the scope and framework for
the IFR analysis to be presented in Volume II.
Volume I identifies evaluation periods, species, and habitats, and
ranks a variety of physical habitat components with regard to their
relative importance for providing fish habitat at different times of
the year. This ranking considers sper.ies life phase, habitat type and
both naturally occurring and anticipated with-project conditions.
Volume II will specifically address the third objective of the IFRR as
originally stated, "prt.vide quantitative relationships (where possi-
ble) and discussions regarding the influences of incremental changes
in streamflow, stream temperature and water quality on fish habitats
in the Talkeetna to Devil Canyon reach of the Susitna River on a
seasonal basis.
The influence of the project induced changes in stream temperature and
water quality will be discussed on a river segment level by habitat
type, season, and species.The influence of streamflow on fish habitat
will be evaluated on both a river segment and microhabitat level.
Site specific habitat responses to instream hydraulics will be iden-
tified at the microhabitat level and sunwnarized in the form of flow
relationship hydrographs at the river. segment level. These hydro-
graphs are intended to describe the composite response of fndividual
study sites by habitat type to changes in mainstem discharge for
specific species and life history phases of interest.
XV
The IFRR technical report ser1es consists of the following:
Technical Report No. 1. Fish Resources and Habitats of the Susitna
Basin. This report, being prepared by Woodward-Clyde Consultants,
will consolidate infonnation obtained by ADF&G Su Hydro on the fish
resources and habitats in the Talkeetna-to-Devil Canyon reach of the
Susitna River. A draft report utilizing data available through June
1984 was p·r epared by WCC in November 1984.
Technical Report No. 2. Physical Processes Report. This report,
being prepared by Ha rza-Ebasco and R&M Consu 1 tants, describes such
naturally occurring physical processes within the middle river segment
as: reservoir sedimentation, channel stability, and upwelling.
Technical Report No. 3. Water Quality/Limnology Report. This report,
being prepared by Harza-Ebasco, will consolidate existing information
on water quality for the Susitna River and provide technical level
discussions of the potential for with-project bioaccumulation of
mercury, adverse effects of nitrogen gas supersaturation, changes in
downstream nutrients, and changes in turbidity and suspended sedi-
ments. A draft report based on 1 i teratu re reviews and project data
available through June 1984 was prepared in November 1984.
Technical Report No. 4. Instream Temperature. This report, prepared
by AEIDC, consists of three principal components: (1) instream
temperature modeling; (2) development of temperature criteria for
Susitna River fish stocks by species and life stage; and (3) eval-
uation of the influences of with-oroject stream temperatures on
existing fish habitats and natural ice processes. A final report
describing downstream temperatures associated with various reservoir
operating scenarios and an evaluation of these stream temperatures on
fish was prepared in October 1984. A draft report addressing the
influence of anticipated with-project stream temperatures on natural
ice processes was prepared in November 1984.
xvi
Technical Report No. 5. Aquatic Habitat eport. This report, being
prepared by E. Woody Trihey and Associates, will describe the avail-
ability of various types of aquatic habitat in the Talkeetna-to-Devil
Canyon river reach as a function of mainstem discharge. A preliminary
draft of this report is scheduled for March 1985 with a draft final
report prepared in FY86.
Technical Report No. 6. Ice Processes Report. This report being
prepared by AEIDC, Harza-Ebasco, and R&M Consultants will describe
naturally occurring ice processes in the middle river, anticipated
changes in those processes due to project construction and operation,
and discuss effects of naturally occurring and with-project ice
conditions on fish habitat.
xvii
I. HITRODUCTION
Instream Flow Relationships Report
The IFR studies are intended to inform a broad spectrum of readers
having widely differing educational backgrounds and degrees of
familiarity with the proposed project, about potentially beneficial or
adverse influences the proposed project may have on fluvial processes
in the middle Susitna River that control the availability and quality
of fish habitat. By meeting this objective, the report will assist
the Alaska Power Authority and resource agencies to reach an agreement
on an instream flow regime (and associated mitigation plan) that will
minimize impacts and possibly enhance existing middle Susitna River
fish resources.
The final draft of Volume I will: (1) identify limiting life history
phases for evaluation species indigenous to the middle Susitna River;
(2) identify and rank habitat .variables influencing these life phases;
and (3) discuss the responses of these habitat variables to project
induced changes in streamflow, quantity and quality. Habitat
characteristics such as channel structure, sediment transport, ice
proce$ses, turbidity and water chemistry are elements of streamflow
quantity and quality.
The primary purpose of this first volume of the Instream Flow
Relationships Report, presented here in draft form, is to present
technical information within a hierarchical structure that reflects
the relative importance of interactions among physical processes
governing the seasonal availability of fish habitats in the
Talkeetna-to-Devil Canyon segment of the Susitna River. The IFRR and
its associated technical report series should not be construed as
impact assessment documents. These reports merely describe a variety
of natural and with-project conditions, that govern availability of
fish habitat. These relationships are necessary for others to
evaluate alternative streamflow and stream temperature regimes,
conduct impact analyses, and prepare mitigation plans.
I-1
Brief discussions of anticipated with-project conditions are provided
in this report . However they only serve to establish a basis for
assigning some relative importance to anticipated with-project
conditions in so far as they might influence the availability of fish
habitat. No quantitative discussions are presented regarding the
effects of with-project conditions on the amount or quality of fish
habitat as might be expected in an impact assessment.
This draft is based upon information available in project documents
and the status of the IFRR technical report series as of October 1984.
Environmental factors that influence the seasonal distribution and
relative abundance of fish in the middle river are principally
discussed by habitat type. The influence of instream hydraulic
conditions on the availability and quality of fish habitat can only be
discussed on a quantitative basis for a few side sloughs and side
channels. Subjective statements are required at this time to extend
these site specific habitat responses to other habitat types within
the middle Susitna River. As more technical information becomes
available, undocumented discussion will be expanded to encompass such
important habitat variables as upwelling, intragravel temperatures and
primary production and their relationship to anticipated with-project
streamflow, temperature and turbidity regimes.
In this report the three principal freshwater life phases of the
Pacific salmon are ranked in their order of importance as determined
by existing habitat conditions in the middle river, and the relative
importance of several environmental factors in providing suitable
habitat for each of these life history phases is identified. To the
extent data and technical information are available the response of
seasonal habitat conditions to altered streamflow, stream temperature
and water quality conditions are also discussed.
1-2
Project Setting
The Susitna River is located in Southcentral Alaska between the major
population centers of Anchorage and Fairbanks. The Susitna Valley is
a transportation corridor and contains both the Alaska Railroad and
the Parks Highway. Yet even with these transportation facilities, the
basin remains largely undeveloped except for several small communities
located in the lower portion of the drainage. Talkeetna, the largest
of these communities, has an approximate population of 280 and is
located on the east bank of the Susitna River at river mile (RM) 98
(River Miles are measured from Cook Inlet).
The proposed Susitna Hydroelectric Project consists of two dams
scheduled for construction over a period of 15 years. Construction on
the first dam, Watana, is scheduled to begin when the FERC license is
issued, possibly in 1987, and would be completed in 1994 at a site
located approximately 184 river miles upstream from the mouth of the
Susitna River. The Watana development would include an 885 ft high
earth fill dam, which would impound a 48-mile long, 38,000 acre
reservoir with a total storage capacity of 9.5 million acre feet (maf)
and a usable storage capacity of 3.7 maf. Multiple level intakes and
cone valves would be installed in the dam to control downstream
temperatures and dissolved gas concentrations, which otherwise might
be harmful to fish resources. An underground powerhouse would contain
six generators with an installed capacity of 1020 megawatts (mw), and
an estimated average annual energy output of 3460 gigawatt hours
(1,000,000 kilowatts = 1 gigawatt). The maximum powerhouse discharge
capacity at full pool would be greater than 21,000 cfs (APA, 1983).
The second phase of the proposed development is const.ruction of the
646 foot high concrete arch Devil Canyon dam, which is scheduled for
completion by 2002. Devil Canyon dam would be constructed at a site
32 miles downstream of Watana dam and would impound a 26-mile long
reservoir with 7,800 surface acres and a usable storage capacity of
0.35 maf. Installed generating capacity would be about 600 mw, with
an average annual energy output of 3450 gwh. A multiple level intake
1-3
structure and cone valves would also be installed in Devil Canyon dam.
The maximum possible outflow from the four generators in the
powerhouse at full pool is 15,000 cfs. The cone valves at Devil
Canyon dam are designed to pass 38,500 cfs. Watana Reservoir, because
of its large size, provides the capaicty to regulate Susitna River
streamflows. Prior to Devil Canyon construction, Watana Reservoir
will be filled with high summer streamflows when energy demand is
lowest, and drawn down to meet high power demands during the winter
when streamflows are lowest. When Devil Canyon becomes operational,
Watana Reservoir will operate in a similar manner, however, winter
drawdowns may not be to as low levels. Devil CaRyon Reservoir water
levels will generally be stable with a small drawdown iR the spring of
dry years and a larger drawdown in the fall of average and dr; years.
The Susitna River is an unregulated glacial river. Middle Susitna
River turbidities have a mean of approximately 200 nephelometric
turbidity units (NTUs) in summer and less than 10 NTU in winter (refer
to Table IV-6). Typical summer flows range from 16,000 to . 30,000
cubic feet per second (cfs) while typical winter flows range between
1,000 and 3,000 cfs. A thick ice cover forms on the river during late
November and December that persists through mid-May. The drainage
area of the Susitna River is approximately 19,600 square miles, which
is the sixth largest river basin in Alaska. The Susitna Basin is
bordered by the Alaska Range to the north, the Chulitna and Talkeetna
mountains to the west and south, and the northern Talkeetna plateau
and Gul kana uplands to the east. Major tributaries to the Susitna
include the Talkeetna, Chulitna, and Yentna Rivers, all of which are
glacial streams with characteristically high turbid summer streamflows
and ice covered clearwater winter flows. The Yentna River is the
largest tributary to the Susitna and adjoins it at RM 28. The
Chulitna River originates in the glaciers on the south slope of Mount
McKinley and flows south, entering the Susitna River near Talkeetna
(RM 99). The Talkeetna River headwaters in the Talkeetna Mountains,
flows west, and joins the Susitna near the town of Talkeetna (RM 97).
The junction of the Susitna, Chulitna and Talkeetna rivers is often
called the three rivers confluence.
1-4
The Susitna River originates as a number of small tributaries draining
East Fork, Susitna, West Fork and Maclaren Glaciers, and follows a
disjunct south and west course 320 miles to Cook Inlet (Figure I-1).
The Susitna River flows south from the glacier in a braided channel
across a broad alluvial fan for approximately 50 miles, then west in a
single channel for the next 75 miles through the steep-walled Vee and
Devil Canyons. The two proposed Watana (RM 184.4) and Devil Canyon
(RM 151.6) dam sites are located in this reach. Downstream of Devil
Canyon, the river flows south again through a well defined and rela-
tively stable multiple channel until it meets the Chulitna and
Talkeetna Rivers (RM 99). Downstream of the three rivers confluence,
the Susitna River valley broadens into a large coastal lowland. In
this reach the down valley gradient of the river decreases and it
flows through a heavily braided segment for its last 100 miles to the
estuary.
Overview of Fish Resources and Project Related Concerns
The Susitna River basin supports populations of both anadromous and
resident fish. Commercial or sport fisheries exist for five species
of Pacific salmon (chinook, sockeye, coho, chum, and pink), rainbow
trout, Arctic grayling, Dolly Varden, and burbot. The commercial
fishery intercepts returning sockeye, chum, coho and pink salmon in
Cook Inlet. Sport fishing is concentrated in clear water tributaries
to the Susitna River for chinook, coho, pink salmon, rainbow trout and
Arctic grayling.
Construction and operation of the proposed project will notably reduce
streamflows during the summer months and increase them during the
winter months, leading to a more uniform annual flow cycle. Stream
temperatures and turbidities will be similarly affected. The most
pronounced changes in stream temperature and turbidity will likely be
observed in mainstem and side channel areas with somewhat lesser
effects occurring in peripheral areas. Depths and velocities in
habitat areas peri phera 1 to the ma i nstem wi 11 be influenced by the
I-5
I-6
0
! c -u ....
2
CL
change in stream flow patterns more so than habitat in other areas
including the mainstem.
The effects that anticipated changes in streamflow, stream temperature
and turbidity will have on fish populations inhabiting the Susitna
River depends upon their seasonal habitat requirements and the
regulatory control which these habitat components exert upon the
population. Some project induced changes in environmental conditions
may have no appreciable effect on existing fish populations and their
associated habitats, whereas other changes may have dramatic
consequences. Thus, in order to understand the possible effects of
the proposed project on existing fish populations and identify
mitigation opportunities or enhancement potential, it is important to
understand the relationships among the naturally occurring physical
processes which provide fish habitat in the middle river and how fish
populations respond to natural variations in habitat availability.
1-7
II. APPLICATION OF AQUATIC HABITAT MODELING TO THE
MIDDLE SUSITNA RIVER
Approach
The goal of the Alaska Power Authority (APA) in identifying environ-
mentally acceptable flow regimes is the maintenance or enhancement of
existing fish resources and levels of production (APA 1982). This
goal is consistent with mitigation goals of the U.S. Fish and Wildlife
Service (USFWS) and the Alaska Department of Fish and Game (ADF&G)
(APA 1982, ADF&G 1982a, USFWS 1981). Maintenance of naturally occur-
ring fish populations and habitats is the ultimate goal of these
agencies' mitigation policies. The focus of the Instream Flow Rela-
tionships Studies (IFRS) is on describing the response of middle
Susftna River fish habitats to incremental changes in mainstem dis-
charge, temperature and water quality.
Fish populations of the Susitna River are thought to fluctuate for
many reasons. Some of the factors affecting population levels exert
their influence outside the river basin. This is particularly true
for anadromous species such as Pacific salmon, which spend portions of
their life cycles in freshwater, estuarine and marine environments.
Ocean survival and commercial catches significantly affect the number
of salmon returning to spawn in the Susitna River and its tributaries.
Within the freshwater environment, other factors such as late summer
and fall high flows, cold-dry winters, predation, and sport fishing
also affect fish populations. In addition, the long-term response of
adult fish populations to perturbations either within or outside their
freshwater environment is seldom i11111ediately apparent. A time-lag
lasting up to several years usually occurs before an effect, whether
beneficial or detrimental, is reflected in an increase or decrease in
the reproductive potential and ultimately the size of the population.
To avoid many of the uncertainties associated with fluctuating popu-
lation levels, fish habitat is often used when making decisions
regard i ng hydroelectric development and instream flow releases
11-1
(Stalnaker and Arnette 1976, Olsen 1979, Trihey 1979). When using
fish habitat as the basis for decision making, the direction and
magnitude of change in habitat quality and availability are accepted
as indicator s of population response. This relationship is not
necessarily linear, but is generally quantifiable (Wesche 1973, Binns
1979). Instream flow recomnendations based on an analysis of fish
habitat rather than fish population levels require exact knowledge of
the seasonal habitat requirements of the species and ev a luation of the
characteristic responses of individuals of those species to variations
in habitat conditions. In the middle Susitna River the abiotic
habitat components of most interest are the locations and flow rates
of groundwater upwelling, the channel structure, quantity and quality
of streamflow including temperature, suspended sediment concentration
and turbidity. Important biological factors include food availabil-
ity, parasitism or disease, inter species competition and predation.
II-2
Framework for Analysis
Fish habitat is the integrated set of environmental conditior.s to
which a typical individual of a species responds both behaviorally and
physiologically. It is generally recognized that temperature, water
quality, water depth and velocity, cover or shelter, and streambed
material are the most important physical variables affecting the
amount or quality of riverine fish habitat (Hynes 1972). Important
biological factors include food availability, parasitism or disease,
and predation. The principal relationships (linkages) among environ-
mental factors which influence salmon populations within the Talkeetna-
to-Devil Canyon segment of the Susitna River are diagrammed in
Figure II-1.
Various approaches exist for evaluation of fluvial systems and their
associated fish habitats. The longitudinal succession approach to
describing riverine ecology and fluvial processes examines a river
from its headwaters to its mouth (Burton and Odum 1945, Sheldon 1968,
Mackin 1948). Watershed characteristics such as climate, hydrology,
geology, topography and vegetative cover (land use) are the principal
determinants of basin runoff and erosional processes which become
manifest as a river system. This approach focuses on the down-valley
transition in channel morphology, water quality and the biological
community which results from the interaction of these watershed
characteristics. Based on the longitudinal succession of the existing
river system as well as anticipated differences in the type and
magnitude of project impacts, the 320 mile length of the Susitna River
was subdivided into the four discrete segments described below. This
report is focused specifically on the fifty mile segmen t from
Talkeetna to Devil Canyon; referred to as the Middle River.
1. Upper Basin (RM 320-232). This segment includes the headwater
reach of the Susitna River and its associated glaciers and
tributary streams above the elevation of the proposed impolind-
ments.
II-3
H
H
I
.p-.
WATER QUALITY
FOOD
PRODUCTION
REARING
STREAM TEMP
WATERSHED
CHARACTERISTICS
ICE PROCESSES
INCUBATION
AND
OVERWINTERING
POPULATION
RESPONSE
STREAM FLOW
AND
HYDRAULICS
UPWELLING
SPAWNING
CHANNEL
STRUCTURE
FigureD-I . Primary linkages among habitat components and their relationship to freahwater life
phase a of aalmon within the "Talkeetna to Devil Ca"yon reach of the ·susitna River.
2. The Impoundment Zone ( RM 150-232). This segment inc 1 udes the
eighty-mile portion of the Susitna River which will be inundated
by the Watana and Devil Canyon impoundments. This single channel
reach is characterized by steep gradient, and high velocity.
Intermittent islands are found in the reach with significant
rapids occurring in Vee Canyon and between Devil Creek and Devil
Canyon.
3. The Middle River ( RM 99-150). This fi fty-mi 1 e segment extends
from Devil Canyon downstream to the three rivers confluence. It
is a relatively st~ble reach comprised of nearly equal lengths of
single channel and split channel characteristics (R&M River
Morphology 1982). Construction and operation of the project will
alter the quantity and temperature of streamflow and the amount
of suspended and bed load sediment in this reach.
4. The Lower River (RM 0.-99). This segment extends one hundred
miles from the three rivers confluence downstr~am to the estuary.
The floodplain is ver) broad containing multiple or braided
channels which meander laterally. Reworking of streambed gravels
in this area is relatively frequent causing instability and
migration of the main flow channel or channels. Project induced
changes in streamflow, stream temperature and sediment concen-
trations will attenuate in this reach due to tributaries such as
the Talkeetna, Chulitna and Yentna rivers which will be unaffect-
ed by project operation.
Another method frequently used in riverine ecology sta :dies is to
describe the manner in which individuals of a species respond to
changes in site-specific habitat variables such as surface and intra-
gravel water temperatures, substrate composition, depth, velocity,
cover, food availability, and predation (Everest and Chapman 1977,
Bovee 1984, Gore 1978). Within the structure of our analysis this
method is referred to as the microhabitat approach and is reflected in
the development of speci P.s-specific habitat su i tability criteria and
numerous site-specific habitat models.
II-5
Because of the notable variation and differences in microhabitat
conditions within the middle Susitna River segment, six major habitat
types are recognized: mainstem, side channel, side slough, upland
slough, tributary and tributary mouth. Habitat type refers to a major
portion of the wetted surface area of the river having comparatively
similar morphologic, hydrologic and hydraulic characteristics. At
some locations, such as major side channels ar.d tributary mouths, a
designated habitat type persists over a wide range of mainstem dis-
charge even though its surface area may change significantly. In
other instances the habitat classification of a specific area may
change from one type to another in response to mainstem discharge
(Klinger and Trihey 1984}. Such an example is the transformation of
some turbid water side channels that exist at typical mid-suiTITier
mainstem discharge levels to clear water sloughs at lower late sum-
mer/fall mainstem flows.
Habitat categories are used to classify specific areas within the
river corridor according to the type of transformation they undergo as
mainstem discharge varies . This approach was chosen as the basic
framework for extrapolating site-specific habitat responses to the
remainder of the middle Susitna River because (1} a significant amount
of wetted surface area is expected to be transformed from one habitat
type to another as a result of project induced changes in streamflow
(Klinger and Trihey 1984); and (2) .a large amount of circumstantial
evidence exists within the ADF&G SuHydro data base and elsewhere that
indicates turbid water channels which transform into clearwater
habitats may provide substantially different summer rearing conditions
than channels that remain turbid.
The hierarchical structure of our analysis, proceeding from micro-
habitat study sites through habitat categories and habitat types
(ADF&G macrohabitats) to the middle rher segment is diagrammed in
Figure II-2. The structure of our analysis is similar to the study
site and representative reach logic referenced in other instream flow
studies and training documents (Bovee and Milhous 1978, Wilson et al.
1981, Bovee 1982).
II-6
lllddle River S•t••nt
Habitat cat•oort•
Studr Sit•
CJ c:::::::::J c::::::J
Fl•ed louncl•r llloroMbitata
V.lable BoundorJ •cnMIIItota
Fig&n D-2. Hierarchical structure of the relationship analyaia.
II -7
The basic difference between the structure of the middle river studies
and other instream flow studies is that habitat types and habitat
categories have been substituted for river segments and representative
reaches. Additionally, our methodology uses wetted surface area of
habitat types as the common denominator for extrapolation rather than
reach length. Given the spatial diversity and temporal variation of
riverine habitat conditions within the Talkeetna-to-Devil Canyon
segment, the hierarchical structure of our analysis appears more
applicable to the middle Susitna River than routine adherence to the
IFG representative reach concept.
11-8
The IFR Model
Throughout the evolution of the Susitna Aquatic Studies identification
of an environmentally acceptable flow regime to protect existing fish
populations and habitats has remained of central importance. Thus
physical process and aquatic habitat modeling has occupied an
important position within the structure of the instream flow studies
and visually discernible characteristics of the riverine environment
have been used to categorize the entire wetted surface area of the
middle Susitna River according to habitat type.
Sufficient data have been obtained and analyzed to identify the
seasonal and microhabitat requirements of resident fish and adult and
juvenile salmon indigenous to the middle Susitna River. In addition,
physical process models have been developed to evaluate stream temper-
ature, ice cover, sediment transport and site specific hydraulic
conditions for a broad range of streamflow and meteorologic con-
ditions. The surface area response of middle river habitat types has
also been estimated. Thus the existing data and analytic base is
sufficient to warrant application within a structured framework to
identify habitat response to alternative streamflow and stream temper-
ature regimes. The influences of water 1uality and groundwater
upwelling on middle river habitats can also be forecast but in a more
subjective manner.
A schematic diagram of the functional and structural components of the
IFR analysis is diagrammed in Figure II-3. At present, this analytic
approach does not exist as a functioning model. The numerous compo-
nents and linkages diagrammed in the figure are still at various
stages of development. However, sufficient data and information have
been asseni>led and subjectively evaluated within the analytic struc-
ture diagrammed in Figure II-3 to make reliable tentative forecasts
and predictive statements.
Application of this conceptual model is reported in this first volume
of the IFRR. Section III describes the fish resources and habitat
II-9
INPUT IIAINaTEM DIICHAR&e lEA ION IPI!CIEI/L.E ITAGE H H I ..... 0 ; HAaiTAT REIPOIIII r------, I [ WUA RIIPOIIII I I, III!PONM _g I I I ... . FUNCTIONAL MODeL MIDDLI RIYIR IIGMIIIT ITMJCTUUL PRAIIIWOM OUTpUT HAaiTAT IUIIPACE ARIA HA .. TAT AYAILAaiJTY ... . HAaiTAT QUALITY ... . Fleure D-1. A eolleMetlo dl•1r•• of tlae etruotur•l ••d fu•otlo••l OOMPo•e•te of .... rel•tlo•elllp •••l,ele for tlae Middle •••It•• Rlwer d11rlne ope• ••ter.
types of the middle river and identifies the evaluation periods and
the primary and secondary evaluation species. Section IV discusses
the principal watershed characteristics and physical processes which
influence the seasonal availability and quality of fish habitat. The
influence of streamflow and i nstream hydrau 1i cs on habitat type and
microhabitat conditions ·is described in Section V. Collectively these
three sections identify and discuss the principal components and
linkages diagrammed in Figure 11-3.
Section VI sunmarizes the major points presented in Sections III
through V, and applies these findings to describe the relative
importance of relationships among physical processes and biologic
responses. Anticipated with-project conditions are generically
discussed in Section VI, but only to the extent necessary for
identifying differences between existing and with-project relation-
ships that will be important to consider in future analyses.
A more detailed description of the linkages between physical processes
and habitat response within the IFR model is provided in Figure 11-4.
The IFR model will be applied to support preparation of Volume II of
the IFRR. Volume I is intended to define the relative importance of
the various physical processes and microhabitat variables to
evaluation species by habitat type and season. In this manner Volume
I will introduces the IFRR model and reduces the scope and complexity
of the IFRR analysis to be reported in Volume II.
One basic difference between the envisioned IFRR analysis and those
previously proposed for the Susitna River is evaluation of watershed
processes and physical habitat components such as ice, temperature and
sediment at the macrohabitat (river segment) level rather than
microhabitat (study site) level. Another major difference is
addressing only a small number of evaluation species in a rigorous
quantitative manner. The interface between physical process and
habitat response models at the macrohabitat level is illustrated in
Figure 11-4.
11-11
IFR MODEL r -----------------,
J.!teYI
MAINSTEM DISCHARGE
SEASON
(Riv.r SetmwJt)
PHYSICAL PROCESS
SYNTE_.
Allalyala
~, ,.._,, •• Iori
..... C.......Stltlllllty ... ,...
INPUT 1 --L---~------~ ---_..1 _______ 1
SPECIES I HABITAT
LIFE HISTORY PHAfE RESPONSE
(Habitat Cotegory)
(Microhabitat Stud.r Site)
ANa 11r a,.clfJc
"-''ool .._.
"rHa'"-t T,e
T
0..11111 IIMIIIo ... for I Site Specific ~ Nalllfot AwallollllltyCMd
.___NA_~_AT_MO_DEL_---..rt' IMIIwlcluol Study Site
T
1
,. ... ~ I Ca pa ....
Awailallle Area (by
~ liaa.etet type) Nat
Li81itecl liy T1•p1rotwe
ar Water Quo I ity Duriftt
S..... lpeciff eel
ea.o.tte Hallltet
lAdle .. .., Halll1at
TJIIII for Soeofw artc1
Life Stage Spaoiflecl
..... _______ ----------------
Figure ll-4. Schem•tlc dl•tr•m allowing t!te lntetr•tlon of phyale•l proceaa •nd
the hult•t reaponH component• of the Rel•tlonahlpa Model.
II-12
A fundamental requirement of the IFRR analysis is a forecast of the
amount of surface area represented by each habitat type at various
levels of mainstem discharge. The surface areas of individual
locations comprising each habitat type in the middle river have been
estimated at four mainstem discharges ranging from 9,000 to 23,000 cfs
using digited measurements on 1 inch = 1,000 feet aerial photographs
(Klinger and Trihey 1984). The surface areas at different locations
may be summed within and across habitat types, and the surface area
response of any specified area to variations in mainstem discharge can
be modeled and its habitat type forecast for discharges ranging from
9,000 to 23,000 cfs. Additional photography has or will be obtained
by June 1985 to extend our modeling capabilities to a range of middle
river streamflows from 5,000 to ave~ 30,000 cfs.
Physical process models have been or are being developed to forecast
reservoir storage, temperature, ice and suspended sediment conditions
in relationship to a variety of historic climatologic, hydrologic and
anticipated power forecasts. These reservoir models in turn support
analysis of downstream temperature, ice, suspended sediment and
channel stability analyses. Sufficient progress has been made with
the physical prot:ess modeling to feel relatively confident that the
influences of instream water quality, temperature, ice and suspended
sediment can be integrated at the macrohabitat level with no foresee-
able adverse effects on the utility of the resultant habitat response
in supporting streamflow negotiations.
At the microhabitat level Weighted Usable Area (WUA) is used as an
index to evaluate the influence of streamflow variations on the site
specific availability of potential fish habitat. WUA is defined as
the total wetted surface area of a study site expressed as an equiva-
lent surface area of optimal (preferred) fish habitat for the life
stage and species being evaluated (Bovee and Milhous 1978). Weighted
Usable Area is most commonly computed using such microhabitat vari-
ables as depth, velocity, substrate composition (spawning fish), and
cover (rearing fish). WUA fore casts for habitats in the middle
Susitna River have been enhanced by also considering such other
11-13
microhabitat variables as upwelling groundwater and turbidity.
Resultant WUA indices will be used in conjunction with surface area
measurements to calculate habitat availability and habitat quality
indices for each study site.
Each study site and approximately one hundred fifty other locations in
the middle river have been subjectively evaluated during a habitat
reconnaissance survey. These data are currently being used to
classify all reconnaissance sites by similar morphologic characteris-
tics and develop field habitat indices that might be used to corrobo-
rate those forecast by the WUA habitat models. Thus the envisioned
output of the IFR model is total surface area of each habitat type not
limited by temperature, water quality or suspended sediment during the
evaluation period, and a composite species specific habitat index for
each habitat type. Both the surface areas and habitat indices will be
functions of the mainstem discharge at Gold Creek.
As previously stated these forecasts are to be presented in Volume II
of the IFRR. This first volume serves to introduce the model and
reduce the complexity of the IFR analysis by identifying the principal
components, evaluation species and periods of the IFR analysis.
II-14
III. FISH RESOURCES AND HABITAT TYPES
Overview of Susitna River Fish Resources
Fish resources in the Susitna River comprise a major portion of the
Cook Inlet commercial salmon harvest and provide fishing opportunities
for sport anglers. Anadromous species that form the base of commer-
cial and sport fisheries include five species of Pacific salmon :
chinook, coho, chum, sockeye, and pink. Important resident species
found in the Susitna River basin include Arctic grayling, rainbow
trout, lake trout, burbot, Dolly Varden, and round whitefish. Scien-
tific and common names of all fish species which inhabit the Susitna
River are presented in Table 111-1.
Adult Salmon Contribution to Commercial Fishery
With the exception of sockeye and chinook salmon, the majority of the
upper Cook Inlet salmon cornnercial catch originates in the Susitna
Basin (AOF&G 1984a). The long-term average annual catch of 3.1
million fish is worth approximately $17 .9 million to the cornnercial
fishe~ (K. Florey, AOF&G, pers. comm. 1984). In recent years commer-
cial fishermen have landed record numbers of salmon ~n the upper Cook
Inlet fishe~ with over 6.2 million salmon caught in 1982 and over 6.7
millior. fish landed in 1983 (Table 111-2).
The most important species to the upper Cook Inlet commercial fishe~
is sockeye salmon. In 1984, the sockeye harvest of 2.1 million fish
in upper Cook Inlet was valued at $13.5 rr.illion (K. Florey, AOF&G,
pers. comm. 1984). The estimated contribution of Susitna River
sqckeye to the commercial fishery is between 10 to 30 percent (AOF&G
1984a). Thus, in 1984 the Susitna River co~tributed between 210,000
and 630,000 sockeye salmon to the upper Cook Inlet fishery, which
represents a value be t ween $1.4 million and $4.1 million.
Chum and coho salmon are the second and third most valuable commercial
species, respectively. In 1984, the chum salmon harvest of 684,000
111-1
Table III-1. Common and scientific names of fish species recorded
from the Susitna Basin.
Scientific Name Common Name
Petromyzontidae
Lampetra japonica
Salmonidae
Coregonus laurettae
Core~nus pfdschfan
Onco ynchus ~orbuscha
oncorhYnchus eta
OncorfiYnchus KTSUtch
oncorhynchus nerka
Onco~nchus tshawytscha
Prosop um cylindraceum
Sa 1 mo ~a f rdneri
Salvel nus malma
Salvelinus ~cush
Thymallus arctfcus
Osmeridae
Thaleichthys pacificus
Esocidae
Esox lucius
Catostomidae
Catostomus catostomus
Gadidae
Lota lota
Gasterosteidae
Gasterosteus aculeatus
Pungftfus pungftius
Cottidae
Cottus spp.
Source : AOF&G SuHydro, Anchorage, Alaska.
III-2
Arctic lamprey
Bering cisco
humpback whitefish
pink salmon
chum salmon
coho salmon
sockeye salmon
chinook salmon
round whitefish
rainbow trout
Dolly Varden
lake trout
Arctic grayling
eulachon
northern pike
longnose sucker
burbot
threespine stickleback
ninespine stickleback
sculpin .
Table III-2. Commercial catch of upper Cook Inlet salmon in numbers of fish by
species, 1954 -1984.
Year Chinook Sockeye Coho Pink Chum Total
1954 63,780 1,207,046 321,525 2,189,307 510,068 4,291,726
1955 45,926 1,027,528 170,777 101,680 248,343 1,594,254
1956 64,977 1,258,789 198,189 1,595,375 782,051 3,899,381
1957 42,158 643,712 125,434 21,228 1,001,470 1,834,022
1958 22,727 477,392 239,765 1,648,548 471,697 2,860,129
1959 32,651 612,676 106,312 12,527 300,319 1,064,485
1960 27,512 923,314 311,461 1,411,605 659,997 3,333,889
1961 19,210 1,162,303 117,778 34,017 349,628 1,683,463
1962 20,210 1,147,573 350,324 2 ,711,689 970,582 5,200,378
1963 17,536 942,980 197,140 30 ,436 387,027 1,575,119
1964 4,531 970,055 452,654 3,231,961 1,079,084 5,738,285
1965 9,741 1,412,350 153,6 19 23,963 316 ,444 1,916,117
1966 9,541 1,851,990 289 ,690 2,006,580 531,825 4,689,626
1967 7,859 1,380,062 177,729 32,229 296,037 1,894,716
1968 4,536 1,104,904 470,450 2,278,197 1,119,114 4,977,201
1969 12,398 692,254 100,952 33,422 269,855 1,108,881
1970 8,348 731,214 275,296 813,895 775 t 167 2,603,920
1971 19,765 636,303 100,636 35,624 327,029 1,119,357
1972 16,086 879,824 80,933 628,580 630,148 2,235,571
1973 5,194 670,025 104 ,420 326,184 667,573 1 ,773,396
1974 6,596 497,185 200,125 483,730 396 ,840 1,584,476
1975 4,780 684,818 227,372 336,359 951,796 2 ,205,135
1976 10,867 1,664,150 208,710 1,256,744 469,807 3,610,278
1977 14,792 2,054,020 192,975 544,184 1,233 ,733 1,049,704
1978 17,303 2,622,487 219,234 1,687,092 571,925 5,118,041
1979 13,738 924,415 265,166 72,982 650,357 1,926,658
1980 12,497 1,584,392 283,623 1,871,058 387 ,078 4,138,648
1981 11,548 1,443,294 494,073 127,857 842,849 2,919,621
1982 20,636 3,237 ,376 777,132 788,972 1,428 ,621 6,252 ,7 37
1983(1) 20,396 5,003,070 520,831 73,555 1,124,421 6,742,273
1984 8,800 2,103,000 443,000 623 ,000 684,000 3,861,800
Average 19,247 1,340,339 263 785 even-1,576,646
' odd -120,416 659,190 3.058,170
(1) ADF&G Prel i minary Data, Commercial Fisheri es Division, Anchorage, Alas ka.
Source : ADF&G Commercial Fisheries Di vision, Anchorage, Alaska.
I II-3
fish was valued at $2.0 million, while the coho salmon harvest of
443,000 fish was worth $1.8 million (K. Florey, ADF&G, pers. cOflll'l.
1984). The estimated contribution of Sus i tna River chum to the upper
Cook Inlet commercial fishery is estimated to be 85 percent, while
the estimated contribution of Susitna River coho to the fishery is
approximately 50 percent (ADF&G 1984a).
Pink salmon is the least valued of the conmercial species in upper
Cook Inlet. In 1984, the pink salmon harvest of 623,000 fish was
worth an estimated $0.5 million (K. Florey, ADF&G, pers. cOflll'l. 1984),
of which Susitna River pink salmon contributed about 85 percent (ADF&G
1984a).
Since 1964 the upper Cook Inlet commercial salmon fishery has opened
in late June to avoid capturing chinook salmon. Thus, most chinook
salmon have entered their natal streams when the commercial fishing
season opens and their harvest is incidental to the commercial catch.
In 1984, the 8,800 chinook harvested in upper Cook Inlet had a commer-
cial value of $0.3 million (K . Florey, ADF&G, pers . coiTIIl. 1984). It
is estimated that the Susitna River contribution of chinook salmon was
about 10 percent of the total catch (ADF&G 1984a).
In the last four years (1981-1984) sockeye, chum and coho salmon
harvests, which account for over 95 percent of the commercial value in
the fishery, have exceeded the long-term average catches for those
species (Table III-2). Record catches for coho and chum were recorded
in 1982 and for sockeye in 1983.
