HomeMy WebLinkAboutSUS495rev33RD3/001
PRELIMINARY DRAFT
IMPACT ASSESSMENT TECHNICAL MEMORANDUM
WATER QUALITY
Prepared by:
Arctic Environmental Information and Data Center
University of Alaska-Fairbanks
707 "A" Street
Anchorage, Alaska 99501
Submitted to:
Harza-Ebasco Susitna Joint Venture
711 "H" Street
Anchorage, Alaska 99501
April 30, 1985
Introduction
Purpose
Scope
Statement of the Problem
Methods and Procedures
The Information Base
Baseline Data
Forecasted Data
Data Gaps
Impact Analysis
Basic Considerations
Nitrogen Supersaturation
TABLE OF CONTENTS
Dissolved Oxygen, pH, and Macronutrient Concentrations
Trace Metal Concentrations
Mercury
Cadmium
Copper
Zinc
Summary and Recommendations
References
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LIST OF TABLES
Table
1.Mean baseline water quality characteristics for upper Susitna
River at Vee Canyon under summer (May-August)and winter
(October-April)conditions.
2~Mean baseline water quality characteristics for middle Susitna
River at Gold Creek under summer (May-September)and winter
(October-April)conditions.
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10
"..,3.Mean baseline water quality characteristics for lower Susitna
River at Susitna Station under summer (May-September)and
winter (October-April)conditions.14
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4.Selected morphometic and hydrologic features of the Watana and
Devil Canyon reservoirs.16
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INTRODUCTION
PURPOSE
This document assesses several water quality issues relative to the
-proposed upper Susitna River basin hydroelectric development.Since fish
species present in the Susitna River drainage are dependent,to a certain
degree,on natural instream water quality,studies were initiated (in the
beginning phases of Susitna environmental investigations)to address the
potential adverse or beneficial effects of water quality parameters on fish.
This report is one in a series on various aquatic impact issues
associated with the Susitna Hydroelectric Project.These issues--instream
temperature,water quality,turbidity,instream ice,and bedload--will be
examined in each of five technical memoranda.These synopses of impacts will
ultimately form the foundation for a comprehensive impact assessment report.
After each of the five documents has been adequately revie~ed,we will
integrate them into a draft impact assessment report.The Alaska Power
Authority and Harza-Ebasco intend to utilize the impact assessment technical
memoranda to discuss issues with agencies arid intervenors in the Susitna
licensing process.
Impact issues were defined in the course of the Susitna licensing
process.After the Federal Energy Regulatory Commission (FERC)reviewed the
original license application and the Alaska Power Authority corrected
deficiencies and provided supplemental information,the license application
was found acceptable.FERC then proceeded with the preparation of an
Environmental Impact Statement (EIS).The decision to prepare an EIS set in
mo~ion a chain of events in accordance with Council on Environmental Quality
mandates (Vide 40 CFR 1500).
33RD3/001
Scoping meetings were held by FERC staff to
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determine the significant issues to be analyzed in depth in the environmental
impact statement and to identify and eliminate from detailed study issues
which were not significant or which were covered by prior environmental
review.
Issues deemed important for assessment in the EIS included twelve fishery
issues.One of these,Issue No.F-2,identified salmon and resident fish
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habitats and populations downstream of the dams as topics to be addressed.
Sub-issue F-2.6 is the significance of change in water quality parameters
(nutrients)on salmon and resident fish habitats and populations downstream of
the dams (Sus 472).
Environmental field investigations and analyses of existing published and
unpublished information have been conducted in order to provide accurate
statements of expected impact of the Susitna project on water quality and fish
resources.The data base and the statements of anticipated effects have been
scrutinized by agency and intervenor representatives in a series of workshops
statements have been obtained from these discussions.Ultimately,the Alaska
Power Authority intends to "settle ll each issue with the agencies and
intervenors;that is,agreement will be sought on the adequacy of the
information base,the impact statements,and the proposed mitigation for
undesirable impacts.This agreement or settlement would provide the basis for
license articles or stipulations authorizing construction and operation of the
Susitna project.
This document,therefore,summarizes work accomplished to date on the
water quality issue.It is intended to serve as a discussion document,for it
contains a presentation of the issue,.a brief synopsis of the relevant
information base,the ramifications of altered water quality to aquatic
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and discussions.
33RD3/001
Suggested refinements to the data base and/or the impact
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habitats and fish,and the projected effects on fish due to various modes of
Susitna project operation.
-Finally,this document is intended to be a working tool,a
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decision-making aid.Other reports containing voluminous data and analyses of
water quality changes and effects on fish are heavily referenced.We have not
repeated detailed information presented elsewhere unless required for clarity.
Presented are statements of effect or no effect and the confidence with which
we make those statements.
SCOPE
This document describes the process of impact assessment;that is,it
illustrates how the impact assessment for the water quality issue was
effects of the Susitna project on water quality parameters and fish resources.
Meteorologic,hydrologic,and water quality data have been collected for
nearly five years.With this information and other data,analyses have been
forwarded discussing the likelihood of change in water quality due to the
project and the effects on fish expected from this change.The mechanisms of
impact,or how changes in water quality adversely or beneficially affect fish,
are presented.This is done so that reviewers can scrutinize the methods and
techniques employed in deriving impact statements from the existing
information base and review assumptions used when making predictions of
unmeasured events.Also presented are analyses of the degree of control the
project will have over water quality parameters.
This report does not delve into flow-related,hydraulic impacts;these
are addressed in the Instream Flow Relationships Report Series (Sus 455).
However,since water quality is affected to a certain degree by river
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conducted.
33RD3/001
A moderate information base exists with which to assess the
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discharge level,an evaluation of the effects of var-wUS'flow regin1E:s is-presented.Included is an assessment of the adequacy of the existing
information base for addressing the issue and,where warranted,suggestions
for improving the analysis.The analytical tools available for conducting
this impact assessment are discussed,including a presentation of the
strengths,weaknesses.and limitations of the models employed for simulating
unobserved conditions.Suggestions for mitigating undesirable with-project
effects are also provided.However,this is not a mitigation report;
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substantial information in this vein can be examined in other documents,most
notably work accomplished by Woodward-Clyde Consultants (Sus 422)•
The significance of the issue and associated impacts,both adverse and
beneficial,are discussed.The magnitude of the fish resource to be impacted
is quantified to the extent feasible and to the extent that the existing
information base would reasonably permit.Since most of the impacts expected
from operation of the Susitna project are in the middle river reach,the size
of the fish populations there is presented relative to the population size of
Susitna River drainage fish stocks as a whole.
STATEMENT OF THE PROBLEM
Water quality in the impoundment zone will change under with-project
conditions from its natural lotic character to an essentially lentic
character.The reservoirs (especially Watana)will act as traps for 70-90%of
the incoming sediment normally transported by the upper river during the open
water season (May-October)and will subject incoming flow to seasonal patterns
of thenmal stratification and community metabolism which will measurably alter
changes in the quantity of downstream flow will alter habitat conditions along-
the quality of the outflow.
