HomeMy WebLinkAboutSUS49533RD3/001
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
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INTRODUCTION
PURPOSE
This document is a comprehensive assessment of 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 Proj ect.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\ved,we will
integrate them into a draft impact assessment report.The Alaska Power
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Authority and Harza-Ebasco intend to utilize the impact assessment technical
memoranda to discuss issues with agencies and 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
motion 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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detrermine the significant issues to be analyzed in depth in the environmental
impact statement and to identify and eliminate from detailed study issues
whieh 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
and discussions.Suggested refinements to the data base and/or the impact
statements have been obtained from these discussions.Ultimately,the Alaska
Pow,er Authority intends to "settle"each issue with the agencies and
int,ervenors;that is,agreement will be sought on the adequacy of the
information base,the impact statements,and the proposed mitigation for
und,esirable 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
33RD3/001 - 2 -
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 \vorking tool,a
deeision-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
conducted.A moderate information base exists ,vith which to assess the
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).
How,ever,since water quality is affected to a certain degree by river
33RD3/001 - 3 -
diBcharge level,an evaluation of the effects of various flow regimes is
information base for addressing the issue and,where warranted,suggestions-
presented.Included is an assessment of the adequacy of the existing
for improving the analysis.The analytical tools available for conducting
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this impact assessment are discussed,including a presentation of the
strengths,weaknesses,and limitations of the models employed for simulating
unob served conditions.Sugges tions for mi tiga ting undesirab Ie wi th-proj ect
effects are also provided.However,this is not a mitigation report;
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 thermal stratification and community metabolism which will measurably alter
the quality of the outflow.This change in vlater quality combined with
changes in the quantity of downstream flow will alter habitat conditions along
33RD3/001 - 4 -
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-proj ect conditions include:temperature.
total suspended sediment concentration (TSS),turbidity,total recoverable and
dissolved metal concentrations (including some heavy metals),macronutrient
.....concentrations,and total organic carbon concentrations.Temperature,TSS,
and turbidity are treated in two other issue papers.This paper will thus
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focus on the remaining parameters as well as pH,dissolved oxygen
concentration,and total dissolved gas supersaturation.
33RD3/001 - 5 -
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(To be written)
33RD3/001
METHODS AND PROCEDURES
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THE INFORMATION BASE
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BASELINE DATA
The main body of data describing the natural water quality
..,..characteristics of the Susitna River is found in the U.S.Geological Survey
(USGS)"\~ater 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
(1954j-;and at its
l
the lower Susi tna River.(1955-j on-----e
and Gold Creek from 1980-82
monthly basis by the USGS at its gauging stations located at Denali (1957-j,
~
Vee Canyon (1962-),and Gold Creek (1949~on the upper and middle Susitna
~.~
River;the Chulitna River (1958-);the Talkeetna River
'f
Sunshine (1971-)and Susitna stations
~
Data collected by R&M Consultants at Vee Canyon
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 minor 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 (~my-August)and winter (October-April)
conditions.
Parameter
(Symbol of Abbreviation)Units of Measure
Summer
USGS 1 R&H 2
v.1inter
USGS 1 R&M 2
%
pcu
mg/l
mg/l
pH Units
mg/l as Ca C0 3
mg/l as Ca C0 3
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
14 6.0
a 1.3
136 141
250 212
7.4 7.1
112 81
96 103
13 14
17 17.5
30 33
3.8 5.2
6.5 8.0
3.7 5.2
12.6 13.1
97 98
9 10
2
15
358
156
98
129
70
7.6
61
58
6
6.7
18
2.4
3.4
2.3
11.9
101
20
10
799
70
94
146
7.7
52
63
14
5.3
21
2.7
3.8
3.5
11.5
99
20
mg/l
HTD
mg/l
-1cm ,25°C)(~mhos
Total Suspended Solids (TSS)
Turbidity
Total Dissolved Solids (TDS)
Conductivity
pH
Alkalinity
Hardness
-2Sulfate(SO 4 )
Chloride (Cl)
Dissolved Calcium (Ca+2 )
Dissolved Hagnesium (Mg+2 )
Sodium (Na+)
1 d (K+)Disso ve Potassium
Dissolved Oxygen (DO)
DO (%Saturation)
Chemical Oxygen Demand (COD)
Total Organic Carbon (TOC)
True Color
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Total Phosphorus
Nitrate-Nitrogen as N (N0 3-N)
~g/l
mg/l
Dissolved
60
0.20
140
0.14
Dissolved
40 50
a 0.30
Dissolved Cadmium (Cd)
Dissolved Copper (Cu)
Dissolved Iron (Fe)
Dissolved Lead (Pb)
Dissolved Mercury (Hg)
Dissolved Nickel (Ni)
Dissolved Zinc (Zn)
~g/l
~g/l
~g/l
~g/l
l.lg/l
l.lg/l
~g/l
1.10
.07
0.37
.....