Sport Fishing
The Susitna River, along with many of its tributaries, provides a
111.1lti-species sport fishery. Since 1978, the Susitna River and its
tributaries have accounted for an annual average of 127,100 angler
days of sport fishing effort (Mills 1979, 1980, 1981, 1982, 1983,
1984). This represents approximately 13 percent of the 1977-1983
!nnual average of 1.0 million total angler days for the Southcentral
III-4
region. Most of the sport fishing in the Susitna Basin occurs in the
lower Susitna River from Alexander Creek (RM 9.8) upstream to the
Parks Highway (RM 84}.
Most sport fishing activity occurs in tributaries and at tributary
mouths, while the mainstem receives less fishing pressure. Coho and
chinook salmon are most preferred by sport anglers in the Susi tna
River. In addition many pink salmon are taken during even-year runs.
The annual sport harvest of coho salmon in the Susitna River is
significant when compared to the estimated total coho escapement. In
1983, almost one of every five coho salmon entering the Susitna River
was caught by sport anglers (Table III-3}. The annual harvest of
chinook salmon in the Susitna River has increased from 2,850 fish in
1978 to 12,420 fish in 1983 (Table III-4), During this period, the
contdbution of the Susitna River chinook sport harvest to the South-
central Alaska chinook sport harvest has increased from 11 to 22
percent. Of the resident species in the Susitna River, rainbow trout
and Arctic grayling are caught by anglers in the largest numbers
(Mills 1984).
Subsistence Fishing
The only subsistence fishery on Susitna River fish stocks that is
officially recognized and monitored by the Alaska Depa r tment of Fish
and Game is near the village of Tyonek, approximately 30 miles (50 km)
southwest of the Susitna River mouth. The Tyonek subsistence fishery
was reopened in 1980 after being closed for sixteen years. From 1980
through 1983, the annual Tyonek subsistence harvest averaged 2,000
chinook, 250 sockeye and 80 coho per year (ADF&G 1984b).
III-5
Table 111-3. Summary of commercial and sport harvest or. Susitna River basin adult salmon returns .
~ommercta1 Rarvest Sport Harvest
Susitna
Upper Estimated Estimated Estimated Basin
Cook Inlyt Estimated 2 Susitna Susitna Total Sport Percent of
Species Harvest Percent Susitna Harvest Escapement 3 Run Harvest 4 Escapement
Sockeye Mean ~ 81 1,443,000 20 ( l 288,600 287,000 575,600 1,283 0 .4
82 3,237,000 20 ~10-30 647,400 279,000 926,400 2,205 0.8
83 5,003,000 10 10-30 500,300 185,000 685,300 5,537 3.0
Pink
81 128,000 85 108,800 127,000 235,800 8,660 6.8
82 789,000 85 670,650 1,318,000 1,988,650 16,822 1.3
83 74,000 85 62,900 150,000 212,900 4,656 3 ....
Chum
1-4 81 843,000 85 716,550 297,000 1,013,550 4,207 1.4
1-4 82 1,429,000 85 1,214,650 481,000 1,695,650 6,843 1.4
1-4 83 1,124,000 85 955,400 290,000 1,245,400 5,233 1.8 I
0\
Coho
81 494,000 50 247,000 68,000 315,000 9,391 13.8
82 777,000 50 388,500 148,000 536,500 16,664 11.3
83 521,000 50 260,500 45,000 305,500 8,425 18.7
Chinook
81 11,500 10 1,150 7,576
82 20,600 10 2,060 10,521
83 20,400 10 2,040 12,420
1 Source: ADF&G Commercial Fisheries Division 2
3 B. Barrett, ADF&G Su Hydro, February 15, 1984 Workshop Presentation 2 Yentna Station + Sunshine Station estimated escapement + 5% for sock!ye
+ 48 % for p1nk 2 + 5% for chum
+ 85 % for cohi
4 Mills 1982, 1983, 1984
Table Ill-~. Sport fish harvest for Southcentral Alaska and Suaitna Basin in numbers of fiah by species, 1978-1983.
Arctic Cra~lt !!S Rainbow Trout Pink Salmon Coho Sa 111100 Chinook Sal110n Ch• SaliiOn Sock•~• Sal110n
South-Suiitna South-Suaitna South-Suaitna South-Suaitna South-Suaitna South-Suaitna South-Suaitna
Year central Basin central Basin central Basin central Baafn central Baa in central Basin central Basin
1978 ~7 ,866 13,532 107,2~3 1~,925 1~3.~83 55,~18 81,990 15,072 26,~15 2,8~3 23,755 15,667 118,299 8~5
1979 70,316 13,31t2 129,815 18,35~ 63,366 12,516 93,23~ 12,893 3~,009 6,910 8,126 ~.072 77,655 1,586
1980 69,1t62 22,083 126,686 15,1t88 153,7~ 56,621 127,958, 16,1t99 2~,155 7,389 8,660 lt,759 105,911t 1 ,30ft
1981 63,695 21,216 11t9,1t60 13,757 6~,163 8,660 95,376 9,391 35,822 7,576 7,810 lt,207 76,533 1,283
H
H 1982 60,972 18,860 1lt2,579 16,979 105,961 16,822
H
136,153 16,66-lt lt6,266 10,521 13,1t97 6,81t3 128,015 2,205
I ....... 1983 56,896 20,235 11t1,663 16,500 lt7 ,26ft lt,656 87,935 8,lt25 57 ,09lt 12,1t20 11,0it3 5,233 170,799 5~537
Average 61,535 18,211 132,908 16,000 131t,lt13 lt2,951t 103,771t 13,157 37,2~ 7,91t3 12,1lt9 6,797 112,869 2,128
(even) (even)
58,26/t 8,611
(odd) (odd)
Source : Hilla (1979-1981t)
Relative Abundance of Adult Salmon
Major salmon-producing tributaries to the Susitna River include the
Yentna River drainage {RM 28), the Chulitna River drainage {RM 98.6)
and the Talkeetna River drainage {RM 97.1). Numerous other smaller
tributaries also contribute to the salmon production of the Susitna
River. The average salmon escapements at four locations in the
Susitna River for 1981 through 1984 are presented in Table 111-5 .
The minimum Susitna River escapements of four salmon species can be
estimated for 1981 through 1984 by adding the escapements at Yentna
Station {RM 28, TRM 04) and Sunshine Station {RM 80) {ADF&G 1984a).
These total escapements are considered minilll.lms because they do not
include escapements below RM 80, excluding the Yentna Riv.er {RM 28)
{AOF&G 1984a). The four-year averages of minimum Susitna River
escapements for sockeye, chum and coho salmon are presented in Table
111-5. The minimum Susitna River escapement for pink salmon is
reported in Table 111-5 as a two-year {1981, 1983) average escapement
for odd-year runs and a two-year {1982, 1984) average escapement for
even-year runs. This separation was made because pink ~almon runs are
numerically dominant in even years {AOF&G 1984a).
Escapements of chinook salmon at Yentna Station have not been quan-
tified because most of the run passes the station before monitoring
begins {AOF&G 1981a, 1982a, 1984a, 1985). Therefore, a minimum
Susitna River escapement for chinook salmon cannot be estimated by the
same method used for the other salmon species. Chinook escapements
have been estimated at Sunshine Station in 1982, 1983 and 1984 {AOF&G
1984a, 1985). The three-year average of chinookr escapements at
Sunshine Station is presented in Table 111-5.
Most salmon spawn in the Susitna River and its tributaries below
Talkeetna Station {RM 103) (AOF&G 1981a, 1982a, 1984a, 1985). Impor-
tant chinook spawning areas are Alexander Creek {RM 9.8), Lake Creek
in the Yentna River drainage {RM 28), the Oeshka River {RM 40.5) and
Prairie Creek in the Talkeetna River drainage (RM 97.1) {AOF&G 1984a,
111-8
Table 111-5. Average salmon escapements in the Susftna River by species and location.
location
Sockeye 1 Chum2 Coho2 Pink 3 Chinook 4 River Mile location Total
Yentna Station 126,750 21,200 19,600 Odd 48,400 Odd 215,950
RM 28, TRM 04 Even 408,300 Even 575,850
Sunshine Station 121,650 431,000 43,900 Odd 45,000 88,200 Odd 729,750
RM 80 Even 730,100 Even 1,414,840
Talkeetna Station 6,300 54,600 5,700 Odd 5,900 16,700 Odd 89,200
RM 103 Even 125,500 Even 208,800
Curry Station 2,400 28,200 1,6op Odd 3,300 13,000 Odd 48,500
RM 120 Even 87,900 Even 133,100
H Minimum Susitna 248,400 452,200 63,500 Odd 93,400 Odd 857,500 H River 5 Even 1,138,400 Even 1,902,500 H
I I
..0
1 Second-run sockeye escapements. Four-year average of 1981, 1982, 1983 and 1984 escapements.
2 Four-year average of 1981, 1982, 1983 and 1984 escapements.
3 Odd is average of 1981 and 1983 escapements. Even is average of 1982 and 1984 escapements.
4 Three-year average of 1982, 1983 and 1984 escapements. Dashes indicate no estimate.
5 Summation of Yentna Station and Sunshine Station average escapements. Does not include escapement to the
Susitna River and tributaries below RM 80, excluding the Yentna River (RM 28).
Source: ADF&G 1984a, 1985.
1985). Most sockeye salmon spawn in the Yentna, Chulitna (RM 98.6)
and Talkeetna drainages (ADF&G 1984a, 1985 ). The Yentna River is also
an important pink salmon spawning area (ADF&G 1984a). The primary
area of chum salmon spawning is the Talkeetna River (ADF&G 1984a,
1985). Most coho salmon spawn in tributaries below RM 80 (ADF&G
1985).
In the middle reach of the Susitna River, chum and chinook are the
most abundant salmon, excluding even-year pin k salmon (ADF&G 1984a,
1985). In this river reach, salmon escapements have been monitored at
Talkeetna (RM 103) and Curry (RM 120) stations since 1981 (ADF&G
1981a, 1982a, 1984a, 1985).
The contribution of the middle Susitna River salmon escapements to the
Susitna River salmon runs can be estimated for 1981 through 1984 by
dividing the Talkeetna Station escapements into the minimum Susitna
River escapements. Based .on the average escapements presented in
Table III-5, the average percent contribution in 1981 through 1984 for
the middle Susitna River is: 2.5 percent for sockeye, 12.1 percent
for chum, 9.0 percent for coho, 6.3 percent for odd-year pink and 11.0
percent for even-year pink salmon. These estimates should be con-
sidered maximum values because (1) the minimum Susitna River escape-
ments, as previously discussed, do not include escapements below RM 80
(excluding the Yentna River); and (2) the Talkeetna Station escape-
ments overestimate the number of spawning salmon in the middle reach.
This overestimation is apparently due to milling fish that return
downstream of Talkeetna Station to spawn.
The number of fish that reach Talkeetna Station and later move
downstream to spawn is significant. In 1984, 83 percent of the
sockeye, 75 percent of the chum, 75 percent of the coho, 85 percent of
the pink and 45 percent of the chinook salmon escapements at Talkeetna
Station were milling fish that returned downstream of Talkeetna
Station to spawn (ADF&G 1985). If the escapement to Talkeetna Station
is reduced to account for the milling factor, the contribution of
III-10
middle SusHna River escapement to the miniDI.Im basin escapement in
1984 becomes: 0.8 percent for sockeye, 3.1 percent for chum, 2.6
percent for coho and 1.9 percent for pink salmon. Chinook salmon were
not included in this analysis because of the lack of minimum Susitna
River escapements, as previously discussed.
III-11
Distribution and Timing of Juvenile Salmon and Resident Species
Juvenile Salmon
The relative abundance of juvenile salmon in the Susitna River can not
be estimated because population estimates of outmigrating juvenile
salmon have been done only for chum and sockeye salmon at Talkeetna
Station (RM 103) and catch per unit effort data are available from
smolt traps at Talkeetna Station but comparable data are unavailable
for other areas.
Most chum salmon rear in the middle Susitna River for one to three
months, while pink salmon spend little time in this reach (AOF&G
1984c). The outmigration of juvenile chum at Talkeetna Station (RM
103) extends from May through mid-August, whereas most juvenile pink
salmon leave this reach~· river by June (AOF&G 1984c). Outmigration
timing of pink and chum juveniles is positively correlated with
mainstem discharges (AOF&G 1984c).
Chinook and sockeye salmon rear from one to two years in the Susitna
River, while coho salmon rear from one to three years (AOF&G 1984c).
Some age 0+ juveniles of chinook, coho and sockeye salmon move out of
the middle Susitna River throughout the summer, with peak downstream
movements at Talkeetna Station occurring in June, July and August
(AOF&G 1984c). Chinook, coho and sockeye juveniles that remain in the
middle Susitna River utilize rearing habitats until September and
October, when they move to overwintering habitats . Chinook juveniles
primarily rear in tributaries and side channels. Side channel use was
highest in July and August of 1983 (AOF&G 1984c). Most coho juveniles
use tributaries ad upland sloughs for rearing (AOF&G 1984c). Sockeye
salmon rear principally in natal side and upland sloughs (AOF&G
1984c). Age 1+ chinook, coho and sockeye and age 2+ coho outmigrate
primarily in June at Talkeetna Station (AOF&G 1984c).
Rainbow trout and Arctic grayling use aquatic habitats within the
middle Susitna River during all phases of their life cycle. However,
III-12
movements to other reaches of the Susitna River may be significant for
other resident species such as Dolly Varden, round whitefish, and
humpback whitefish (ADF&G 1984c).
III-13
Identification and Utilization of Habitat Types
The complex of primary, secondary and overflow channels that exists
wi hin the Talkeetna-to-Devil Canyon segment of the Susitna River
provides a great diversity of habitat conditions.
Six major aquatic habitat types, having comparatively similar
morphologic, hydrologic and hydraulic characteristics, have been
identified within the Talkeetna-to-Devil Canyon reach of the Susitna
River : mainstem, side channel, side shugh, upland slough, tributary,
and tributary mouth (Figure III-1) (ADF&G 1983c). Within these
aquatic habitat types, varying amounts and qualities of fish habitat
may ex i st within the same habitat type, depending upon site-specific
thennal, water quality, channel structure and hydraulic conditions.
Differentiation of aquatic habitat types is useful for evaluating the
seasonal utilization patterns and habitat preferences of the fish
species/life stages which inhabit the middle Susitna River, as well as
determining the influence of seasonal variations in streamflow on the
availability of potential aquatic habitat. The seasonal utilization
of the middle Susitna River habitat types by fish is primarily depen-
dent upon the abiotic conditions they offe r the species and life
stages under consideration. Abiotic habitat conditions are primarily
influenced by streamflow, stream temperature and water quality, which
in the middle Susitna River vary markedly among habitat types and with
the season of the year (ADF&G 1983c).
Mainstem Habitat
Mainstem habitat is defi ned as those portions of the Susitna River
wh ·ich normally convey the largest amount of streamflow throughout the
year. Both single and multiple channel reaches, as well as poorly
defined water courses flowing through partially vegetated gravel bars
or islands, are included in this aquatic habitat category.
Mainstem habitats are thought to be predom i nantly used as migrational
corridors by adult and juvenile salmon during summer. Isolated
II I-14
Note: A more detailed deecrlptlon of theee habitat typee
can be found •n thle eectlon of thle report.
LEGEND
I. Mainstem Habitat
2. Side Channel Habitat
3. Side Slough Habi tat
4 . Upl and Slogh Habitat
5. Tributary Hab it at
6. Tributary Mouth Habitat
Figure m-I . General habitat types of the Susitna River.
I I I -15
observations of chum salmon spawning at upwelling sites along shore-
line margins have been reported (ADF&G 1982a). Also, ma.instem
habitats are utilized by several resident species, most notably Arctic
grayl i ng, burbot, longnose sucker, rainbow trout and whitefish.
Turbid, high-velocity, sediment-laden summer streamflows and low,
cold, ice-covered, clearwater winter flows are characteristic of
mainstem habitat type. Channels are relatively stable, high gradient
and normally well armored with cobbles and boulders . Interstitial
spaces between these large streambed particles are generally filled
with a grout-like mixture of small gravels and glacial sands.
Isolated deposits of small cobbles and gravels exist. However, they
are usually unstable.
Groundwater upwellings and clearwater tributary inflow appear to be
inconsequential determinants of the overall characteristics of main-
stem habitat except during winter when they dominate mainstem water
quality conditions.
Side Channel Habitats
Side channel habitat is found in those portions of the river which
normally convey streamflow during the summer, but become appreciably
dewatered during periods of low flow. For convenience of classifi-
cation and analysis, side channels are defined as conveying less than
10 percent of the total flow passing a given location in the river.
Side channel habitat may exist in well-defined channels, in poorly
defined water courses flowing through submerged grave 1 is 1 ands, or
along shoreline or mid-channel margins of mainstem habitat.
J uvenile chinook appear to make the most extensive use of side channel
ha bitats, particularly during July and August (ADF&G 1984c). A
l ·mited amount of chum salmon spawning also occurs in side channel
habitats where upwelling is present and velocities and substrate
composition are suitable (ADF&G 1984d). Resident species > such as
burbot and whitefish, also ut i lize side channel habitats.
I II-16
In genera 1, the turbidity, suspended sediment and thenna 1 character-
istics of side channel habitats reflect mai-nstem conditions. The
exception is in quiescent areas, where suspended sediment concen-
trations are less. Side channel habitats are characterized by
shallower depths, lower velocities and smaller streambed materials
than mainstem habitats . However, side channel velocities and sub-
strate composition often provide suboptimal habitat conditions for
both adult and juvenile fish.
The presence or absence of clearwater inflow, such as groundwater
upwellings or tributaries, is not considered a critical component in
the designation of side channel habitat. However, a strong positive
correlation exists between the location of such clearwater inflows and
the location of chum salmon spawning sites that exist within side
channel habitats (ADF&G 1984d). In addition, tributary and ground-
water inflow prevents some side channel habitat from becoming com-
pletely dewatered when mainstem flows recede in September and October.
These clearwater areas are suspected of being important for primary
production prior to the fonnation of a winter ice cover.
Side Slough Habitats
With the exception of the clearwater tributaries, side slough habitats
are probably the most productive of all the middle Susitna River
aquatic habitat types. Side slough habitats typically exist in
overflow channels, which originate from riverine physical processes
such as flood events resulting from high streamflow or breakup ice
jams. Clearwater inflows from local runoff and/or upwelling are
ccmponents of this aquatic habitat type. Periodic overtopping by high
mainstem discharge events is the most distinguishing characteristic of
side slough habitat (ADF&G 1983c).
A non-vegetated alluvial benn connects the head of the slough to the
mainstem or a side channel. A well vegetated gravel bar or island
parallels the slough separating it from the mainstem (or side
channel). During intermediate and low-flow periods, mainstem water
I 11-17
surface elevations are insufficient to overtop the alluvial benn at
the upstream end (head) of the slough. However, the mainstem stage at
these flows is often sufficient at the downstream end (mouth) of the
slough to cause a backwater effect to extend a few hundred feet
upstream into the slough (Trihey 1982).
Approximately 80 percent of all middle Susitna River chum salmon
spawning in non-tributary habitats and essentially all sockeye salmon
spawning occurs in unbreached side slough habitat (ADF&G 1981, 1982a,
1984a). In early spring, large numbers of juvenile chum and sockeye
salmon can be found in unbreached side sloughs. During summer,
moderate numbers of juvenile coho and chinook make use of side-slough
habitats, with chinook densities increasing during the fall-winter
transition (ADF&G 1984b). Small numbers of resident species, such as
rainbow trout, Arctic grayling, burbot, round whitefish, cottids and
longnose suckers, are also found in side slough habitats.
Considerable variation in water chemistry has been documented among
side sloughs. This is prinCipally a function of local runoff pat-
terns, basin characteristics, and groundwater upwelling when the side
sloughs are not overtopped. Once overtopped, side sloughs display the
water quality characteristics of the mainstem (ADF&G 1982b). Pre-
sumably side sloughs provide better habitat for aquatic organisms than
mainstem or side channel areas largely because side sloughs convey
turbid-water less frequently than other channels and contain warmer
water year round.
During periods of high mainstem discharge, the water surface elevation
of the mainstem is often sufficient to overtop the alluvial benns at
the heads of some sioughs. When this occurs, discharge through the
side slough increases markedly from turbid mainstem flow. Such
overtopping events affect the thennal, water quality and hydraulic
conditions of side slough habitat (ADF&G 1982b). Depending upon their
severity, overtopping events may flush organic material and fine
sediments from the side slough, or totally rework the channel geometry
and substrate composition.
III-18
Streambed materials in side slough habitats tend to be a heterogeneous
mixture of coarse sands, gravels and cobbles often overlain by fine
glacial sands in quiescent areas. Perhaps because of the upwelling or
the less frequent conveyance of mainstem water, streambed materials in
side slough habitats do not appear to be as cemented or grouted as
sim1lar size particles would be in side channel habitats.
When side sloughs are not overtopped, surface water temperatures
respond independently of mainstem temperatures (ADF&G 1982b). Surface
water temperatures in unbreached side sloughs are influenced by the
temperature of groundwater upwelling, the temperature of surface
runoff and climatologic conditions. In many instances during winter,
the thennal effect of the upwelling water is sufficient to maintain
relatively ice free conditions in the side sloughs throughout winter
(Trihey 1982, ADF&G 1983a).
Upland Slough Habitats
Upland slough habitats are clearwater systems which exist in relic
side channels or overflow channels. They differ from side slough
habitats in several ways. The most apparent reason for many of these
differences is because the elevation of the upstream berm, which
separates these habitats from adjacent mainstem or side channels, is
sufficient to prevent overtopping in all but the most extreme flood or
ice jam events. Upland sloughs typically possess steep well-vegetated
streambanks with near-zero flow velocities, and sand or silt covering
larger substrates. Active or abandoned beaver dams and food caches
are commonly observed in upland slough habitats presenting barriers to
fish movements.
The primary influence of the mainstem or side channel flow adjacent to
the upland slough is to regulate its depth by backwater effects. The
water surface elevation of the adjacent mainstem or side channel often
controls the water surface elevation at the mouth of the upland
slough. Depending upon the rate at which the mainstem water surface
elevation responds to storm events relative to the response of local
III-19
runoff into the upland slough, turbid mainstem water may enter the
slough. The rap i d increase in mainstem water surface elevations and
suspended sediment concentrations in association with peak flow events
is suspected of being a primary transport mechanism of fine sediments
into the backwater areas of upland sloughs. Local surface water
inflow and bank erosion may be major contributors of sediments in
reaches upstream of backwater areas and beaver dams.
Upwelling is often present in upland sloughs, however, little spawning
occurs in these habitats (ADF&G 1984a). The most extensive use is by
juvenile sockeye and coho salmon (ADF&G 1984c). Resident species
common in upland sloughs include round whitefish and rainbow trout.
Tributary Habitat
Tributary habitats reflect the integration of their watershed charac-
teristics and are independent of mainstem flow, temperature and
sediment regimes. Middle Susitna River tri butary streams convey clear
water which originates from snowmelt, rainfall runoff or groundwater
base flow throughout the year.
Tributaries to the middle Susitna River provide the only reported
spawning areas for chinook salmon, and nearly all the coho and pink
salmon spawning areas that occur in this river segment (ADF&G 1984a).
Approximately one-third of the chum salmon escapement to the middle
Susitna River spawn in tributary habitat. Pink salmon juveniles
outmigrate shortly after emergence and most juvenile chum leave within
one to three months, but a large percentage of emergent chinook and
coho remain in tributary streams for several months following emer-
gence (ADF&G 1984c). Resident species such as Arctic grayling and
rainbow trout also greatly depend on tributary streams for spawning
and rearing habitat.
I II-20
Tributary Mouth Habitat
Tributary mouth habitat refers to that portion of the tributary which
adjoins the Susitna River. The areal extent of this habitat responds
to cha nges in mainstem discharge. By definition, this habitat extends
from 1t he uppermost point in the tributary influenced by mainstem
backwa/ter effects to the downstream extent of its clearwater plume.
This mabitat type is an important feeding station for juvenile chinook
(ADF&G 1982a), rainbow trout and Arctic grayling (ADF&G 1984c),
especially during periods of salmon spawning activity. Tributary
mouth habita t associated with the larger tributaries within the middle
Susitna Ri ver ~lso provides significant spawning habitat for pink and
chum salmon (ADF&G 1984a).
II 1-21
Selection of Evaluation Species
Selection of evaluation species is thought to be consistent with the
guidelines and policies of the Alaska Power Authority, Alaska
Department of Fish and Game and U.S. Fish and Wildlife Service. These
guidelines imply that species with commercial, subsistence and
recreational uses are given high priority. The habitats of those
species that are likely to be significantly influenced by the project
are of the greatest concern. The following discussion provides a
synopsis of the baseline data used in the selection of primary and
secondary evaluation species .
The primary species and life stages selected for evaluation were chum
salmon spawning adults and incubating embryos, and chinook salmon
rearing juveniles. These species and life stages depend on side
slough and side channel habitats, which are expected to be
significantly affected by project operation . The secondary evaluation
species/life stages that may receive secondary consideration in
subsequent analyses of flow effects on aquatic habitats include: chum
salmon juveniles and returning adults, chinook salmon returning
adults, all freshwater life phases of sockeye and pink salmon, rainbow
trout rearing and overwintering, coho salmon juveniles and returning
adults, Arctic grayling rearing and overwintering, and all life phases
of burbot.
Surveys of spawning adult salmon conducted during 1981-83 by the
Alaska Department of Fish and Game (ADF&G 1984a) indicate that tribu-
taries and side sloughs are the primary spawning areas for the five
species of Pacific salmon that occur in the middle reach of the
Susitna River (Figure III-2). Comparatively small numbers of fish
spawn in mainstem, side channel, upland slough and tributary mouth
habitats. Chum and sockeye are the most abundant salmon species that
spawn in non-tributary habitats in the Talkeetna-to-Devil Canyon reach
of the Susitna River (ADF&G 1984a). The estimated number of chum
salmon spawn i ng in non-tributary habitats within the middle Susitna
111-22
LE8END
MS -MAl NITEM
IC -SIDE CHANNEL
IL -UPLAND and SIDE SLOUGHS
T -TRIBUTAIUEI
• -PRIMARY SMWNI,. HABITAT + -SECONDARY SMWNIH HABnar
M8 SC SL T
COHO
M8 SC SL T
CHINOOK
M8 SC SL T
SOCKEYE
M8 SC SL T
PINK
-IC SL T
CHUM
Figure I-2. Relative distribution of salmon spawning within
different habitat types of the middle Suaitna
River. (ADF&G 1984c).
III-23
River averaged 4,200 fish per year for the 1981-83 period of record
(ADF&G 1984a). This represents about two-thirds of the peak survey
counts in all habitats during 1981-1983 (ADF&G 1984a). Approximately
1,600 sockeye per year (99 percent of peak survey counts) spawned in
slough habitat during the same period. Limited numbers of pink salmon
utilize side channels and side sloughs for spawning during even-
numbered years (ADF&G 1984a). Similarly, only a few coho salmon spawn
in non-tributary habitats of the Susitna River (ADF&G 1984a).
It is estimated that approximately 10,000 chum salmon have returned
annually to the middle Susitna River to spawn during the 1981-1983
period of record, of which nearly 50% spawn in tributaries. Approxi-
mately 80 percent of all chum salmon spaw~ing in non-tributary
habitats within the middle Susitna River occurs in side slough habi-
tats, with Sloughs 21, 11, 9, 9A and 8A accounting for 75 percent of
the annual slough spawning (ADF&G 1981, 1982, 1984a). Extensive
surveys of side channel and mainstem areas have documented compara-
tively few spawning areas (ADF&G 1981, 1982, 1984a).
Within the Talkeetna-to-Devil Canyon reach, spawn1ng sockeye salmon
are distributed among eleven sloughs, with Sloughs 11, 8A, and 21
accounting for more than 95 percent of the spawning in 1981-1983
(AOF&G 1984a). In 1983, 11 sockeye salmon were observed spawning
alongside 56 chum salmon in the mainstem approximately 0.5 miles
upstream of the mouth of the Indian River (ADF&G 1984a). This is the
only recorded occurrence of sockeye salmon spawning in middle Susitna
River areas other than slough habitats.
Chum and sockeye salmon spawning areas commonly overlap at all of the
locations where sockeye spawning has been observed (ADF&G 1984a).
This overlap is likely a result of similar timing and habitat require-
ments (ADF&G 1984a and d). Chum salmon are more numerous in slough
habitats and appear to be more constrained by passage restrictions and
low water depth during spawning than sockeye sa·lmon. Hence, the
initial evaluation and analysis of flow relationships on existing
III-24
salmon spawning in the middle Susitna River is on chum salmon spawning
in sloughs.
Depending upon the season of the year, rearing juvenile salmon utilize
all aquatic habitat types found within the middle Susitna River in
varying degrees. Among the non-tributary habitats, juvenile salmOn
densities are highest in side and upland sloughs and side channel
areas (Figure III-3). Extensive sampling for juveniles has not been
conducted in mainstern habitats, largely due to sampling gear ineffi-
ciency in typically deep, fast, turbid waters. little utilization of
these habitats is expected except in the lateral margins that have low
velocities.
Coho salmon juveniles are most abundant in tributary and upland slough
habitats. In general, these habitats do not respond significantly to
variations in mainstem discharge (Klinger and Trihey 1984). Sockeye
juveniles, although relatively few in number, make extensive use of
upland slough and side slough habitats within the middle Susitna
River. In contrast, juvenile chum and chinook salmon are quite
abundant in the middle Susitna River and are most numerous in side
slough and side channel habitats (ADF&G 1984c). These habitats
respond markedly to variations in mainstem discharge (Klinger and
Trihey 1984). For this reason, these two species, chinook and chum,
have been selected for evaluating rearing conditions for juvenile
salmon within the middle Susitna River. Because juvenile have a
longer freshwater residence period, they are a primary evaluation
species/life stage. Juvenile chum are one of the secondary evaluation
species/life stages.
With the exception of burbot, important resident species in the middle
Susitna River are mainly associated with tributary habitats. Both
rainbow trout and Arctic grayling are important sport species in the
basin. The spawning and rearing for these two species occur primarily
in tributary and tributary mouth habitats. Both species use mainstem
habitats for overwintering. A limited number of both species rear in
III-25
H
H
H
I
N
0\
... •
60
Ill 50 (,)
IC
Ill
~ 20
10
0
60
50
40 ... • Ill 50 (,)
IC
Ill
~ 20
10
0
14.4
17.1
2 .9 4 .9
I
TR18UTARI£S UPLAND 5tOE SlOE
SLOUGHS CHAHHELS SLOUGHS
CHUM
, ...
8 .5 II. 7
11 . I
TRI8UTARI£S UPLAND SIDE SIDE
SLOUGHS CHAHHELS SLOUGHS
CHINOOK
RELATIVE
A8l*OANCE
Of JUVENILE
SALMON
... •
60
... 50 u
IC
Ill ~ 20
10
0
60
50
40 ... • Ill 30 (,)
IC
Ill
~ 20
10
0
11.1
II. I
0 9 1 10 .•
TRI8UTARI£S UPLAND SIDE SIDE
SLOUGHS CHAHHfLS SLOUGH S
COHO
48.7
41 .3
o.e
1.1
TRi f1 UTArilf~ Uf\.ANP ~I f.[ SIDE
SLOUGHS tHAHHfLS SLOUGH S
SOCKEYE
Figure m-3 . Relative abundance and diatribution of juvenile salmon within different habitat
types of the middle Suaitna Ri~er (ADF8G 1984c).
I
mainstem influenced habitats (ADF&G 1984c). Due to their use of
mainstem-influenced areas, overwintering and rearing Arctic grayling
and rainbow trout are selected as secondary evaluation species.
Burbot are found almost exclusively in mainstem, side channels and
slough months, as they apparently prefer turbid habitats (ADF&G
1984c). Because of their dependence on mainstem influenced habitats,
all life phases of burbot may be evaluated.
As the IFR analysis continues, other species whose populations may be
influenced by with-project conditions will be considered for
evaluation. Species/life stages such as chum, chinook and pink salmon
spawning may be evaluated in side channel and mainstem habitats.
These species currently spawn primarily in habitats other than the
mainstem and side channels of the middle Susitna River. The physical
characteristics of mainstem and side channel habitats in this reach
may approach those in other Alaskan river systems utilized by these
species under possibl~ with-project streamflow, water temperature and
water quality regimes.
II I-27
IV. WATERSHED CHARACTERISTICS AND PHYSICAL PROCESSES
INFLUENCING MIDDLE RIVER HABITATS
Watershed Characteristics
Basin Overview
Tributaries in the upper portions of the Susitna River drainage basin
originate in the glaciers of the Alaska Range, which is dominated by
Mount Deborah {12,339 feet) and Mount Hayes {13,823 feet). Other
peaks average between 7,000 and 9,000 feet in altitude. Tributaries
in the eastern portion of the basin originate in the Copper River
lowland and in the Talkeetna Mountains, with elevations averaging
between 6,000 and 7,000 feet and decreasing northward and westward.
To the northwest, the mountains fonn a broad , rolling glacially-
scoured upland dissected by deep glaciated valleys. Between these
ranges and Cook Inlet is the Susitna lowlands, a broad basin increas-
ing in elevation from sea level to 500 feet, with local relief of 50
to 250 t eet {Figure IV-1).
The drainage basin lies in a zone of discontinuous pennafrost. In the
mountainous areas, discontinuous pennafrost is generally present. In
the lowlands and upland areas below 3,000 feet, there are isolated
masses of pennafrost in areas with fine-grained deposits. The basin
geology consists largely of extensive unconsolidated deposits derived
from glaciers. Glacial moraines and gravels fill U-shaped valleys in
the upland areas. Gravelly till and outwash in the lowlands and on
upland slopes are overlain by shallow to moderately deep silty soils .
Windblown silt covers upland areas. Steep upper slopes have shallow,
gravelly and loamy deposits with many bedrock exposures. On the south
flank of the A 1 aska Range and south-facing s 1 opes of the Ta 1 keetna
Mountains, soils are well-drained, dark, and gravelly to loamy .
Poorly drained, gravelly and stony loams with pennafrost are present
on northfacing slopes of foothills, moraines, and valley bottoms.
Water erosion is moderate on low slopes and severe on steep slopes.
IV-1
"' c: ..
E .. "' ~ ..
e ~ "' e
~ : -:i ..
Q " . , -IJ'
IV-2
c • 0
CD ... • >
if
0 c -•• ~
(I)
• .6: -.s ~ .::
Jl
.c ...
0
Jl -• c
e
0 • ... -(I)
Vegetation above the tree line in steep, rocky soils is predominantly
a 1 pine tundra. Well-drained upland soils support white spruce and
grasses, whereas poorly drained valley bottom soils support muskeg.
The upper drainage basin is in the continental climatic zone, and the
lower drainage basin is in the transitional climatic zone. Tempera-
tures are more moderate and precipitation is less in the lower basin
than those in the upper basin. Storms which affect the area generally
cross the Chugach Range from the Gulf of Alaska or come from the North
Pacific or southern Bering Sea across the Alaska Range west of the
upper Susitna Basin. The heaviest precipitation generally falls on
the windward side of these mountains, leaving the upper basin in
somewhat of a precipitation shadow except for the higher peaks of the
Talkeetna Mountains and the southern slopes of the Alaska Range.
Therefore, precipitation is much heavier in the higher elevations than
in the valleys.
Basin Hydrology
The Susitna River is typical of unregulated northern glacial rivers,
with relatively high turbid streamflow during sunmer and low clear-
water flow during winter. Sources of water to the Susitna River can
be classified as: glacial melt, tributary inflow, surface runoff, and
groundwater inflow. The relative importance of each of these contri-
butions to the mainstem discharge at Gold Creek varies seasonally
(Figure IV-2). Snowmelt runoff and spring rainfall are elements of
surface runoff which cause a rapid rise in streamflows during late May
and early June. Over half of the annual floods occur during this
period.
IV-3
Figure IV-2 . Estimated percent contribution to flow at Gold Creek.
SUMMER WINTER
Figure Ill 2
The glaciated portions of the upper Susitna Basin also play a signifi-
cant role in shaping the annual hydrograph for the Susitna River at
Gold Creek (USGS stream gage station 15292000). Located on the
southern slopes of the Alaska Range, these glaciated regions receive
the greatest amount of precipitation that falls in the basin. The
glaciers, covering about 290 square miles or approximately 5% of the
basin upstream of Gold Creek, act as reservoirs storing water in the
winter and releasing water in su!TII'Ier to maintain moderately high
streamflows throughout the summer. Valley walls in those portions of
the upper basin not covered by glaciers, consist of steep bedrock
exposures or shallow soil systems. Rapid surface runoff originates
from the glaciers and upper basin whenever rainstorms occur, typically
in 1 ate sunmer and early fall. Many annua 1 peak flow events have
occurred duri~g August. Approximately 87 percent of the total annual
flow of the middle Susitna River occurs from ~lay through September;
IV-4
over 60 percent occurs during June, July and August (Table IV-1). R&M
Consultants and Harrison {1982) state that "roughly 38 percent of the
streamflow at Gold Creek originates above the gaging stations on the
Maclaren River near Paxson and on the Susitna River near Denali •.. "
Table IV-1. Summary of monthly streamflow statistics for the Susitna
River at Gold Creek (Harza-Ebasco 1985).