33RD3/001
This change in water quality combined with
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the entire length of the middle river during the open water season and in both
the middle and lower rivers during the winter months.Thus,a 240-mile reach
will be affected by impoundment.
The:water quality parameters of greatest biological significance that
will likely be changed under with-project conditions include:temperature,
total suspended sediment concentration (TSS),turbidity,total recoverable and
dissolved metal concentrations (including some heavy metals),macronutrient
addressed in a separate issue paper as are TSS,turbidity,and total organic
carbon.This paper will thus focus on the remaining parameters as well as pH,
dissolved oxygen concentration,and total dissolved gas supersaturation .
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concentrations,and total organic carbon concentrations.Temperature is
33RD3/001 - 5 -
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METHODS AND PROCEDURES
Short of conducting field and laboratory experiments,the principal tools
available to assess the water quality impacts associated with impoundment of
the Susitna River are:1)the historical baseline water quality and flow
records collected by the USGS;and 2)the body of information in the
literature concerning water quality processes in lakes and reservoirs.
The procedure used to prepare this assessment consisted of:1)reviewing
the literature concerning post-impoundment water quality effects elsewhere in
the world;2)identifying the principal physical,chemical,and biological
processes which together alter the water quality of an impounded river;
3)deducing on the basis of baseline and forecasted data which processes would
likely result in substantial changes in the natural water quality regime of
the Susitna River;and 4)identifying which parameters would be most affected
in the Susitna River and describing any likely ecological consequences.
Exhaustive literature reviews conducted by AEIDC and Harza-Ebasco (Tom
Stuart,H-E,Anchorage,pers.comm.)revealed no studies concerning the
impoundment of glacial rivers and relatively few studies on downstream water
quality effects.Thus,most of the conclusions presented here are based on
qualitative analogies drawn from documented events associated with reservoirs
t-)
studied for the most part in temperature latitudes,taking into account the
glacial character and lower water temperatures displayed by the Susitna River.
Impacts are assessed for both the one-and two-dam scenarios as well as for
the construction and filling phases of the proposed projects.
33RD3/001 - 6 -
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THE INFORMATION BASE
BASELINE DATA
The~main body of data describing the natural water quality
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characteristics of the Susitna River is found in the U.S.Geological Survey
(USGS)"Water Resources Data for Alaska"annual report series.This
information is summarized through 1981 in R&M Consultants,Inc.and L.A.
Peterson and Assoc.(1981a"b).These data are collected routinely on a
monthly basis by the USGS at its gauging stations located at Denali (1957-),
Vee Canyon (1962-),and Gold Creek (1949-)on the upper and middle Susitna
River;the Chulitna River (1958-);the Talkeetna River (1954-);and at its
Sunshine (1971-)and Susitna stations (1955-)on the lower Susitna River.
Data collected by R&M Consultants at Vee Canyon and Gold Creek from 1980-82
are summarized in R&M Consultants,Inc.(1982).Limited additional data for
mainstem,slough,and tributary sites can be found in various Alaska
Department of Fish and Game reports (ADF&G,Su-Hydro 1981).
Water quality data collected at .Vee Canyon can·be used to describe some
of the chemical characteristics of the water that will flow into Watana
reservoir (Table 1).The basic pattern these data present for the upper river
is similar in most respects to the annual cycle displayed in the middle river
for which a much more complete and longer data record is available.The most
significant difference is the absence of dissolved gas supersaturation at Vee
Canyon.Other minbr differences (e.g.,higher mean pH,potassium,and
chemical oxygen demand levels in summer and a lower mean turbidity)can be
attributed either to the influence of clearwater tributaries entering upstream
of the station or to the relatively small number of data points available for
analysis.
33RD3/001 - 7 -
Table 1.Mean baseline water quality characteristics for upper Susitna River
at Vee Canyon under summer (Hay-August)and winter (October-April)
conditions.
Summer Winter
Parameter
USGS 1 R&H 2 USGS 1 R&M 2(Symbol of Abbreviation)Units of Measure
Total Suspended Solids (TSS)mg/l 799 358 14 6.0
Turbidity NTU 70 156 0 1.3
Total Dissolved Solids (TDS)mg/l 94 98 136 141
Conductivity (llmhos -1 25°C)146 129 250 212cm,
pH pH Units 7.7 7.6 7.4 7.1
Alkalinity mg/l as Ca C0 3 52 61 112 81
Hardness mg/l as Ca C0 3 63 58 96 103
Sulfate (S04-2 )mg/l 14 6 13 14
I"""Chloride (Cl)mg/l 5.3 6.7 17 17 .5
Dissolved Calcium (Ca+2)mg/l 21 18 30 33
.-Dissolved Magnesium (Mg+2 )mg/l"2.7 2.4 3.8 5.2
. +mg/lSodJ.Um (Na )3.8 3.4 6.5 8.0
.-Dissolved Potassium (K+)mg/l 3.5 2.3 3.7 5.2
Dissolved Oxygen (DO)mg/l 11.5 11.9 12.6 13.1
DO (%Saturation)%99 101 97 98-Chemical Oxygen Demand (COD)mg/l 20 20 9 10
Total Organic Carbon (TOC)mg/l 2-True Color pcu 10 70 15
Dissolved Dissolved
~Total Phosphorus l1g/l 60 140 40 50
Nitrate-Nitrogen as N (N0 3-N)mg/l 0.20 0.14 0 0.30
Dissolved Cadmium (Cd)l1g/l
Dissolved Copper (Cu)l1g/l-Dissolved Iron (Fe)l1g/l 1.10 0.37
Dissolved Lead (Pb)J.lg/l
Dissolved Hercury (Hg)J.lg/l
Dissolved Nickel (Ni)J.lg/l
r-Dissolved Zinc (Zn)l1g/l .07
1
2 R&Ml Consultants,Inc.1982;R&H Consultants L.A.Peterson and Assoc.1981.
R&M Consultants,Inc.1982.
33RC1/001d - 8 -
The water quality records for Gold Creek (RM 136)provide the best
possible description of baseline conditions in the middle river and can also
be used to approximate many characteristics of the Watana reservoir inflow
(Table 2).
Natural water quality conditions in the middle river change seasonally as
a result of changes in mainstem flow and sediment content.During winter,
surface flows average less than 2,000 cfs and are derived almost entirely from
groundwater or outflow from the Tyone River system.Thus,total dissolved
solids (TDS)and alkalinity,for example,are at their highest annual levels,
while tl~mperature,total gas concentrations.total suspended solids (TSS),
turbidity.and the trace metals and phosphorus associated with inorganic
particulates are at their lowest levels of the year.The maximum observed
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dissolved Cd, Cu.Hg,and Zn concentrations recorded at Gold Creek were I,5,
0.2,and 14 llg/l,respectively.Most of the riverbed surface area is covered
in winter by thick ice and deep snow with the exception of peripheral channels
bearing upwelling groundwater and channels carrying very fast moving mainstem
water (velocity leads).
Although surface flow is low and water temperatures are between 0 and
4 C,benthic algal and invertebrate growth is taking place during this five-
to six-month period and supporting a large percentage of the overwintering
fish community of the system.