Rax1mum
MonthlR Flow {cfs}
Month ean Rinimum
January 2,452 1,542 724
Februar_v 2,028 1,320 723
March 1,900 1,177 713
April 2,650 1,436 745
May 21,890 13,420 3,745
June 50,580 27,520 15,500
July 34,400 24,310 16 '100
August 37,870 21,905 8,879
September 21,240 13,340 5,093
October a,212 5,907 3,124
November 4,192 2,605 1,215
December 3,264 1,844 866
Average 15 2900 9 2651 4 2785
As air temperatures drop during fall, glacial melt subsides and
streamflows decrease. By November, streamflows have decreased to
approximately one tenth of midsuiTITier values. An ice cover, which
generally persists until mid-May, forms on the middle Susitna River
during November and December. During winter, flow in the Susitna
River is maintained by the Tyone River which drains Lake Louise,
Susitna Lake and Tyone Lake, and by groundwater inflow to severa 1
smaller tributaries and to the Susitna River itself. Al t hough ground-
water inflow is thought to remain fairly constant throughout the year,
its relative importance increases during winter as inflows from
glacial melt and non-point runoff decrease.
IV-5
Streamflow Variability
Peak flows for the Susitna River nonmally occur during June in asso-
ciation with the snowmelt flood. Rainstonns may also cause floods
during late sumner. Most annual peak flows occur dur~ng June or
August (Table IV-2). Snowmelt flood peaks are generally 3 to 5 days
in duration, whereas late sumner flood peaks are often single day
events.
Table IV-2 Percent distribution of annual peak flow events for the
Susitna River at Gold Creek 1950-1982 (R&M Consultants
1981).
Month Ma}
June
July
August
September
Percent
9
55
9
24
3
Little difference exists among monthly ratios for the 1-, 3-, and
7-day low flows to their respective monthly flows during June-
September (R&M Consultants 1981). Flow is relatively stable during
the summer, with occasional sudden increases as the basin responds to
the highly variable, and sometimes erratic, precipitation patterns.
Susitna River streamflows show the most variation throughout the
months of May and October, the transition periods commonly associated
with spring breakup and the onset of freeze up. From November through
April, low air temperatures cause surface water in the basin to
freeze, and stable but gradually declining groundwater inflow and
baseflow from headwater lakes maintain mainstem streamflow.
The natural flow regime of the middle Susitna River streamflows will
be significantly altered by project operation (Figure IV-3). With-
project streamflows will generally be less than existing streamflows
from May through August as _water is being stored in the reservo i rs for
release during the winter. Variability in the middle Susitna Ri ver
will be caused primarily by tributary inflow and baseline and peaking
IV-6
releases from the reservoirs. Floods will also be reduced in frequen-
cy and magnitude (Figure IV-3) generally occurring in late summer when
the reservoirs are full and water must occasionally be released.
With-project streamflow during September is expected to be less
variable but similar to the long tenn average monthly natural flow.
Flows from October through April will be greater in magnitude and more
variable than natural streamflows. Daily fluctuations in streamflow
are expected to occur throughout winter as the project responds to
meet changes in the daily and weekly load. However, these fluc-
tuations are not expected to exceed ±10 percent of the base discharge
for the day (W. Dyok, Harza-fbasco, 1984, pers. comm.).
Influence of Streamflow on Habitat
Mainstem and Side Channel Habitat. The large amount of water that is
conveyed during the summer in steep mainstem and side channel water
courses generally results in inhospitable conditions for fish.
Mainstem and side channel gradients within the middle Susitna River
are on the order of 8-14 ft/mile (R&M Consultants 1982a). Although
flood peaks seldom exceed twice the long tenn average monthly flow for
the month in which they occur (R&M Consultants 1981), the average
monthly flows for June, July, and August are nearly 2.5 times the
average annual discharge of 9700 cfs/day (Scully et al. 1978}. As a
result of the steep channel gradient, mid-channel velocities are often
in the range of seven to nine feet per second (fps) for normal mid-
summer streamflow conditions. Velocities of 14 to 15 fps have been
measured by the USGS at the Gold Creek stream gage station in asso-
ciation with 62,000 to 65,000 cfs flood flows (L. Leveen, USGS , 1984,
pers. comm. ) •
As a result of being subjected to persistently high velocities,
streambed materials in mainstem and side channe l habitats typically
range in size from cobbles (5 inches) to boulders (10 inches or
larger) (R&M Consultants 1982a). Isolated deposits of smaller
IV-7
1/)
~
0
0
0
0 -w
C> a:: <(
'l:
0
1/)
0
H <
I
00
100 ~ 90
80
70
60
50
4(1
30
20
10
....... II""""
~ ~
~
,
~
~ ..... .. .... ... ,..
~ ~ ... / , ,
~
, ,
...tt' ,
~ , , ,
; -7 "'' , t,~ ,
, ,
, ~ " ,
I
I /
' "'"' ---~.~ ~-----
1.02 I. II 1.25 2 5
RECURRENCE I~JTERVAL (YEARS)
NOTE : BASED ON WEEKLY RESERVOIR
SI~ULI\TIONS .
----
10 20
LEGEND
Natural
Watona
50 100
Wolooo/Ocvil Canyoo 2002
Wotona/Devil Conyon 2010
Fiourenf3.Compari•on between natural and anticipated with-project cmnual
flood frequency curve• for the middle Su1itna River.
(Source : Ala1ka Power Authority 1183 )
streambed materials, including sand, also exist within the mainstem
and side channels, but only at protected locations. These smaller
streambed materials are generally unstable and transient (R&M Consul-
tants 1982a).
High summer streamflows characteristic of the Middle Susitna River are
not considered to be beneficial to salmon production in mainstem or
side channel habitats. As stated above, high streamflows during
summer tend to transport spawning gravels into or out of these habi-
tats. In those locations where salmon have spawned, high streamflows
may wash out the redds or deposit sediments over them. Juvenile
salmon in these habitats are also displaced downstream by high flows
(ADF&G 1984c).
Low seasonal streamflows can also be undesirable. During spawning,
low streamflows may restrict fish access to spawning areas or result
in shallow depths at potential spawning locations. Thus, the avail-
able spawning habitat area may be reduced. Low streamflows during
incubation may cause dewatering of redds, low dissolved oxygen levels,
high temperatures, or, during the winter, freezing of embryos (Hale
1981). Low seasonal streamflows may also adversely influence juvenile
salmon rearing by restricting fish access to streambank cover or
dewatering rearing habitats.
Side Slough Habitat. Side sloughs are overflow channels along the
floodplain margin that convey clear water originating from small
tributaries, and/or upwelling groundwater. A non-vegetated alluvial
berm connects the head of the slough to the mainstem or a side chan-
nel. A well-vegetated gravel bar or island parallels . the slough,
separating it from the mainstem (or side channel). During intermedi-
ate and low-flow periods, mainstem water surface elevations are
insufficient to overtop the alluvial berm at the upstream end (head)
of the slough. However, mainstem stage is often sufficient at the
downstream end (mouth) of the slough to cause a backwater to extend at
least a few hundred feet upstream into the slough.
IV-9
During high mainstem discharges, the water surface elevation (stage)
of the mainstem is often sufficient to overtop the alluvial berm at
the head of many of the sloughs. When this occurs, discharge through
the side slough increases markedly. Such overtopping affects the
thenmal, water quality and hydraulic properties within the side
slough. Overtopping during late August and early September provides
unrestricted passage by adult salmon to spawning areas within the side
sloughs . Overtopping during early summer flushes organic material and
fine sediments from the side sloughs, but in some instances transports
large amounts of sand i nto the slough. The turbidity associated with
the overtopping flows provides cover for juvenile chinook salmon and
allows them to utilize habitat that was previously unavailable (ADF&G
1984c).
The influence of overtopping on various physical conditions will be
discussed in subsequent sections of this report. However, prior to
those discussions, it is important to recognize the dominant influence
of streamflow variability in determining the timing, frequency and
duration of discharges which can cause overtopping (Table IV-3).
Upwelling
Water which rises from the streambed has been recognized as strongly
influencing the spawning behavior of chum and sockeye salmon in Alaska
(Kogl 1965, Wilson et al . 1981, Koski 1975, ADF&G 1984d). This water
is commonly referred to as "upwelling" by fisheries biologists because
of its characteristic flow direction into the stream channel.
Downwelling and intragravel flow are two other types of subsurface
flow which occur in stream channels that are i mportant to maintaining
aquatic life in streambed materials (Figure IV-4). However these two
types of flow differ from upwelling in both their flow direction and
origin. As the term implies, downwelling flows from the stream into
the streambed and is generally thought to be in a near vertical
direction. Intragravel flow is generally considered to be flow in
streambed gravels parallel to the down valley gradient of the channel.
IV-10
Table IV-3.
Breaching
Flow (cfs)
12,000
16,000
19,000
23,000
25,000
27,000
33,000
35,000
40,000
42,000
12,000
16,000
19,000
23,000
25,000
27,000
33,000
35,000
40,000
42,000
Frequency and duration of naturally occurring over-
topping events during the outmigration and spawning
periods for the middle river related to incremental
breaching flows based on analysis of Gold Creek record
1950-1984.
4-5 6-10 Total
1 day 2 days 3 days days days >10 days days
June 3 through June 16
0 0 0 0 0 33 459
1 2 2 2 3 27 412
3 2 2 0 4 23 357
5 4 3 1 12 13 300
0 4 3 3 13 10 263
3 6 2 3 11 8 218
3 3 5 3 6 3 118
1 5 4 3 6 1 94
0 3 2 2 3 1 55
2 0 1 3 2 1 46
August 12 through SeEtember 8
2 1 2 0 1 35 826
4 3 6 5 7 25 628
2 4 6 9 13 15 431
7 6 8 4 7 6 224
3 7 3 3 6 3 141
3 3 2 3 3 3 99
1 0 1 2 3 1 46
0 0 1 3 2 1 42
1 2 1 1 3 0 31
0 1 1 2 2 0 26
NOTE: The controlling elevation of an alluvial berm may change with
time, due to sediment transport and ice processes .
IV-11
H < I ......
N
Water Surface
Moi nstem
_lM~~a.!!_d Soil
Saturatld hif--
A. CROSS-SECTION Of MAINSTCM AND SLOU8H
Water Surface
Flow _ __. .. _
B. SIDE VIEW OF SLOUGH OR MAINSTEM
Figure W-4 . Upwelling doWnwellinG and intergravel flow.
Because the water flowing in the stream channel provides both the
source and driving mechanism for downwelling and intragravel flow,
these two types of subsurface flow generally have temperatures and
water chemistry very similar to the surface water. Upwelling, how-
ever, generally has temperature and chemical composition characteris-
tics differing from the water flowing above the streambed . As this
groundwater flows through the soil from its source to its upwelling
location, its thennal and water chemistry properties become more
defined by the soil properties.
Broadly defined, groundwater is the hydrologic term for water occur-
ring beneath the land surface. Groundwater exists in saturated and
unsaturated soil zones. The interface between these two zones is
called the water table. The plan shape and slope of the water table
is determined by the subsurface geologic structure and type of soil
material present. The elevation of the water table at any point is
primarily a function of water supply.
Water supply for groundwater generally consists of precipitation and
adjacent surface water bodies. Precipitation infiltrates into the
soi 1 , flows through the unsaturated zone as "i nterfl ow 11
, and reaches
the saturated zone. Because of t h is increased water supply, the
groundwater table rises in elevation. Bank seepage appears when the
water table reaches the ground surface on exposed slopes, streambanks,
rock outcrops, or steep hillsides. During periods of drought caused
by lack of precipitation or cold air temperatures the elevation of the
water table generally declines unless maintained by adjacent water
bodies.
In river valleys 1 ike that of the middle Susitna River, where the
underlying materials are alluvial deposits of glacial outwash (R&M
Consultants 1982d), the groundwater flow patterns may be quite com-
plex. The general slope of the water table is similar to the valley
slope. The mountains or hills which parallel the river form an
impermeable boundary for the alluvial deposits. Hence, in the middle
IV-13
Susitna River, groundwater is generally thought to be flowing down
valley in an unconfined aquifer in an alluvial, intermontane valley,
bounded by the impenneable mountains on each side (R&M Consultants
1982d). Wherever the water table intersects the streambed, upwelling
is likely to occur.
The groundwater table elevation, as determined by the structural
geology and the corresponding relationship between the sources of
groundwater flow, will control upwelling. Downwelling flows will
occur if the surface water level in the channel is higher than t he
groundwater table elevation. Upwelling flows will occur when the
elevation of the groundwater table exceeds the water surface elevation
in the channel. Upwelling may also occur in a manner similar to pipe
flow. A lens of coarse sediments permitting groundwater flow may be
flanked by deposits of finer sediments that prohibit groundwater flrn~.
Flow may thus become concentrated in the flow-conducting lens. When
the 1 ens intersects a channe 1 , thl flow is re 1 eased from between the
flanking de'posits and upwelling may result. Piped groundwater flow
may occur under the berms at the heads of side sloughs and elsewhe r e
as long as the required geologic conditions are present and a water
source, such as the mainstem, exists.
In addition to the influence of subsurface alluvial deposits on the
location and rate of upwelling water, water supply is also important.
In the river valley the most persistent water supply is the river
itself. Through downwelling, the river supplies water to the
unconfined aquifer. At some down-valley location, the groundwater
will yield this water as upwelling. In the middle Susitna River, much
of this upwelling appears to be along the east bank.
Because the water table rises and falls seasonally and across years in
response to water supply, upwellings can be ei the!'" persistent or
intermittent. Upwelling flow rates a 1 so depend upon fluctuations in
the local groundwater table.
IV-14
The groundwater system can be divided into two components: a regional
component driven by the down valley gradient and a temporal component
influenced by changes in mainstem stage and precipitation infiltra-
tion. The regional groundwater component is constant throughout the
year, and corresponds to the minimum groundwater levels observed under
natural conditions. These minimum groundwater co'lditions appear to
occur during the late winter period of low mainstem discharge and no
infiltration due to freezing conditions.
The temporal groundwater component augments the regional groundwater
component. When the mainstem stage is high, the mainstem may supply
downwelling flows which increase the groundwater table elevation.
Precipitation infiltrating the soil may also serve as a source for the
groundwater, as does local runoff onto alluvial fans at the base of
the slopes. The raised elevation of the groundwater table due to the
temporal component results in increased areal extents and rates of
upwelling flows. Thus, the -fluctuations of the groundwater table due
to the temporal component variations, which . are induced by changes in
river sta~e and precipitation, will have a pronounced effect on
upwelling.
The groundwater table appears to reach a minimum elevation in the late
Novermer to early Decermer period; upwe 11 i ng flows wi 11 correspond-
ingly reach a minimum rate and areal extent . The temporal groundwater
component will be reduced as the mainstem stage lowers and infiltra-
tion of precipitation ceases due to freezing temperatures. The
remaining upwelling flows will be supplied by the regional groundwater
component. At sites where upwelling is continuously provided by the
regional groundwater component, viable habitat will be maintained;
high mortality is suspected at sites where upwelling is reduced due to
the reduction in temporal upwelling. As ice formation increases the
mainstem stage, the temporal groundwater component will again augment
the regional groundwater component and increase upwelling rates and
areal extents. However, as mainstem flow continues to drop through
the winter, b.> mid-April the water table drops to nearly the same
level as existed prior to freeze-up.
IV-15
Under with-project conditions, upwelling flows may not be reduced to
the extent of upwelling flows experienced under natural conditions
during the late fall period. The mainstem stage is anticipated to be
maintained at a higher elevation during project operation than under
natural conditions in the late fall. The temporal groundwater compo-
nents will therefore continue to augment the regional component in the
late October to early November period. Habitat dewatered or frozen as
the temporal groundwater component is reduced under natural conditions
may become viable throughout the year as the temporal groundwater
component is maintained by higher with-project mainstem stages. The
magnitude of the increase in viable habitat is unquantified and is
likely to remain so until determined through a monitoring program.
Biological Importance of Upwelling. Upwelling is one of the most
important habitat variables influencing the selection of spawning
sites by chum and sockeye salmon in the middle Susitna River (ADF&G
1984d). In addition, upwelling flows contribute to local flow in
sloughs and side channels and facilitate fi~h passage.
Incubation appears to be the life stage most critically affected by
upwelling in the middle Susitna River. Chum and sockeye salmon
embryos, and embryos of other species spawned in the area of upwelling
flows, benefit from the upwelling flows. During incubation, upwelling
provides for successful development of embryos, principally because of
its thermal -characteristics . It also ensures the oxygenation of
embryos and alevins, transports metabolites out of the incubating
environment, and inhibits the clogging of streambed material by fine
particulates.
Upwelling flows appear to reach a minimum immediately prior to ice
staging when mainstem discharges range from 3,000 to 5,000 cfs .
During this period upwelling flows are considered to originate exc lu-
sively from the regional groundwater component of upwelling. These
low mainstem discharges and minimum upwelling flows probably limit the
incubation success of embryos that were spawned under higher mainstem
IV-16
and upwelling flows. Many embryos are likely dewatered and frozen.
Therefore, the viable incubation habitat is probably that which is
effective during this transition period of low upwelling flows.
Mainstem discharges that are higher than the 3,000 to 5,000 cfs would
likely increase the upwelling flows in sloughs above natural con-
ditions. Thus, a stable flow regime throughout the spawning and
incubation period would probably increase the viable incubation
habitat because embryos would develop under upwelling flows similar to
those at spawning.
Groundwater upwelling also appears to be an important factor influenc-
ing the winter distribution of juvenile salmon and resident fish.
Upwelling flows may comprise the predominant source of water in
sloughs when runoff from precipitation ceases due to freezing. f \
constant water flow in sloughs and side channels provides over-
wintering habitat for juven.ile sockeye, chinook, and coho salmon and
resident species. The water temperature of sloughs and side channels
is usually higher than mainstem waters because of upwelling waters.
Warmer temperatures apparently attract overwintering fish and may
reduce their winter mortality (ADF&G 1984c).
IV-17
Sediment Transport Processes
In this section, sediment transport is used generically to include all
the physical processes which result in the movement of bed and sus-
pended load. Bed load is defined as that portion of the solid mass
being transported within 0.3 ft of the channel bottom. Suspended load
refers to that portion of the solid mass present in the water column
above 0.3 ft from the channel bottom.
It is well documented that the results of sediment transport pro-
cesses, such as streambed stability and composition, are important
parameters describing aquatic habitat. McNeil (1964) has observed
that streani>ed stability can influence the success of salmonid egg
incubation. Several researchers have shown that substrate composition
influences the survival of eggs to fry in salmonid populations (McNeil
and Ahnell 1964, McNeil 1965, Cooper 1965, Phillips et al. 1975). The
suitability of aquatic habitat for rearing is also influenced by
substrate composition.
On a macrohabitat level, the channels of the middle Susitna River are
quite stable given the range of streamflows and ice conditions to
which they are subjected. Review of aerial photography taken over an
approximate 35 year period (from 1949-51 to 1977-80) indicates the
plan fonn of the middle Susitna River has changed little (AEIOC
1984a). Although many non-vegetated gravel bars have appeared, and
some peri phera 1 areas have changed, a preponderance of channe 1 s and
habitats appear unchanged over this period .
Channel Stability of Habitat Types
Each of the six habitat types previously identified in the middle
Susitna River can be characterized by the relative influence that
specific sediment transport processes have on their formation and
maintenance (Table IV-4}.
IV-18
H
< I ......
..0
Table IV-4. Sediment transport processes and components and their relative importance in the formation and
maintenance of habitat.
Sediment Load Components Sediment Transport Processes
Flooding
Due to
Ice Jams Mechanical
High Flow During Scour by Anchor Ice Shore Ice
Habitat Type Suspended Bed Events Breakup Ice Blocks Processes Processes
Mainstem and Large
Side Channels Secondary Primary Primary Secondary Secondary Minor Minor
Side Channels and
Side Sloughs Primary Secondary Primary Primary Secondary Minor Minor
Tributary and
Tributary Mouth Minor Primary Primary Minor Minor Minor Minor
Upland Slough Secondary Minor Secondary Minor Minor Minor Minor
Ma i nstem and Large Side Channels. The plan form of the middle Susitna
River appears to be shaped by i ce processes, whereas the size of its
channels are a result of hydrologic processes. Hydrologic events, or
more specifically floods, are probably the dominant channel forming
process whereas normal summer streamflows represent the primary
sediment transport process. Channel forming discharges are usually
those which occur only once every several years . High discharges
cause high velocities with the capacity to erode and transport signif-
icant quantities of substrate from the bed and banks of the channel .
These high discharges would also change the shape of the channel, but
likely occur only once in 20 years or more. Discharges occurring more
frequently, such as the mean annual flood or bankfull discharge, would
reshape the channel to reflect the hydraulic conditions associated
with this lower, but more frequent, discharge. Some local changes in
bed geometry would likely occur, but these persistent lower floods are
unl1 ~~1 v to reform the channel to its original condition.
Streambed mater ial in the mainstem and large side channels is of
sufficient size to resist erosion or transport by flood flows less
than 35,000 cfs. The cobbles and boulders constitute an armor layer
which has developed as a result of previous flood events transporting
smaller substrate sizes downstream . The cobbles and boulders remain
as a well graded protective layer for the more heterogeneous under-
lying materials. High discharges would have the capacity to erode the
armor layer and transport underlying streambed materials downstream ,
but a new armor layer would likely develop as the flood recedes and
cobbl es and boulders eroded from upstream locations are redeposited.
The entire bed elevation of the middle Susitna River may decrease
during these events si nce the sands and gravels eroded from the
materials underlying the armor coat would l i kely not redeposit .
Evidence of such long-term channel degradation has been documented
through analysis of aerial photography (AEIDC 1984a).
Resistance of large substrate in the middle Susitna River to erosion
is increased by the cementing characteristics of the fine sands and
silts which fill interstitial spaces between them. Although the flow
IV-20
is relatively clear in the winter , high concentrations of fine glacial
sand and silt are transported through the middle Susitna River through-
out the summer. Some of these fine materials are deposited or washed
into the armor layer. The stability of the streant>ed allows these
fine silts to accumulate and completely fill the voids between the
armor layer. This prevents water from flowing through voids surround-
ing larger streambed materials, greatly increasing the armor layer's
resistance to erosion. If water could flow through the voids, the
erodibility of sediment particles would increase.
Several different ice processes also influence the shape and character
of mainstem and large side channel habitats: 1) mechanical scour by
block ice, 2) scour caused by ice jams during breakup, 3) sediment
transport by uprooted anchor ice, and 4) scour and sediment tran oort
by shore ice. In comparison to sediment transport processes associ-
ated with high streamfl ows, ice scour by either of the first two
processes is of secondary importance. The last two are only of minor
importance.
Mechanical scour by block ice is primarily a spring breakup phenome-
non. As large ice floes are moved downstream, block ice may impact
streant>anks or channel bottoms. Suspended sediment samples collected
in late May or early June following breakup typically contain large
percentages of sand, which may indicate stream channel or bank scour
(Knott and Lipscomb 1983). Bank erosion by ice-block abrasion may be
extensive (Knott and Lipscomb 1983).
Ice jams during breakup cause local staging and flow constrictions
which increase flow velocities and scour potential. High velocity
flow directed towards a channel bottom or bank can result in severe
local scour. The sudden release of an ice jam can also cause signifi-
cant scour potential in the form of a flood wave conveying large
blocks of ice.
Anchor ice also contributes to sediment transport. During anchor ice
formation, suspended sediments are filtered by ice crystals and
IV-21
incorporated into the ice structure (see Ice section). Bed materials
are also encased in ice, serving to anchor the ice mass to the channel
bottom. In the fall during anchor ice fonnation, the bonding of
anchor ice masses to the channel bottom is sensitive to increases in
temperature and direct solar radiation. If the bond is partially
r ejuced by meltlng, flow momentum and/or buoyant forces may be suffi-
cient to uproot the ice mass. This results in the downstream trans-
port of sediments and streambed particles frozen into the ice IMSS.
Scour of anchor ice during freezeup by changes in local flow veloc-
ities or contact with floating ice blocks may also contribute to this
process.
Shore ice contributes to sediment transport by directly scouring
channel margins and also by encasing and uprooting bed materials and
the shoreline vegetation. The denudation of shoreline vegetation
indirectly serves to increase sediment transport by increasing the
susceptibility of the shoreline to scour by high flow events .
Although the relative contribution of sediment transport by shore ice
is thought to be minor, the process can significantly influence the
character of fish habitats along the channel margin.
Side Channels and Side Sloughs. Of the sediment transport processes
described in the previous section, two have dominant roles in the
fonnati on and maintenance of side s 1 oughs and side channe 1 s. These
are: 1) high flow events, and 2) flooding caused by ice jams during
breakup. Mechanical scour by block ice, anchor ice processes, and
shore ice processes are less active in these habitats.
Side sloughs and side channels are relatively stable channels. Their
size and shape imply that they were formed by high flows. The
frequency of high flows through side sloughs and side channels is
generally low, but it varies significantly between sites. These high
flows may be important in maintaining and flushing fine sediments from
these habitats. Some sites have formed as a result of ice jams. An
ice jam can raise the upstream water level causing flow to divert
around the main channel, thereby developing a new channel . Slough 11
IV-22
apparently formed when an ice jam developed below the railroad bridge
at Gold Creek in 1976 .
Sediment transported into side sloughs and side channels is primarily
from three sources : 1) the mainstem, 2) tributaries, and 3) overland
flow. Of these sources, the mainstem probably dominates. The sedi-
ment transported into these habitats is characteristically fine.
Overtopping flows from the mainstem, which spill over the gravel berm
at the upstream end of these sites, originate in the upper part of the
water column and thus typically contain fine particle sizes only.
These materials deposit in pools within the channel or in the back-
water that is often present at the mouth of the channel.
Tributaries and Tributary Mouths. Of the sediment transport processes
described in the prev i ous sections, high flow events have the dominant
role in shaping tributary mouths. Most tributaries in the middle
Susitna River are steep gradient systems with a capacity to transport
large quantities of sediment during flood events.
When a rainstorm causing a flood is widespread, the Susitna River
would likely have a high discharge concurrent with, or soon after, the
high discharge in the tributary. Most sediments carried by the
tributary will be transported downstream by the Susitna River.
However, during localized storms, a tributary may flood while the
Susitna River remains relatively low. In such cases, the delta at the
mouth of a tributary may build up with large deposits of gravels and
cobbles. The delta may extend well out into the Susitna River
mainstem. Subsequent high discharges in th~ Susitna River will erode
the delta.
Upland Sloughs. Upland slough habitats are largely isolated from
mainstem sediment transport processes. The exception is in the
vicinity of the slough mouths, where mainstem flow may intrude as a
backwater during periods of high mainstem discharge. Suspended
sediments may settle out in these backwater areas and contri bute to
slough sedimentation.
IV-23
With-Project Sediment Transport and Channel Stability
Sediment transport processes would change with project operation
(Table IV-5). The operation of a reservoir will alter the natural
hydrologic regime of the middle Susitna River. High erosive dis-
charges will occur less frequently and with reduced magnitudes. This
will result in less frequent breaching of side sloughs and side
channels. Sediment transport by hydrologic processes will be reduced
throughout the middle Susitna River system . Channel stability will be
increased. Sedimentation and encroachment of streambank vegetation
will be more likely to occur in side channels and side sloughs.
Less frequent and lower flood events in the Susitna River would allow
tributary deltas to enlarge over their natural size. However, tribu-
tary mouths are best analyzed individually. Local characteristics,
such as orientation to mainstem flow and tributary gradient, greatly
influence delta formation .processes. The above is a generalized
scenario which may be characteristic of many tributaries in the middle
Susitna River.
Reduced flood peaks and frequency associ a ted with project operation
would reduce sediment transport int o upland slough mouths via back-
water intrusion. Ice processes do not significantly influence sedi-
ment transport in upland sloughs.
Both Watana and Devil Canyon reservoirs will trap nearly all sediments
of sand size and larger. Project discharges will also carry lower
concentrations of fine silts, but the concentration will be more
uniform throughout the year. Such low concentrations may not cause
cementing of the armor layer, but the lower flood regime may not be
sufficient to disturb streambed materials and remove the fine sedi-
ments which presently fill interstitial spaces between coarse sands
and fine gravels .
The assessment of with-project ice processes resulting in sediment
transport is dependent on project design and operation. For this
IV-24
H
<:
I
N
V'l
Table IV-5. With-project influence on sediment transfer processes and sediment loading.
!Sediment load Components Sediment Transport yrocesses
Ice Jams
High Flow During
Habitat Type Suspended Bed Events Breakup
Mainstem and large Reduced Reduced Reduced 1 Milder, less
Side Channels Magnitude Frequent
and Freq-2 Reduced uency
Side Channels and Reduced Reduced Reduced 1 Milder, less
Side Sloughs Magnitude Frequent
and Freq-2 Reduced uency
Tributaries and No Change No Change Reduced 1 Minimal
Tributary Mouths Magnitude 2 Reduced and Freq-
uency
Upland Sloughs Reduced Reduced Reduced 1 Milder, less
Magnitude Frequent
and Freq-2 Reduced uency
1 Assumes thermal operating regime is reservoir inflow temperature matching.
2 Assumes thermal operating regime is warm-water release throughout winter.
Mecham cal
Scour by Anchor Ice
Ice Blocks Processes
Reduced Minimal
Effect
Reduced Reduced
Increased Increased
Reduced Reduced
Reduced No Effect
Reduced Reduced
Reduced Increased
Reduced Reduced
-
Shore Ice
Processes
Increased
Reduced
Increased
Reduced
No Effect
Reduced
Reduced
Reduced
reason, this assessment will proceed based on two possible project
thermal operating regimes: 1) reservoir inflow temperature matching,
and 2) winter-long warm-water releases.
Reservoir Inflow Temperature Matching. Under with-project conditions,
ice jams may still occur in the mainstem, but will be reduced i n
frequency and magnitude. There will be a greater tendency for the ice
cover to melt in place because of warmer-than-natural stream tempe ra-
tures during April and increased project flow stability. This will
result in less mainstem and side channel scour and less frequent
diversions of mainstem flow through side slough habitats. The sedi-
ment transport capacity due to ice jams will be reduced. In addition.
the channel stability of mainstem, side channel. and side slough
habitats is expected to increase.
Mechanical scour by block ice will also be less severe than natural
levels in most habitats. This process occurs primarily during break-
yp. Reduced project discharges will provide less energy to drive ice
blocks forcefully into channel banks and bottoms. In some side
sloughs with low overtopping discharges, mechanical scour by block ice
may be increased. Project flows will be higher during the winter and
the breaching of some side sloughs may result .
Project influence on anchor ice sediment transport processes is
expected to be minimal. The principal influence will be to delay
anct.or ice fonmati on by one to two months. However, there may be some
increase in sediment transport in those side sloughs and side channels
that wi ll be breached by project discharge levels during periods of
ice cover.
Sediment transport by shore ice processes will probably be increased
from natural levels. The increased elevation forecast for a with-
project ice cover would result in a substantial amount of vegP tated
shore 1 i ne being frozen into the with-project ice cover. Howeve r ,
lower and more stable project discharges during sunmer would likel y
minimize streambank scour along channel margins.
IV-26
Warm-water Releases. If a warm-water release throughout winter could
prevent a solid ice cover forming on the mainstem, the sediment
transport capacity would be reduced for all ice processes. Mainstern,
side channel, and side slough habitats will become extremely stable.
Sensitive side slough habitats with low overtopping discharges will
not be subjected to increased sediment transport by anchor ice, shore
ice, or mechanical scour by block ice, as with reservoir inflow
temperature matching.
Tributary mouth and upland slough habitats will have the same with-
project channel stability as for reservoir inflow temperature
matching.
IV-27
Instream Water Quality and Limnology
Baseline Condition
Water quality encompasses numerous physical and chemical characteris-
tics, including the temperature, density, conductivity, and clarity of
the water, as well as the composition and concentration of all the
dissolved and particulate matter it contains. Water quality greatly
influences fish habitat qua 1 i ty by virtue of its direct effects on
fish physiology and behavior and because it largely governs the type
and amount of aquatic food organisms available to support fish growth.
Each of the aquatic habitat types associated with the middle Susitna
River differs not only in terms of its morphology and hydraulics, but
a l so in the basic pattern of its water quality regime. Therefore, the
relative importance of a specific habitat type to fish may change in
response to seasonal change .in either streamflow or water quality. In
the middle Susitna River, turbidity is an influential and visually
detectable water quality parameter that may be used to classify the
six aquatic habitat types into two distinct groups during the open
water season: clear water or turbid water. In order to gain a
greater understanding of each habitat type, it is useful to 1) examine
the water quality characteristics of both clear and turbid water
aquatic habitats; 2) identify how the water quality of these aquatic
habitat types changes on a seasonal basis; and 3) determine how these
seasonal changes in turn influence the quality of the aquatic habitat
types.
Highly turbid water accounts for the greatest amount of wetted surface
area in the middle Susitna River from June to September (Klinger and
Trihey 1984). During this period, when surface runoff and glacial
melting are greatest, total dissolved solids, conductivity,
alkalinity, hardness, pH, and the concentrations of the dominant
anions and most cations tend to be at their lowest levels of the year,
while stream temperature, turbidity, true color, chemical oxygen
demand, total suspended solids, total phosphorus, and the total
IV-28
concentrations of a variety of trace metals are at their highest
values for the year (Table IV-6). Average nitrate-nitrogen concen-
trations remain relatively constant throughout the year with greater
variation during the summer as discharge fluctuates.
The basic water chemistry of the clear water flow of the middle
Susitna River in winter. and of certain groundwater fed habitat types
throughout the year, can be generalized from an evaluation of the
water quality record for the Susitna River at Gold Creek during
winter. Surface water flow throughout the basin is low and the
concentration of suspended sediment and the trace metals, and
phosphorous associated with it, is also low or below detection limits.
During winter months, middle Susitna River discharge is comprised
almost entirely of outflow from the Tyone River System (lakes Louise,
Susitna, and Tyone) and groundwater inflow to tributaries and the
mainstem itself. Groundwater spends a greater amount of time in
contact with the soil and . underlying rocks of the watershed than
surface runoff or glacial meltwa~er and thus contains more dissolved
substances. The longer contact with subsurface materials also results
in groundwater temperatures which are warmer in winter and cooler in
summer than surface water temperatures.
The specific water quality characteristics of clear or turbid water
flowing through a given channel may differ from the general
descriptions provided above. depending on local variations in the
amount of local surface runoff or the composition and distribution of
rocks, soils , and vegetation. Nonetheless, a generalized seasonal
water quality regime unique to each habitat type seems to prevail. and
having knowledge of it provides useful insight into the direct and
indirect role water quality plays as a component of fish habitat
within the Talkeetna to Devil Canyon segment of the Sus i tna Ri ver.
Mainstem and Side Channel Habitats
A comparison of the sunmer and winter water quality record for the
Susitna River at Gold Creek (Table IV-6) reveals a seasonal contr ast
IV-29
Table IV-6 . Mean baseline water quality chara cteristics for middle Susitna
River at Gold Creek under (a) turbid summer (June-August)
conditions and (b) clear, winter (November-April) conditions.
Parameter Units of Turbid Clear
(Symbol or Abbreviation) Measure (summer) (Winter)
Total Suspended Solids (TSS) mg/1 700 5
Turbidity NTU 200 <1
Total Dissolved Solids (TDS) mg/1 90 150
Conductivity (~mhos cm -1 , 25°C) 145 240
pH pH units 7.3 7 .5
Alkalinity mg/1 as Caco 3 50 73
Hardness mg/1 as Caco 3 62 96
Sulfate (SO -2) mg/1 14 20
Chloride (Cf) + mg/1 5.6 22
Dissolved Calcium (Ca 2l mg /1 19 29
Dissolved ~agnesium (Mg 2) mg/1 3.0 5.5
Sodium (Na ) + mg/1 4.2 11 .5
Dissolved Potassium (K ) mg/1 2.2 2.2
Dissolved Oxygen (DO) mg/1 11.5 13.9
DO (% Saturation) % 102 98 %
Chemical Oxygen Demand (COD) mg/1 11 9
Total Organic Carbon (TOC) mg/1 2.5 2.2
True Color pcu 15 5
Total Phosphorous ~g/1 120 30
Nitrate-nitrogen as N (N0 3-N) mg/1 0.15 0.15
Total Recoverable Cadmium
[Cd(t)] ~g/1 2.0 <1
Total Recoverable Copper
[Cu(t)] ~g/1 70 <5
Total Recoverable Iron
[Fe(t)] ~g/1 14,000 <100
Total Recoverable Lead
[Pb(t)] ~g/1 55 <10
Total Recoverable Mercury
[Hg(t)] ~g/1 0.30 0.10
Total Recoverable Nickel
[Ni(t)] ~g/1 30 2
Total Recoverable Zinc
[Zn(t)] ~g/1 70 10
Source : Alaska Power Authority 1983
IV-30
in the water quality conditions of the mainstem and its associated
side channels. During winter almost all the flowing water is covered
with ice and snow. However high velocity areas and small isolated
areas of warm · (3-4°C) groundwater upwelling maintain a few scattered
open leads.
A winter-spring transition algal bloom probably occurs at open leads
along the mainstem and side channel margins or at mid-channel shoals
and riffle areas (Hynes 1970). The large amount of mainstem areas
which may be involved in this process suggests that the mainstem
contribution to autochthonous production may be substantial.
During spring break-up, stream flow rapidly increases during May from
approximately 2,000 cfs to 20,000 cfs or greater, while suspended
sediment concentrations fluctuate considerably (9 -1,670 mg 1-1 ), but
average approximately 360 mg 1-1 (Peratrovich et al. 1982). Most of
the benthic production that. occurred during the winter-spring transi-
tion is likely dislodged and swept downstream. A portion of .this
material may follow the natural flow path along the mainstem margin
and into peripheral overflow channels and sloughs. Thus high spring
flows may redistribute fish food organisms and retain some of the
winter-spring transition organic production. At prevailing springtime
turbidities (50 to 100 NTU), the mainstem margin and side channels
apparently continue to support a low to moderate level of primary
production wherever velocity is not 1 imiting . The euphotic zone at
this time is estimated to extend to an average depth between 1.2 and
3.5 ft (Van Nieuwenhuyse 1984).
In sui'IIT!er, mainstem flows are at their highest levels. The total
surface area available for primary production is 1 imited by high
turbidities that reduce the depth of useful light penetration to less
than 0.5 ft (Van Nieuwenhuyse 1984). Many of the hemi-metabolous
insect species are suspected to be in the egg stage or in early instar
phases at this time. Juvenile fish migrating out of their natal
tributaries move to low velocity rearing habitats, which seem to be
IV-31
concentrated in peripheral areas of the mainstem and side channels.
side slough, and upland slough aquatic habitats {AOF&G 1984c).
Largely because of its water quality {especially its high suspended
sediment concentration), high velocities and large substrate, the
principal function of mainstem habitat during the summer months is to
provide a tr1nsportation corridor for inmigrating spawning salmon and
outmigrating smolts. Mainstem water quality also has a significant
influence on the seasonal water quality regime of side slough habitats
when overtopping of side slough occurs.
Field observations made in 1984 by EWT&A suggested that during a
typical autumn transition period, a second pulse of primary production
often occurs in the mainstem. dominated this time by green filamentous
algae rather than diatoms. This second bloom. induced in part by
moderating stream flows, but mostly by a notable reduction in tur-
bidity levels to less than 20 NTU, probably exceeds the winter-spring
transition bloom in terms of biomass produced and surface .area
affected. The depth of the euphotic zone at turbidities of 20 NTU
approximates 5 ft (Van Nieuwenhuyse 1984). This fall-winter period of
abundance stops at freezeup. Some of this production is dislodged and
swept away or frozen in place .
Side Slough Habitat
Side sloughs present a unique seasonal pattern of streamflow and water
quality that is important to many fish species inhabiting the middle
Susitna River. Side slough habitat consists of clear water maintained
by groundwater upwelling or local surface runoff in overflow channels.
One distinguishing characteristic of side slough habitat is the
periodic overtopping of the upstream end of the slough by high
mainstem discharge levels that temporarily transforms the side slough
to side channel habitat.
In winter, side sloughs contain numerous groundwater upwelling sites
which may be distinguished by the presence of open leads (ADF&G
IV-32
1983a}. Thus they provide intragravel habitat for incubating embryos
and overwintering opportunities for juvenile arradromous and resident
fish.
Duri~q the winter-spring transition period, surface water temperatures
exceed intragravel water temperatures during the day (Trihey 1982,
ADF&G 1983a}. Chum, sockeye and pink fry emerge from nata 1 areas
within the sloughs during this transition period and primary produc-
tion rates probably increase at this time.
Because side sloughs are located along the lateral portions of the
flood plain, spring breakup in the sloughs is generally less severe
than it is in either the tributaries or mainstem and side channel
habitats. The most significant changes in side slough water quality
occur during the summer. Side sloughs are connected at their upstream
end to the mainstem or side channels by head berms of various ele-
vations. As mainstem discharge increases to the point of overtopping
the head berms, side sloughs are inundated with turbid mainstem water.
Overtopping of· the upstream berm wi 11 be more frequent, of 1 onger
duration, and the cause of greater quantities of flows in locations
where berms are relatively low. During each overtopping, the side
slough water quality and temperature are dominated by the characteris-
tics of the mainstem.
Sloughs are also subject to turbid backwater effects at their down-
stream juncture with the mainstem or a side channel (mouths}. Much of
the suspended sediment load carried in by the mainstem water settles
in the backwater, and thus presents a substrate different from that
found farther upstream in the sloughs.
Field observations by EWT&A suggest that some of the sediment carried
through sloughs seems to become part of an organic matrix of unknown
composition (probably involving bacteria, fungi, and other microbes}
which in turn is usually covered by a layer of pennate diatoms and/or
colonial and filamentous algae. This benthic community, which covers
most streambed material greater than 2 to 3 inches in diameter, can be
IV-33
observed throughout the system in mainstem and side channel habitats
as well. It is possible ·that the phosphorus associated with the
sediment plays some role in making this possible and studies
(Stanford, Univ. of Montana, pers. comm. 1984) elsewhere indicate that
as much as 6 percent or more of this sediment-bound total phosphorus
can become biologically available --perhaps to the diatoms. This
might help explain how primary producers can still ma i ntain a viable
presence even under short-term highly turbid conditions.
During late September and early October 1984, fall-winter transitional
algal blooms were observed by EWT&A in most side sloughs and thus
probably occur every year. The 1984 bloom was characterized by dense
mats of filamentous green algae growing on gravel substrate of one
inch in diameter up to the largest cobble.
Upland Slough Habitat
Upland slough habitat is distinguished from side slough habitat by the
lack of overtopping of the upstream slough end by high mainstem
discharges. Thus, groundwater upwelling and local runoff dominate the
water quality characteristics of upland slough habitats except at the
slough mouths, which are influenced by turbid backwater effects from
the mainstem.
Tributary and Tributary Mouth Habitats
As for all other aquatic habitat types, the seasonal water quality
pattern displayed by the tributaries is closely linked to their annual
flow regimes. This pattern is of considerable interest since it is in
the tributaries--most notably Portage Creek, Indian River, and Fourth
of July Creek--where most of the fish production originates (AOF&G
1981, 1982, 1984a). These streams pro vide spawning, rearing, and
overwintering habitat that either does not exist, or only exists in
limited amounts in other habitat types. Tributaries, in effect, may
represent the most productive of the aquatic habitats in the middle
Susitna River. The ionic composition of tributary water likely
IV-34
conforms to the hydrologic principle that the soils of a stream basin
generally govern the quantity and the quality of the solids contained
in the water flowing from it. However, productivity levels in tribu-
taries may be due more to the hydraulic and hydrologic conditions than
to water qua 1 ity. The moderate concentrations of macronutri ents
(phosphorus and nitrogen} that prevail in these streams probably
represent only that which leaks from the internal cycling taking place
in the soils of the local watershed.
In winter, tributary flow is minimal and is predominantly comprised of
groundwater rising up through the bed of the stream channel. Since
much of the winter mainstem flow is comprised of contributions made by
groundwater and tributary sources, tributary water chemistry is
probably reflected in the winter water chemistry characteristics of
the mainstem (Table IV-6}. Thus, the water quality characteristics of
tributaries during winter reflect a well-buffered, well-oxygenated
environment for embryo incubation and adult and juvenile over-
wintering.
During the four to six week transition between winter and the onset of
the spring freshet, portions of the ice and snow cover on the tribu-
tary melt away. Water temperatures may increase slightly and a pulse
of primary production probably occurs in response to a lengthening
photoperiod (Hynes 1970). The ab i1 i ty of 1 i ght to reach the a 1 ga 1
corrmunity is assisted by absence of leaf cover on stream bank vege-
tation ·and presence of rotten ice that effectively transmits light
(LaPerriere, Univ. of Alaska, pers. COITIIl. 1984). The emergence of
some fish species and many insects is apparently timed to occur during
this brief early-spring interlude of plentiful food and relatively
tranquil stream flows.
Typically, by mid-May air temperatures have increased to 8°C and the
spring freshet has filled the tributary channel with runoff from
melting snow. Flooding from ice jams redistributes much of the cobble
substrate, displaces juvenile salmon from overwintering habitat, and
flushes out organic and inorganic debris as we 11 as lllJCh of the
IV-35
benthic community (Hynes 1970). This erosion causes an increase in
suspended sediment concentration and turbidity. Likewise, color,
total organic carbon, and chemical oxygen demand increase sub-
stantially, while, as in the mainstem, the inflow of surface runoff
dilutes winter concentrations of dissolved solids. It is likely that
the spring freshet serves as a functional reset mechanism for the
system, in effect cleansing it in preparation for the ecological
events to follow.
Typical water quality in tributaries during the sulliTler (June to
mid-September) probably approximates the winter condition except for
lesser concentrations of dissolved solids (Hynes 1970). Summer stream
temperatures are warmer and fluctuate diurnally. This background
condition is frequently punctuated by storm runoff events.
Summer is the season when juvenile fish are most active. Rearing is
supported primarily by the growth and recruitment taking place within
the aquatic insect community (especially chironomids). The carrying
capacity of tributaries, however, does not appear adequate to support
the large numbers of rearing juveniles, so many juveniles outmigrate
at this time to continue their development elsewhere (ADF&G 1984c).
During late September and early October a second transition period
occurs as streamflow, photoperiod, and temperature gradually decline.
Algal biomass and productivity are probably at their annual peak, as
is the standing crop of benthic macroinvertebrates (Hynes 1970). The
algal mat is not only a food source for a variety of insect larvae and
nymphs, but serves as microhabitat for many aquatic organisms includ-
ing juvenile fish. The leaves shed from riparian vegetation may
provide further microhabitat and insect food substrate.
By late October, surface water temperatures are 0°C and an ice cover
begins to form. Unstable border ice and anchor ice probably dislodge
a substantial portion of the benthic community, causing it to be swept
downstream. Much of what remains of this community may be frozen in
place as the ice cover formation continues. Freezeup is usually
IV-36
complete by late November or early December when the winter phase of
the annual cycle begins once again.
With-Project Relationships
Temperature and suspended sediment seasonally influence aquatic
habitat types in the middle Susitna River, and therefore are important
in the distribution and production of fish. It is evident that these
water quality parameters will be more directly affected by con-
struction and operation of the proposed project than other water
quality parameters (AEIDC 1984b, Peratrovich et al. 1982). Stream
temperature is discussed in Section IV of this report, hence the
following discussion focuses on suspended sediment and turbidity.
The downstream water quality regime will change as a result of project
operation. The reservoir(s) is estimated to trap approximately 70 to
98 percent of the total volume of sediments that are annually trans-
ported through the middle Susitna River (R&M Consultants 1982, Harza-
Ebasco 1984a). The sediment remaining in suspension and released
downstream year round will consist predominantly of fine particles
(<5~ in diameter) (APA 1983), which create a turbidity far greater in
proportion to their mass than larger particles. Estimates for the
expected concentration of total suspended sol ids released from the
reservoir(s) year round range from 0 to 345 mg 1-1, with the expected
average between 30 and 200 mg 1-1 (Peratrovich et al. 1982). Concen-
trations of this magnitude would result in year round turbidities
ranging between 60 and 600 NTU based on a ratio of 2 to 1 NTU/mg/1-1
(R&M 1984) with corresponding euphotic zone depths of approximately 3
and 0.4 ft (Van Nieuwenhuyse 1984).
A reduction in suspended sediment levels in the middle reach of the
Susitna River would likely result in existing sediments and fine sands
in streambed materials being transported downstream (Harza-Ebasco
1984a). Additionally, if short term peak flow events disturbed
streambed materials prior to the cementation of these materials and
cleared the interstitial spaces of fine sediments, the hydraulic
IV-37
connection between surface and subsurface flow would protably improve.
Reduced turbidity and increased subsurface flow, in turn, would be
expected to increase the success rate for mainstem and side channel
spawning by salmon and the colonization rates of periphyton and
benthic invertebrates during the summer.
Primary production in the middle reach of the Susitna River presently
appears to be concentrated in the spring and fall periods of low
turbidities. Constant, year-round turbidity levels in the range of 60
to 600 NTU would likely reduce the level of primary production during
these transition periods, although primary production may increase
during summer months.
IV-38
Instream Temperature and Ice Processes
Instream Temperature Criteria
Within the range of temperatures encountered in northern river sys-
tems, rncreases ·in stream temperature generally cause an increase in
the rate of chemical reactions, primary production, and cycling of
allochthonous food sources. The fish inhabitants of the river system
adjust their body temperatures to match the temperature of the water.
As temperatures increase, rates of digestion, circulation and respira-
tion increase. Thus, there is an overall increase in the rate of
energy input, nutrient cycling and energy use as the river system
warms.
Each species of fish is physiologically adapted to survive within a
tolerance range of stream temperature. Within this tolerance range
there is a narrower range of "preferred" temperatures at which metabo-
lism and growth rates of individuals are most efficient. Outside the
tolerance range are upper and lower incipient lethal limits.
The preferred temperature range for adult salmon in the middle Susitna
River is 6 to l2°C (AEIDC 1984b). Juvenile salmon prefer slightly
warmer temperatures for rearing, generally ranging from 7 to l4°C
(Table IV-7). These temperatures are consistent with the preferred
temperature range of 7 to 13°C reported by McNeil and Bailey (1975)
for Pacific salmon. The preferred temperature range for incubation is
generally between 4 and l0°C.
The time required for the incubation of salmon embryos is directly
related to stream temperature. Development rates increase with rising
stream temperature up to approximately l4°C. Above this, further
temperature increases are considered detrimental. Salmon embryos are
also vulnerable to cold temperatures until they have accumulated
approximately 140 centigrade temperature units (CTU' s)1 . After this
.lV-39
Table IV-7 . Preliminary stream temperature criteria for Pac1fic salmon
developed from literature sources for application to the Susitna
River.
Species Life Phase
Tem~erature Range {°C~
Tolerance Preferred
Chum Adult Migration 1.5-18.0 6.0-13.0
Spawning 1.0-14.0 6.0-13.0
Incubation 1 0-12.0 2.0-8.0
Rearing 1.5-16.0 5.0-15.0
Smolt Migration 3.0-13.0 5.0-12.0
Sockeye Adult Migration 2.5-16.0 6.0-12.0
Spawning 4.0-14.0 6.0-12.0
Incubation 1 0-14.0 4.5-8.0
Rearing 2.0-16.0 7.0-14.0
Smolt Migration 4.0-18 .0 5.0-12.0
Pink Adult Migration 5.0-18.0 7.0-13.0
Spawning 7.0-18.0 8.0-13.0
Incubation 1 0-13.0 4.0-10.0
Smolt Migration 4.0-13.0 5.0-12.0
Chinook Adult Migration 2.0-16.0 7.0-13.0
Spawning 5.0-14.0 7.0-12.0
Incubation 1 0-16.0 4.0-12.0
Rearing 2.0-16.0 7.0-14.0
Smolt Migration 4.0-16.0 7.0-14.0
Coho Adult Migration 2.0-18.0 6.0-11.0
Spawning 2.0-17.0 6.0-13.0
Incubation 1 0-14.0 4.0-10 .0
Smolt Migration 2.0-16.0 6.0-12.0
1 Embryo incubation or development rate increases as temperature rises.
Accumulated temperature units or days to emergence should be determined for
each specfes for incubation. SP.e Figure IV-0-1
Source: AEIOC 1984b
IV-40
initial period of sensitivity to cold temperatures has passed,
incubating embryos can tolerate temperatures near 0°C.
Table IV-8 provides a comparison between the nunt>er of CTU's that
resulted in 50 percent hatching and 50 percent emergence of chum
salmon alevins under both field and laboratory environments. The
number of temperature units that resulted in 50 percent hatching and
50 percent emergence of chum and sockeye alevins at selected middle
Susitna River sloughs appear similar to that required by Alaskan
stocks of these species under controlled conditions (ADF&G 1983a).
Collectively these data indicate that 400 to 500 CTU's can be used as
an index for 50 percent hatching of chum and sockeye eggs.
A simplified way of forecasting emergence time using the information
provided in Table IV-8 and other pertinent data from the 1 iterature
was developed by AEIOC (1984b). The relationship between mean incu-
bation temperature and development rate for chum embryos is presented
in the form of a nomograph (Figure IV-5).
This nomograph can be used to forecast the date of 50 percent emer-
gence given the spawning date and the mean daily intragravel water
temperature for the incubation period. A straight line projected from
the spawning date on the left axis through the mean incubation temper-
ature on the middle axis identifies the date of emergence on the right
axis.
1A centigrade temperature unit is the index used to measure the
influences of temperature on embryonic development and is defined as
one 24 hour period l°C above freezing (0°C). Hence stream tempera-
tures between 4 and 5°C would provide 140 centigrade temperature units
in about one month.
IV-41
Table IV-8. Comparison of accumulated centigrade temperature units (cru•s)
needed to produce 50 percent hatching of chum salmon eggs and 50
percent emergence of chum salmon alevins at selected sites on the
Susitna River with those required under controlled incubating
environments elsewhere in Alaska.
Brood cru•s required cru•s required
location Year for 50 % Hatching for 50% Emergence 1
Susitna River -Slough SA 1982 539 2
Susitna River -Slough 11 1982 501 232
Susitna River -Slough 21 Mouth 1982 534 283
Clear Hatchery 3 1977 420 313
Clear Hatchery 3 1978 455 393
Eklutna Hatchery 4 1981 802 209
USFWS laboratory -Anchorage 5 1982 306
USFWS Laboratory -Anchorage 5 1982 448
USFWS Laboratory -Anchorage 5 1982 489
USFWS Laboratory -Anchorage 5 1982 472
1 Calculated from the time of 50 percent hatching to the time of 50 percent
emergence
2 No emergence had occurred as of April 20
3 Raymond (1981)
4 loren Waldron, Eklutna Hatchery, personal communication
5 Adapted from Waangard and Burger (1983)
IV-42
Spawning
Date
T(C)
1.0
Emergence
Date
June 10
June I
Jon 20
Jon iO
Jon I
FigureB-s. Chum salmon spawning time versus mean incubation
t....,_rature nomooraph . (Source: AEIDC 1984b ) .
TV-6.1
Instream Temperature Processes
Stream temperature in northern rivers responds primarily to the
seasonal variation of the local climate and hydrologic conditions.
Heat transfer between the atmosphere and an open water surface prin-
cipally occurs through convection , evaporation/condensation and
radiation. Heat transfer by convection and evaporation/condensation
responds directly to wind speed and the temperature differential
across the air-water interface. Radiative heat transfer consists of
two types: shortwave and longwave radiation. Both short-and long-
wave radiation are significantly influenced by basin topography,
percent cloud cover, and surrounding vegetation. At higher latitudes
incoming shortwave radiation is highly variable because of. seasonal
differences in the solar azimuth which influences the intensity of the
shortwave radiation per unit area and the length of the daylight
period.
Cooling or warming of the river by the processes described above will
not be a 1 tered by the construction or operation of the proposed
project. However, the amount and temperature of water influent to a
river also affects its temperature. Construction and operation of the
proposed Susitna Project will substantially alter these existing
seasonal relationships by the redistribution of the available water
supply and its associated heat energy through the year. The reservoir
will store heat in the sunwner while releasing water with lower than
natural temperatures between break-up and mid-summer. For the remain-
der of the year, temperatures of the released water would be greater
than natural as the reservoir discharges the stored heat.
Sources of water influent to the Susitna River are classified as:
glacial melt, tributary inflow, non-point surface runoff, and ground-
water inflow. The relative importance of each of these to mainstem
flow and temperature at Gold Creek varies seasonally.
Tributary and non-point surface runoff increase during snow melt
periods and in response to rainstorms, and glacial melt water is
IV-44
predominantly a summer phenomena. Groundwater inflow, however,
appears to remain fairly constant throughout the year. Hence its
relative importance increases during winter as inflows from glacial
melt and surface runoff cease. Tributary inflows themselves diminish
to base levels maintained by groundwater inflow from their sub-basins.
The temperature of influent groundwater remains near 3 to 4°C through-
out the year (ADF&G 1983a). Glacial melt water at the headwaters of
the Susitna River is near 0°C, but it is warmed by the heat transfer
processes described earlier as it flows downstream. Temperature of
tributary waters are generally cooler than the temperature of the
mainstem, especially during May and June when most of their streamflow
consists of snow melt (Figure IV-6). Tributary water teiT'perat\Jres
determine mainstem surface water temperatures at tributary mouths.
Tributary flows characteristically hug the mainstem shoreline after
converging with the Susitna River, forming a plume that may extend
several hundred feet downstream.
Mainstem water temperatures normally range from zero during the
November-April period to 11 or 12°C from late June to mid-July. Water
temperatures typically increase from 0 to 6 or soc during May and
gradually decrease from 9 or l0°C in early September to 0°C by mid to
late October. Water temperatures in side channels follow mainstem
temperatures except in side channel areas which do not convey mainstem
water during periods of low flow. Except when overtopped by mainstem
flow, surface water temperatures in side sloughs are independent of
mainstem water temperatures even though both may occasionally be the
same temperature (Table IV-9).
Slou~hs receive nearly all of their clear water flow from local runoff
and groundwater inflow. Due to their relatively large surface areas
in comparison to their depth and flow rate, sloughs are quicker to
warm and cool. Hence daily fluctuations in side slough surface water
temperatures are more exaggerated than for mainstem or side channel
water temperatures (ADF&G 1984f). When sloughs receive substantial
inflow from snowmelt or rainfall runoff, their surface water tempera-
IV-45
-u -
~
E-o ~ "-1
~
I ~ l'il
<: E-<
I
~
C1\
15
14-Simula ted Tributary Temp erature
13 -c Hean '81/'8 2 Tempera ture at
RM 150
12 -+ + Me an '81/'82 Tempe r a ture at
RM 110
. 11 -c + + + +
0 0 0 + []
10 -e; + c + + c 0
[J 0 c
9 -tl ~
8----+ ---:-,.. -0
/ -.. .... 0 7 -/' ......
.... 0 / ....
6-/ ...
' / ' 5-/ ,,
/ ' ' / ' 4-, .,
t 1!1' 3-I ' I .,
I
2-
1!1 ' ' .,
1 -' 0 ,BJ
I~ 0 ' l J UN E I J ULY I AUGUST I SEPTEMBER I OCTOBE R
Figure N -6 . Compariaon between average weekly atream temperature• for the Suaitna
River and ita tributariea . (Adapted from AEIDC 1984 b).
H
<:
I
+' ......
Table IV-9. Comparison between measured surface water temperatures (degrees C) in side sloughs and simulated
average monthly mainstem temperatures
19S2 19S2 19S3
Location RM Feli Rar ~pr ~ug Sep Oct Rov Dec Jan Feli Rar ~pr
Slough SA Mouth 125.4 6.5 2.4 1.7 0 0 0.4 1.3
Slough SA Upper 126.4 5.S 4.4 2.5 3.S
Slough 9 12S.7 S.9 5.9 2.3 3.S
Slough 11 135.7 2.5 3.1 3.3 3.1 2.9 2.9 2.9 2.9 3.0 3.5
Slough 21 14l.S 1.6 1.9 3.1 2.2 1.1 o.s
Mains tern
LRX 29 126.1 0.0 0.0 2.9 10.9 6.5 0.6 0.0 0.0 0.0 0.0 0.0 3.0
LRX 53 140.2 0.0 0.0 2.5 10.S 6.4 0.6 0.0 o.o 0.0 0.0 0.0 2.6
Note: Mainstem temperatures are simulated without an ice cover and warm earlier in the spring than what
naturally occurs. Thus the April mainstem temperatures are probably warmer than what would occur.
Source: ADF&G 1983.
Ray
3.3
4.7
6.0
tures will reflect the temperature of that runoff. During winter,
slough flow is primarily maintained by upwelling which possesses very
stable temperatures around 3°C (ADF&G 1983a). Surface water
temperatures are significantly influenced by the thermal quality of
the upwellings; often remaining above ooc throughout most of the
winter. Surface water temperatures typically reach 5 or 6°C in
quiescent areas within side sloughs by mid-April, approximately one
month before similar temperatures are available in mainstem and side
channel areas.
Side sloughs are occasionally overtopped by mainstem water during
staging at freezeup, severely disrupting the relationship between
intragravel and surface water temperatures. Once the slough is
overtopped, the small volume of relatively wann slough water, which
serves to buffer submerged upwelling areas from extreme cold, is
immediately replaced by a large volume of 0°C water and slush ice. As
the overtopped condition persists, the wanning influence of the
upwelling is diminished and intragravel water temperatures may
decrease from 3 or 4°C to near 0°C (ADF&G 1983}.
A similar condition occurs during spring breakup as ice jams may cause
large volumes of near zero degree mainstem water to flow through side
sloughs flushing them of their substantially warmer surface water.
Although little data are available for this period, intragravel water
temperatures are not suspected to be as adversely affected by over-
topping events during breakup as they are by overtopping during
freeze-up.
With-Project Temperature Conditions. Construction and operation of
Watana dam will directly affect seasonal water temperatures by redis-
tributing streamflow and its associated heat content throughout the
year. Those portions of the Susitna River most affected by with-
project stream temperatures will be mainstem and side channel areas
that convey water released from the reservoir. With-project sunrner
flows are expected to be lower and winter flows higher than naturally
occurring streamfl ows. It is anticipated that stream temperatures
IV-48
will be similarly affected, but not to the same degree as streamflow.
Addition of Devil Canyon reservoir would amplify the deviation in both
su11111er and winter with-project stream temperatures from naturally
occurring mainstem temperatures at any given location within the
middle Susitna River (Table IV-10). In effect, the addition of Devil
Canyon Reservoir results in naturally occurring stream temperatures
being affected further downstream.
Table IV-10. Simulated mi~dle Susitna River mean summer mainstem
temperatures for natural, Watana only, and Watana/
Devil Canyon conditions.
Natura 1
Watana only {1996 Demand)
Watana/Devil Canyonz (2002 Demand)
RM 150
8.4
7.4
6.4
RM 130
8.5
7.5
6.8
RM 100
9.0
8.5
7.9
1 Average of four May-September stream temperature simulations using
meteorologic and hydrologic conditions associated with the summers
of 1971, 1974, 1981 afld 1982.
2 With increased load demand in later years of operation, less
frequent use of the Devil Canyon cone valves would result in
slightly warmer mean summer temperatures (AEIDC 1984b}.
Project design and operation have a notable influence on the tempera-
ture and flow rate of water discharged from the dam{s). Within the
anticipated operating range of the project, the temperature of the
reservoir outflow has a greater influence on downstream water tempera-
tures than flow rate. Table IV-11 displays the simulated downstream
temperatures for two situations : water week 34 (May 20-26), where the
downstream release temperatures are equal but release rates differ,
and water week 45 (August 5-11) where release rates are-equal but
their temperatures differ. The weekly simulation period is the same
within each example thereby eliminating downstream temperature differ-
ences resulting from climatic influences. The 1.8°C temperature
difference shown in the second case results in a much greater down-
IV-49
Table IV -11. Downstream temperatures (°C) resulting from di fferences in summer
reservo i r release flows and temperatures.
Water Week 34 Wat e r Week 45
{Ma~ 20 -26 2 1981} (August 5 -11 2 1974}
Dam Release : Dam Release:
6080 cfs 5270 cfs 10,950 cfs 10,950 cfs
Temp: Temp:
3.9°C 3.9°C 8.1 °C 9.9°C
Middle
River Cross 2002 2020 2002 2020
Section River Mile Demand Demand Demand Demand
68 150 4.5 4.5 8.2 9.9
53 140 4.9 5.0 8.5 10.1
33 130 5.4 5.5 8.6 10 .1
23 120 6.0 6 .1 9.0 10.4
13 110 6 .5 6.7 9.4 10.7
3 99 7.1 7.3 9.8 11.0
IV-50
stream temperature difference than that resulting from 810 cfs flow
decrease (13 percent decrease in flow) shown in the first case.
The most notable effect of project construction and operation on
natura 1 stream temperatures is de 1 ayi ng the temperature rise during
early summer and extending warm stream temperatures into fall
(Figure IV-7). As with mid-summer stream temperatures9 the tempera-
ture of the middle Susitna River during winter is directly influenced
by climate and project operation. The location at which 0°C water
occurs downstream from the dam 9 and consequently the maximum upstream
extent of the ice front, is controlled by annual winter climate.
However, its location also varies in response to reservoir outflow
temperature and, to a lesser degree, flow rate.
Due to the occurrence of warmer stream temperatures during fall, ice
front deve 1 opment on the middle Sus i tna River is expected to be
delayed from two to seven weeks {Harza-Ebasco 1984b). In addition,
the location of the ice front under with-project conditions is not
expected to extend as far upstream as it does under natural con-
ditions. Among the variables influencing winter stream temperature,
basin meteorology is the most significant.
Short periods of -15 to -25°C air temperatures increase the cooling
rate of water downstream from the dams and result in the production of
frazil ice. There is a rapid upstream progression of the ice front
during these periods {Gemperline 1984). Table IV-12 provides simulat-
ed data indicating the influence of winter air temperature on simulat-
ed downstream water temperatures.
The second most important variable, and one over which project design
and operation has some degree of control, is the temperature of the
reservoir outflow. The amount of water being released from the
reservoir also influences winter stream temperature but it is not as
significant a variable as outflow temperature, or basin climate.
Table IV-13 displays downstream temperatures for two cases: (1) where
IV-51
H
<:
I
V1
N
,10
LEGEND
---Natural
---I Dam (1996 Demand)
2 Dams ( 2002 Demand) -----
----
MAY JUNE JULY AUG SEPT OCT
DATE
Figure JSZ-7.Comparison of simulated natural and with-project monthly
temperatures of the Susitna River at R.M .I30 for the one
and two dam scenarios (Source : AEIDC 1984 b).
Table IV-12 . Comparison between simulated downstream water temperatures for
constant reservoir outflow conditions and different air
temperatures.
Water Week 8 Water Week 18
{Nov. 19-26, 1981} {Jan. 28-Feb. 3 2 1983}
Dam Release: Dam Release :
7,590 cfs 7,600 cfs
Middle River Release Temp: 1.9°C Release Temp : 1.9°C
River Cross Mile Air Temp: {Talkeetna) Air Temp: {Talkeetna)
Section -ll.6°C -3.4 °C
68 150 1.8 1.9
53 140 1.3 1.6
33 130 0.6 1.2
23 120 0 .8
13 110 0 .5
3 99 0 0
Note: Both simulations are for Devil Canyon dam, 2002 Demand.
IV-53
Table IV-13. Downstream temperatures (°C) resulting from differences in winter
reservoir release flows and temperatures.
Middle
River Cross
Section
68
53
33
23
13
3
River Mile
150
140
130
120
110
99
Water Week 9
{Nov. 26 -Dec. 2 1970)
Dam Release:
7770 cfs 12 ,370 cfs
Temp:
1.3 °C
2002
Demand
1.3
0.7
0
0
0
0
IV-54
1.3°C
2020
Demand
1.3
0.9
0.4
0
0
0
Water Week 22
{Feb. 25 -March 3 2 1982}
Dam Release :
7190 cfs 8000 cfs
Temp:
2.8°C 1.7°C
2002 2020
Demand Demand
2.7 1.7
2.2 1.2
1.5 0.7
0.8 0.1
0.2 0
0 0
dam release temperatures are the same but f1ow volumes change (in this
case a 59 percent increase) and (2) where ~~m release flows are
relatively constant (note: actually a 11 percent increase) and release
temperatures differ. As in the previous example for summer releases,
the differences in release temperatures result in the greatest down-
stream temperature differences.
Ice Processes
The most important factors affecting freezeup of the Susitna River are
air and
morphology.
water temperature, instream hydraulics, and channel
Breakup is primarily influenced by antecedant snowpack
conditions, air temperature and spring rainfall. The upper Susitna
River is commonly subjected to freezing air temperature by mid-
September, and slush ice has been observed in the Talkeetna-to-Devil
Canyon reach as early as late September. Initial phases of ice cover
deterioration commonly begin by mid-April, with ice out on the middle
Susitna River generall.Y being complete by mid-May (R&M Consultants
1983).
Figure IV-8 presents a generic flowchart which diagrams the i ce
formation process on the Talkeetna-to-Devil-Canyon reach of the
Susitna River, based on a recognition of pertinent climatic and
physica 1 factors. In order to understand the flow chart and subse-
quent discussions in this text, brief definitions have been adopted
from R&M (1983) for the most common types of ice found in the middle
reach of the Susitna River.
o Frazil -Individual crystals pf ice generally believed to
form around a nucleating agent when water becomes super-
cooled.
o Frazil Slush -Frazil ice crystals have strong cohesive
properties and tend to agglomerate into loosely packed
clusters that resemble slush. The slush eventually gains
sufficient mass and buoyancy to counteract the flow turbu-
lence and float on the water surface.
IV-55
1~------------------------~cooling
Backwaters and Mainstem and
sloughs sidechannels
I SNOW ICE I
Quiescent water
low velocity
(<1 ft/sec)
1
SHORE ICE -~------------~--~
Turbulen water
high velocity
(>1 ft/sec)
~
Snowfall
! . UpstreBlll progress1.on
of unconsolidated
ice cTer .
With compress1on
BUMMOCKED
ICE COVER
REFREEZING
FIGURE IJ:-8. Flowchart of general Ice forming proce••e• on the middle
reach of the Su•ltna River.
IV-56
o Snow Slush -Similar to frazil slush but fanned by loosely
packed snow particles in the stream.
o Black Ice -Black ice initially forms as individual crystals
on the water surface in near zero velocity areas in rivers
or underneath an existing ice cover. These crystals develop
in an orderly arrangement resulting in a compact structure
which is far stronger than slush ice covers. Black ice
developing in the absence of frazil crystals is characteris-
tically translucent. This type of ice can also grow into
clear layers several feet thick within the Susitna slush ice
cover.
o Shore Ice or Border Ice -This forms along flow margins as a
result of slush ice drifting into low velocity areas and
freezing against the channel bed.
o Ice Bridges -These generally form when shore ice grows out
from the banks to such an extent that a local water surface
constriction results. Large volumes of slush ice may not be
able to negotiate this constriction at the same rate as the
water velocity. An accumulation of slush subsequently
occurs at the constriction, sometimes freezing into a
continuous solid ice cover or bridge. This ice bridge
usually prevents slush rafts from continuing downstream,
initiating an upstream accumulation or progression of ice.
o Hummocked Ice -This is the most common form of ice cover on
the Susitna mainstem and side channel areas. It is fanned
by continuous accumulation of consolidated slush rafts that
progressively build up behind ice bridges, causing the ice
cover to migrate upstream during freezeup.
IV-57
Freezeup
Frazil Ice Generation. Most river ice covers are formed as a result
of the fonnation and concentration of frazil ice. When river water
becomes slightly supercooled (0°C), frazil crystals begin to form by
nucleation or by a mass exchange mechanism between the water surface
and the cold air. Fine suspended sediments in the water during
freezeup season may be the nucleating agent in the Susitna River. In
the mass exchange mechanism, initial nucleation occurs in the air
above and the ice crystals fall to the water surface (Ashton 1978).
Frazil crystals initially form principally as small discoid crystals
only a few millimeters in diameter. These grow rapidly to larger size
and begin to accumulate as frazil slush masses, which are often
contributed to by snowfall into the river forming floating snow slush.
The combined slush usually breaks up in turbulence into i ndividual
slush floes that continue drifting downriver until stopped by jamming
at river constrictions (Ashton 1978; Michel 1971; Osterkamp 1978).
Frazil ice generally first appears in the river between the Denali
Highway bridge and Vee Canyon by mid-September. This ice drifts
downriver, often accumulating into loosely-bonded slush floes, until
it melts away or exits into Cook Inlet. During freezeup, generally
about 80 percent of the ice passing Talkeetna into the lower river is
produced in the upper Susitna River, while the remaining 20 percent is
produced in the Talkeetna and Chulitna Rivers. Below the Yentna
confluence, usually more than 50 percent of the ice is produced by the
Yentna River.