Breakup usually occurs in May following a brief (three to four week)
spring transition period of increasing temperatures.lengthened photoperiod,
and accelerating ice and snow melt.Middle river stream flow rapidly
increases from approximately 5,000 cfs to 20,000 cfs,while fluctuating
suspended sediment concentrations average approximately 360 mg/l (Peratrovich
et al.1982)generating mean turbidities of less than 50 NTU.
33RD3/001 - 9 -
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Table 2.Mean baseline water quality characteristics for middle Susitna River
at Gold Creek under summer (May -September)and winter (October -
April)conditions.
33RCl/OOla -10 -
Source:U.S.Geological Survey as summarized in R&M Consultants (1982).
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2
Data collected by R&M Consultants,1980-82 (R&M Consultants 1982).
All trace metals are U.S.G.S.data as summarized in R&M Consultants
(1981);winter values are for Sunshine Station.
33RCl/OOla -11 -
Under normal weather conditions,approximately 90%of the total annual
streamflow occurs between May and September with maximal discharges in June,
July,and August.These summer discharge maxima are typically between 30,000
and 40,000 cfs.These high summer flows,resulting largely from surface
runoff and glacial melting in the headwaters,serve to dilute the dissolved
solids load derived from bedrock and soil weathering.Thus,such parameters
as TDS a.nd alkalinity are at their lowest annual levels,while temperature,
TSS,turbidity,total recoverable trace metals,and total phosphorus are at
their highest annual levels.
Water entering Devil Canyon in summer is generally·nearly saturated with
dissolved gases (mostly oxygen,nitrogen,and minute amounts of argon),but
becomes supersaturated by the aerating action of rapids and the pressurization
which occurs in plunge pools within Devil Canyon.The degree of gas
supersaturation increases with discharge.This flow effect has been
documented for discharges ranging between 10,000 and 32,500 cfs (ADF&G
Su-Hydro 1983 Basic Data Report)and naturally occurring supersaturation
conditions as high as 116%have been observed at the mouth of Devil Canyon.
Water can remain supersaturated as far downstream as Curry (Dana Schmidt,
ADF&G Su-Hydro,personal comm.).No instances of gas bubble disease embolisms
in fish have been documented to date,however.
A brief (one-month)fall transition period typically begins in late
September and extends through most of October during which mainstem flows
average between 6,000-12,000 cfs.TSS concentrations and turbidity levels
decline rapidly and the resulting hydraulic and light transmission properties
of the 1dver are generally at their most favorable for algal growth wherever
suitable substrate exists.Preliminary estimates indicate that the quantity
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of algal biomass produced daily in the middle river alone during this period
may exceed 30,000 metric tons.
The water quality records for Susitna Station (RM 25)provide the best
possible description of baseline conditions in the lower river (Table 3).By
the time water flowing from the middle river reaches the Susitna gauging
station,it has been diluted over fivefold by flows from the glacial
Talkeetna,Chulitna,and Yentna Rivers as well as numerous smaller clearwater
tributaries.The annual pattern of water quality conditions in the lower
river is similar to the pattern displayed by the middle river.Generally,the
lower river displays lower TDS concentrations year-round than the middle
river,while mean TSS concentrations are approximately the same.Despite the
similarity of mean TSS concentration,lower river water tends to be nearly
twice as turbid and higher in total phosphorus and most trace metal
concentrations than the middle river.This indicates a longitudinal change in
the particle size composition of the sediment load as it is transported
through the system (Le.,lower river water carries a higher proportion of
finer sediment particles which exert a greater turbidity per unit weight and
offer more surface area for adsorption of phosphorus and trace metals than the
relatively larger particle sizes transported in the middle river).This
increase in total recoverable concentrations does not appear to be attended by
increased concentrations of dissolved phosphorus or trace metals,either in
winter or summer.The maximum observed dissolved Cd,Cu,Hg,and Zn
concentrations recorded at Susitna station were 1,7,0.2.,and 20 llg/l,
respectively.
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Table 3.Mean baseline water quality characteristics for lower Susitna River
at Susitna Station under summer (May September)and winter
(October -April)conditions.
r-
[Parameter Units Summer Winter
!"""'Tot_al.Suspended Solids (TSS)mg/l 745 5
Turbidity NTU 233 1.5
~.Total Dissolved Solids (TDS)mg/l 73 123
Conductivity ]..lmhos -1 25°C 122 205cm,
....pH pH units 7.7 7.3
Alkalinity mg/l as CaC0 3 44 69
Hardness mg/l as CaC0 3 54 85
!""'l
(5°4-2 )Sulfate mg/l 13.2 17.3
Chloride (CI)mg/l 2.7 13
Dissolved Calcium +2 mg/l(Ca )17 27
Dissolved Magnesium (Mg+2 )mg/l 2.5 4.3
+mg/l~Sodium (Na )2.7 7.7
Dissolved Potassium (K+)mg/l 1.4 1.7
Dissolved Oxygen (DO)mg/l 11.5 11.6
DO (%Saturation)%97 80
Chemical Oxygen Demand (COD)mg/l-Total Organic Carbon (TOC)mg/l 4.4 1.6
True Color pcu 10 0-Total Phosphorus ]..lg/l 400 50
Nitrate-nitrogen as N (N0 3-N)mg/l .0 0.19
r-Total Recoverable Cadmium [Cd(t)]]..lg/l 9 8
I
I Total Recoverable Copper [Cu (t)]]..lg/l 50 30
~Total Re.coverable Iron [Fe(t)]]..lg/l 20,000 500
Total Recoverable Lead (Pb (t)]]..lg/l 100 80
Total Recoverable Mercury [Ng (t)J ]..lg/l 0.12 0.04.....
Total Recoverable Nickel (Ni(t)]]..lg/l 75 13
Total Recoverable Zinc [Zn(t)J ]..lg/l 50 50....
33RC1/001b -14 -
FORECASTED DATA
Few quantitative forecasts of with-project water quality conditions in
the impoundment zone or downstream are presently available.Detailed,
quantitative predictions regarding reservoir temperature profiles and middle
river temperatures under a wide range of meteorological and hydrological
scenarios are found in APA (1984)and AEIDC (1984).The results of these
.....intensivE~modeling efforts and a discussion of environmental consequences are
presented in a separate issue paper and will only be briefly summarized here.
The temperature profile of any reservoir varies with hydrologic and
meteorologic conditions as well as the morphology of the reservoir and its
operational schedule for any given year.The Watana reservoir will be long,
narrow,and deep with a relatively short hydraulic residence time (Table 4).
The topography of the impoundment area will provide little opportunity for the
development of an extensive littoral zone.The general annual temperature
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profile pattern for Watana Reservoir will be characterized by a fall turnover
in November roughly coincident with the formation of an ice cover during which
isothermal conditions of approximately 4 C will prevail.This will be
followed by inverse stratification in which epilimnetic temperatures will drop
from near 0 C at the surface to approximately 2.5 C near the metalimnion.