Talkeetna to Gold Creek. The leading edge of the lower Susitna Ri ver
ice cover usually arrives at the confluence of the Susitna and
Chulitna Rivers (RM 99) between early November and early December
(Table IV-14). The rate of upstream progression is significantly
slower on the middle reach of the Susitna River.
The ice front progression rate decreases as the ice front moves
upriver. In 1982, the progression rate slowed from an average of 3.5
IV-58
Table IV-14. Summary of freeze up observations for several locations within the Talkeetna to Dev il Canyon
reach of the Susitna River.
location River Mile 1980-1981 1981-1982 1982-1983 1983-1984
Ice Bridge or Ice Front At
Sus i tna-Chulitna confluence Nov . 29 Nov. 18 Nov. 5 Dec. 8
leading Edge Near
Cold Creek Dec . 12 Dec. 31 Dec. 27 Jan. 5
~eroximate Freez ing Oates at
Susitna Chulitna
Confluence 98.6 Hid-Nov. Nov. 5 Dec. 9
II 103.3 Nov. 8
II 104.3 Dec.
II 106 .2 Nov. 9
II 108.0 Dec. 2
II 112.9 Dec. 3
lane Creek 113.7 Nov. 15
McKenzie Creek 116.7 Nov. 18
II 118.8 Dec. 5
Curry 120.7 Nov. 20 Dec. 21
Slough 8 124.5 Nov. 20
II 126.5 Dec . 8
II 127 .o Hid-Dec. Nov. 22
Slough 9 128.3 Nov. 29
II 130.9 Dec. 1 Jan. 5
Slough 11 135.3 Dec. 6
Cold Creek 136.6 Dec. 12 Early Jan . Jan. 14 Jan. 15
Portage Creek 148.9 Dec. 23
R&M Consultants 1980-81, 1982, 1983, 1984.
IV-59
miles per day near the confluence to 0.05 miles per day by the time it
reached Gold Creek (RM 136). This is probably due to the increase in
gradient moving upriver and to the reduction in frazil ice generation
in the upper Susitna River as it develops a continuous ice coier. The
upper Susitna River freezes over by border ice growth and intermediate
bridging before the advancing leading edge reaches Gold Creek.
local groundwater levels are often raised when the leading edge
approaches. This is probably due to staging effects raising the water
level in the mainstem, which then is propagated through the permeable
river sediments into surrounding sloughs and side channels.
Many sloughs fail to form a continuous ice cover all winter due to up-
welling of relatively warm (l-3°C) groundwater (Trihey 1982, ADF&G
1983a). However, ice does form along slough margins, restricting the
open water area to a narrow, open lead. Some sloughs that do form ice
covers after being inundated with mainstem water and ice later melt
out because of the groundwater thermal influence. These leads often
then remain open all winter.
As slush ice accumulates against the leading edge, it consolidates
from time to time through compression and thickening. Staging accom-
panies this process, sometimes lifting the ice cover and allowing it
lateral movement and often extending the ice from bank to bank .
Water flowing under the ice cover throughout the winter often causes
frictional erosion of the underside of the ice, opening leads in the
cover. This usually occurs rapidly after the initial stabilization of
a slush ice cover. These leads usually slowly freeze over with a
secondary ice cover, and most leads are closed by March.
The slush ice front progression from the Susitna/Chulitna confluence
generally terminates in the vicinity of Gold Creek , about 35 to 40
miles upstream from the confluence, by December or early January.
Gold Creek to Devil Canyon. Freezeup occurs gradually in the reach
from Gold Creek (RM 136) to Devil Canyon (RM 150), with a complete ice
IV-60
cover in place much later than in the reach below Gold Creek, usually
not until March (R&M Consultants 1983). The ice front does not
generally progress beyond the vicinity of Gold Creek because of the
lack of frazil ice input after the upper river freezes over. Also, ice
is late in forming here because of the relatively high velocities in
this reach, caused by the steeper gradient and single-channel charac-
teristics of the reach.
Wide border ice layers build out from shore throughout the freezeup
season, narrowing the open water channel in the mainstem and fre-
quently forming ice bri dges across the river, separated by ope n leads.
In the open water areas, frazil ice adheres easily to any object it
contacts within the river flow, such as rocks and grave 1 on the
channel bottom, forming anchor ice. Anchor ice may form into low dams
in the stream bed, especially in areas narrowed by border ice,
increasing local water turbulence which may increase frazil gen-
eration. Slight backwater areas are sometimes induced due to a general
raising of the effective channel bottom, affecting flow distribution
between channels and causing overflow onto border ice . Within the
backwater area, slush ice may freeze in a thin layer from bank to
bank.
little staging occurs in this reach during freezeup, and sloughs and
side channels are generally not breached at their upper ends. They
usually remain open all winter due to groundwater inflow . Open leads
occur in the mainstem , especially in high velocity areas bet~een ice
bridges, but few new leads open after the formation of the initial ice
cover. There is minimal ice cover sag in this reach.
Ice Cover at the Peak of Development. Once the initial ice cover
forms it remains quite dynamic, either thickening or eroding. Slush
ice adheres to the underside of the ice cover in low velocity areas
and becomes bonded by 1 ow temperatures. The ice cover becomes most
stable at its height of maturity, generally in March (R&M Consultants
1983). The only open water at that time is in the numerous leads that
IV-61
persist over turbulent areas and areas of groundwater upwelling, and
little frazil slush is generated.
Breakup . Under natural conditions, the Susitna River ice cover
disintegrates in the spring by a progression beginning with a slow,
gradual deterioration of the ice and ending with a dramatic breakup
drive accompanied by ice jams, flooding, and erosion (R&M Consultants
1983). The duration of the breakup period depends on the intensity of
solar radiation, air temperatures, and precipitation .
A pre-breakup period occurs as snowmelt begins in the area, usually by
early April. Snowmelt begins first at the lower elevations near the
Susitna River mouth and slowly works northward up the river. By la ~e
April, snow has usually disappeared on the river south of Talkeetna
and snowmelt is proceeding into the reach above the Susitna/Chulitna
confluence. Tributaries to the lower river have usually broken out in
their lower elevations, and open water exists at their confluences
with the Susitna River. Increased flows from the tributaries erode
the Susitna ice cover for considerable distances downstream from their
confluences.
As water levels in the river begin to rise and fluctuate with spring
snowmelt and precipitation, overflow often occurs onto the ice since
the rigid and impermeable ice cover fails to respond quickly enough to
these changes. Standing water appears in sags and depressions on the
ice cover. This standing water reduces the albedo, or reflectivity, of
the ice surface, and open leads quickly appear in these depressions.
As the water level rises and erodes the ice cover , ice becomes under-
cut and collapses into the o~en leads, drifting to their downstream
ends and accumulating in small ice jams. In this way, leads become
s t eadily wider and longer. This process is especially notable in the
reach from Talkeetna-to-Devil Canyon. In the wide, low-gradient
river below Talkeetna open leads occur less frequently and extensive
overflow of mainstem water onto the ice cover is the first indicator
of rising water levels .
IV-62
The disintegration of the ice cover into individual fragments or floes
and the drift of these floes downstream and out of the river is called
the breakup drive . The natural spring breakup drive is largely
associated with rapid flow increases, due to precipitation and snow-
melt, that lift and fracture the ice surface . When the river dis-
charge becomes high enough to break and move the ice sheet, the
breakup dr ive begins. Its intensity is dependent upon meteorologica1
conditions during the pre-breakup period.
Major ice jams generally occur in shallow reaches with a narrow
confining thalweg channel along one bank, or at sharp river bends.
Major jams are commonly found adjacent to side channels or sloughs,
and may have played a part in forming them through catastrophic
overflow and scouring at some time in the past. This is known to have
happened at Slough 11 in 1976, as reported by local residents in the
area, when a large ice j am overflow event altered a previously-
existing small upland slough into a major side slough.
Breakup ice jams commonly cause rapid, local stage increases that
continue rising until either the jam releases or the adjacent sloughs
or side channels become flooded. While the jam holds, flow and large
amounts of ice are diverted into side channels or sloughs, rapidly
eroding away sections of riverbank and often pushing ice well up into
the trees.
Generally, the final destruction of the ice cover occurs in early to
mid-May ~hen a series of ice jams break in succession, adding their
mass and momentum to the next jam downstream. Th i s continues until
the river is swept clean of ice except for stranded ice floes along
shore. Ice that has been pushed well up onto banks above the wate r
level may last for several weeks before melting away in place.
IV-63
Effects of With-Project Instream Temperatures on Susitna River Ice
Processes.
I CECAL modeling runs show that operation of the Susana River Hydro-
electric Project would h~ve significant effects on the ice processes
of the Susitna River, especially in the Talkeetna to Devil Canyon
reach, due to changes in flows and water temperatures in the river
below the dams. Generally, winter flows would be several times
greater than they are under natural winter conditions, and winter
water temperatures would generally be between 0.5°C and 3°C where they
are normally 0°C immediately below the dams (AEIDC 1984b). The !CECAL
computer model developed by Harza-Ebasco Susitna Joint Venture was
used to simulate river ice conditions under various scenarios of
project operations, with Watana operating a lone and in conjunction
with Devil Canyon dam, under varying power demand situations, and with
differing climatic conditions (Harza-Ebasco 1984c).
With-Project Simulations, Freezeup. Frazil ice that is generated in
the upper river area, principally in the Vee Canyon to the Denali
Highway area, normally drifts downstream into the lower and middle
reaches of the Susitna River and provides the source for initial ice
bridging and subsequent ice cover formation for most of the these
reaches. With Watana dam and reservoir in place, this frazil would be
trapped in the reservoir, unable to reach its normal destinations.
Consequently, freezeup of the river below the dam would be delayed.
Later, with the construction of Devil Canyon dam and reservoir, most
of the frazil-generating rapids within Devil Canyon would be
inundated, further reducing frazil produc t ion reaching the middle and
lower river reaches, and further delaying river freezeup.
Arrival of the ice front at the Yentna River mouth usually occurs in
late October or early November under natural conditions. This timing
is not expected to be significantly altered with-project in spite of
the reduced frazil input from the upper Susitna River because the ice
contributions from the Yentna River and other major tributaries would
remain the same. Based on this, November 1 was used by !CECAL as a
IV-64
representative date for the passage of the ice front by the Yentna
River mouth. However, reduced frazil input would slow the advance rate
of the leading edge. These effects would combine with the higher
winter flows and warmer water temperatures to produce a delay of ini-
tial freezeup at the Susitna/Chulitna confluence ranging from about
2-5 weeks with Watana operating alone to 4-6 ~eeks with Watana and
Devil Canyon operating together (Table IV-15).
The warmer water temperatures released from the dams would not cool to
the freezing 1 eve 1 for a number of mi 1 es downstream of the dams,
preventing ice from forming all winter in this reach, except for some
border ice attached to shore. The maximum upriver extent of ice cover
prog-ression below the project, with Watana operating alone, would vary
from RM 124 to RM 142 depending on winter climate and operational
scenario. Similarly, with both Watana and Devil Canyon operating, the
maximum ice cover extent would be from RM 123 to RM 137. The ice
front would reach its maximum position between mid-December and late
March for Watana alone and mid-January to mid-March for Watana and
Devil Canyon together, but would fluctuate considerably in position
for the rest of the winter depending on prevailing air temperatures.
Under natural conditions, secondary ice bridges may form between the
Susitna/Chulitna confluence and Gold Creek before the ice front
progression in the middle Susitna River has reached Gold Creek. With
the project in place these low flow conditions would not occur;
therefore, !CECAL simulations are based only on the initiation of one
ice bridge at RM 9 in late October and the subsequent ice cover devel-
opment on the lower river. !CECAL assumes only one leading edge
progression above the Chulitna confluence.
Increases in winter discharges in the river below the dams would cause
stages during freezeup to be significantly higher than natural. In
that reach, where the ice cover forms, stages are expected to be 2 to
7 feet h_igher than natural with Watana operating alone, while with
both dams operational, stages should be about 1 to 6 feet higher than
IV-65
Table IV-15. !CECAL simulated ice front progression and meltout dates
(Harza-Ebasco Susitna Joint Venture, 1984c).
Maximum
Natural Starting Date Upstream
and Si111.1lated at Chulitna Melt-out Extent
Conditions Confluence Date (River Mile)
Natural Conditions
137N 1971-72 Nov. 5
1976-77 Dec. 8
Mayio:85B
137N
1981-82 Nov. 18 137N
1982-83 Nov. 5 May 10 137N
Watana Only -1996 Demand
May 1£E 1971-72 Nov. 28 140
1976-77 Dec. 25 May 3 137
1981-82 Dec. 28 April 3 137
1982-83w Dec. 12 March 20 127
1971-72 Dec. 17 March 27 127
Watana Only -2001 Demand
May 15E 1971-72 Nov. 28 142
1982-83 Dec. 19 March 16 124
Both Dams -2002 Demand
May 3E 1971-72 Dec. 2 137
1976-77 Jan. 10 April 20 126
1981-82 Dec. 30 March 12 124
1982-83 Dec. 22 March 20 123
Both Dams -2020 Demand
1971-72 Dec. 3 April 15 133
1982-83 Dec. 14 March 12 127
Legend: B -Observed natural break up.
E -Melt-out date is extrapolated from results when
occurring beyond April 30
N -Ice cover for natural conditions extends upstream of
Gold Creek (River Mile 137) by means of lateral ice
bridging.
I -Computed ice front progression upstream of Gold Creek
(River Mile 137) is approximation only. Observations
indicate closure of river by lateral ice in this reach
for natural conditions.
Notes: 1. "Case C" instream flow requirements are assumed for
with-pr~ect simulations.
2. 1971-72 simulation assumes warm, 4°C reservoir
releases. All other with-project simulations assume an
"inflow-matching" temperature policy.
IV-66
natural (Table IV-16}. Dcwnstream from the ice front, more sloughs
and side channels would be overtopped more frequently.
Winter discharges would be higher than normal but no freezeup staging
would occur upstream from the ice front's maximum position. Water
levels in that reach would be 1 to 3 feet lower than natural freezeup
staging levels with Watana operating alone, and 1 to 5 feet lower with
both dams operating. Therefore, no sloughs in this reach should be
overtopped. However, lack of freezeup staging in this reach of the
river may reduce groundwater upwelling in the sloughs. Natural
freezeup staging causes approximately the same hyd r aulic head to exist
between the mainstem and adjacent sloughs as occurs during sunmer.
With the project i n place and no freezeup staging occurring, the
hydraulic head would be reduced, despite the increased winter flows .
Since the ice .edge would not advance as far, or as rapidly, during
project operations as during natural conditions, more areas of open
water would exist, and they would remain longer than usual. This
could cause the incidence of more anchor ice during cold periods.
This might cause the formation of slight backwater areas because of
the general raising of the channel bottom, possibly affecting flow
distribution between channels with low berms.
Where an ice cover forms, the maximum total ice thickness with Watana
operating alone are expected to be generally similar to natural ice
thickness. With both dams operating, maximum total ice thickness
should be about 1 to 2 feet less than natural ice thickness.
With-Project Simulations, Breakup. Breakup processes are expected to
be different in the Susitna River below the project, especially in the
Ta l keetna to Devil Canyon reach. Since the maximum upstream extent of
the ice cover below the dams would be somewhere between RM 124 and RM
142, there would be no continuous ice cover between this area and the
damsite, and consequently no breakup or meltout in that reach. Any
border ice attached to shore would probably slowly melt away in place;
occasional pieces of border ice might break away from shore and float
IV-67
Table IV-16. Occurrences where with-project1 maximum river stages
are higher than natural conditions.
Watana Watana and
Slough or . River Only 2 Devil Cany~n
Side Channel Mile Operating Operating
Whiskers 101.5 6/6 6/6
Gash Creek 112.0 6/6 5/6
6A 112.3 6/6 5/6
s 114.1 6/6 6/6
MSII 115.5 6/6 6/6
MSII 115.9 6/6 6/6
Curry 120.0 6/6 3/6
Moose 123.5 6/6 4/6
SA West 126.1 5/6 4/6
SA East 127.1 4/6 2/6
9 129.3 4/6 2/6
9 u/s 130.6 3/6 0/6
4th July 13l.S 3/6 2/6
9A 133.7 3/6 1/6
10 u/s 134.3 4/6 1/6
11 d/s 135.3 3/6 0/6
11 136.5 4/6 2/6
Notes:
1 11 Case C11 instream flow requirements and 11 inflow-matching 11 reservoir
release temperatures are assumed for with-project simulations.
2 For example, 4/6 means that 4 of the 6 with-project simulations
resulted in a higher maximum river stage than the natural
conditions for corresponding winters.
Source: Harza-Ebasco Susitna Joint Venture, 19S4a
IV-6S
downstream. Ice in the river reach above the project would break up
normally, but would not drift into this area as it normally does
because it would be trapped in the reservoir~.
The normal spring breakup drive is usually brought on by rapid flow
increases that lift and fracture the ice cover. The proposed project
reservoirs would regulate such seasonal flows, yielding a more steady
flow regime and resulting in a slow meltout of the ice cover in place.
The warmer-than-normal water temperatures released from the project
wou 1 d cause the upstream end of the ice cover to begin to decay
earlier in the season than normal. Gradual spring meltout wi th
Watana operating alone is predicted to be 4 to 6 weeks earlier than
normal, and 7 to 8 weeks earlier than normal with both dams operating.
By May, flow levels in the river would be significantly reduced from
natural levels as the project begins to store incoming flows from
upstream. The result is ex.pected to be that breakup drive processes
that now normally occur in the middle Susitna River area would be
effecti vely eliminated. Instead, a slow and steady meltout of river
ice in this reach would probably occur . Since there would be no
extensive volume of broken ice floating downstream and accumulating
against the unbroken ice cover, ice janming in the middle Sus i tna
River would usually not occur or would be substantially reduced in
severity. This would eliminate or substantially reduce river staging
and flooding normally associated with ice jams, thereby eliminating or
greatly reducing the overtopping of berms and the flooding of side
sloughs.
In the lower river below the Susitna/Chulitna confluence, breakup
would approximate natura1 conditions due to the substantial flow
contributions from major tributaries. Ice thicknesses in this reach,
however, may be somewhat thicke r than normal because of the higher
Susitna River winter flows from the project.
IV-69
Environmental Effects
Ice jams during breakup commonly cause rapid and pronounced increases
in local water surface elevations under natural conditions . The water
continues to rise until either the jam releases or the rising water
can spill out of the mainstem into adjacent side channels or sloughs.
This may cause sections of riverbank to be eroded. Ice scars have
been documented on trees in some localized areas as high as 15 feet
above the stream bank. The sediment transport associated with these
events can raise or lower the elevation of berms at the upstream end
of sloughs. Ice floes left stranded in channels and sloughs during
breakup can deposit a layer of silt as they melt.
Ice processes in the mainstem river are important in maintaining the
character of the slough habitat. Besides reworking substrates and
flushing debris and beaver dams from the sloughs that could otherwise
be potential barriers to upstream migrants, ice processes are also
considered important for maintaining the groundwater upwelling in the
side sloughs during winter months. This is critical in maintaining
the incubation of salmon eggs as described previously in the sediment
transport (Section IV-B). The increased stage associated with a
winter ice cover on the Susitna makes it possible for appro ximately
the same hydraulic head to exist between the mainstem and an adjacent
side slough during periods of low winter flow as that which exists
during norma 1 suiTJTier. The river stage observed during mid-winter
1981-82 associated with the ice cover formation on the Susitna River
appeared very similar to the water surface elevation associated with
summer discharges of 18,000 to 19,000 cfs (Trihey 1982). The alluvial
deposits that form gravel bars and islands between the mainstem river
and side sloughs are highly permeable, making it possible for water
from the river to flow downgradient through the alluvium and into the
sloughs. Thus the increased stage associated with an ice cover on the
river may provide an important driving mechanism for ma i ntaining the
upwelling in the side sloughs throughout the winter .
IV-70
Ice processes may also have negative impacts on fisheries habitat.
Ice scouring can remove redds. Mafnstem water entering the slough
near an ice jam can expose juvenile fish and incubating eggs to near
zero degree water, causing mortality. The removal of substrate by
anchor ice, scouring or flooding can greatly effect cover availability
for rearing fishes. Freezing processes, such as anchor ice, can also
encase many types of cover, making it useless to juvenile fish.
Benthic organisms and small fish can also be displaced by sudden
fluctuations i n flow caused by ice jams.
IV-71
V. INFLUENCE OF STREAMFLOW AND INSTREAM HYDRAULICS
ON MIDDLE RIVER HABITATS
Habitat Types and Categories
As used in this document, habitat type refers to portions of the
riverine environment having visually distinguishable morphologic,
hydrologic and hydraulic characteristics that are comparatively
similar. Habitat types used here are not defined by biological
criteria, rather, they are based on explicit hydraulic and turbidity
considerat i ons . Thus, both high and low value fish habitat may exist
within the same habitat type. The relative value of one fish habitat
type over another is derived from seasonal fish utilization and
densities within the middle Susitna River. Six major riverine habitat
types have been identified within the Talkeetna-to-Devil Canyon reach
of the Susitna River: mainstem, side channel, side slough, upland
slough, tributary, and tributary mout~.
The total surface area of each habitat type in the Talkeetna-to-Devil
Canyon reach has been estimated for mainstem discharges ranging from
9,000 to 23,000 cfs at Gold Creek (USGS gage 15292000) using digital
m~'asurements on 1 inch = 1,000 feet aerial photographs (Klinger and
Tri hey 1984).
Surface areas of clearwater habitat types, such as upland sloughs,
tributaries and tributary mouths, collectively represent approximately
one percent of the total wetted surface area within the middle Susitna
River (Klinger and Trihey 1984). The surface areas of these habitat
types exhibit little response to mainstem discharge (Figure V-1). At
times the surface areas may respond more to seasonal runoff and loca l
precipitation than to variations in mainstem discharge .
Comparatively large differences exist regarding the magnitude and rate
of response of mainstem, side channel, and side slough surface areas
to mainstem discharges . At 9,000 cfs, mainstem and side channel
V-1
2500
1500
1000
500
400
-300 en
Ql ... u ca 200 -ca
Ql ... <
Ql u 100 ftl -... ;::,
Cl)
iii
0
~ 50
40
30
20
10
MAINSTEM
10
5
TRIBUTARY MOUTH
UPLAND SLOUGH
0 .5
L--.L--'--'----"'--'--..I.---'--'--...L----Ji..---L.-...L--'--.....1 0 .1
9 10 11 12 13 14 15 16 17 18 1 s 20 21 2 2 23
Ma instem Di scharge at Gold Cr eek {x10~, c f s)
Figure Y-1 . Surface area responses to mainstem discharge
in the Talkeetna -to-Devil Canyon reach of the
Susitna River ( RM 101 to 149)
U_')
~
0
!:
0
lEi -N'
Ill
Q.
CJ)
c: ..
;' n
Ill
> ..
Ill
I» -:; .. -
surface areas are approximately 37 percent less than their combined
surface area at 23,000 cfs. However, side slough surface area is
nearly 200 percent greater at the lower discharge. As a result, the
total surface area of clearwater habitat types within the river
corridor represents 8.2 percent of the total wetted surface area at
9,000 cfs, whereas 1 ess than 2 percent of the tota 1 wetted surface
area consisted of clearwater habitat types at 23,000 cfs.
Subreaches of the middle Susitna River possess various amounts of each
habitat type. The diversity of habitat types within subreaches of the
middle Susitna River is directly related to mainstem discharge and the
complex channel morphology. The greatest diversity occurs from RM 113
to 138 in the Lane Creek-to-Gold Creek subreach (Klinger and Trihey
1984). This river segment has a stable multiple channel pattern an d
numerous partially vegetated gravel bars. The least diversity occurs
in the single channel segments between RM 103 and RM 109, and upstream
of RM 145. These subreaches consist almost entirely of mainstem
habitat regardless of discharge.
For some specific areas within the middle Susitna River corridor, such
as major side channels and tributary mouths, a designated habitat type
persists over a wide range of mainstem discharge even though its
surface area and habitat quality may change significantly. In other
instances, the classification of soecific areas may change from one
habitat type to another in response to mainstem discharge (Klinger and
Trihey 1984). Such an example is the transformation of some turbid
water side channels at 23,000 cfs to clear water side sloughs at lower
mainstem flows. An important characteristic of these sites, with
regard to their va 1 ue as fish habitat, appears to be the frequency,
duration, and time of year they exist as one habitat type or the other .
(ADF&G 1984d).
Closely related to habitat transformation is the concept of variable
boundary habitats (i .e. microhabitat location changes with discharge).
Within the middle Susitna River, rearing habitat is an example of a
variable boundary habitat, particularly in mainstem and side channel
V-3
areas where the combination of low-velocity flow and turbidity appear
to be the dominant microhabitat variables. As discharge changes, the
spatial distribution of turbid, low-velocity conditions suitable for
rearing fish also changes within the river corridor.
Rather than track the spatial movement of suitable variable boundary
habitats, the transformations and changes in habitat suitability were
monitored at specific areas of the river in response to incremental
changes in streamflow. This provides a systematic framework for
analyzing riverine habitat. A specific area is defined as any
location within the middle Susitna River corridor with a designated
perimeter that contains a portion of the non-mainstem surface area.
The total surface area of all specific areas equals the total non-
mainstem surface area. Specific areas are classified by habitat type
and their wetted surface areas measured on aerfa 1 photographs at
several mainstem discharges. Specific areas frequently contain
individual side channels, side sloughs, or upland sloughs. Occasion-
ally a large side channel or slough was subdivided into two or more
specific areas.
A significant amount of wetted surface area is expected to be trans-
formed from one habitat type to another as a result of project-induced
changes in streamflow (Klinger and Trihey 1984). The approach
described above was chosen as the basic framework for the extrapo-
lation methodology because it focuses on the dynamic change in _the
system and allows examination of the system as flows change from a
sunrner mainstem discharge of 23,000 cfs to a lower discharge level.
Habitat transformations are referenced from a mainstem discharge of
23,000 cfs at Gold Creek because 23,000 cfs is a typical mid-sunrner
discharge (APA 1983) and continuous overlapping aerial photography was
available.
Eleven habitat categories are used to describe the transformation of
specific areas from one habitat type to another as mainstem discharge
decreases below 23,000 cfs (Table V-1). Figure V-2 presents a flow
chart of the possible habitat transformations that may occur as
V-4
Table V-1. Description of Habitat Categories
Category 0 -Tributary mouth habitats which persist as tributary
mouth habitat at a mainstem discharge less than
23,000 cfs.
Category I -Side slough and upland slough habitats at 23,000 cfs
which persist as the same habitat type at lower
mainstem discharges
Category I I -Side channel habitats which transform to clearwater
habitat at a mainstem discharge less than 23,000 cfs,
and possess sufficient upwelling to maintain an open
lead throughout winter.
Category III -Side channel habitats which transform to clearwater
habitat at a mainstem discharge less than 23,000 cfs
but do not possess sufficient upwelling to maintain an
open lead throughout winter.
Category IV -Side channel areas which persist as side channel
habitat at a mainstem discharge less than 23,000 cfs.
Category V -Mainstem or side channel shoals which transform into
distinct side channels at a mainstem discharge less
than 23,000 cfs.
Category VI -Mainstem or side channel shoals which become
appreciably dewatered but persist as shoals at a
mainstem discharge less than 23,000 cfs .
Category VII -Mainstem or side channel shoals which transform to side
slough habitat at a mainstem discharge less than
23,000 cfs, and possess sufficient upwelling to
maintain an open lead throughout winter.
Category VIII -Mainstem or side channel shoals which transform to
clearwater habitat at a mainstem discharge less than
23,000 cfs but do not possess sufficient upwelling to
maintain an open lead throughout winter.
Category IX -Any water course which is wetted at 23,000 cfs but
becomes dewatered at a lower mainstem discharge.
Category X -Mainstem habitats which persist as mainstem habitat at
a mainstem discharge less than 23,000 cfs.
V-5
TOTAL WETTED
AREA @ 23,000 cfs
TURBID WATER 111'
23,000 cfs
'
DISTINCT CHAN·
NEL @ 23,000 cfs
CLEAR WATER @'
9,000 cfs
~
WITH APPARENT
THERMAL LEADS
~ ------:::~mE CHANNELS
::::::-TQ SLOUG~S ... ---... -
K
!---)
II
CLEAR WATER @
23,000 cfs
0
DISTINCT ®
9,000 cfs .--~ :-_-----~a:J..Ca.a...lll!!l ·-------v .------~~ftll~-------
SID_E_ Slo.UGHS: I
-l:JPLA~Q ~~G~~ -~~=:Jir~jj)=tJi>~:.::l
L...-.--------1 -----------------0------
TURBID WATER @ REMAIN INDISTINCT
.----------. / 9,000 cfs @ 9,000 cfs
INDISTINCT CHAN· V
NEL @ 23,000 cfs ............ ~---y---___,.JI ~ CLEAR WATER @ , WITH APPARENT
·-:-:-=-=~~~=-:-:-:-: :-:-:-:-p.nwN;;._-:-::: v 1 f
:..:_· ______ ----------------!
-..=:=:=-.. :-=:-::: -:--:::-::--: =-=---
.SHOALS TO _
-:-.-:-·SL.C?liG~S:-::--VI I
9,000 cfs . \ THERMAL LEADS
DEWATERED @ _._ 1 :::::::~::::=:1 WITHOUT APPARENT ~~=~-~~~~ViA~---1 V 111
...._ __ 9_,o_o_o _cf_s_--Jt---+ ~~=~~===~=:±! 1
X THERMAL LEADS t---.._:-:--··=::~~l.S::::-:-.
TURBID WATER @ ~~-:-:-:-:-:-:-:-:-:-_-:.-_-_-:-:-,
'----9_,o_oo_c_f_s _ __Jt--~, @~~~~~~~ T v
WITHOUT APPARENT
THERMAL LEADS
111
Figure Y-2 . Flowchart dlacribing poiaible habitat tranaformation that may occur with decrea••• in
mainstem dlacharge .
mainstem discharge decreases from 23,000 cfs to 9,000 cfs. Analysis
of any middle river flow of interest lower than 23,000 cfs for which
aerial photography exists can be substituted for the 9,000 cfs dis-
charge level in Figure V-2.
When the habitat transfonnations at all 167 of the specific areas
delineated in the middle Susitna River are sumnarized, a ready illus-
tration of overall riverine habitat behavior with decreasing mainstem
discharge is obtained (Table V-2). This analysis is directly ap-
plicable to the assessment of project effects on middle Susitna River
fisheries habitats.
Inspection of the relative numbers of specific areas in the various
categories at several mainstem reference flows reveals some inter-
esting trends (Figure V-3). With decreasing mainstem discharge, there
is a notable decrease in the number of side channel sites (Cate-
gory IV), and an increase .in side sloughs (Category II). There is
also an increase in dewatered areas (Category IX), which indic~tes the
loss of potential habitat for fish. The implications associated with
the decrease in side channel and the increase in side slough habitat
types to fish are less obvious. Although it is possible to generally
characterize some of the attributes of the specific areas that belong
in these categories, a more refined analysis of microhabitat variables
(e.g., depth, velocity, substrate, etc.) is necessary to fully assess
the capability of a riverine habitat to support fish.
V-7
Table V-2. Number of specific areas classified in each habitat
category for seven mainstem discharges.
Habitat
Mainstem Discharge at Gold Creek
Category 18000 16000 12500 10600 9000 7400
I 32 32 32 32 32 32
II 10 15 24 25 27 33
III 5 6 10 10 13 12
IV 52 47 36 35 28 23 v 4 ~ 7 9 11 10
VI 21 21 17 11 7 7
VII 2 2 3 5 5 4
VIII 2 2 3 4 6 5
IX 6 6 8 9 13 18
X 33 32 27 27 25 23
Total 167 167 167 167 167 167
V-8
5100
32
33
15
23
11
6
4
3
20
20
167
.. ..
I ..
l
I .. ..
••
0
.. ..
l ...
l
t -
ao
•o
0
.. ..
I ...
; .. I -
••
•
._. .. c.o.,..... •
10
j ...
l -J ao
• •
0 ·-·-·-·--,_ .... ·-·-·-·--,_ ....
,._ (Cf'S) ,._ (Cf'S)
-· .. c.o.....• ..
l ...
; -J 10
•o
0 ·-·-·-·--,_ .... ·-·-.. _ ·--,_ ....
,._ (Cf'l) ,._ (C~)
.......... .. .,.._..s
..
l ...
; -J ao
10
0 ·-·-·-·--,_ .... ·-·-·-·--,_ ....
,._ (Cf'SI ,._ (Cf'l)
Figure y-3 . Number of specific areas classified in each habitat category
for various Gold Creek moinstem discharges.
V-9
i
l
I
J
l
I
.. c:.o_... .. .,....... .
.. 10 .. I .. -l JO I • 10
10 10
0 0
~-~-1,_ ·--7-.... ·-·-··-·o--·-....
,_(CFS) "-(Cnl
10
.,....... 7
10
c .. ......,.
10 10 .. j .. -l -I • 20
tO 10
0 0 ·-·-··-·--·-.... ·-·-··-·--·-....
,_(crsl new (CFS)
Figure~-3 continued . Number of specific areas classified in each habitat
category for various Gold Creek mainstem discharges.
V-10
Passage
Fish passage is defined as the movement of fish from one location to
another. The ability to move freely into and out of habitats on a
seasonal basis is important in maintaining fish populations. For
anadromous species, adults move upstream into spawn i ng areas and
juveniles move from natal areas to rearing habitat and finally outmi-
grate to marine environments. Restriction of passage conditions can
inhibit or eliminate utilization of even high quality habitat. Three
levels of difficulty are defined for fish passage in the middle
Susitna River (ADF&G 1984e):
1. Successful Passage (unrestricted): Fish passage into and/or
within the spawning area is uninhibited, and would not
affect natural production in the area.
2. Successful Passage With Difficulty & Exposure : Fish passage
into and/or within the spawning area is accomplished, but
with stress and exposure to predation with the potential of
reducing the level of successful spawning in the area. This
condition over a long period of time may result in a decline
in natural production in the area.
3. Unsuccessful Passage: Fish passage into and/or within the
spawning area may be accomplished by a limited number of
fish; however, exposure to excessive stress and increased
predation (which are associated with these conditions) may
eventually eliminate or greatly reduce the nc>tura 1 produc-
tion in the area.
These three levels define the relative level of difficulty that most
fish of the same species/life stage have with passage even though
certain individuals may have a greater or lesser degree of success
than the majority of fish (ADF&G 1984e).
V-11
Passage reaches (PR) are sub-sections of stream channel with hydraulic
or morphologic characteristics that impede the movement of fish. The
length of a passage reach is based on the length of stream channel
having such characteristics (Figure V-4); the nonuniformity of natural
stream beds necessitates some averaging of characteristics when
evaluating the reach length.
Physical parameters that cause passage restrictions include shallow
depth of flow, high flow velocity, and barriers such as debris or
beaver dams. Passage criteria for chum sa 1 mon, based on flow depth
and flow velocity, have been developed (AOF&G 1984e, Thompson 1972).
If the reach over which these parameters are limiting is long, passage
would be more difficult, since the swimming speed of salmon and their
ability t o navigate through shallow depths decreases with increasing
reach length (Bell 1973). limited resting areas in a passage reach
also makes passage more difficult.
Affected life Stages. Although the adult and juvenile migration .and
rearing 1 ife stages of the anadromous and resident species in the
middle Susitna River involve movement from one location to another and
thus are potentially affected by passage, adult chum salmon migration
is the species/life stage with the greatest potential to be affected
by passage restrictions. Adult chum salmon show less ability than
other salmonid species to surmount obstacles (Bell 1973, Scott and
Crossman 1973). Adult chinook salmon also have potential for being
affected by passage restricti ons due to their large size. Depth
criteria for chinook salmon is greater than for other salmon species
(Thompson 1972). Adult coho, sockeye, and pink salmon could be
affected by passage restrictions if the conditions were difficult or
unsuccessful for chum or chinook; thus, the analysis of passage
conditions for chum or chinook salmon is conservatively taken as being
representative of coho, sockeye, and pink salmon. Resident adult
trout and other resident species typically have shallower minimum
depth criteria for passage than salmon and thus would not be
restricted by depth as often as salmon would be, but the maximum
V-12
V-13
-. • -I
i • • • • c -·o a
. ..
• 0
0 • • 0
Q.
.
c
0 --0 ..
:1
0 ·-... c
0
Cl
velocity criteria for trout is lower than that for salmon (Thompson
1972).