Hypolimnetic temperatures will approach 4 C.This condition will usually
persist until Mayor June.During the summer,the epilimnion will gradually
warm with maximal surface temperatures of 10-13 C occurring in August and
September.
November.
Stratification will remain in place until the turnover in
Available forecasts indicate that a spring turnover might also
occur in June during unusually dry years (e.g.,1974-75).
33RD3/001 -15 -
Table 4.Selected morphometric and hydrologic features of the Watana and
Devil Canyon reservoirs.
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Parameter
Maximum Length (1)
Mean Width (b')
Maximum Surface
Area (A )m
Volume (V)
Maximum Depth (Z )m
Mean Depth (Z)
Relative Depth (Zr)
Shoreline (L)
Shoreline
Development (D L)
Mean Hydraulic
Residence Time
Normal Drawdown
Watana
48 mi (77 km)
1.25 mi
60 mi 2
9.5xl0 6ac ft (11.7xl0 9m3 )
735 ft (223 m)
250 ft (76 m)
1.6%
183 mi (295 km)
6.7
1.65 yrs
120 ft (36.6 m)
Devil Canyon
26 mi (42 km)
0.46 mi
12 mi 2
1.lxl06ac ft (1.4xl0 9m3 )
565 ft (171 m)
140 ft (42 m)
2.7%
76 mi (123 km)
6.2
60 days
50 ft (15.2 m)
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Based on:Acres American 1983.
(Sus.Hydro Project,Fed.Energy Reg.Comm.License App,Exhibit F,Supporting
Design Report,(Preliminary),Feb.1983,by Acres.)
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Model forecasts for downstream river temperatures show a general
dampening of the variations that occur naturally and this will affect
conditions as far downstream as Talkeetna.Mean summer river temperatures
under Watana only would be approximately 1 C cooler than natural at river
miles (RM)150 and 130,and 0.6 C cooler at RM 100.Addition of the Devil
Canyon dam would increase this seasonal change to approximately 2.0,1.7,and
1.2 C cooler at RM 150, 130,and 100,respectively.Under both scenarios,
downstream temperatures would peak later in the summer with the greatest
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-deviation from natural temperatures occurring in September-October.Winter
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releases would range from 0.4 to 6.4 C from October to April.Natural winter
temperatures are °C.These alterations in the natural temperature regime are
well wit:hin the tolerance limits for adult and juvenile salmon and are not
expected to significantly impact migration or spawning activity with the
exception of a possible delay in chinook inmigration to Portage Creek.Some
reduction of juvenile growth might occur due to cooler summer temperatures.
The anticipated warmer fall and winter river temperatures could sufficiently
alter both burbot and whitefish spawning and incubation timing to eliminate
these species from the middle river.
A preliminary,crude estimate of with-proj ect TSS concentrations and
turbidity levels can be found in Peratrovich,et al.(1982)and a discussion
of their potential ecological consequences appears in EWTA and WCC (1984).A
formal reservoir modelling effort is currently underway to provide more
precise estimates of anticipated TSS concentrations (Tom Stuart,Harza-Ebasco,
personal communication).
Predictions regarding some of the parameters addressed in this paper are
found in the original license application and these are based largely on a
study conducted by L.A.Peterson and Assoc.and R&M Consultants (1982).
-33RD3!OOl -17 -
This study concluded that:
1.Both the Devil Canyon and Watana reservoirs will be oligotrophic based on
the results obtained from the Vollenweider phosphorus loading model
(Vollenweider 1976).
3.
2.A short-term unquantifiable increase in dissolved solids.conductivity,
and most of the major ions may occur after closure due to inundation and
leaching of rocks and soils in the impoundment area.
Approximately 70-97 percent of the suspended sediment load carried into
the Watana reservoir by the inflow will settle.resulting in
4.
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significantly less turbid conditions in summer.but higher turbidity
levels in winter.
Evaporative losses from both reservoirs will not exceed 1 percent of
their total volume and will thus not produce a significant increase in
dissolved solids concentrations.
5.The amplitude and phase of the river's annual temperature cycle will
change under with-project conditions.
The concentrations of "many"metals will be reduced in Watana Reservoir
due to precipitation and settling.
7.Both reservoirs will maintain relatively high oxygen levels because
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8.
existing oxygen demand is low.
The reservoirs will support only low levels of phytoplankton production
which will be limited by high turbidities and the presence of an ice and
snow cover during the winter •
Field studies are currently being conducted by AEIDC and EWTA to develop
a model that will provide quantitative estimates of the trophic status of the
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middle river under with-project conditions.
available in June 1985.
DATA GAPS
Preliminary results will be
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The USGS water quality records for the Susitna,River and some of its
major tributaries provide the best available information with which to perform
a rigorous hydrochemical analysis.To date,this has not been done.However,
the data summaries conducted by R&M Consultants do provide mean,maximum,and
minimum values for a large number of water quality parameters.These values
are grouped according to three seasons:winter,summer,and breakup.The use
of such seasonal means,however,does not provide the best possible level of
resolution for the purposes of biological interpretation and can lead to
distortions.For example,R&M Consultants (1982)reports a summer mean TSS
concentration for Gold Creek of 740 mg/l based on the USGS data records and a
mean of 268 mg/l based on its own field work conducted during 1980-82.The
much higher value obtained from the USGS records reflects the fact that during
the glac:ial surges which occurred in the 1950s,USGS gathered water samples
almost daily,while in later years sampling frequency dropped to just a few
each year (Jim Knott,USGS,Anchorage,personal communication).Also,the use
of means unaccompanied by any statistical measure of confidence interval is
highly irregular.
The lack of a formal hydrochemical analysis in which the water chemistry
characteristics of the Susitna River are interpreted in the context of the
vegetation,soils,geology,and hydrology of its watershed makes it difficult
to provide quantitative estimates of proj ect impacts on water quality.This
is exacerbated by the relative paucity of heavy metal data (especially for Vee
Canyon and at all stations during the winter months)and by the lack of any
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quantitative baseline information on the trophic dynamics of the river.
Another important data gap is the absence of any data on baseline tissue Hg
levels for resident fish and land otters inhabiting the middle river or on Hg
speciation.Also,only very limited water chemistry data are available for
middle river sloughs and tributaries where most of the fish production of this
reach originates.
For the most part these shortcomings,however,do not prevent qualitative
estimates which should provide a reasonable degree of certainty regarding
potential ecological impacts •
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IMPACT ANALYSIS
BASIC CONSIDERATIONS
A variety of complex interactions determine the seasonal and spatial
variations in water quality frequently observed during and long after
impoundment of a river,but the most significant for forecasting general
conditions in the Susitna reservoirs are temperature,trophic status,volume,
and residence time.This is true because most of the negative impacts on
..-
water quality normally associated with reservoirs (e.g.,oxygen deficits and
winter fish kills,lowered pH and higher metals and carbon dioxide
concentrations in the hypolimnion,releases of hydrogen sulfide gas,etc.)are
biologically induced,either directly or indirectly,and are thus highly
dependent on temperature and on the amounts and rates of organic carbon supply
to the hypolimnion.A large volume ensures that products of hypolimnetic
-decomposition or chemical reduction are highly diluted,while a short
residence time limits the amount of time available for such processes to take
place.
The Watana Reservoir will have a large volume,a short residence time,
low temperatures,and low levels of autochthonous productivity.These
F-
I
-
factors,combined with the high levels of suspended sediment that will be
carried in by the inflow to blanket the inundated soils and vegetation on the
reservoir bottom,will be conducive to relatively good reservoir water quality
conditions compared to many reservoirs and lakes located in temperate
latitudes.Thus,while the morphology and glacial character of the Susitna
River essentially eliminate many of the problems normally associated with
reservoirs (affecting such parameters as pH,dissolved oxygen,dissolved
solids,phosphorus,nitrogen,and total organic carbon),they also pose new,
33RD3/00l ...21 -
largely unmitigable problems,especially with respect to potential downstream
impacts.The most important among these relates to downstream suspended
sediment concentrations.
A common problem from which the Susitna River will perhaps not be exempt
is elevated trace metal concentrations.The implications of an altered
,..,.
sediment transport regime are discussed in a separate issue paper so this
paper will focus largely on questions concerning with-project trace metal
concentrations and related parameters.Another water quality concern is the
potential for releasing supersaturated water below the dams.This topic will
be addressed first.
NITROGEN SUPERSATURATION
Dissolved gas supersaturation occurs downstream of some hydroelectric
facilities and,if at sufficiently.high levels (generally >115%),can have
chronic or lethal effects on aquatic organisms (Boyer 1973,Fickeison and
Schneider 1976).When aquatic organisms encounter supersaturated water,the
dissolved air diffuses through their respiratory organs and its concentration
within the body approaches an equilibrium dictated largely by ambient water
temperature and pressure.When the organism moves to an area of lower
......pressure or higher temperature,the gases dissolved in the blood and other
body fluids,come out of solution resulting in embolisms that block
circulation"and disrupt normal tissue structure.,:
I
Even though dissolved gas
concentrations in excess of 115%supersaturation have been measured below
Devil Canyon (ADF&G 1982),no detrimental biological effects have ever been
observed.As we have seen,gas supersaturation does not naturally occur
upstream of Devil Canyon (Table 1).
33RD3/001 -22 -
-
High head dams produce gas supersaturation by one or more of three
mechanisms:
1.Spillway releases plunging into stilling basins entrain air bubbles to
sufficient depths to force excess gas into solution.
2.llithdrawal of cold (4 C)N2 -saturated water from the high pressures
f<"//
prevailing in the hypolimnion of a reservoir~exposes the water to the
warmer,lower pressure conditions existing at the surface,thus causing
supersaturation.
.-3•Leakage of air into power turbines exerts sufficient pressure to force
excess air into solution.
The potential for disruption of downstream aquatic communities depends on
.-
the level,duration,timing,and downstream extent of supersaturation events,
as well as on the species,age,and condition of the organisms exposed.For
example,smaller organisms (e.g.,macroinvertebrates and juvenile fish)are
less sensitive to the harmful effects of gas supersaturation than larger
organisms (Fickeison and Schneider 1976;Dawley et ale 1975).Large releases
of supersaturated water during the period of adult salmon inmigration
(midsummer to fall)would,thus,presumably have greater negative effects on
fish production than similar releases occurring at other times of the year.
The activities associated with construction of the proposed dams will not
result i.n unnaturally high levels of gas supersaturation.The present design
for Watana Dam calls for multilevel intakes that will withdraw water only from
the top 120 ft.of Watana Reservoir.These levels are well above the
33RD3/001 -23 -
.-
hypolimnion,but should deeper intake structures be added,they would likely
only be used during the winter in an effort to increase downstream water
temperatures above the natural winter level of 0 C.Powerhouse flows will be
discharged beneath the tailwater surface to prevent entrainment of air.
Controlled releases designed to fulfill environmental stipulations or to pass
flood flows will be routed through six Howell-Bunger cone valves with a
combined capacity of 24,000 cfs.These cone valves will release water in a
spray,thus preventing plunging and gas supersaturation.Without Devil Canyon
Dam,the releases from Watana Dam will still pass through the entire length of
Devil Canyon,resulting in supersaturation.The levels of supersaturation,
-
.....
.-
however,should not exceed natural levels except possibly when spillway
releases become necessary during l-in-50-year flood events.Natural dissolved
gas concentrations under such flood conditions are not known so it is not
possible to determine to what extent,if any,entrainment of air into spillway
plunge pools might increase gas supersaturation levels downstream of Devil
Canyon or whether the length of the downstream reach affected would be
significantly greater.Under such extreme circumstances,the possible
negative effects associated with gas supersaturation would pale in comparison
to the disruptions caused by strictly physical processes.
Devil Canyon Dam will withdraw water from the upper 50 ft.of the
reservoir via two intake structures.Four turbines with a rated capacity of
3,680 cfs will discharge powerhouse flows via a 6,OOO-foot-Iong tailrace
tunnel that will bypass the lower portion of Devil Canyon rapids and release
water below the tailwater level.With both dams in place,the amount of water
released downstream from the proposed project will exceed the mean annual
flood of 50,000 cfs only during l-in-50-year flood events.Thus,except on
33RD3/001 -24 -
-
",..,.
rare occasions,dissolved gas concentrations below Devil Canyon will always be
lower than under natural conditions.
DISSOLVED OXYGEN,pH,AND MACRONUTRIENTS
Whether or not the impoundment zones are cleared of vegetation prior to
inundation,both Watana and Devil Canyon Reservoirs are likely to e~perience
some decline in hypolimnetic dissolved oxygen concentration (Campbell et al.
1975;Smith and Justice 1975;Therien et a1.1982).Given the relatively
-
.....
.-
large volumes and short residence times of the reservoirs,however,the
potential for discharging oxygen deficient «5 mg/l)water downstream is
minimal.If it should occur,the reaerating action of the cone valves and the
Devil Canyon rapids will quickly eliminate any saturation deficit and thus
preclude potential negative impacts on downstream aquatic communities •
The buffering capacity afforded by its moderate alkalinity levels
presently maintains a slightly alkaline pH in the Susitna River (Tables 1-3).
Seasonal fluctuations naturally range between 6.0 and 8.1,a range typical of
North American freshwater (Wetzel 1975).Approximately 8,300 acres of wetland
vegetation will be flooded by impoundment with both dams in place.Of this,
t~:,\t........
less than 1,200 acres (or about 2.7 percent of the total impounded area)all
classified as "bog-like"by the U.S.Fish &Wildlife Service.Flooding of
such a relatively small area of acidic bog habitat is unlikely to produce any
perceptible change in pH levels,either in the reservoirs or in downstream
riverine habitats (see Allan 1978;Baxter and Glaude 1980;Campbell et a1.
1975;Duffer and Harlin 1971;Duthie 1979;Geen 1975;Gunnison et a1.1983;
L.A.Peterson et al.1982;Smith and Justice 1975).