Parameters affecting passage of resident and juvenile anadromous
species into, out of, and within their rearing habitats include
shallow flow depth and high velocities. The most restrictive con-
ditions for juvenile passage would be entrapment, where pools contain-
ing juveniles become isolated when surface flows reduce to zero. High
velocities (>2.0 fps) in channels with few interstitial spaces between
streambed particles, or with few cobbles and boulders to provide low
velocity resting areas, would also be difficult passage reaches for
juveniles.
Passage of outmigrating smolts would have similar criteria to those of
juveniles. Entrapment would be most critical, as their downstream
direction of migration reduces. the importance of velocity as a passage
criteria parameter.
Mainstem Habitats. The p_arameter with the greatest potential to
restrict passage within mainstem habitats is velocity. The mainstem
is used as a migration corridor by adult, juvenile, and smolt sal-
monids. Mean channel velocities ranging from 5 to 9 fps are commonly
associated with typical midsummer flows (R&M Consultants 1982b).
Shoreline velocities and velocities near the channel bottom are
generally . well below the maximum velocity criteria developed by
Thompson (1972) of 8 fps for adult salmon, but occasionally very near
the maximum velocity criteria of 4 fps for trout. An analysis of the
timing of adult salmon migration indicates that discharges at Gold
Creek ranging from 12,000 to 60,800 cfs did not appear to affect adult
salmon migration to sloughs and side channel entrances • However,
adult milling activity appeared to increase with increased discharges
(ADF&G 1984e). Water depth is sufficient for successful passage at
mainstem discharges within the natural range; barriers such as debris
dams do not exist in the mainstem of the middle Susitna River.
V-14
Side Channel Habitats. Side channel habitats may be used for
migration by adult and juvenile salmonids. Some side channels are
used by ch!fm and sockeye salmon for spawning. Passage conditions in
side channel habitats are similar to those of mainstem habitats during
111.1ch of the open water season. During breaching, ve 1 oci ty is the
parameter with the greatest potential for affecting fish passage as
depth would be sufficient for successful passage.
At lower mainstem discharges, the dept~ a~ the head of side channels
becomes the most significant parameter affecting passage. As the
water surface elevation in the mainstem decreases to a level below
that required for breaching, the head of the side channel becomes
exposed, preventing passage through that reach and potentially trap-
ping fish in downstream pools. Many side channels receive inflow frorn
• groundwater or tributary sources along their length . As flow accumu-
lates along the slough, passage is first provided for juveniles and
outmigrating smolts due to ·their shallow minimum depth requirements .
If sufficient flow accumulates, adult passage could become successful..
Backwater from the mainstem may be sufficient to provide for success··
ful passage through lower passage reaches in a side channel.
Side Slough Habitats. Side sloughs are utilized by chum and sockeye
salmon for spawning. Thus, successful spawning in sloughs relies on
successful passage into and within the sloughs. Successful spawning
would lead to the need for successful passage conditions for outmi-· .
grating smolts. Juvenile salmon and resident fish also use sloughs
for rearing.
Side slough habitats have similar passage characteristics to side
channel habitats except breaching is less frequent. Thus, the depth
restrictions described for unbreached side channel sites would apply
to side slough habitats more frequently during the spawning seaso,,
Passage into and within side slough sites is provided by breaching,
backwater, or local flow conditions. Even in side slough sites ,
breaching is relatively frequent during . the spawning season under
V-15
natura 1 flow regimes. Backwater pro vi des for passage through the
first and sometimes second passage reaches upstream of the slough
mouth during much of the spawning season. Slough flow, when increased
by rainstonn runoff from the local area, may provide for passage of
adults through some reaches upstream of backwater effects.
Upland Slough Habitats. As with side sloughs, upland sloughs are
utilized by adult salmon for iiiiTiigration and spawning and juvenile
salmon for rearing, and salmon smolts for outmigration. Passage into,
within, or out of upland sloughs relies primarily on backwater and
local flow, since breaching is an infrequent event.
Tributary Habitats. Tributary habitats are utilized primarily by
adult chinook, coho, and chum salmon for spawning, coho juvenile for
rearing, <.nd chinook, coho, and chum salmon for smolt outmigration.
Passage into or out of tributary habitats could be affected by reduced
mainstem flows of the pr~ject. Studies have indicated that most
tributaries wi 11 adjust to the new mainstem elevations through a
degradation process (R&M 1982c, Trihey 1983).
Passaqe and Habitat Availability
The relationship between habitat availability and passage conditions
under natural conditions is assessed by identifying how often the
depth required for passage is available. As introduced earlier, the
depth at passage reaches in a slough or side channel is a function of
the cumulative effect of backwater, breaching, and local flow in the
channel.
Analysis of escapement timing to sloughs and flow history during the
1981-1983 spawning season provides the infonnation necessary to
delineate the period in which combinations of backwater, breaching,
and local flow are most important for passage.
Escapement Timing. Selection of the period from August 12 through
September 8 for chum salmon passage into and within sloughs and side
V-16
channels of the middle Susitna River is based on chum migration timing
in the mainstem at Curry Station (RM 120) and the dates of first and
peak counts in six sloughs that contain the majority of slough-
spawning chum salmon in the middle Susitna River. These sloughs (SA,
9, 9A, 11, 20 and 21) are located between RM 125 and 142.
The peak of the chum salmon run passes Curry Station during the first
two weeks of August (ADF&G 19S1, 19S2a, 19S4a). Since the average
migration speed of chum salmon ranges between 4.5 miles per day (mpd)
and 7.7 mpd (ADF&G 19S1, 19S2a, 19S4a}, most chum salmon would be
expected to cover the 5 to 22 miles from Curry Station to the si x
sloughs mentioned in one to five days. Therefore, chum salmon are
expected to be abundant in the six sloughs during the first three
weeks of August.
The dates that chum salmon were first observed in Sloughs SA, 9, 9A,
11, 20 and 21 have ranged from August 4 to September 11, while the
dates of peak counts at these six sloughs have ranged from August 1S
to September 20 (ADF&G 19S1, 19S2a, 19S4a). Thus the period of
August 12 through September S covers the majority of first obser-
vations of chum salmon in sloughs and most of the period of p~!ak
counts.
The slough utilization by chum salmon is one to two weeks later than
the predicted · dates based on migration timing in the mainstem .
Factors that may expla i n this difference, either singly or together ,
are: (1) stock diff~rences; (2) milling behavior ; (3) slough observa-
tion conditions; and (4) passage conditions.
Stock Differences. The dates of first and peak counts in tributaries
are one to two weeks earlier than in sloughs (ADF&G 19S1, 19S2a,
19S4a). Hence, the first part of the run passing Curry Station may be
a separate stock destined primarily fo r tributaries.
Milling Behavior. Fish may mill in the mainstem near the mouths of
slcughs before entering the sloughs to spawn.
V-17
Slough Observation Conditions. When sloughs are overtopped by turbid,
high velocity mainstem water, observation conditions deteriorate .
Poor observation conditions may result in fish utilization remaining
undetected until the slough water clears.
Passage Conditions. Passage conditions, which are influenced by
breaching, backwater, and local flow (ADF&G 1984e), may delay p~ssage
of chum salmon into and within sloughs in some years. For example, in
1982, mainstem discharge at Gold Creek was below 20,000 cfs from early
August to mid-September, which reduced backwater and breaching influ-
ences and may have restricted chum passage into sloughs. A rainstorm
event from August 29 to September 3 increased local flows, which
appeared to provide successful passage conditions at most sites. All
sloughs (9, 9A, 11, 20 and 21) except Slough 8A contained peak numbers
of chum salmon between August 30 and September 6 (ADF&G 1982a).
Frequency of Passage
Passage conditions can be further evaluated by establishing how often
the depth required for passage occurs under natura 1 or proposed
project flows and what condition (breaching, backwater, or local flow)
is responsible for passage. For example, the specified depth for
successful passage at a passage reach located near the mouth of a
slough may be equalled or exceeded ao percent of the time due to
backwater only, 20 percent of the time due to breaching only, and 40
percent of the time if the average groundwater flow was supplemented
by surface inflow. Since backwater, breaching, and groundwater
upwelling are functions of mainstem discharge, the frequency of a
certain depth being equalled or exceeded is obtained from a flow
frequency analysis for the period of interest. Analysis of the
contribution of local flow (surface flow and groundwater upwelling) to
passage conditions will be completed as 1984 field data become avail-
able.
Breaching flows occur relatively frequently at side sloughs and side
channels under natural conditions. The frequency of overtopping was
V-18
evaluated at selected sloughs and side channels (Table V-3}. This
table presents the number of years each site was breached at least one
day during the evaluation period of 12 August - 8 September. The
frequency of years that individual sloughs and side channels breach
varies according to their breaching flow. For example, the frequency
of years for breaching flows at Slough 21 (25,000 cfs}, Slough 9
(19,000 cfs), and the lower portion of Side Channel 21 (12,000 cfs),
are 49, 89, and 97 percent. Although the number of years in which at
least one breaching event occurred was similar for Slough 9 and Side
Channel 21, the average number of breached days per year for Slough 9
(13 .9) was about half that of Side Channel 21 (24 .3). Associated with
the decrease in frequency of years at Slough 21 is a decrease in the
average number ·of days breached (8.3}. The importance of multiple
event breaching flows for passage at a site depends on their timing
within the spawning season. Several closely clustered events may be
less beneficial to passage than a few well spaced overtoppings.
Figure V-5 presents a frequency analysis of the percent of years that
a flow is equalled or exceeded at least once during the period 12
August to 8 September. The 50 percent occurrence flow is approxi-
mately 22,500 cfs. From this analysis, it can be concluded that
channels with breaching flows below 22,500 cfs will be breached, on
the average, once every two years.
The backwater associated with mainstem discharge under natural con-
ditions provides passage through passage reaches in the mouths of some
sloughs. In Slough SA, for example, a mainstem discharge of
10,600 cfs is required to produce the backwater required for success-
ful passage at PRI. This discharge occurred in 97 percent of the last
35 years. At PRII a mainstem discharge of 15,600 is needed, which
also occurred 97 percent of the time (Figure V-6). During the August
12 -September 8 period, naturally occurring flows provided passage at
PRI for an average of 25.6 days and at PRII an average of 18.5 days
out of a possible 26 days.
Under anticipated project flows, the frequency of occurrence of the
mainstem flows required to breach sites or cause the backwater effects
V-19
Table V-3 . Frequency of breaching flows at selected sloughs and side
channels under natural conditions for period of 12 August
to 8 Septeni>er.
Controlling Years
Discharge Frequency Occurred
Site (cfs) (%) (out of 35)
Slough SA 27,000 34 12
33,000 14 5
Slough 9 19,000 8 31
Slough 11 42,000 14 5
Upper Side
Channel 11 16,000 97 34
Side
Channel 21 12,000 97 34
Slough 21 25,000 49 17
V-20
-0 u. 80,000 0 -~ w w a:
0 60,000 0
...J
0
(!)
t-< <: w 40,000 I
N (!) ....... a: < z
0
0
0 20,000
~ w
t-
0 z -< 0 ~
NUMBER OF YEARS
5 10 15 20 25 30 35
0 25 50 75 100
PERCENTAGE OF TOTAL YEARS
Figure Y-!5. Breaching flow occurrence during 12 Augulf to 8 September
baaed on Suaitna River Diacharge Period 19!50-1984.
--560 I ---z
0 .. i= "c ,)> ,)..,
..J
.., 855
Water Surface at
15,600 CFS---~~~ ..... ------...,
10,600 CFS-.;_-+•+-------~
Mouth
of
Slough
ADFSG
Goge
1253W5
~--FLOW
-5+00 0+00 5+00 10+00
STREAMBED STATION (feet)
Figure ]l-6 Thalweg profile of Slough 8A .
BEAVER DAM
1~+00 20+00 251"00
necessary for passage will in general be significantly reduced during
the spawning season . The importance of local flow in compensating for
some of these reductions in passage conditions will be described in
the final draft of this report.
V-23
Microhabitat Response to Instream Hydraulics
Depth and velocity of flow respond to variations in streamflow,
affecting the availability and quality of fish habitat. The effect of
streamflow variations on the availability of spawning and rearing
habitat has been modeled at several side slough and side channel study
sites (AOF&G 1984c; 1984d). This modeling process used computer
software developed by the USFWS Instream Flow and Aquatic Systems
Group (Bovee and Milhous 1978, Bovee 1982, Milhous et al. 1984).
Spatial distribution of depths and velocities within a study site were
simulated at several different site-specific flows using the IFG-4 and
IFG-2 hydraulic models. Using the simulated depths and velocities in
combination with numeric descriptors for other microhabitat variables
(upwelling, cover, and substrate), physical habitat at the study site
ca n be described as a function of streamflow. The numeric description
of upwelling, depth, velocity, substrate and cover available to fish
at various flow levels are then compared to weighting factors repre-
senting their suitability to fish. These weighting factors are
obtained from habitat suitability criteria for each species and life
stage being evaluated. An index of habitat availability called
Weighted Usable Area (WUA) is calculated by this modeling process.
Because several of the microhabitat variables used respond to stream-
flow variations, weighted usable area can be considered a streamflow
dependent habitat availability index.
Spawning Salmon
Microhabitat Preferences. . The influence streamflow variations may
~ave on spawning habitat is generally evaluated using three micro-
habitat variables: depth, velocity and substrate (Bovee 1982, Wesche
and Richard 1980). However, a fourth variable, upwelling, is also
considered important for successful chum and sockeye salmon spawning
in the middle Susitna River habitats (ADF&G 1984d). Upwelling has
also been identified as an important habitat component for spawning
V-24
chum salmon at other locations in Alaska (Kogl 1965, Koski 1975,
Wilson et al. 1981, Hale 1981).
Of the four microhabitat variabl es used in the modeling processes,
upwelling appears to be the most important variable influencing the
selection of redd sites by spawning chum and sockeye salmon . Spawning
is commonly observed at upwelling sites in side slough and side
channel areas possessing a relatively broad range of ~epths, veloc-
ities and substrate sizes. Other portions of these same habitats
possessing similar depth, velocities, and substrate sizes but without
upwelling are apparently not used by spawning chum and sockeye salmon
(ADF&G 1984d). Because of this strong preference evident from field
observations, a binary criterion was used for this microhabitat
variable. The habitat suitability criterion for upwelling assumes
optima 1 suitabi 1 ity for areas with upwelling and non-suitability for
areas without upwelling .
In regard to its overall influence on the quality of spawning habitat,
substrate could rank second to upwelling in importance. However, the
substrate criteria developed by ADF&G for chum and sockeye salmon
spawning in side slough and side channel habitats assign optimal
suitability to streambed material sizes from one to nine inches
(Figure V-7, Part A). This range includes much larger particle sizes
than are commonly cited in the literature as being suitable for
spawning chum and sockeye salmon. literature values typically range
from coarse sands to five-inch material, with 1/4 to three inches
being the most suitable size range (Hale 1981).
This discrepancy between the ADF&G criteria and the 1 iterature is
probably related to the dominant influence upwelling has on the
se 1 ect ion of redd sites. Apparently, such a small amount of good
quality spawning substrate exists in middle Susitna River habitats
that both chum and sockeye salmon use whatever streambed material
sizes are associated with the upwellings . Another consideration is
that salmon recorded as spawning in large substrate sizes (>6 inches)
V-25
X w
0 z A. >-
1-
.J
CD
<t
1-
::>
(/)
B.
c.
.4
.3
.2
.I
I 2
Sl
1.0
.9
.8
X .7 IJJ
0 z .6
>-1-.5 :::i
ii5 .4 <t·
1-
::> .3
(/)
.2
.I
0
0
1.0
I
.9 9
I .8 I
X .7 I w I 0
~ .6 I
I ,_ I ~ .5 I .J
ii5 .4 I
<t I t: .3 I ::> l (1).
.2· 1 .I
0
0
4
\
\
\
\
5 6 7 B 9 10 II 12 13
SG LG AU CO 80
SUBSTRATE CODE
SOCKEYE
SU ITASI LITY CRITERIA
\ ~
SUITAIII.ITY
n:g'x
\
\
\'
~
0 .0 1.0
1.0 t.O
2 .0 0 .5
).0 0 .1
c.s o .o
o---<l SOCK EYE
SUITA~ILITY CRITERIA
SOCKlT[ CHUM SUISTIIAT[
CODE
I'AIITICI.[ IUITAIII.ITY fUITAII LITY
__!!!!_ IHDU
I .. $11.T 0.000 z 0 .000
) S& SAND 0 .000
4 0 .100
5 SG VI· t" 0 .500
6 0 .1~0
' I.G l·l" 1.000 • 1.000
' IIU ).,-1.000
10 o .,oo
II
t2
13
co s.oo" 0 .250
1 0 >to"
0 .100
0 .000
~SOCKEYE
CHUM
SUITABILITY CRITERIA
~
o .o
I .S z.e
4 .5
SUITAIII.ITY
tHOU
1.0
t .O
o.z
o .o
---1 CHJ,IM
IHO(I
0 .\100
0 .000
0.025
0 .050
0 .200
o .,oo
1.000
1.000
1.000
0.150
0 .700
0 .2 50
o .ooo
~CHUM
1.0 2.0 3.0 4.0 5 .0
VELOCITY (FT/SEC )
SOCKEYE CHUM
SUITABILIT Y CRITERI:O SUITABILITY CRITERIA
SUITAIILIT'I' SUITAIII.ITY &!!!. lrlt)[X D[I'TM I NQI'I
o .oo o .o 0 .00 o .o
o .zo o .o o .zo o .o
o.so o .z o.so o .z
0 .50 o ., 0 .10 1.0
0 .75 1.0 1 .00 1.0
1 .00 1.0
0.-~ SOCKEYE -CHUM
1.0 2 .0 3 .0 4 .0 5 .0 6 .0 7.0 8 .0
DEPTH (FT)
Figurei-7. Habitat
chum and
auitability criteria for slough apawning
aoc keye aalmon. (ADFSG, 1984d)
V-26
may actually have been excavating their redds in smai •~r streambed
particles surrounding the cobbles and boulders.
In comparison to streambed particle sizes identified in the literature
as spawning substrate, the overall quality of substrate in side slough
and side channel habitats for spawning salmon is low. The predominant
substrate type in side sloughs consists of sands and silts in low
velocity areas or large gravels and small cobbles intermixed with
large cobbles and small boulders in free flowing reaches (ADF&G
1982b). Substrate composition is often similar within and between
side slough spawning areas (ADF&G 1982b, 1984d) and spawning salmon
use a broad range of particle sizes in middle river habitats (ADF&G
1984d). Be c ause of the broad range of particle sizes utilized by
slough spawnel"s, naturally occurring substrate composition does not
appear to have as much influence on the selection of redd sites by
chum and sockeye salmon as other microhabitat variables. The limited
influence of one to nine ·inc h streambed material size on slough-
spawning chum and sockeye salmon is evident in the broad range of
particle sizes identified in Figure V-7a as being optimal by ADF&G.
Velocity is often considered one of the most important microhabitat
variables affecting spawning salmon (Thompson 1974, Wilson et al.
1980, Bjornn et al. 1981). The habitat suitability criteria developed
by ADF&G for both spawning chum and sockeye salmon assigns optimal
suitabilities to velocities less than 1.3 fps (Refer Figure V-7,
Part B). As the mean column velocity at the spawning site increases
above 1.0 fps, suitability declines more rapidly for sockeye than for
chum. Microhabitat areas with mean column velocities e xceeding
4.5 fps are considered unusable by both species.
The ADF&G criteria assign slightly lower suitabilities to velocities
between 2 and 3 fps than criteria available in the literature (Bovee
1978, Wilson et al. 1981, Estes et al. 1980, Hale 1981). This dis-
crepancy may exist because most data used to develop velocity suit-
ability criteria for spawning and sockeye salmon in the middle Susitna
River were collected in side slough habitats that typically have a
V-27
narrow range of low velocities. Habitat suitability criteria devel-
oped by other investigators in Alaska were based on data principally
collected in higher velocity habitats of other river systems. For
this evaluation, the velocity suitability criteria developed by ADF&G
for spawning chum and sockeye spawners are considered most applicable
to sites possessing slough-like velocities. Again, for the present
evaluation velocity criteria from the 1 iterature are considered more
appi icable to evaluating microhabitat preferences of spawning chum
salmon in the mainstem and side cl ;annels with higher velocities of the
middle Susitna River.
Habitat suitability criteria for depth indicate that depths in excess
of 0.8 feet provide optimal spawning depths for chum and sockeye
salmon (Figure V-7, Part C). This depth is slightly more conservative
but consistent with the 0.6 foot depths used elsewhere (Smith 1973,
Thompson 1972). Microhabitat areas with depths less than 0.8 feet
provide suboptimal spawning. and depths of 0.2 feet or les s are un-
usable . These minimum depth criteria are consistent with values
presented by others as minimum depth requirements for spawning chum
salmon (Kogl 1965, Wilson et al. 1981).
Habitat Availability. WUA indices (habitat response curves) have been
developed by ADF&G for spawning chum and sockeye salmon at seven side
slough and side channel locations. Both chum and sockeye salmon have
been observed spawning within four of these study sites or in the i r
immediate vicinity (ADF&G 1984a,d). Although minor differences occur
at each of these four study sites between the habitat response curves
for spawning chum and sockeye salmon, the curves for the two species
are similar (Figure V-8). The minor dif ~erences that exist between
the habitat response curves for these two species are attributable to
differences between depth and velocity suitability criteria. A
slightly higher suitability is assigned to depths between 0.2 and
0.8 feet for sockeye whereas a slightly higher suitability is assigned
to velocities in excess of 1 fps for chum salmon.
V-28
f
~-
if
~!
j
< I
N
\0
.. ...
~--· i' ~1
~
SLOUCH lA n S tOE C UAPJN C&. '. ~"
l £ ~ ..
u 22
20 20
II f 11 ..
14
12
10
•
~ II
ij ,.
ll
~:;, 10 ~ • Ill
I I
• •
2
0
0 20 40 10 110
0
0 Ol
0
Sift rLOW (CrS)
C MU >.t • SOCt<C'I'£
SLOUIOH 2 1 L0~1 CR SlOt , ... _..,,(•. II a 26
2.l H ·
2l 22 .
20 20
II f .. .. :~ ,.
12
10 -----------. •
I
0 II Ill--y 14 ~;
~·! u
Ut-10 .. -~
::J • Ill
I ---·--. ~
2
0 0 ·
0 10 0 200 .soo 400 0 o.• 0 .1 1.2 1.1 2 2 .•
~
sore now (crs)
':~4 U\t • SOCMCY[ 0
jft\ow e e,oa~ s1 c r,ow (C )
CHU.. • $ :.t<cvt
Figure ll-8. Comparieon of WUA reepon••• to eite flow for epawning chum and
eockeye ealmon at four middle Sueitna River ltud' eitee. ( Adapted
from ADF&G 1984 d).
Except for a few isolated observations , all sockeye salmon spawning in
the middle Susitna River has occurred in side sloughs that are also
utilized by chum salmon. The timing and spawning habitat requirements
of sockeye salmon are similar to chum salmon (AOF&G 1984d), and chum
salmon are both more numerous and widespread than sockeye in middle
Susitna River spawning habitats . Thus the analysis will focus on the
response of chum salmon spawning habitats, and will use those WUA
indices to estimate the response of sockeye salmon spawning habitats .
Response curves for tota 1 surface area and weighted usab 1 e area for
spawning chum salmon are presented by habitat category in Figure V-9.
Habitat Category I contains those areas that exist as clearwater side
slough habitats at mainstem discharges of 23,000 cfs and less. Cate-
gory II sites convey turbid mainstem water at 23,000 cfs but become
clearwater side slough habitats at a lower discharge . Habitat Cate-
gory III refers to side channels that continue to carry turbid water.
Of most interest in Figure V-9 is the relatively low WUA indices
forecast at all sites in comparison to total surface area . The
magnitude of this difference underscores the inappropriateness of
using wetted surface area as a measure of spawning habitat.
The other notable feature in these graphs for Category I and II is the
location of optimal WUA values. The highest value occurs at a rela-
tively high discharge after the slough is overtopped by mainstem
flows . The habitat response curves for these two categories generally
increase rapidly as the channe 1 is overtopped and then 1 eve 1 s off,
either slightly increasing or decreasing with additional increases in
di scharge. For Habitat Category III sites, the WUA does not respond
as markedly to flow increase at the site over the range of mainstem
discharges analyzed. Weighted useable area values remain low . and
relatively constant as flow changes. A comparison of the WUA function
relative to total surface area indicates the small amount of spawning
habitat currently available in category III sites. The magnitude of
the WUA function is controlled by such f i xed boundary microhabitat
variables as upwelling and substrate, while the slope of the WUA curve
reflects the influence of depth and velocity.
V-30
•!!
10
7 0
E' 10
h
il JO
~ 40
I JO :·
2.0
10
0
ISO
1.0
llO
120
E' 110
100
~ eo -, 1 0
iJ 70
~::. 10
I so
40
l O
2 0
10
0
~20
~00
210
210
2 AO
E' uo
1..,.200 i} ::
gt lAO I 120
100
10
10
AO
20
0
HABIT AT CAT EGORY I
S LOL:G H SA SLO U GH 21
CHUW SAUolc.HSI'-CHUW-HSP-100 -10
.0
E' 70
!.::-10
iJ eo r .0
~0
2 0
10
0 20 40 10 100 200 ~ 400
SlfC r\.O'ft (C.rs) SITE n.ow (crs)
HABIT AT CATEGORY II
S LOUGH 9
CHUW~SP..-c:
. U PP ER S IDE CHANNEL 1 1
~-NSI'A-
120
110
100
10
E' 10
!.::-70 !I 10
~ so
I •o
~
20 .,.. 1110 D I I I D a a o 10
0
~a-0 a a a ~ a a a • a ...... ~ 0
0 200 •oo 1 00 0 40 DO 120 110 200
IlK n.-(CI'S) SIK n.-(C~)
HABIT AT CATEGORY Ill
LOWER SID E CHANNEL ·1 1 SIDE CHA ~NEL 21
CHUW~P....-c
210
240
uo
200
E'. 110
~ 110
iJ :: r·:
10
AO
20
0
0 o.• 0. ~ .o.• 1.1
Figure ll-9. Total surface area and WUA i ndex for spawn i ng ch um salm on
at Habitat Cate9')ry I , I I 1 and Ill study sites . (Adapt ed f rom
ADF8 G 1984 d ) .
V-31
The maximum amount of spawning habitat potentially available at an}
site under natural conditions is determined by the total surface area
of the upwelling. To demonstrate this point, the total surf ace area
of upwellings at the Side Slough 21 and Upper Side Channel 11 study
sites were increased by 16 and 53 percent respectively and WUA r~cal
culated (Figure V-10). By arbitrarily increasing the total surface
area of groundwater upwelling at these sites, WUA forecasts increased
at both sites without a notable change occurring in the shape of the
habitat response curve for either site. This demonstrates that a
general increase or decrease in the amount of upwelling will affect
the total amount of spawning habitat available over a relatively broad
range of site flows. As will be demonstrated in a later example for
rearing fish, substrate quality has a sim1lar effect on the amount of
habitat potentially available. Variable boundary microhabitat con-
ditions important to spawning salmon (depth and velocity) principally
determine the accessibility and quality of the fixed boundary con-
ditions (upwelling and substrate) as spawning habitats.
The habitat response curve for Slough 21 peaks when the mainstem
discharge is approximately 28,500 cfs, while the response curve for
Upper Side Channel 11 peaks when the mainstem discharge is near
23,000 cfs (Figure V-11). At these discharge levels, the alluvial
berm at the upstream end of each site is overtopped and the site-
specific flows are approximately 70 cfs in Slough 21 and 150 cfs in
Upper Side Channel 11 (AOF&G 1984d). Base flow at both sites is
approximately 5 cfs whenever the mainstem discharge is less than that
required to overtop their upstream berms (AOF&G 1984d). The depth of
flow over upwelling areas forecast by hydraulic models of these sites
indicate that depths typically range 1 ess than 0. 5 feet at base flow
but increase to 1. 0 feet or greater when overtopped, covering more
upwelling areas with adequate water depth (Figure V-12). Velocities
respond similarly to overtopping, typically increasing from the 0 to
0.5 fps range to approximately 1.5 fps (Figure V-13).
Depths and velocities associated with baseflow and controlled flow
conditions were compared to habitat suitability criteria presented
V-32
< I w w
-• • .. -
~
~ •
-• • .. -c
!) •
22,000
20,000
18,000
16,000
14,000
12,000
10.000
epoo
spoo
4/)00
2ptJO
0
22,000
20,000
4,000
2,000
0
SLOUGH 21 LEI END
---lncreoud Upwell ing
---ADFSG WUA ,----~ ----~ ............ ___ --v -----:::::-::-:::--------~ -----------------
!50 100 I !SO 200 2!50 300 3!50 400
l i TE FLOW ( CFS)
UPPER SIDE CHANNEL II
/
'/
/
/
,, -------------~~-----,. --
0~----~----~----~----~----~----~----~----~----~--~
0 50 7!5 100 12 !5 1!50 17!5 200 22!5 2!50
SITE FLOW ( C FS)
Figure I-10. Simulated influence of increaaed upwelling on WUA for spawning chum
ealmon at Slough 21 and Upper Side Channel II.
S L OUGH 21
IOO,--------------C~M~U~~~~~M~O~N~~~AW~N~I~NO~----------~
c
!1 0
eo
:: l'
so
I
4 0 -
30-
:z o J
10 ------------~ 0 +---------r---~--~----~--~----r---~
0 10 :zo 30
(Thouaoncte)
..WNSTE·A DISCMAACE (Cf"S)
NUA (STD-COM!I.·t£0) o GROSS SUR,.AC[ MEA
UPP£R SIDE CHANNEL 11
C>iUM SALMON SPAWNINC
1~~.,-------------------------------------------~
/
I
/ --
10
S I DE CHANNEL 21
:Z&O ~-------------C~M~U~M~SALN~~O~N~$-PA_w_N_IN_G~------------,
240
:z:zo
:zoo
110
1&0
1 40
120
100
10
&0
40
:zo
o+---~--~~~--~w.~~~~~--~
0 10 :zo 30
CThou1onda)
MAINSTEI.t DISCMARCE (CrS)
40
SLOU GH 21
26 "T""--------CMUt.t ~ON SPAWNING
24
22
20
11
I&
14
12
10
I
I
A I \ ____________ _}
:z
0~--~----~--~----~--~----~--~--~
0 10
0
20
l'ntoueonele)
MAINSTt:LI DISCMAACE (Cf"S)
WUA (STD-COM81NEO)
30
UPPER SIDE CHANNEL 11
:ZI,--------------C~M~U~M~S~~M~ON~S~~=AM~<IN=G~------------,
:Z4
:z:z
20
1111 IG , ..
12 i
10 ~
e
•
2
o+---~~--r---~--~----~--~----~--~
0 10 20
(iho..,scn-=a) t..U.!t<ST[~I DISCHA.~C!: (CF"S)
30
S IDE C HANN EL 21
C ... UM SAU.OO« SPAWNING 2&~------------~--~~~~--~~------------,
24
1 4 ~
i
I :Z l
10:
·~ s-
4-
2 ..:
o+---~----r----r--~----~---r--~~~
0 20 30
(Tho t.~aorusa )
MAINSTEI.t OISCMARCE (CF"S)
10
Figure y-11. Surface area and
Habitat Category
WUA respcnses to moinstem discharge
I , II, and Ill spawning sites. (Adapted from
ADF8 G 1984 c).
< I
w
U1
>-u z
20 FLOW • 50 CFS
~ 10 SUBOPTIMAL
0
1&1 a:
OPTIMAL RANGE
I&.
>-u z
.1&1
20
::) 10 0
1&1 a:
I&.
0 0.5
FLOW • 5 CFS
SUBOPTIMAL
1.0 1.5 . 2 .0 2 .5 3 .0 3 .5
DEPTH DISTRIBUTION
OPTIMAL RANGE
o~~~~~~~~~r-r-~~-r~~~~~~~~~~~~~--~--~
o 0.5 1.0 1.5 2 .0 2 .5 3 .0 3 .5
DEPTH DISTRIBUTION
Figure ll:-12. Frequency distribution of cell depth over upwelling areas in
Upper Side Channel II at aile flows of 5 and 50 cfa.
>
(.) z
U.l
:3
0
U.l a::
LL.
t4----------OPT I MAL RANGE ---------.. •+14----SUBOPTIMAL----t .. .,..l
10 FLOW• 50CFS
o .o 0.1 0 .2 o .3 0 .4 o .e o .8 0.1 o .8 o .9 1.0 1.1 1.2 1.3 1.4 1.e 1.8 1.1 1.8
VELOCITY DISTRIBUTION (CFS)
t4----------OPTIMAL RAN8E---------...., .. ~~4--sUBOPTIMAL ~I
FLOW= e cFs
o .o 0.1 0 .2 o .3 o .4 o .e o.8 o.1 o .8 o .9 1.0 1.1 1.2 1.3 1.4 1.e 1.8 1.1 1.8
VELOCITY DISTRIBUTION (CFS)
Figure 'll:-13. Frequency distribution of cell velocity over upwelling areas in Upp•r Si de
Channel II at site flows of 5 and 50 cfs.
earlier for spawning chum salmon (Refer Figure V-7). The comparison
indicates that the rap i d increase in WUA indices for Slough 21 and
Upper Side Channel 11 (Figure V-11) is attributable to an increase of
depth over upwelling areas (Figures V-12 and 13). The gradual
decrease in WUA indices at higher site flows is due to mean column
velocities over upwelling areas exceeding the 0 to 1.3 fps optimum
range established for slough spawners. It is important to recognize
how shallow water influences the availability of spawning habitat at
Category I and II sites under non-breached conditions. The analysis
presented in Section IV regarding the infh·e nce of overtopping events
on passage depths for adult salmon is also applicable for evaluating
the long-term importance of breach i ng flows on the availability of
spawning habitat in side sloughs.
Side sloughs provide a relatively small but persistent amount of
spawning habitat for chum salmon over a wide range of mainstem dis-
charge. The apparent stability of side slough spawning habitat
primarily from the base flow (upwelling and local runoff) that is
present during the spawn i ng season whenever mainstem flows are insuf-
ficient to overtop the berm at the head of the slough. Figure V-14
presents flow and habitat duration curves for habitat categories I,
II, and III. Each habitat duration curve was constructed using daily
WUA values derived from average daily flows at the site. Site
specific daily flows were determined from average daily mainstem flow
at Gold Creek using the regression equations presented by ADF&G
(1984d) for breached conditions, and estimating average daily base
flows for non-breached conditions on the basis of field experience and
a limited number of flow measurements.
Slough 21 provides an example of a category I habitat that is quite
stable. The habitat duration curve indicates that the habitat value
equalled or exceeded 90 percent of the time is nearly the same as that
equalled or exceeded 10 percent of the time. The higher habitat
values are associated with breaching flows as discussed previously.
V-37
1100
1000
900
:eoo
u 700
!600
.500
0400
it300
<:
I
w
00
.,
~ u
z
• 0
.J
lo..
200
100
1100
1000
900
800
700
6 00
500
400
300
200-
100
0
10
SLOUGH 2 1
f"low Purat l on Curve
20 3 0 40 50 60 7 0 80
TIME I:.QU ALE D OR EXCE E OEO
UPPER SIDE CHA ~NEL
f low Duration Curve
T I ME EQUAL E D OR EXC E EDED
Cataeorr 1
15,000
~~.ooo
11.000
c 9 ,000
~ 1/)00 • 5,000
~poo
1/)00
90 100 0
Cateeorr II
II 15,000
~~.ooo
11.000
c 9,000
~ 1/)00 • 5 ,000
3/)00
1/)00
0
10
10
20
SLOUGH 21
Habitat Duration Curve
30 40 50 eo 10 80 80
PERCENT TIM£ EQUALED OR EX~EOED
UPPER SIDE CHANNEL I I
Habitat O..rotlon Cur"
100
20 30 40 50 eo 10 80 80 100
PERCENT TIM£ EQUALED OR EX~EOED
1100
1000
900
fl) 800 &&.. 700 u
z 600
• 500
0 400
..J 300 ~
200
100
0
< I
fl)
&&..
u
z
• 0
.J
~
w
\0
1100
1000
900
800
700
600
500
400
300
200
100
0
SLOUGH 9
Flow Dur-ation C11rvu
0 30 40 50 60 70 80 90
TIME EQUALED OR EXCEEDED
SlOE CHANNEL 21
Flow Duration Curve•
TIME EQUALED
Category II
t5,000
13,000
11,000
9,000
7po..