The concentrations of either biologically available phosphorus or
nitrogen (or both)typically limit the basic biological productivity or
33RD3/001 -25 -
r
-
-
-
-
trophic status of an inland water body.In the case of clearwater lakes,the
relationship between macronutrient concentrations and trophic status is fairly
/.I
'I
well established (Wetzel 1975).For glacial lakes and for rive_~f in general,
however,other regulating factors often take precedence,thus complicating
efforts to classify their trophic status strictly in terms of macronutrient
concentrations.In the case of the Susitna River,the principal "complicating
factor"is the seasonal pattern of light limitation imposed by the river's
natural turbidity regime.
However,to evaluate the extent to which existing or with-project
macronutrient concentrations might limit the productivity of the Susitna
River,it is reasonable to adopt the trophic classification scheme for
clearwater lakes as a lower limit.
Natural phosphorus and nitrogen concentrations in the Susitna River
display great seasonal variability ranging from below detection to levels more
than ample to support moderate algal biomass (10-20 ~g/l total P and <500 ~g/l
total N)or even high biomass (>20 ~g/l total P and >500 ~g/l total N).
However,substantial amounts of algal growth occur throughout most of the
river only during periods of moderate flow and low «20 NTU)turbidity (i.e.,
during transition periods in the fall and spring).This information strongly
suggests that productivity is not limited by macronutrient concentrations
throughout most of the open water season,but rather by lack of light and by
scour and sedimentation of the streambed.Likewise,based on the fact that
algal blooms in streams frequently occur below sewage outfalls and the results
of recent studies in Iowa indicating nutrient limitation in streams (Bushong
and Bachman 1985),it is likely that the productivity of the Susitna River
during these transition periods is limited by concentrations of biologically
available phosphorus and nitrogen.
33RD3/001
Without further study,however.it is
-26 -
"""'
-
impossible to state how much of the total P measured in Susitna River water at
any given time becomes biologically available and thus to predict what the
lower limit of primary productivity might be under such circumstances.
Since the bulk of the macronutrient load of the Susitna River is
presently associated with suspended sediment particles,the project reservoirs
will act as nutrient sinks and phosphorus and nitrogen exports to downstream
areas should be reduced (Hannan 1979;Wetzel 1975).Based on available data
for glacial lakes,however,it can be expected that the trophic status of both
Watana and Devil Canyon reservoirs will be oligotrophic and will be limited by
turbidity rather than nutrient levels (Koenings 1985).
Predictions regarding the trophic status of downstream habitats are less
easy to make.Just as downstream flow and turbidity levels will be much more
stabili2:ed under with-project conditions,so too will annual patterns of
primary productivity.Thus,the large pulses of productivity observed in the
spring and especially in the fall,under natural circumstances,will likely be
j
attenuated;while summer levels may increase,producing a steadier,but lower
level pulse of longer duration.If downstream with-project turbidities are
.....
greater than 20-30 NTU,it is extremely likely that the magnitude of this
productivity will be limited (as in the reservoirs)by light and not by
with-project macronutrient concentrations.
TRACE METAL CONCENTRATIONS
The potential for increased trace metal concentrations following
impoundment and any likely ecological consequences within the resulting
reservoirs or downstream have not previously been addressed,either in the
license application or in subsequently published project documents.The
nature and extent of these potential changes are of considerable importance,
33RD3!OOl -27 -
especially for downstream salmon and resident fish populations since fish
densities in the reservoirs themselves are likely to be very low and largely
unexploited by man.As in the case of with-project suspended sediment
-
.....
--
transport,the potential change in the seasonal pattern of trace metal
transport in the Susitna River will affect both its middle and lower reaches.
The main concern is not that elevated heavy metal concentrations will
result in fish kills or even impede growth and propagation,but rather that
even small increases in bioavailable heavy metal concentrations in reservoir
and riverine water will cause sufficiently large increases in fish tissue
heavy metal (especially mercury)contents to render the meat unfit for human
(or other animal)consumption.
Under natural conditions,the Susitna River has displayed concentrations
of aluminum (AI),bismuth (Bi),cadmium (Cd),copper (Cu),iron (Fe),
manganese (Mn),mercury (Hg),nickel (Ni),and zinc (Zn),that exceed water
quality criteria established for the protection of freshwater organisms (R&M
Consultants and L.A.Peterson and Assoc.1981).Of these,only Fe can be
considered relatively nontoxic,while Cd,Cu,Hg,and Zn are known to be
highly toxic to aquatic organisms depending on the forms and concentrations in
which they are present,the species,condition,and age of the exposed
organisms,and a variety of physiochemical properties of the water (e.g.,
temperature,hardness,dissolved oxygen concentration,pH)(Welch 1980,
Forstner and Wittmann 1979).
No data are available at this time which could be used to determine what
proportion of these naturally high metal concentrations is bioavailable nor
what their background levels are in the tissues of fish,invertebrates,or
benthic algae inhabiting the Susitna River.Muscle tissue in rainbow trout
collected from Nancy Lake,however,contained very high levels (1000 ppb)of
33RD3/001 -28 -
.....
-I
-
mercury (presumably methylmercury)(Tom Stuart,Harza-Ebasco,pers.comm.).
The meat in a can of tuna averages 250 ppb (EPA 1980).
Of the four heavy metals of concern here,biomagnification has been
documented only for Hg as a direct result of impoundment (Bodaly et ale 1984,
Abernathy and Cumbie 1977,Cox et ale 1979,Meister et al.1979).This metal
will thus be addressed first.
MERCURY
An examination of the USGS Water Resource Data reports reveals that total
Hg concentrations in the Susitna River naturally range from zero to 0.8 ~g/l
while dissolved Hg varied between 0 and <0.5 ~g/l.The latter are on the high
end of the range of dissolved Hg concentrations found in unpolluted North
American surface waters (Moore and Ramamoorthy 1984)and well above the
0.01 ~g/l global average for freshwater (Forstner and Wittmann 1979).
Approximately 25 to 50%of the total Hg transported by the river is in
dissolved form.Typically,this percentage is less than ten (Jackson et al.
1978,Lockwood and Chen 1973,Moore and Ramamoorthy 1984,Rudd et al.1983).
Presumably,the bulk of this dissolved Hg load is bound to humic substances
(i.e.,humics,humic acids,fulvic acids,and yellow organic acids)which have
been shown to contribute about 60%to 80%of the dissolved organic carbon of
freshwaters (Reuter and Perdue 1977).The attractive forces between Hg and
these humic substances range from weak (physical adsorption)to strong
(chelation)•This mobilization of Hg by organic matter facilitates the
..-
-
transformation of elemental Hg to mercuric ion'(Hg +2)which in turn is the
substrate for microbial methylation.It is in the methylated form that Hg is
Hg +2mosttoxic.A variety of bacteria and fungi are capable of transforming
(both in organic and inorganic form)to methylmercury even in well oxygenated
33RD3/001 -29 -
water (Forstner and Wittmann 1979)thus releasing it to the water itself and
into the food chain.Fish become contaminated with methylmercury either
directly,by absorbing it through their skin and gills,or indirectly from the
food they consume (EPA 1980).Once absorbed or ingested,the uptake rate is
very fast,while excretion is extremely slow.Thus,bioconcentration factors
for fish can be as high as 10,000 times ambient levels in the water (EPA
1980).
Available literature strongly suggests that mercury levels in resident
fish inhabiting Watana and Devil Canyon reservoirs will increase by an
unquantffiable amount within one to three years after closure of the dams
(Abernathy and Cumbie 1977,Bodaly et al.1984).With aging of the
-
-
.-
reservoirs,and recruitment and mortality within reservoir fish populations,
Hg concentrations in fish tissue should decline,but may always remain higher
than baseline levels.The release of methylmercury through microbial action
in the inundated organic soils of the reservoirs should be slowed to some
extent (perhaps as much as 50%)by the prevailing cold (4 C)water
temperatures (Wright and Hamilton 1982)and by the blanketing action of
inflowing sediment settling to the reservoir bottoms (L.A.Peterson and Assoc.
1982).The cold temperatures may,however,also act to extend the length of
the reservoir aging process compared to reservoirs located in warmer regions
(Bodaly et al.1984).Also,the low level of primary productivity anticipated
for the limited phytoplankton community of the reservoirs should act to
minimize increases in methylmercury bioaccumulation in fishes (Rudd and Turner
1983b).
No information is available in the literature concerning Hg enrichment in
fish dOvffistream of newly impounded reservoirs.Whether or not this process
will be enhanced downstream of the Susitna reservoirs depends largely on which
33RD3/001 -30 -
--
form of Hg is exported from the reservoirs and in what concentrations.
Another important factor will be the with-project trophic status of the river
after impoundment.
After impoundment,as now,most of the Hg transported by the river will
-be adsorbed to suspended sediment particles in an inorganic form.Some
-
reduction in this inorganic Hg load can be expected as a result of settling in
the reservoirs,but the amount of this reduction will not be directly
proportional to the mass of sediment lost to the reservoirs.This is because
the finer particles transported by the river after impoundment offer a greater
surface area for adsorption in proportion to their mass than the larger
particles (>S-lOp)that will settle out in the reservoirs.
The concentrations of methylmercury that might be released by the
reservoirs cannot be quantified at this time.It is likely that releases will
rise sharply during the first 5 to 10 years after closure and will then
decline gradually over the life of the project.Concentrations dovmstream,
however,will reflect not only the quantities released by the reservoirs,but
-in situ mobilization as well.The latter process could be greatly accelerated
by an increase in primary productivity levels brought on by reduced
with-project turbidities downstream.By increasing the amount of organic
-
carbon available for microbial decomposition,methylmercury formation would
increase.Because of its high enrichment capacity,even a small increase in
ambient methylmercury concentrations could result in very high concentrations
in the tissues of downstream fish,especially resident species.Assuming
-
these fish are presently safe to eat,such an increase could make them unfit
for human consumption in the future.The only way to mitigate for such an
event would be to monitor Hg content in fish tissues after impoundment and
inform the public if any danger exists.
33RD3/001 -31 -
-
-.
CADMlUH
Cadmium (Cd)concentrations in the Susitna River are presently relatively
low.Total Cd ranges from 0 to 10 ~g/l and dissolved concentrations greater
than 3 11g/l have never been recorded (R&M 1982).The global average for
dissolved Cd in freshwater is 0.07 11g/l (Forstner and Wittmann 1979).
No documented instances of Cd leaching from soils inundated by
impoundments exist,but it could occur.However,given its low natural levels
in the Susitna drainage,it does not seem likely that its enrichment in fish
inhabiting the reservoirs or downstream habitats will be significantly
accelerated under with-project conditions.If acceleration does occur for Cd,
it will most certainly occur for Hg as well.
COPPER
Copper (Cu)is an essential micronutrient for plants which performs
several vital enzymatic functions and plays a maj or role in chlorophyll
syntheses.It is also important in invertebrate blood chemistry and the
-
synthesis of hemoglobin.Natural total Cu concentrations in the Susitna River
range from <10 11/1 to 190 ~g/l;dissolved concentrations range from 0 to
12 ~g/l (R&M 1982).The average concentration of soluble Cu in U.S.
freshwater is 15 ~g/l (EPA 1976).Holland (1960)reports a dissolved eu
concentration of 178 ~g/l as producing acute toxicity in juvenile chinook
salmon tested in water of similar temperature,pH,alkalinity,and hardness as
Susitna River water.
Copper concentrations will likely increase somewhat after impoundment,
but given its high affinity for humic substances (Schnitzer and Khan 1982),
almost all of the dissolved Cu will be in the organocomplexed form which is
significantly less toxic to aquatic organisms than either free Cu ions or
33RD3/001 -32 -
hydroxocopper.No studies have revealed any biomagnification of Cu following
impoundment so the risk of negative impacts to Susitna River fish stocks is
lo'tir.It is possible that increases in Cu concentrations might be offset to
some extent by increased uptake by a more productive,with-project benthic
algal community.
ZINC
Zinc (Zn)is also a micronutrient which becomes toxic when present in
excess concentrations.Total Zn levels in the Susitna River vary from 10 to
200 ]..lg/l;dissolved levels from 0 to 30 ]..lg/l.The world average for
freshwater is 10 ]..lg/l dissolved Zn (Forstner and Wittmann 1979).As for Cu,
the toxicity of Zn to aquatic organisms depends on the form in which it is
present and on the pH,temperature,alkalinity,and hardness of the ambient
-
-
-water.The TL50 (the concentration of dissolved Zn lethal to 50%of the
-
.....
-
organisms tested after 96 h of exposure)is reported by Herbert and Shurben
(19164)as 910 ]..lg/l for juvenile rainbow trout tested in water of comparable
summertime alkalinities and pH levels to the Susitna River (although water
terr~erature was 17.7 C).
No reports of elevated Zn concentrations either in or downstream of newly
impounded reservoirs are available.If this were to occur in the Susitna
River,it is doubtful that they would be of sufficient magnitude to impair the
growth and propagation of aquatic organisms.As in the case of Cu,almost all
of the dissolved Zn would be chela ted or otherwise bound to humic substances •
33RD3/001 -33 -
--
SUM}UffiY AND RECOMMENDATIONS
Impoundment of the Susitna River at Watana and Devil Canyon will
substantially alter the annual water quality regime of approximately 240 miles
of the river.In addition to changing the annual pattern of sediment
transport (discussed in a separate issue paper),impoundment will,under both
the one-and two-dam scenarios,result in:
1.reduced nitrogen supersaturation levels below Devil Canyon during the
summer months,and increased levels during the winter months that in
either case will exceed 110%only under extreme (l-in-SO-year)flood
conditions;
-2.a net reduction in downstream macronutrient transport by virtue of the
settling action of the reservoirs on suspended sediment particles
>10-1S~in beta diameter;
"""
3.essentially no change in dissolved oxygen and pH levels,except perhaps
in the hypolimnion of the reservoirs in winter;and
4.potentially higher concentrations of bioavailable mercury,cadmium,
copper,and zinc with the strong possibility of biomagnification of
methylated mercury both in the reservoirs and downstream.