5,000
3,000
1/)00
100 0 10
Category Ill
15,000
13,000
11,000
c 9,000
:) 1/)00 • 5,000
3/)00
1/)00
0 10
20 30
SLOUGH 9
Habitat Duration C~o~rvee
40 50 eo 10 10 90
PERCENT TIME EQUALlED OR IE:lCCZEDIE:D
SlOE CHANNEL 21
Habitat Ourat i ol'l Curvu
20 30 40 eo eo 70 10 90
PERCENT TIME EQUALlED OR UCZEDIE:D
Figure V-14 Ccont'd). Flow and habitat duration curvea for apawnlng chuM aaiM~n by habitat categorlea.
100
100
P.abitat category II sites are also relatively stable. Upper side
channel 11 has a flat habitat duration curve from 100 to 50 percent
equalled or exceeded. Higher habitat values associated with breached
conditions occur more frequently than in category I.
Rearing Salmon
Microhabitat Preferences. Field studies were conducted by ADF&G to
determine the seasonal movement and habitat requirements of juvenile
chinook, chum, coho and sockeye salmon in the middle Susitna River
(ADF&G 1984c). Juvenile coho salmon rear predominantly in tri butary
and upland slough habitats. The few sockeye juveniles rearing in the
middle Susitna River are most commonly found in upland slough habi-
tats. Juvenile chum and chinook salmon are the most abundant salmon
species that rear in side slough and side channel habitats. By early
summer (end of June) most juvenile chum salmon have outmigrated from
middle Susitna River habitats, and a large inmigrati on of chinook fry
is occurring from natal tributaries. These i11111ature chinook redis-
tribute into side channels and side sloughs during the remainder of
the sumner. With the onset of fall and colder mainstem and side
channel water temperatures, chinook juveniles may move into warmer
water downstream from upwelling areas in side slough habitats to
overwinter (ADF&G 1984c) •
. Rearing habitat is cor.1110nly evaluated using three variables:
velocity, and cover ·(Bovee 1982, Wesche and Reckard 1980).
depth,
Habitat
suitability criteria have been developed by ADF&G to describe the
preferences of juvenile chum and chinook salmon for these microhabitat
variables. Habitat suitability criteria developed by ADF&G indicate
that water depths exceeding 0.15 feet provide optimal conditions for
rearing chinook (ADF&G 1984b). This compares well with Burger et al.
(1982) who found chinook using depths between 0.2 feet and 10 feet.
Cover is used by juvenile salmon as a means of avoiding predation and
obtaining protection from hi gh water velocities. Instream objects,
such as submerged macrophytes, 1 a rge substrate, organic debris, and
V-40
undercut banks provide both types of shelter for juvenile salmon
(Burger et a 1. 1982, Bustard and Narver 1975, Bjornn 1971, and
Cederholm and Koski 1977}. One significant result of the AOF&G field
studies determined the use of turbidity by juvenile chinook as cover.
Juvenile chinook were co111110nly found in low-velocity turbid water
(50-200 NTU) without object cover but were rarely observed in
low-velocity, clear water (under 5 NTU) without object cover.1 The
influence of turbidity on the distribution of juvenile chinook in side
channel habitats was so pronounced that habitat suitability criteria
for velocity and object cover w~re developed by ADF&G for both clear
and turbid water conditions (Figures 15 and 16).
These criteria curves assign optimal suitability values to velocities
between 0.05 and 0.35 fps for turbid water, and between 0.35 and
0.65 fps for clear water. The Susitna River criteria for juvenile
chinook in clear water are different from velocity criteria developed
in other Alaska studies (Burger et al. 1982, Bechtel 1983) and those
used by the U.S.F.W.S. Instream Flow Group (IFG) (Nelson pers. comm.
1984}. literature values typically indicate optimal velocities for
juvenile chinook in clear water are less than 0.5 fps. The criteria
presented by both Burger et al. (1982) and Bechtel (1983) (Figure 17)
can be considered comparable to ADF&G's criteria fo r juvenile chinook
insofar as the Burger and Bechtel criteria were developed for juvenile
chinook (under 100 mm) rearing in large glacial rivers in Alaska.
Although the chinook criteria from the literature were dev~loped from
data collected in clear water (less than 30 NTU), they are more
similar to the Susitna River velocity criteria for turbid water
* ADF&G selected 30 NTU to distinguish between "clear .. and "turbid"
water conditions (ADF&G 1984b}. This is recognized as a reason-
able preliminary threshold value . However, because of the
limited number of data points that are available to define
juvenile chinook behavior at turbiditi es between 5 and 50 NTU and
above 200 NTU, turbidity ranges will be parenthetically expressed
in our discussion of juvenile chinook behavior in clear (under 5
NTU) and turbid (50 to 200 NTU) water conditions. Turbidity
ranges may be fur~her defined as a result of the 1984 ADF&G field
studies.
V-41
SUITABILITY INDEX
1.0 ,--Velocity Clear Turbid
I \ 0 .0 018 0 .42
\ 0 .05 0 .28 1.0 I 0 .20 0 .57 1.0 \ 0 .35 1 .0 1.0 I \ 0.50 1 .0 0 .80
I 0 .65 1.0 0 .60
0 .8 \ 0.80 0 .68 0.38 I \ 1.10 0 .44 0 .25
1.40 0 .25 0 .15
\ 1.70 0 .18 0 .07
\ 2.00 0 .12 0 .02
2 .30 0 .06 0 .01
\ 2 .60 0 .0 0 .0
0 .6 \ Clear water leas than 5 NTU
)( \ Turbid water 50 to 200NTL
"' \ 0 z \ LEGEND \ ---Turbid < ~ 0 .4 \ -clear I ... ~ ' N _. ' ~ ' ' ' :::;)
U) 0 .2 ' ' ' ', ' ', ..........
0.0 ---
0 0 .5 1.0 1.5 2.0 2 .5 3 .0
VELOCITY f.p.a.
Figure 'll-15. Velocity criteria for juvenile Chinook in clear and turbid water.
X w c z
>-.....
....J
ffi
;:!
5 en
< .....
I ~ ~ <D w ex
I
2 3 4 5 6
No Cover Emergent Aquat1 c O.br1s and Ovemanging Undercut
Vegetat i on Vegetation O.adfall Ri parian Banks
PERCENT COVER by COVER TYPE
7
Large
GroVIII
8 9
Rubble Cobble or
3"-5'' Boulders
over 5"
LEGE ND
GJ -Clear
--Turbid
Percent Cover
0 .1 o-5
0 .2 e-25
0 .3 26 -50
04 51 -75
0 .5 76-100
Figure ][-Us. ADF&G cover criteria for juvenile chinook in clear and turbid water .
)(
~ z
> t: _. -~ t:
:::l
U)
<:
I
~
~
1.0 ~ .-.,
0 .8
0 .6
0 .4
0 .2
0
\
~\
'·\
'· \
'. \
I \
\
0 .5
\
\
\
\
\
\
' ' ' ' '
1.0
LEGEND
...,___Burger et al.t112 31-IOMm
--Burger et · al. t 112 It-t OOM
. -·--·Bechtel t 113
' ' ' ' '
1.5
' ' ' ' ' '
2 .0 2 .~
VELOCITY f.p .e.
FigureY-17. Velocity euitability criteria for jw.nile chinook in the
Kenai and Chakachamna rivere; Alaeka . (Source : Burger
et al. 1982 and Bechtel 1983 ).
(50-200 NTU). The apparent reason for this discrepancy is the differ-
ence in field methods used by ADF&G and the other investigators.
Mean column velocities were measured by both ADF&G and other investi-
gators to develop habitat suitability curves for juvenile chinook.
However, the location at which the mean column velocity was measured
relative to the apparent locations of juvenile chinook were different.
AOF&G reported the mean column velocity at the midpoint of a 6 foot by
50 foot cell (mid-cell velocity) regardless of the location of fish
within the cell. The velocity criteria developed by Burger and
Bechtel are based on mean column velocities measured in the immediate
vicinity of individual fish observations or captures (point
ve 1 ocities).
Assuming that immature fish in clear water are more likely to be found
along stream banks (where lower velocities and cover are generally
more available), the practice of measuring mid-cell veloc i ties a
minimum distance of 3 feet (one half the width of the ADF&G sample
cell) from the streambank would result in slightly higher mean column
velocities being measured than if point velocities had been measured.
Hence it is understandable that the 0.35 to 0.65 fps velocity range
selected by ADF&G as being optimal for juvenile chinook is slightly
higher than the 0 to 0.5 fps velocity range selected by other
investigators.
In turbid water (50-200 NTU) it appears that juvenile chinook do not
associate with object cover to ~he same degree they do in clear water
(AOF&G 1984c). Rather, they are randomly distributed in low velocity
areas with little or no object cover. In these low-velocity turbid
areas, it is quite likely that mid-cell velocities measured 3 feet
from the streambank differ 1 ittle from point velocities measured in
microhabitats along the shoreline that would be inhabited by juvenile
chinook in a clearwater stream. Therefore, it is not surprising that
the 0 to 0.4 fps velocity range selected by ADF&G as being optimum for
juvenile chinook in turbid water differs little from the 0 to 0.5 fps
V-45
velocity range selected by other investigators using point velocity
measurements rather than mid-cell velocities as their data base.
It can be inferred from the ADF&G habitat suitability criteria that in
low-velocity water ( <0.4 fps) where juvenile chinook do not require
protection from water currents, they are more likely to be found
within the water column away from object cover if the water is turbid
(50 to 200 NTU) than if it is clear (less than 5 NTU). At velocities
greater than 0.4 fps, the distribution of juvenile chinook in turbid
water will likely become more strongly influenced by velocity, and
when velocities exceed 1.0 fps, object cover is probably as important
to juvenile chinook in turbid water as it is to them in clear water.
However, since these young fish probably cannot visually orient in
turbid water, they cannot make use of object cover that may be avail-
able and are therefore redistributed in microhabitats by velocity
currents.
Whenever mainstem discharge recedes sufficiently for turbid water in
small side channel areas to clear, juvenile chinook often redistribute
from low-velocity turbid water pools to clear water riffles near the
upstream end of the site. In these clearwater riffle areas object
cover appears important, and juvenile chinook are most commonly found
among streamed particles or near organic debris, regardless of the
velocities present (ADF&G 1984c).
Based on the preceding discussions of habitat suitability criteria and
the behavior of juvenile chinook, it appe~rs that velocity and cover
are the two most important abiotic microhabitat variables influencing
j uvenile chinook rearing habitat. Of the two, cover appears most
influential, although velocity is also limiting above 2.6 F.P.S.
Although offering no protection from velocity, turbid water appears to
provide juvenile chinook adequate concealment from predators. They
therefore make extensive use of turbid (50-200 NTU) low-velocity
(<0.4 fps) areas. In clear water, juveniles generally seek conceal-
ment within interstitial spaces among streambed particles.
V-46
Utilization of these interstitial spaces also provides enough pro-
tection from velocity so that the juveniles are frequently found
during daylight in riffle areas possessing velocities between 0.35 and
0.65 fps (ADF&G 1984c).
The difference in velocity ranges utilized by juvenile chinook in
clear and turbid water is thought to be most strongly influenced by
food and cover availability. Given the high suspended sediment
concentrations that presently exist in side channel habitats,
interstitial spaces between streambed particles are generally filled
with fine glacial sands in most areas where velocities of 0.4 fps or
less would exist at moderate to high mainstem discharges. At low
mainstem discharges (when water at the site clears), the most likely
place to find a good food supply is interstitial spaces not filled
with fine sediments in riffle areas that were subjected to relatively
high velocities when the site was breached. These types of riffle
areas generally occur at the head of the site.
Based on this logic, the following modificat i ons have been made to the
ADF&G habitat suitability criteria for juvenile chinook. The cover
and depth criteria developed by ADF&G for chinook in clear water have
been adopted. However, the ADF&G velocity criteria for both clear and
turbid water have been combined such that the optimal or preferred
velocity range extends from 0.05 fps to 0.65 fps for clear water
situations. As velocity increases above 0.65 fps, the habitat suit-
ability decreases in accord with the ADF&G clear water criteria. This
approach incorporates the behavioral response of juvenile chinook to
low-velocity flow observed by other investigators (Burger et al. 1982,
Bechtel 1983) where more suitable object cover was associated with
clear low velocity flow than generally exists in middle Susitna River
habitats. The importance of object cover in providing both conceal-
ment and protection from velocity is expressed in the clear water
cover criteria developed by ADF&G for middle Susitna River habitats.
Whenever the water is turbid, the ADF&G depth and turbid water
ve 1 oci ty criteria are app 1 i ed in conjunction with a modi fica t ion of
the ADF&G turbid water cover criteria.
V-47
The ADF&G cover criteria for turbid water were modified by multiplying
the clear water percent cover suitability values for each cover type
by a turbidity factor. This turbidity factor is the fitted mean catch
per cell in turbid water divided by the mean catch per cell in clear
water for corresponding percent cover categories (Table V-4).
Table V-4. Calculation of turbidity factors for determination of the
influence of turbidity on clear water cover criteria for
juvenile chinook salmon.
Percent Number of Fish Per Cell Turbidity
Cover l:lear Tumid Factor
0-5% .8 3.5 4.40
6-25% 2.4 4.2 1.80
26-50% 4.0 4.8 1.20
51-75% 5.6 5.5 1.00
76-100% 7.3 6.2 0.80
Source: ADF&G (1984c)
Application of these turbidity factors to the ADF&G clear water cover
criteria increases the suitabi 1 i ty of percent cover category under
turbid water conditions if 50 percent or less object cover is present.
Turbidity has no discernible influence if 51 to 75% present and
slightly decreases habitat suitability if more than 76 percent object
cover is present (Figure V-18}. The decrease in suitability of the
higher percent cover categories in turbid water conditions may be
attributed in part to the inability of juveniles to orient themselves
and fully utilize the available cover. Because the turbid water
suitability values calculated for the emergent streambank vegetation
and no-cover types were unrealistically low (approximately 0.04}, the
value, 0.30, was arbitrarily chosen for these cover types under turbid
water conditions. This seemed appropriate because 0.30 was the value
calculated for the majority of other cover types under turbid water
conditions when zero to 5 percent cover was attributable to the
quality of the cover types under clear water conditions. By applying
the modified cover and velocity criteria, it is felt that a rearing
habitat model can be developed that can reliably respond to a broader
V-48
1.0
X
UJ a z
>-t--
::J
ffi
~
5
{/) 0 .
t--
< ~ I m ~
\0 <{ z
3 4 5 6
No Cover . Emergent Aquatic Debria and Overhanging Undercut
Vegetation Vegetation Deadfall Riparian Ba nka
PERCENT COVER by COVER TYPE
7
Large
Gravel
8 9
Rubble Cobble or
3"-~" Boulden
OYer 5"
Figure l[-18. Re11ised cover criteria for juvenile chinook in clear and turbid water.
LEGEND
IZJ-Clear
--Turbid
Percent Cover
0 .1 o-5
0 .2 6-25
0 .3 26-50
0 .4 51 -75
0.5 76-100
range of hypothetical with-project conditions than could be evaluated
using the ADF&G criteria which primarily described existing
conditions.
Habitat Availability. WUA indices forecast using both the ADF&G
criteria, and the modified velocity criteria for juvenile chinook
rearing at Side Channel 21 and Upper Side Channel 11 are compared in
Figure V-19. Increasing the range of low velociti~s suitable for
juvenile chinook in clear water at these study sites did not substan-
tially change the WUA indices previously forecast by ADF&G. This is
attributable to the importance of cover to juvenile chinook in clear
water and to the poor cover conditions associated with low-velocity
areas in these sites under natural conditions. Although slight, the
most notable changes occurred at low discharges (5-10 cfs), where
low-velocity water is more likely associated with larger substrates in
the mid-channel zone.
WUA indices forecast for juvenile chinook using cover criteria for low
and high turbidity conditions are presented in Figure V-20. Identical
habitat response curves are forecast under low-turbidity conditions
because the ADF&G clear water cover criteria remains unchanged.
Application of the modified turbid water cover criteria results in
approximately a 25 percent reduction in WUA indices from the ADF&G
forecasts. However, the basic shape of the habitat response curves
remains unchanged.
Under project :>peration, the larger suspended sediments (sands and
silts) that are currently transported by the river are expected to
settle out in the reservoirs. Without continual recruitment of these
sediments into habitats downstream of the reservoirs it is anticipated
that the finer material presently filling interstitial spaces among
larger streambed particles will be gradually removed. The effect of
an increase in cover suitability resulting from the removal of fine
sediments from interstitial voids was simulated by upgrading all
recorded percent cover categories at two study sites by one category
and recalculating WUA indices for juvenile chinook. This simulation
V-50
<:
I
U1
~
-... -.. -
-... -.. -i c
UPPER SIDE CHANNEL 11
20000
15000
------------10000
0 50 100 150 200 250
liTE FLOW (CFI)
40000
SIDE CHANNEL 21
30000
------~----
20000
10000 ~----------~------------~------------~------------~------------,
0 50 100 150 200 250
liTE FLOW (CFI)
Figure I-11. Comp•rlaon between WUA forec•ata ualng ADFAG low turbidity veP .. .;Ity
criteria (aolld line) and modification low turbidity velocity criteria
(daahed line).
50 •000 Upper Side Cllanntl II
411,000
r 4o ,ooo -~ 311,000 c
"' 30,000 a:: c 211,000
20,000
15,000
10,000
50,000
41,000
;:;--4 o,ooo -!t::. 35,000
(J 2!1 50 711 IOU 1211
SITE FLOW ( CF S)
Upper Side Channel II
. .....__~
Low Turbidity
IIIIJ 175
Hjgh Turbidity
~ 30,000 ,., Z!UV~
c 211,000 -------------------_ ....... _
~~ , -----------------· IIS,OOO
SITE FLOW (CFS)
50,000
45,000
-40,000 ,._
-16.000 -~ 30,000
a:: c
20,000
15,000 -
Side Channel 21 Low Turbidity
10,000.
~----~----~-----r-----,----~~----~--~
ea,ooo
-511,000 .... --c 41,000
"' a:
C( 311,000
211,000
1!1,000
0
0
100 400 tOO tOO 1000 1200
SITE FLOW (CFS)
Side Channel 21 High Turbidity
-------------------
200 400 1000 1100 1400
SITE fLOW (Cf S)
FIGURE Jl-20. Comparison between WUA forecasts using AOF&G (solid line) and modified cover
criteria (dashed line) for Juvenile chinook.
resulted in increased WUA indices at Upper Side Channel 11 and Side
Channel 21 of approximately 60 percent depending on the suitability
criteria applied (Figure V-21).
Rearing habitat for juvenile chinook under low-and high-turbidity was
modeled using a combination of the revised clear-water velocity
criteria, modified high-turbidity cover criteria and ADF&G criteria
for depth, velocity and cover (Table V-5). WUA indices
Table V-5. Habitat suitability criteria use1 in revised model to
forecast WUA for juvenile chinook salmon under low and
high turbidities.
Low Turbidity (<30 NTU)
ADF&G Cover Criteria
ADF&G Cover Criteria
Revised Velocity Criteria
High turbidity (> 30 NTU)
ADF&G Depth Criteria
Modified Cover Criteria
ADF&G Velocity Criteria
forecast for juvenile chinook salmon at Side Channel 21 and Upper Side
Channel 11 using the ADF&G and revised rearing habitat criteria are
compared to total surface area in Figure V-22 as functions of mainstem
discharge. The upstream berms at these sites can be overtopped at
mainstem discharges of 9,200 cfs and 13,000 cfs, respectively. Hence
low turbidity exists at the Side Channel 21 site whenever the mainstem
discharge is less than 9,200 cfs, and high turbidities prevail when-
ever the mainstem discharge exceeds 9,200 cfs. The same relationship
between mainstem discharge and turbidity exists for Upper Side
Channel 11 except the threshold discharge is 13,000 cfs.
Given the habitat suitability criteria developed f~r juvenile chinook
and typical middle riv~r conditions, depth of flow is a relatively
inconsequential microhabitat variable unless it is less than 0.15
feet. Thus, the general shape of habitat response curves for juvenile
chinook is determined primarily by the interaction between cover
availability and velocity. Because juvenile chinook salmon in the
middle Susitna River use naturally occurring turbidity levels as a
form of cover, notable increases in WUA are caused by the breaching of
V-53
< I
V'l +--
40,000
31,000
10,000
c 11,000
"' ~ 10,000
40,000
SI,OOO
aa,ooo
~•.ooo
01:
c 14,000
10,000
11,000
II.POO
Upper Side Cllonnel II Low Turltldlt'
-------·
0 • I I ao 71 100 II& 110 171 100 Ill
SITE FLOW ( CF S)
Upper Side CIIOMII II Hlgll Turltldlt'
"""'""'-' ............. --------
0 II
LEGEND
10 71 100 Ill
!ITE fLOW (Cfl)
--WITH REDUCED SEDIMENT
-WITHOUT REDUCED SEDIMENT
110 171 tOO Ill
ao,ooo
41,000
40,000
11,000
~ 10,000
~ 11,000
10,000
11,000
Low Ttlr~ld i t'
...... __
10,000+------r------r-----~----~~----~----~------,
0
10,000
41,000
40,000
11,000
: so,ooo
01:
ca1,ooo
10,000
11,000
10,000
0
tOO 400 100 100 1000 I tOO 1400
SITE FLOW (CfS)
\Side c ..... , 21 "'til TurtlldltJ
\
\~
'
100
-""" ,_..,__ ---__ .......... ____ _
400 100 IOU 1000 1200 1400
SITE FLOW (CfS)
Figure Y-21 . Simulated effect of reducing fine sediment deposition within the streambed at two study
sites using revised chinook rearing criteria.
< I
V1
VI
c
Ul ac c
UPPER SIDE CHANNEL 11
100000 TOTAL SURFACE AREA
50000
ADFAQ WUA
~-----------------~_...._,_..~ " REVISED MODEL ----------
o~------------~~----~------~---------------r--------------~-
10000
200000
100000
14000 1iooo
MAINSTEM FLOW (CFI)
SIDE CHANNEL 21
22000
TOTAL SURFACE AREA
-~---ADFAQ WUA ---------REVISED MODEL ----------------
21000
0+---------~~--------~----------,-----------r----------,--------5000 10000 15000 20000 2&000 30000
MAINSTEM FLOW (CFS)
Fiourell-22. Compariaon between WUA forecaata uaino ADF&G and
revised rearing habitat model.
a clear water study site by turbid mainstem flow. The magnitude of
the WUA increase is proportional to the increase in wetted surface
area possessing suitable velocities.
The initial increase in WUA indices depicted in Figure V-19 is attrib-
utable to the influence of turbidity on improving otherwise poor cover
conditions at these sites. Subsequent increases in WUA result from
increases in wetted surface area with suitable velocities for juvenile
chinook. Turbidity has a lesser effect on increasing WUA indices at
the Side Channel 21 site than the Upper Side Channel 11 site because
less favorable velocities typically exist at the Side Channel 21 site.
This trend for habitat Category III sites to possess less favorable
rearing velocities than habitat Category I or II sites is suspected to
be widespread in the middle Susitna River.
The relationship between weighted usable area and wetted surface area
is plotted as a flow dependent percentage in Figure V-23. At higher
main.stem discharges a lesser percentage of the total wetted surface
area is available as rearing habitat. This is attributable to wetted
areas with suitable velocities for rearing fish becoming available at
a lesser rate as discharge continues to increase; a common occurrence
in well defined steep gradient channels. The most efficient use of
streamflow to provide rearing habitat at these sites appears to occur
at low mainstem discharges where the site remains turbid and a greater
percentage of the total wetted surface area is associated with suit-
able velocities for rearing fish.
V-56
~ z
l&J
(,)
a:
l&J
Q.
<:
I
U1 .......
40 LEGEND
3!5 Upper Side Channel II
Side Channel 21
30 ,,...,
2!5 _,, ' ---,, ' 20 '
1!5
10
, __ ----..... .......... .......... ..... _ ------------
5
0~----~------r------r----~~----~----~------~----~------T------e,ooo a,ooo 10,000 12,000 14,000 16,000 18,000 20,000 22,000
· MAINSTEM FLOW, GOLD CREEK (CFS)
Figure .Y-23. Percent of total wetted surface area providing WUA for rearing
chinook at Side Channel 21 and Upper Side Channel II.
VI. EVALUATION OF HABITAT COMPONENTS WITHIN
THE IFR FRAMEWORK
Watershed and Climatological Influences on Physical Habitat Components
The primary environmental factors of the basin that influence fish
habitat in the middle river segment are water supply, air temperature,
and channe 1 morpho 1 ogy. Of these, water supply and air temperature
vary both seasonally and annually (AEIDC 1984b) whereas middle river
channel morphology is considered constant (R&M Consultants 198 2a,
AEIDC 1984a). The relationships between air temperature and water
supply determine the seasonal response of middle Susitna River flow,
water temperature and water quality. Annual variations in basin
precipitation and climate account for year-to-year fluctuations in
these three primary habitat components. Summer streamflow variability
is moderated both by glaciers (which cover about 290 square miles of
the upper Susitna Basin) and by three large lakes in the Tyone River
drainage. Because glacial flow results in high turbidity and sus-
pended sediment concentrations in summer, the water quality of the
middle Susitna River changes markedly with the seasons.
The streamflow, thermal, and water quality regimes (turbidity and
suspended sediment) are the driving variables that control the
availability of fish habitat in the middle Susitna River • As dis-
cussed in Section IV, "easonal changes in these three driving vari-
ables significantly influence the seasonal characteristics and utility
of each habitat type in the middle r iver. These seasonal changes, in
turn, attended by seasonal changes in biological activities and
habitat utilization patterns.
The climatology, geology, and topography of the watershed determine
the channel pattern and channel structure of the river as well as
seasonal and daily variations in streamflow, stream temperature and
water quality. Among the many watershed characteristics affecting
streamflow, water t e~perature and water quality, air temperature and
water supply are most important. Air temperature regulates seasonal
VI-1
changes in streamflow patterns; precipitation governs its variability.
Streamflow, stream temperature, and water quality either directly or
indirectly control the seasonal availability and quality of fish
habitat in the middle Susitna River.
Of the three, streamflow is most important because it is directly
related in varying degrees to all physical processes influencing fish
habitat in the middle Susitna River. High streamflows reshape channel
geometry, which at lower discharge levels controls site-specific
hydraulic conditions. Summer streamflows transport large amounts of
suspended sediment, which cause high turbidities and generally degrade
water quality. The relatively poor quality of illainstem and side
channel habitat in summer is caused by high velocities with associated
high suspended sediment concentrations. The suspended sediment load
is considered limiting to the colonization of streambed materials by
algae and aquatic insects, which generally provide an important food
source for fish.
Streamflows and stream temperatures during winter play an integral
rol~ in middle Susitna River ice processes, which directly affect
channel structure, shoreline stability and the general qualHy of
winter fish habitat. River ice affects instream hydraulics, most
notably constricting the channel, reducing velocity and increasing
river stage (Harza-Ebasco 1984c). This increase in water surface
elevation during winter has both positive and negative effects on fish
habitat. Higher water surface elevations during winter appear impor-
tant for raising local groundwater tables within the river corridor,
thereby maintaining upwellings in slough and side channel areas
throughout winter (R&M Consultants 1982d, Harza-Ebasco 1984d). These
upwellings provide a source of relatively warm water (2-3°C) through-
out winter (Trihey 1982, ADF&G 1983) essential for the successful
incubation of salmon eggs and for use by overwintering fish. However,
if river stage increases above the streambed elevation at the upstream
end of the slough or side channel, then near ooc water from the
mainstem will flow through these channels, greatly reducing the
VI-2
thennal effect of upwelling areas and their value as winter habitat
(AOF&G 1983).
Seasonal Utilization of Middle River Habitats
Mainstem and side channel habitats are predominantly used as migra-
tional corridors by adult and juvenile salmon. Adult inmigration
begins in late May and extends to mid-September. Juven i le outmi-
gration occurs from May through October. A 1 imited amount of chum
salmon spawning occurs at upwelling areas along shoreline margins in
these habitats (AOF&G 1984a), and chinook juveniles use low-velocity
areas for rearing (ADF&G 1984c). Several species of resident fish use
mainstem and side channel habitat for overwintering and summer rearing
(ADF&G 1984c). The more important species appear to be burbot,
rainbow trout and Arctic grayling.
Side slough habitats provide important spawning, rearing, and over-
wintering habitat. One prominent physical feature of this habitat is
upwelling groundwater, which maintains clear water flow in these
habitats during periods of low mainstem discharge. Approximately half
of the chum salmon (5,000) and all of the sockeye salmon (1,500) that
spawn in the niddle Susitna River depend upon side slough habitats
(ADF&G 1984a). Most chum and sockeye spawning activity occurs between
mid-August and mid-September. Upwelling attracts spawning salmon and
provides incubation conditions that result in high survival rates
(ADF&G 1984c). Fry begin to emerge i n April, and rear near these
natal spawning areas until June (AOF&G 1984c). Chum f~v outmigrate in
June and early July to marine habitats, while sockeye juveniles
generally move into accessible upland slough habitats to rear.
Juvenile chinook enter side slough habitats in August and overwinter
until late spring, when they begin their outmigration to marine
habitats.
Upland sloughs provide rearing and overwintering habitats for juvenile
sockeye, coho and chinook salmon (AOF&G 1984c). Some spawning by chum
salmon also occurs in this habitat, but it is fairly restricted (ADF&G
VI-3
1984a). Sockeye fry rear in upland slough habitats throughout the
sunmer, but most 1 eave the middle Sus itna River prior to freezeup
(ADF&G 1984c).
Tributary mouth habitats provide important areas for spawning, rearing
and overwintering. Pink, chum, and chinook salmon have been observed
spawning in tributary mouth habitats in mid-August (ADF&G 1984a).
Juvenile chinook and coho salmon occupy these habitats for both
rearing and overwintering (ADF&G 1984c).
Evaluation Periods and Species
Both the biological activities and the physical processes \'ary season-
ally. In order to integrate the physical processes and biological
activities in the evaluation of seasonal changes in habitat, the year
was divided into four segments. The four segments were established on
the basis of timing of the four principal life stages of the fresh-
water residency of salmon: Spawning ·, incubation, overwintering, and
su11111er rearing (Figure VI-1). Although these periods overlap, the
habitats occupied by overlapping life stages and the physical require-
ments differ sufficiently to warrant separate analyses. To facilitate
the analysis of the effects of streamflow on habitat, the biological
activities were defined in water weeks (Table VI-1). Water weeks
begin October 1 and consist of 51 consecutive 7-day periods. The
fifty-second week (September 23-30) contains eight days, and
February 29 is omitted .
Table VI-1. Abbreviated phenology chart.
Species
Chum
Chu m
Chinook
Chinook
life stage
Spawning
Incubation
Overwintering
Sunmer rearing
Activity period
August 12 to September 15
August 12 to March 24
September 16 to May 19
May 20 to September 15
Water Weeks
45 through 50
45 through 25
51 through 33
34 through 50
Seasonal habitat requirements are species-and 1 ife stage-specific.
Evaluation species have been selected on the basis of their importance
VI-4
i
2
Ill .... • z c
2
,..
at c .... :»
!!
at ....
• % e :»
0
..J •
> REMARKS ~ JiM
FEB MAR APR MAY JUN JUL AUG IEP O~T NOV DEC
I ' I I I I I I I I ----,. ;, ---~II
IM ... --· ----.. -----.~I .. __ "' __ _;,
s -k• --RI
-
I ~·-·· ~--·-·· 1-•••• .. ~···-· ~-cs 4•-g ~-·-· --~----i-RS ......
~---·
R
OM
IM
s
~--.. ~---
~.---
R ~---
~M -
IM
.
8
..
·-·-· I t--·--.. l
~--·--R -<
~~ -J
--
. . . . . . . . .....
--· ~·--
~
-· . ----. --
--. ---'• . .: J
--. . -------..... _ .. ~--
~-....... ~--· ---::----
------
--
---
----
---. -.
"'.., lo --. .... , .. ·-·-· r---------
··-. -1----·--· . --
. ..
HlciH
ME DIU"
LOW .•
. ....... . ....... ..........
----~:.M ~aiirs ---· ----~------~-------
~--------c1 "----~---~--PI ----------------1--------~-_!(_\, ---. -· ~------cs
--RI ----------p ---~-KI
"----1 8
--PI C8
-KI ---~-----88 ----t--CI ---· PI ---KS K&--~----------------· ~S PI Clf ---· 88
--------KIS ~--
--------CS PI
1-------
·-·-·· PI p ---jcSR8 CIR
--· -----llf-IS81 1---
~---~-----cs
~-------~-c8 ·-·-·--·-PI .,.. ___ ---
Kl CHINOOK SALMON
8S COHO SALMON
C8 CHUM SALMON
PI PINK SALMON
R8 SOCKEYE SALMON
1----------
Sl ~---
--------
~---"'---"'--Ka
--PI cs ---•-R8
~---·-~~-c. --· --· ----~R8
It-·-·. ~----·-·-· ~---------
---~---· ---
----K8 Iss Rl
IM IN MIGRATION
S SPAWNING
I INCUBATION
R REARING
OM OUT MIGRATION
-,., .. , .....
1---1-t e e l f .... •-c• ...... ,..-1,.,,.,_ !:;:' ...........
---1----,., .. , ..... ,.,._ ------. ... , ............
f-.•~ •·•~c • ---·---..............
-------
88
1 ... , .... , t O" , ... _
~--·-... ,,, .. de'••
·:-:.-.J;::._·:.:~.:··· ---.....
~---~---
BASED PRIMARILY ON ADF&G FIELD DATA
RGUR! la~1. PHENOLOGY AND HABITAT UTILIZATION OF MIDDLE
•· SUSITNA RIVER SALMON IN MAINSTEM, TRIBUTARY,
AND SLOUGH HABITATS.
to commercial and sport fisheries, and the potential of project
construction and operation substantially altering on their existing
habitat. The primary evaluation species and life stages for natural
conditions are chum salmon spawning and incubation, and juvenile
chinook salmon rearing (Refer: Section III). These species and life
stages were selected because they greatly depend on slough and side
channel habitats that will le significantly altered by project opera-
tion (APA 1983).
Relative Ranking of Existing Physical Habitat Components
Spawning and incubation are associated with fixed boundary habitat
conditions, while rearing and overwintering generally occur under
variable boundary conditions. Fixed boundary conditions are more
closely associated with localized structural features of the channel
(such as substrate or upwelling), whereas variable boundary habitats
are more strongly influenced by transient hydraulic conditions within
the channel, such as depth, velocity and turbidity. Both the quality
and location of variable boundary habitats respond to changes in
streamflow, while only the quality of fixed boundary habitats respond.
Availability of spawning and incubation habitat appears limited
throughout the middle Susitna River. Table VI-2 summarizes the
results of subjectively applying the IFR model introduced in Section
II and the technical infonmation presented in Sections III through V.
This table is intended to summarize the relative degree of influence
physical habitat components exert on middle river habitats for the
evaluation periods identified. These subjectively derived indices are
later compiled in Table VI-3 to indicate the habitat types and species
life phases most limited by existing conditions .
The presence of upwelling water is the most important microhabitat
variable influencing the selection of spawning areas by chum salmon
and it significantly affects egg-to-fry survival rates(ADF&G 1984c,
1984b). Table VI-2, Parts A and B summarize the influences of
VI-6
Table Vl-2. Evaluat i on of the relative degree1 of influence physical habitat componenh exert on the
suitability of middle Susitna River habitat types.
Habitat * Parameters Hainstem
PART A
'Riliiitem fl ow -3
Upwelling +3
Substrate co.position -3
Suspended sediment -1
Turbidity 0
Water Olemistry 0
Water Temperature 0
Index value -4
PART B
'Ril"ii'it em f 1 ow -3
Upwelling +1
Substrate composition -1
Suspended sediment -1
Turbidity 0
Water chemistry 0
Water temperature -3
Ice processes -2
Index value -9
PART C
RiT'iiStem fl ow -2
Upwelling +1
Substrate composition -2
Suspended sediment 0
Turbidity 0
Food availability 0
Water chemhtry 0
Water temperature -2
Ice processes -2
In de x value -7
PART 0
Hafnstem flow -3
Upwelling 0
Substrate composition -2
Suspended sediment -3
Turbidity +1
Food availability -2
Water chemistry 0
Water temperature 0
Index value -9
Evaluation scale
+3 extremely beneficial
+2 moderately beneficial
+1 slightly beneficial
0 no effect
-1 slightly detrimental
-2 moderately detrimental
Side Side Upland
Channel Slough Slough
Seawning
-2
(August 12
+2
-Seetember 15)
0
+3 +3 +3
-2 +1 -2
-1 0 0
0 0 0
0 0 0
0 0 0
-2 +6 +1
Incubation !August 12 -March 24~
-2 +2 0
+2 +3 +3
-1 +l -1
-1 0 0
0 0 0
0 0 0
-3 +2 +2
-2 -1 0
-7 +7 +4
Overwintering
-3 (S:~tember 16 -Ha~ 19)
+2
+1 +3 +2
-2 +2 -1
0 0 0
0 0 0
0 0 0
0 0 0
-2 +2 +2
-3 -1 0
-9 +8 +5
Summer Rearing
-2 !H!~ 20 -Seetember 15)
+3
+1 +2 +2
-2 +2 +1
-2 -1 0
+1 +1 +2
-2 +2 +2
0 0 0
0 -1 0
-6 +7 +10
* . -3 extremely detrimental
Typ1cal conditions for the habitat type during the season evaluated.