Since no incidents of gas bubble disease have been observed in the
Susitna River in over five years of intensive study,it is unlikely that
reductions in summer nitrogen supersaturation levels will have any noticeable
--33RD3/001 -34 -
-
positive impact on downstream fish production.Likewise t since winter levels
will be below 110%t no harmful effects are likely to result from the relative
increases anticipated for winter months.
The reservoirs created by impoundment will be relatively unproductive
(oligotrophic)and phytoplankton growth will be limited year-round by
prevailing turbidity levels other than macronutrient concentrations.The net
downstream trophic status unless with-project turbidity levels approach
'I
reduction of macronutrient transport downstream will probably not effect
-20-30 NTU.Even under these circumstances t the supply of bioavailable
-
.....
nitrogen and phosphorus could very well exceed the demand.
The potential for increased mercury bioaccumulation in reservoir and
downstream aquatic organisms will not likely threaten fish production.but
could render the meat of resident species unfit for human (or other animal)
consumption.This negative impact should be most acute during the first
1-10 years after closure and should decline thereafter.Resident fish tissue
mercury levels will likely be higher than baseline levels throughout the life
of the project t however.
The chain of events leading to fish production in any waterbody is only
as strong as its weakest link.For the Susitna River t the "weakest link"
appears to be fish food production which in turn is based largely on primary
(benthic algal)production.Algal productivity in the Susitna River is
regulated by a host of physical factors (e.g.,desiccation t freezing.
temperature.unstable substrate.scour,and sedimentation)and by water
qualitYt especially turbidity and macronutrient concentrations.Under natural
conditions t the river appears to alternate between light limitation and
nutrient (and perhaps temperature)limitation on a roughly six-month cycle.
33RD3/001 -35 -
-
......
Based on field observations s the transition between the two phases apparently
occurs when turbidities reach 20-30 NTU.
The "weakest links"in the chain of studies conducted to assess the
potential impact of the proposed Susitna Hydroelectric Project are the lack of
any baseline primary productivity data and the failure to perform any formal
hydrochemical analyses.Field studies designed to address the relationship
between primary productivity and the factors that presently limit it (and will
likely limit it under with-project conditions)are presently underway.Final
results will be available in December 1985.The need for a formal
.-hydrochemical analysis s combined with baseline assessments of heavy metal
speciation and mercury levels in resident fish tissues should be obvious s
especially in light of the fact that all water quality impacts (with the
exception of nitrogen supersaturation)are entirely unmitigable.
therefore recommended that:
It is
..,..,
.~.
1.a formal analysis of the water chemistry characteristics of the Susitna
River be performed by a reputable chemical hydrologist as soon as
possibles and that the results be made available to the Aquatic Studies
Team in time for the FERC hearings scheduled to begin in the--fall:---.:..of
198,5;
i
2.data on baseline levels of mercury in resident fish tissues be gathered
and that this effort be incorporated into any with-proj ect monitoring
plan;and
33RD3/001 -36 -
.....
.....
r-'
I
i
,~
3.primary productivity in middle river habitats be monitored for at least
five years after closure of the dams in order to assist in the
interpretation of any with-project changes in fish production (as
measured by an outmigrant monitoring program).
33RD3/001 -37 -
-
-
REFERENCES
Abernathy,A.R.,and P.M.Cumbie.1977.Mercury accumulation by largemouth
bass (Micr~opterus salmoides)in recently impounded reservoirs.Bull.
Environ.Contam.Toxicol.17(5):595-602.
Allan,R.J.1978.Natural controls of dissolved solids in Boundary
Reservoir,Saskatchewan.Canadian Wat.Res.J.3(3):78-96.
Alaska Dept.of Fish &Game/Su-Hydro.1981.Sub task 7.10 t Phase I Final
-
Draft Report.Aquatic habitat and instream flow project.Prepared for
Acres American Inc.2 vols.
Alaska Dept.of Fish &Game/Su-Hydro.1982.Subtask 7.10,Phase I Final
Draft Report.Aquatic Studies Program.Prepared for Acres American Inc.
218 pp.
Alaska Dept •.ofFish &Game/Su-Hydro.1982.Phase II,Basic Data Report.
Vol.4:Aquatic habitat and instream flow studies.Appendix D.Prepared
for Acres American Inc.
-.
-
Alaska Dept.of Fish &Game/Su-Hydro.
Report.Anchorage.
1983.Phase II,Vol.4,Basic Data
33RD3/001 -38 -
Alaska Power Authority.1983.Final application for license for major
-
project,Susitna Hydroelectric Project,before the Federal Energy
Regulatory Commission,accepted by FERC July 27,1983.Vol.5-A and B,
Chap.1 and 2.Alaska Power Authority,Susitna Hydroelectric Project.
2 vols.
Alaska Power Authority.1984.Connnents on the Federal Energy Regulatory
-
Commission draft environmental impact statement of May 1984.Vol.6,
Appendix IV,temperature simulations,Watana and Devil Canyon Reservoirs.
Arctic Environmental Information and Data Center.1984.Assessment of the
-
effects of the proposed Susitna Hydroelectric Project on instream
temperature and fishery resources in the Watana and Talkeetna reach.
Alaska Power Authority.
Baxter,R.H.,and P.Glaude.1980.Environmental effects of dams and
impoundments in Canada:experiences and prospects.
Aquat.Sci.205,34 pp.
Can.Bull.Fish
~
1
--
Bodaly,R.A.,R.E.Hecky,and R.J.P.Fudge.1984.Increases in fish mercury
levels in lakes flooded by the Churchill River diversion,northern
Manitoba.Can.J.Fish.Aquat.Sci.41(4):682-691.
-33RD3/001 -39 -
Boyer,P.B.1973.Gas supersaturation problems in the Columbia River.In:
.....Man-Hade Lakes:Their Problems and Environmental Effects.
-
N.C.Ackermann,G.F.White and E.B.Worthington,eds.,Am.Geophys.
Union,Washington,D.C.pp.701-705.
Bushong,S.and R.Backman.1985.In situ determination of limiting
nutrients in streams.Presentation at 48th Annual Meeting of the
American Society of Limnology and Oceanography,June 18-21,1985,
Minneapolis.
Campbell,P.G.,B.Bobee,A.Caille,M.J.Demalsy,J.L.Sasseville,and
S.A.Visser.1985.Pre-impoundment site preparation:a study of the
effects of topsoil stripping on reservoir water quality.Verh.Internat.
Verein.Limnol.,19,pp.768-1777.
Cox.J.A.,J.Carnahan,J.DiNunzio,J.McCay,and J.Meister.1979.Source
of mercury in fish in new impoundments.Bull.Environ.Contam.Toxicol.
23:779-783.
-Dawley,E.,B.Monk,M.Schiewe,F.Ossiander,and W.Ebel.
bioassay of supersaturated dissolved air in water,
49 pp.
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