VI-7
Tributary
Mouth
-1
+3
+2
0
0
0
0
+4
_,
+2
+1
0
0
0
-2
-2
-2
+1
+1
+2
0
0
0
0
+1
-2
+3
-2
+1
+2
0
+2
+3
0
0
+6
existing physical habitat components on spawning and incubation in
each habitat type. Use of mainstem habitats by spawning chum salmon
is limited by several factors. Velocities between 5 and 9 fps (Harza-
Ebasco 1984e) preclude spawning in many mainstem areas, and substrates
are generally large and well-cemented with silts and sands (R&M
Consultants 1982e, AOF&G 1983b). Upwelling areas within side channels
are used by spawning salmon, but only to a limited degree. Side
channel habitats generally have low quality substrate, and are also
limited by velocity except in isolated locations along streant>ank
margins. During the spawning season mainstem discharge is usually
adequate to provide adult spawners access to upwelling areas in side
channel habitats (Harza-Ebasco 1984f, Klinger and Trihey 1984).
Exclusive of the major clear water tributaries, spawning most fre-
quently occurs in side slough habitats where upwelling is prevalent
and other physical habitat conditions are suitable (AOF&G a and d).
Naturally occurring velocities seldom 1 imit spawning conditions in
side slough habitats. However, side slough habitats are often limited
by shallow depths, and spawning salmon must utilize the available
substrate. Shallow slough flows cause passage problems which some-
times inhibit spawning salmon from using upstream reaches, and reduce
the quality of accessible upwelling areas. Breaching flows, which
appear to be important for passage and the short term improvement of
spawning, frequently occur in side sloughs (Section V).
Both incubation and overwintering are adversely influenced by
naturally occurring cold water temperatures, winter ice and low
streamflows (Table VI-2, Part B and Part C). The presence of
upwelling groundwater throughout winter (Trihey 1982, AOF&G 1983a),
creates favorable incubation conditions in sl~ugh habitats and
resulted in egg-to-fry ~urvival rates up to 35 percent in 1983-1984
(AOF&G 1984b). Many sloughs have ice-free areas but ice covers do
form over deeper poo 1 s and at the s 1 ough mouths. In winter poo 1
habitats in sloughs generally provide adequate depth and water temper-
atures where small fish occupy interstitial spaces between the larger
substrate materials.
VI-8
At times sloughs are overtopped by mainstem flows during winter.
These overtopping events are caused by ice cover formation (see
Section IV). The influx of cold mainstem water into side slough
habitats reduces intragravel water temperatures and adversely affects
incubation rates and embryo growth. Overtopping events also adversely
affect overwintering habitat as wa~er temperatures drop to near 0°C.
Anchor ice may form on the streambed r freezing embryos and small fish.
Such overtopping events do not appear to be conmon under natural
conditions at the most productive slough habitats.
The influence of cold water temperatures is most adverse in mainstem
and side channel habitats where near 0°C water temperatures exist for
approximately seven months. In addition, a thick ice cover (4-6 ft)
forms over these habitats during winter (R&M Consultants 1983). The
formation and break-up appear to have substantial detrimental effects.
Shorefast and slush ice form along channel margins filling low-
velocity areas, where fis~ might otherwise overwinter, with ice.
Upwelling exists in mainstem and side channel areas but its thermal
value is significantly reduced due to the large volume of 0°C water in
these channels. Velocities in much of the mainstem are excessive for
overwintering habitat since fish would have to expend energy to
maintain position. Portions of mainstem and side channel habitats
possessing large bed elements that would provide velocity barriers
generally have interstitial spaces filled with densely packed glacial
silts and sand; thereby preventing small fish from burrowing into the
streambed.
During summer chinook juveniles rear in tributary and tributary mouth
habitats, side channels, side sloughs. Most rearing fish were cap-
tured in tributary habitats; side channels had the next highest
abundance (ADF&G 1984c). Many of the main channel and large side
channels contain areas with high velocities and high suspended sedi-
ments not suitable for small fish (Table VI-2, Part D). Although
turbidity is used by juvenile chinook for cover, high turbidity also
limits light penetration and reduces primary production levels in
these habitats. Low primary production results in a low aquatic food
VI-9
base for rearing fish. Turbidity thus has both beneficial and detri-
mental effects on rearing habitat. Side channel habitats that
fluctuate between clear and turbid in response to streamflow vari-
ations, or that have a clear water input, would appear to provide
better rearing habitats than areas that remain turbid throughout
summer. While the area is clear, primary production rates would be
high, stimulating production of benthic prey items. Under higher
turbidities, the young chinook could move into these areas and feed
without unduly exposing themselves to predation. However, if rearing
areas remain turbid continuously, aquatic food production would likely
be reduced. Turbid areas with clear water inflow would also provide
rearing habitat. Food production occurring in clearwater areas would
be transported into turbid side channels with better cover.
Substrate in many mainstem and side channels has glacial fines filling
interstitial spaces reducing cover value of large substrate. Rearing
areas in mainstem and side channel habitats are located in low-
velocity areas along the late~al margins, in backwater areas, or
behind velocity barriers . Depths of less than 2 ft are most commonly
associated with low-gradient reaches. In these areas, streamflow
fluctuations can cause large changes in wetted area. Low-velocity
areas generally increase as discharge decreases.
In contrast to mainstem and side channel habitats, clearwater habitats
such as side sloughs and upland sloughs, provide a higher quality foo~
base and physical environment for juvenile fish, if sufficient cover
is present. Although the water temperatures in most of the channel
are generally lower (10°C) than optimum (12-14°C), they are suitable
(AEIDC 1984). Unless the slough is overtopped and conveying mainstem
water, velocities in most of the channel are generally within the
tolerance range for juvenile fish.
Under natural streamflow, stream temperature, and water quality, the
most stressful period for fish within the middle Susitna River appears
to occur during winter (Table VI-3). High streamflows, suspended
sediment concentrations and turbidities during summer appear to have a
VI-10
Table VI-3. Tabulation of habitat and evaluation period indices for the middle
Susitna River.
Side
Period Mainstem Channel
Spawning -41 -2
Incubation -9 -7
Overwintering -7 -9
Su11111er Rea·ri ng -9 -6
Habitat Index -29 3 -24
1 Inde x value from Table Vl-2
2 Inde x values totaled from left to right
3 Column total
Side
Slough
+6
+7
+8
+7
+28
VI-11
Evaluation
Upland Tributary Period
Slough Mouth Index
+1 +4 +52
+4 -2 -7
+5 +3 0
+10 +6 +8
+20 +11
significant adverse influence on mainstem and side channel habitats
when compared to adjacent clearwater habitats. The limited amount
(surface area) of spawning habitat that exists in five side sloughs
(21, 11, 9, 9A and SA) accounts for approximately 95 percent of the
sockeye, and 75 percent of the chum salmon spawning in non-tributary
habitats within the middle Susitna River. Therefore, improvement of
incubation/overwintering; reduction of high sunmer strea~lows,
suspended sediment concentrations and turbidities; and maintenance or
enhancement of existing clearwater spawning habitats appear to be
three reasonable goals to pursue when establishing instream flow
requirements for the middle Susitna River.
Inherent Project Influences on Existing Physical Processes
The most notable proj~ct induced changes in the middle river segment
will be alteration of natural streamflow, stream temperature and
sediment transport regimens (Figure VI-2). These anticipated changes
in t!Jrn cause changes on stream channel stability, upwelling, tur-
bidity, and winter ice. Understanding project induced changes in
these habitat components and degree of control associated with project
operations will provide a basis for estimating the potential habitat
for spawning, rearing, and overwintering in the middle Susitna River.
Some changes in habitat components are inherent in construction and
operation of the project. Others we can choose or influence through
operation, facility design or location.
With-project summer streamflows are expected to be approximately one
half naturally occurring average monthly values whereas winter flows
are estimated to ~ncrease five fold (APA 1983). Overall there will be
less variability in the annual flow cycle and a marked reduction in
flood peaks, resulting in more stable middle Susitna River flows.
Since mid-summer streamflows will be lower and winter flows higher, a
notable difference will exist regarding site specific hydraulic
conditions in peripheral habitats. Many areas will be dewatered that
VI-12
STREAM FLOW
Mainstem
(xiOOOcfs)
Side Slougtl (ch)
WATER TEMPERATURE
Mainatem (°C)
lntergrovel Flow
(OC)
WATER QUALITY
Turlliditr ( NTU)
Suspen..1ed Solids
ICE PROCESSES
Ice Front Period
Upstreom Extent
of Ice Cover
Overwlnterl ftQ
l WITH· ,_.OJICT --.... __ --------
NATURAL ..,.. ___ .
0 NAT'UJtAL
0 0 0 • WITH•,..o.IECT
100 110 ISO •-.. 100 114 124•141 Depen41nl on CliMate
DATE
Figure n-2. Comparison of natural and with-project habitat compon•ts.
VI-13
presently convey streamflow during SUITITler whereas the opposite trend
will prevail during winter. Mid-channel areas will also experience a
change in hydraulics that will affect the amount and quality of fish
habitat relative to present levels.
The 8.6 million acre-foot impoundment behind the proposed Watana dam
will effectively trap nearly all the sand and larger size materials
currently being transported downstream from upstream sources (R&M
1982f, Harza-Ebasco 1984a).
Detention time for Watana Reservoir is estimated to be 1.6 years (APA
1983) thus downstream water quality will be affected by limnological
processes occurring in the reservo i rs. The Watana reservoir will
contain turbid glacier melt water throughout the year. Downstream
flows are expected to change from highly turbid in summer and clear in
winter to moderately turbid all year (Peratovich et al. 1982).
Downstream temperature is also expected to be altered by the large
impoundments. The reservoirs will attenuate existing mid -summer
stream temperatures and store solar energy during summer for redistri-
bution during fall and winter months. This will promote warmer stream
temperatures in the fall and winter, probably delaying freeze-up
(AEIDC 1984b, Harza-Ebasco 1984c).
Anticipated instream water quality and temperature are important to
flow negotiations in that with-project conditions may either alter or
provide mitigative opportunities being considered. Although it is
necessary to evaluate the influence of project design and operation on
with-project water quality and temperature, it must be recognized that
certain unavoidable conditions (project effects) may exist over which
project design and operation have limited control.
However, in many situations design and operation of the proposed
Susitna project will afford varying degrees of control over the
streamflow, stream temperatures and water quality of the middle
VI-14
Susitna River. The degree of control that might exist over these
macrohabitat conditions will in turn influence other important habitat
components at the microhabitat level (Figure VI-3).
Control over with-Project Relationships
The degree of control that project design and operation can exert over
macrohabitat conditions in the middle Susitna River is strongly
influenced by basic laws of physics governing energy transfer and the
seasonal changes in air temperature. The influence of mainstem
discharge, temperature and water quality on middle Susitna River fish
habitat is also highly dependent upon the location of affected habi-
tats with respect to the dam site ( s) and the rna i nstem channe 1. The
further downstream from the project, the less influence project
operation has on streamflow (Harza-Ebasco 1984f), stream temperature
(AEIDC 1984b), and water quality. It is also evident that aquatic
habitats peripheral to the mainstem are most sensitive to dewatering
by variations in mainstem discharge (.EWT&A 1984, ADF&G 1984d) whereas
habitats directly associated with the mainstem are most significantly
influenced by variations in mainstem temperature and water quality
(ADF&G 1982b).
Therefore the nature and degree of change that may be intentionally
caused by project design and operation is bounded by watershed charac-
teristics and physical laws of science as well as project economics .
Some unavoidable effects of project construction may be beneficial to
middle Susitna River fish habitats. Most notably is the entrapment of
nearly all suspended sediment currently being transported by the
middle Susitna River. Reduction in mid-summer suspended sediment
concentrations is expected to result in more hospitable habitat
conditions for invertebrates and immature fish that typically inhabit
streambed materials. Associated with the reduction in suspended
sed i ments will likely be a reduction in mid-summer turbidities, which
may improve the depth of light penetration and stimulate algal growth
on a more stable and coarse graded streambed.
VI-15
Project .Design and Operation
FOOD
PRODUCTION
LEGEND
Degree o f Control
HIGHEST .
!
-LOWEST
WATER
QUALITY
FlgureJl:I-3. Ranking of habitat component in accord with the degree of control project
design and operation might pro.~ ide them.
Mainstem turbidities are also expected to remain higher than natural
throughout winter. At present it is not known whether project design
or operation could significantly control downstream turbidities, nor
has the effect of the project induced change in natural turbidity
levels been estimated. However, overwintering fish are thought to
primarily use low velocity lateral habitats, such as sloughs, slough
mouths or tributary mouths. It is likely that the high winter flows
will increase upwelling and thus may increase the amount of clear-
water, low velocity habitat in the winter. The actual gain in habi-
tat, if any, would depend on the upstream extent of the ice front and
the effects of staging on slough habitats.
With-project stream temperatures are expected to be cooler in summer
and wanner in winter. Project design and operation can exert a
moderate degree of control over mainstem water temperatures (AEIDC
1984}. Winter is the most important season in which to evaluate the
degree of control which project design and operation has over middle
Susitna River temperatures is winter. Cold stream temperatures and .
associated ice processes appear to be the most limiting habitat
component for existing fish populations (Table VI-2}. The increase of
stream temperatures throughout winter would likely improve over-
wintering in mainstem and side channel habitats. Groundwater tempera-
tures in slough habitats may increase slightly (0.2°C}. This slight
increase is not expected to have a measureable effect on surface water
temperatures. Were mainstem and side channel temperatures sufficient
to prevent formation of an ice cover, it is expected that terrestrial
vegetation would stabilize along shorelines and partially vegetated
gravel bars. This change would likely improve summer rearing due to
greater availability of terrestrial insects and shoreline cover.
Lack of winter ice cover would also greatly reduce the adverse effects
currently associated with the naturally occurring overtopping of side
slough spawning habitats. Lack of an ice cover would reduce staging
and therefore the frequency at which side slough habitats are over-
topped. In addition those channels which convey water warmer than 0°C
may provide improved overwintering and incubation.
VI-17
Project operation can provide a high degree of control over streamflow
in the middle Susitna River (Harza-Ebasco 1984f). Surrmer flow could
be regulated to provide relatively stable depths and velocities, or
could be intentionally fluctuated to flush undesirable sediment from
the streambed . Streamflow fluctuations during fall could assist adult
salmon gain access to side slough spawning habitats (ADF&G 1984e,
wee 1984 Mitigation). However recurrent fluctuations such as those
commonly associated with hydropower peaking would 1 ikely be detri-
mental to mainstem and side channel habitats. During winter, higher
than natural, but stable, streamflows would likely improve over-
wintering in mainstem and side channel habitats. However, the inflow
of colder mainstem water could adversely affect incubation and over-
wintering conditions in side slough habitats if mainstem water surface
elevations associated with higher winter streamflows were sufficient
to cause recurrent mid-winter breaching events.
VI-18
VII REFERENCES
Alaska Department of Fish and Game. 1981. Susitna Hydro Aquatic
Studies -Phase I Final Draft Report: Adult anadromous fisheries
project. Prepared for Acres American, Inc. Buffalo, NY.
Alaska Department of Fish and Game. 1982a. Susitna Hydro Aquatic
Studies Phase II Final Data Report: Volume 2. Adult
Anadromous Fish Studies. Anchorage, AK 239 pp.
Alaska Department of Fish and Game. 1982b. Susitna Hydro Aquatic
Studies -Phase I Report: Aquatic Studies Program. Prepared for
ACRES American Incorporated, Buffalo, NY 137 pp.
Alaska Department of Fish and Game'. 1983a. Susitna Hydro Aquatic
Studies -Phase II Data Report: Winter aquatic studies {October
1982 -May 1983), Anchorage, AK. 137 pp.
Alaska Department of Fish and Game. 1983b. Susitna Hydro Aquatic
Studies -Phase II Report. Volume I: Sulmlarization of Volumes
2, 3, 4; Parts I and II, and 5. Anchorage, AK. 126 pp.
Alaska Department of Fish and Game. 1983c. Susitna Hydro Aquatic
Studies: Phase II Basi -c Data Report. Volume 4: Aquatic habitat
and instream flow studies, 1982, Appendix C {Draft). Anchorage,
AK 221 pp.
Alaska Department of Fish and Game. 1984a. Susitna Hydro Aquatic
Studies, Report No. 1: Adult Anadromous Fish Investigations, May
-October 1983. Prepared for Alaska Power Authority, Anchorage,
AK. 380 pp.
Alaska Department of Fish and Game. 1984b.
fishery, 1983. Prepared by James
Commercial Fisheries. Soldotna, Alaska.
Tyonek subsistence salmon
Browning, Division of
Alaska Department of Fish and Game. 1984c. Susitna Hydro Aquatic
Studies, Report No. 2: Resident and juvenile anadromous fish
investigations, May -October 1983. Dana C. Schmidt, Stephen ~
Hale, Drew L. Crawford, Paul M. Suchanek (eds.), Prepared for:
Alaska Power Authority, Anchorage, AK . 395 pp.
Alaska Department of Fish and Game. 1984d. Susitna Hydro Aquatic
Studies, Report No. 3: Aquatic Habitat and Instream Flow
Investigations, May -October 1983. Part II, Chapter 7: An
Evaluation of Chum and Sockeye Salmon Spawning Habitat in Sloughs
and Side Channels of the Middle Susit1a River. Prepared for
Alaska Power Authority, Anchorage, AK. 178 pp.
Alaska Department of Fish and Game. 1984e. Su$itna Hydro Aquatic
Studies, Report No. 3: Aquatic Habitat and lnstream Flow
Investigations, May -October 1983. Chapter 6: An evaluation of
passage conditions for adult salmon in sloughs and side channels
Vll-1
of the Middle Susitna River.
Authority, Anchorage, AK. 178 pp .
Prepared for Alaska Power
Alaska Department of Fish and Game. 1984f. Susitna Hydro Aquatic
Studies, Report No. 3: Aquatic Habitat and Instream Flow
Investigations, May -October 1983. Chapter 3: Continuous water
temperature investigations. Prepared for Alaska Power Authority,
Anchorage, AK. 145 pp.
Alaska Department of Fish and Game. 1985. Susitna Hydro Aquatic
Studies, Report No. 1: Adult Anadromous Fish Investigations, May
-October 1984. Draft. Prepared for Alaska Power Authority,
Anchorage, Ak . 177 pp. and appendices.
Alaska Power Authority. 1982.
and Wildlife Mitigation
Anchorage, AK.
Susitna Hydroelectric Project: Fish
Pol icy. Alaska Power Authority.
Alaska Power Authority. 1983. Application for license for major
project, Susitna Hydroelectric Project, before the Federal Energy
Regulatory Corm~ission. Volume SA . Exhibit E, Chaps. 1 and 2.
Susitna Hydroelectric Project. 1 vol.
Alley, D.W ., Jr. and H.W. Li. 1978. Microhabitat segregation and
seasonal movements by fishes in a Sierra foothill stream.
Manuscript submitted to Trans . Am . Fish . Soc. 37 pp.
Arctic Environmental Information and Data Center. 1984a. Geomorphic
change in the Devil Canyon to Talkeetna reach of the Susitna
River since 1949. Arctic Environmental Information and Data
Center, University of Alaska, Anchorage. Preliminary report for
Alaska Power Authority, Susitna Hydroelectric Project, Anchorage,
AK. 1 Vol.
Arctic Environmental Information and Data Center. 1984b. Assessment of
the effects of the proposed Susitna Hydroelectric Project on
instream temperature and fishery resources in the Watana to
Talkeetna reach. Final Report Volume 1. Prepared for Alaska
Power Authority, Anchorage, AK. 130 pp.
Ashton, George D. 1978. "River Ice", Annual Review of Fluid Me chan i cs.
Barrett , B. 1984. SuiiiJiary of abundance and distribution of adult
salmon in Susitna River sub-basins. Presented at: Aquatic
Habitat Workshop No. 1, Susitna Hydroelectric Project, Northern
Lights In n , Anchorage, Alaska, February 15, 1984.
Bechtel Civil and Minerals,
Project, Interim Report .
Francisco, California.
Anchorage, Alaska.
Inc. 1983. Chakachamna Hydroelectric
Bechtel Civil and Minerals, Inc . San
Prepared for Al aska Power Authority.
Bell, M. 1973. Fisheries handbook of eng i neering requirements and
biological criteria. U.S. Army Corps of Engineers, North Pacifi c
Division. Portland, OR.
VII-2
Bjornn, T.C. 1971. Trout and salmon movements in two Idaho streams as
relat ~d to temperature, food, streamflow, cover, and population
density . Trans. Amer. Fish. Soc. vol . 100 :3.
Bovee, K.D. 1978. Probability-of-use criteria for the family
salmonidae. Instream flow information paper No.4 FWS/OBS-78/07,
Ft. Collins, Colorado.
Bovee, K.D. 1982. A guide to stream habitat analysis using the
instream flow incremental methodology. Instream Flow Information
Paper No. 12, Fish and Wildlife Service, U.S. Dept. of the
Interior.
Bovee, K.D., and R. Milhous. 1978. Hydraulic simulation in instream
flow studies theory and techniques. Cooperative Instream Flow
Service Group, U.S. Fish and Wildlife Service, Fort Collins, CO.
Instream Flow Information Paper No. 5. 130 pp.
Buck, H.D. 1956. Effects of turbidity on fish and fishing. Trans. of
N. Am. Wildl . Conf. 21:249-261.
Burger, C.V., D.G. Wangaard, R.L. Wilomt, and A.N. Palmisano. 1982.
Salmon investigations in theKenai River, Alaska 1979-1981. U.S.
Fish and Wildlife Service, Anchorage, Alaska.
Burton, G.W. and E.P. Odum. 1945. The distribution of stream fish in
the vicinity of Mountain Lake, Virginia. Ecology 26 :182-194 .
Bustard, D.R. and D.W. Narver. 1975. Aspects of the winter ecology of
juvenile coho salmon (Oncorhynchus kisutch) and steelhead trout
(Salmo gairdneri). J. Fish Res. Bd. Can. 32 :667-680.
Cederholm, C.J. and K.V. Koski. 1977. Effects of stream
channelization on the salrnonid habitat and populations of Lower
Big Beef Creek, Kitsap County, Washington 1969-73 . Univ . of
Wash. Coop. Unit, Seattle, WA.
Cooper, A.C. 1965. The effect of transported stream sediments on the
survival of sockeye and pink salmon eggs and alevin. Bulletin
XVIII. International Pacific Salmon Fisheries Conmission, New
Westminster, B.C., Canada. 71 pp.
Dettman, D.H. 1977. Habitat selection, daytime behavior, and factors
influencing distribution and abundance of rainbow trout (Salmo
na i rdneri) and Sacramento squawfi sh ( Pt~chocheil us grandi s) in
eer Creek, California. M.S. Thesis, On versity of California,
Davis, CA. 47 pp.
Dyok, W. 1984. Harza-Ebasco Susitna Joint Venture, Anchorage, Alaska.
Personal Communicat i on.
Estes, C.C., K.R. Hepler and A.G. Hoffman. 1981. Willow and Deception
Creeks instream flow demonstration study. Vol. 1. Prepared for
VII-3
the U.S. Department of Agriculture, Soil Conservation Service,
Interagency Coop. Susitna River Basin Study. Alaska Department
of Fish and Game. Habitat and Sport Fish Divisions. Anchorage,
Alaska.
Everest, F.H., and D.W. Chapman. 1972. Habitat selection and spatial
inter-action by juvenile chinook salmon and steelhead trout in
two Idaho streams. J. Fish. Res. Bd. Can. 29 :91-100.
Florey, K. 1984. ADF&G Commercial Fisheries. Anchorage, Alaska.
Personal Communication.
Gemperline, E.G. 1984. Comments on: Assessment of the effects of the
proposed Susitna Hydroelectric Project on instream temperature
and fisheries resources in the Watana to Talkeetna reach, Draft
report by Arctic Environmental Information and Data Center.
Harza-Ebasco Susitna Joint Venture. Anchorage, Alaska. 6 pp.
Gore, J.A. 1978. A technique for predicting instream flow
requirements for benthic macroinvertebrates. Freshwater Biology
8:141-151. .
Hale, S.S. 1981. Freshwater habitat relationships: chum salmon
(Oncorh~nchus keta). Alaska Dept. of Fish and Game, Habitat
Protect1on Brancn:-Anchorage, AK. 93 pp.
Hansen, T. 1984. ADF&G Su Hydro, Anchorage, AK. Personal
Communication.
Harza-Ebasco Susitna Joint Venture. 1984a. Susitna Hydroelectric
Project: Reservoir and river sedimentation, Prepared for Alaska
Power Authority, Anchorage, AK. 36 pp.
Harza-Ebasco Susitna Joint Venture. 1984b. Susitna Hydroelectric
Project: Susitna River Ice Study. Prepared for Alaska Power
Authority. Anchorage, AK. 180 pp.
Harza-Ebasco Susitna Joint Venture. 1984c. Susitna Hydroelectric
Project: Instream Ice Calibration of Computer Model. Prepared
for Alaska Power Authority . Anchorage, AK. 20 pp.
Harza-Ebasco Susitna Joint Venture. 1984d. Alaska Power Authority
comments on the FERC Draft Environmental Impact Statement of May
1984. Volume 9, Appendix VII -Slough Geohydrology Studies.
Document 1780.
Harza-Ebasco Susitna Joint Venture. 1984e. Middle and lower Susitna
River water surface profiles and discharge rating curves. Alaska
Power Authority Susitna Hydroelectric Project. Anchorage, AK.
Document 482.
Harza-Ebasco Susitna Joint Venture. 1984f. Weekly flow duration
curves and observed and filled weekly flows for the Susitna River
Basin. Alaska Power Authority Susitna Hydroelectric Project.
Anchorage, AK. Document 2318.
VII-4
Harza-Ebasco Susitna Joint Venture. 1985. Susitna Hydroelectric
Project -Streamflow Time Series, Susitna River at Watana and
Devil Canyon (Draft Report, January 1985). Prepared for Alaska
Power Authority, Anchorage, Ak.
Hynes, H.B.N. 1970. The ecology of running waters. University of
Toronto Press. 555 pp.
Hynes, H.B.N. 1971. The biology of polluted waters. University of
Toronto Press. 202 pp.
Klinger, S. and E.W. Trihey. 1984. Response of aquatic habitat
surface areas to mainstem discharge in the Talkeetna to Devil
Canyon reach of the Susitna River, Alaska. E. Woody Trihey and
Associates. Report for Alaska Power Authority, Susitna
Hydroelectric Project, Anchorage, AK. Document 1693. 1 vol.
Knott, J.M. and S.W. Lipscomb. 1983. Sediment discharge data for
selected sites in the Susitna River Basin, Alaska, 1981-82.
Open-file Report 83-870. U.S. Department of the Interior,
Geological Survey, Anchorage, AK. 45 pp.
Kogl, D.R. 1965. Springs and groundwater as factors affecting
survival of chum salmon spawn in a sub-arctic stream. M.S.
Thesis, Univ. of Alaska, College . 59 pp.
Koenings, J.P. 1984. ADF&G F.R.E. Div., Soldotna, pers. comm.
Koenings, J.P. and G.B. Kyle. 1982. Limnology and fisheries
investigations at Crescent Lake (1979-82). ADF&G F.R.E. Div.,
Soldotna.
Koski, K.V. 1975. The survival and fitness of two stocks of chum
salmon (Oncorhynchus keta) from egg deposition to emergence in a
controlled-stream envlranment at Big Beef Creek. Ph.D. Thesis,
Univ. Washington, Seattle. 212 pp.
LaPerriere, J. 1984. University of Alaska -Fairbanks. Personal
Communication.
LeVeen, L. 1984. U.S ; Geological Survey, Anchorage, AK. Personal
Communication.
Mackin, J. Hoover, 1948. "Concept of the Graded River," Geolotcal
Society of America Bulleting, Vol. 59, pp. 463-512, May, 194.
McNeil, W.J. 1965. Effect of the spawning bed environment on
reproduction of pink and chum salmon. Fish. Bull. 65(2):
• 495-523.
McNeil, W.J. and W.H. Ahnell. 1964. Success of pink salmon spawning
relative to size of spawning bed materials. Special Scientific
Report -Fisheries No. 469, U.S. Fish and Wildlife Service.
15 pp.
VII-S
McNeil, W.J. and J.E. Bailey. 1975. Salmon ranchers manual. U.S.
National Marine Fisheries Service, Auke Bay, AK. 95 pp.
Michel, B. 1971. Winter regime of rivers and lakes. Cold Regions
Research and Engineering Laboratory, U.S. Army Corps of
Engineers, Hanover, NH. 130 pp.
Milhous, R.T., D.L. Weyner, and T. Waddle. 1984. Users guide to the
Physical Habitat Simulation System. Instream Flow Information
Paper 11. U.S. Fish Wildl. Serv. FWS/OBS -81/43 Revised.
475 pp.
Mills, M.J. 1979. Alaska Statewide Sport Fish Harvest Studies. ADF&G
Federal Aid fn Fish Restoration. Volume 20. F-9-11, SW-1.
Mills, M.J. 1980. Alaska Statewide Sport Fish Harvest Studies 1980.
Alaska Department of Fish and Game. Federal Aid in Fish
Restoration. Volume 21. F-9-12, SW-1. 65 p.
Mills, M.J. 1981. Alaska Statewide Sport Fish Harvest Studies -1980
Data. ADF&G Federal Aid in Fish Restoration. Volume 22.
F-9-13, SW-1.
Mills, M.J. 1982. Alaska Statewide Sport Fish Harvest Studies. ADF&G
Federal Aid in Fish REstoration. Volume 23. F-9-14, SW-1.
Mills, M.J. 1983. Alaska Statewide Sport Fish Harvest Studies: ADF&G
Federal Aid in Fish Restoration. Volume 24. SW-I.
Mills, M.J. 1984. Alaska Statewide Harv~st Studies. ADF&G Federal
Aid in Fish Restoration. Volume 25. SW-IA.
Nelson, P. 1984. Instream Flow Group, Fort Collins, CO, pers. comm.
Olsen, R.W. 1979. Methodologies for use in project-related studies.
In: Proceedings frmo Hydropower: A national energy resource.
'March 11-16, 1979, Engineering Foundation Conference. In
cooperation with U.S. A~ Corps of Engineers. Easton, Maryland.
pp. 157-169.
Osterkamp, T.E. 1978. Frazil ice fonmation: a review. J. Hydr. Div.
of Amer. Soc. Civil Engin. 104(N9):1239-1255.
Peratrovich, Nottingham and Drage, Inc. and Hutchinson, I.P.G. 1982.
Susitna reservoir sedimentation and water clarity study.
Prepared for Alaska Power Authority, Susitna Hydroelectric
Project, Anchorage, AK.
Phillips, R.W., R.J. Lantz, E.W. Claire, J.R. Moring. 1975. Some
effects of gravel mixtures on emergence of coho salmon and
steelhead trout fry. Trans. Amer. Fish. Soc. 1975(3):461-466.
R&M Consultants, Inc. 1981. Regional flood peak and volume frequency
analysis. Prepared for Alaska Power Authority, Susitna
Hydroelectric Project, Anchorage, AK.
VII-6
R&M Consultants, Inc. 1982a. Susitna Hydroelectric Project -River
Morphology. Prepared for Alaska Power Authority, Anchorage, AK.
105 pp.
R&M Consultants, Inc. 1982b.
Hydraulic and Ice Studies.
Anchorage, AK. 178 pp.
Susitna Hydroelectric Project
Prepared for Alaska Power Authority,
R&M Consultants, Inc. 1982c. Susitna Hydroelectric Project
Tributary Stabi 1 ity Analysis. Prepared for Alaska Power
Authority, Anchorage, AK. 13 pp.
R&M Consultants, Inc. 1982d. Susitna Hydroelectric Project; task 3 -
hydrology; slough hydrology preliminary report. Prepared for
Alaska Power Authority, Anchorage. 1 Vol.
R&M Consultants, Inc. 1982e. Susitna Hydroelectric Project :
Streambed material survey. Unpublished report. Prepared for
Alaska Power Authority, Anchorage, AK.
R&M Consultants, Inc. 1982f. Susitna Hydroelectric Project: Reservoir
Sedimentation Closeout Report. Prepared for Alaska Power
Authority, Anchorage, AK.
R&M Consultants, Inc. 1983.. Susitna Hydroelectric Project : Susitna
River Ice Study (Task 4). Prepared for Harza-Ebasco Susitna
Joint Venture. Anchorage, AK. 183 pp. + Maps.
R&M Consultants, Inc. 1984. Susitna Hydroelectric Project -Suspended
Sediment and Turbidity, Settling Column Study (Draft Report,
November 1984). Prepared for Alaska Power Authority, Anchorage,
Ak. 74 pp.
R&M Consultants, Inc., and W.O. Harrison 1982. 1982 Susitna basin
glacial studies. Prepared for Alaska Power Authority, Susitna
Hydroelectric Project, Anchorage, AK.
Raymond, J.A. 1981. Incubation of fall chum salmon (Oncorh~nchus
keta) at Clear Air Force Station, Alaska. F.R.E. Div1sion,
~ka Dept. Fish and Game, Juneau, AK. 25 pp.
Schmidt, D. 1984. ADF&G SuHydro, Anchorage, pers. comm.
Scott, W.B. and E.J. Crossman. 1973. Freshwater fishes of Canada.
Bull. Fish. Res. Bd. Canada 184. 966 pp.
Scully, D.R., L.S. Leveen, and R.S. George. 1978. Surface water
records of Cook Inlet Basin, Alaska, through September 1975.
U.S. Geological Survey, Anchorage, AK. Open-file Report 78-498.
102 pp.
Sheldon, A.L. 1968. Species diversity and longitudinal succession in
stream fishes. Ecology 49(2):193-198.
VII-7
Smith, A.K. 1973. Development and ,application of spawning depth and
velocity criteria for Oregon salmonids. Trans. Am. Fish. Soc.
102{2):312-316.
Stalnaker, C.B., and J.l. Arnette, eds. 1976. Methodologies for the
determination of stream resource flow requirements: an
assessment. Utah State University, logan, UT. Report for U.S.
Fish and Wildlife Service. 199 pp.
Stanford, J. 1984. University of Montana. Personal Communication.
Thompson, K. 1972. Determining streamflows for fish life.
Pages 31-46 in Proc. Instream Flow Req. Wkshp., Portland, OR.,
March 15-16,-rg72.
Trihey, E.W. 1979. The IFG incremental methodology. Pages 24-44 in
G.L. Smith, ed. Workshop in instream flow habitat criteria and
modeling. Colorado Water Resources Research Institute, Colorado
State University, For Collins, CO. Information Series No. 40.
Trihey, E.W., et al. 1982. 1982 Winter temperature study. Open File
Report. Prepared for Alaska Power Authority, Susitna
Hydroe 1 ectri c Project, Anchorage, AK. 145 pp.
Trihey, E.W. 1983. Preliminary assessment of access by spawning
salmon into Portage Creek and Indian River. Prepared for Alaska
Power Authority, Anchorage, AK. 31 pp.
U.S. Fish and Wildlife Service. 1981. Endangered and Threatened
Wi 1 dl i fe and Plants. Federa 1 Register 50 CFR 17.11 and 17.12.
January 1, 1982.
Van Nieuwenhuyse, E.E. 1984. Preliminary analysis of the
relationships between turbidity and light penetration in the
Susitna River, Alaska. Technical memorandum prepared for
Harza-Ebasco Susitna Joint Venture, Anchorage. 7 pp.
Wangaard, D.B. and C.V. Burger. 1983. Effects of various water
temperature regimes on the egg and alevin incubation of Susitna
River chum and sockeye salmon. National Fishery Research Center,
U.S. Fish and Wildlife Service. Anchorage, AK . 41 pp.
Wesche, T.A., and P.A. Rechard. 1980. A summary of instream flow
methods for fisheries and re 1 a ted research needs. Water
Resources Research Institute, University of Wyoming, Eisenhower
Consortium Bulleting 9, laramie, Wyoming, USA.
Wilson, W.J., E.W. Trihey, J.E. Baldrige, C. D. Evans, J.G. Thiele,
D.E. Trudgen. 1981. An assessment of environmental effects of
construction and operation of the proposed T.error lake
hydroelectric facility, Kodiak Island, Alaska. Arctic
Environmental Information and Data Center, University of Alaska,
Anchorage. Prepared for Kodiak Electric Association, Inc.,
Kodiak, AK. 419 pp.
VII-8