1
2 R&M Consultants,Inc.1982;R&M Consultants L.A.Peterson and Assoc.1981.
R&M Consultants,Inc.1982 .
33RCl/00ld - 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 1-1atana 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
solids (TDS)and alkalinity,for example,are at their highest annual levels,
.....
i
groundwater or outflow from the Tyone River system.Thus.total dissolved
while temperature,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
dissolved Cd.Cu,Hg,and Zn concentrations recorded at Gold Creek were 1,5,
0.2,and 14 ~g/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 -
Table 2.Mean baseline water quality characteristics for middle Susitna River
at Gold Creek under summer (May -September)and winter (October -
April)conditions.
Parameter Units of
(Symbol or Abbreviation)Heasure Summer Winter
Total Suspended Solids (TSS)mg/l 740 12
....TUJrbidity NTU 126 <1
Total Dissolved Solids (TDS)mg/l 93 154
Conductivity (]lmhos -1 25°C)128 279cm,
pH pH units 7.3 7.5
Alkalinity mg/l as CaC0 3 51 72
Hardness mg/l as CaG0 3 64 98
-2Sulfate(S04 )mg/l 16 21
-1 mg/l 22Chloride(Cl )5.5
Dissolved Calcium (Ga+2 )mg/l 20 30
r-Dissolved Magnesium (Mg +2)mg/l 3.2 5.4
Sodium (Na+)mg/l 4.1 11.3
Dissolved Potassium (K+)mg/l 2.4 2.3
Dissolved Oxygen (DO)mg/l 11.9 13.9
DO (%Saturation)%102 97
Chemical Oxygen Demand (COD)mg/l 10.9 8.4
Total Organic Carbon (TOC)mg/l 2.0 2.6
True Color pcu 10 5
Tot:al Phosphorus ]lg/l 130 30
-Nitra te-ni trogen as N (N0 3-N)1 mg/l 0.12 0.16
33RG1/001a -10 -
Table 2.(cont'd)
Parameter Units of Turbid Clear
(Symbol or Abbreviation)Measure (Summer)(Winter)
Total Recoverable Cadmium 2 wg/l 1
[Cd (t)]
Total Recoverable Copper )Jg/I 65 ND
[Cu (t)]
Total Recoverable Iron wg/l 16,000 ND
[Fe(t)]
Total Recoverable Lead )Jg/I 50 ND
[Pb (t)]
Total Recoverable Mercury )Jg/I 0.12 0.04
[Hg(t)]
Total Recoverable Nickel wg/l 65 45
[NiCt)]
Total Recoverable Zinc wg/l 50 50
[Zn(t)]
ND None Detected
Source:U.S.Geological Survey as summarized in R&M Consultants (1982).
1
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&H Consultants
(1981);winter values are for Sunshine Station.
33RC1/001a -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 ds.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 and 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 SuHydro
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 SuHydro,
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
i"
I decline rapidly and the resulting hydraulic and light transmission properties
of the river are generally at their most favorable for algal growth wherever
suitable substrate exists.Preliminary estimates indicate that the quantity
33RD3/001 -12 -
,...,
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 (RN 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
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 (i.e.,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
....
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tributaries.The annual pattern of water quality conditions in the lower
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
concentrations recorded at Susitna station were I,
respectively.
....
winter or summer.
33RD3/001
The maximum observed dissolved
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Cd,Cu,
7,0.2.,
Hg,
and
and Zn
20 ]..lg/l,
Table 3.Mean baseline water quality characteristics for lower Susitna River
at Susitna Station under summer (May September)and winter
(October -April)conditions.
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 llmhos -1 25°C 122 205ern,-pH pH units 7.7 7.3
Alkalinity mg/l as CaC0 3 44 69
Hardness mg/l as CaC0 3 54 85
Sulfate (S04-2 )mg/l 13.2 17.3
Chloride (Cl)mg/l 2.7 13
Dissolved Calcium (Ca +2)mg/l 17 27
Dissolved Magnesium (Mg+2 )mg/l 2.5 4.3..... +Sodl.um (Na )mg/l 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
i
Total Organic Carbon (TOC)mg/l 4.4 1.6
True Color pcu 10 a
Total Phosphorus llg/l 400 50
Nitrate-nitrogen as N (NO -N)mg/l .0 0.193
Total Recoverable Cadmium [Cd(t)]llg/l 9 8
Total Recoverable Copper [Cu (t))llg/l 50 30
Total Recoverable Iron [Fe(t)]llg/l 20,000 500
Total Recoverable Lead (Pb (t)]llg/l 100 80
Total Recoverable Mercury [Ng(t))llg/l 0.12 0.04
Total Recoverable Nickel (Ni(t)]llg/l 75 13
Total Recoverable Zinc [Zn(t)]llg/l 50 50....
33RCl/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
sCEmarios are found in APA (1984)and AEIDC (1984).The results of these
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intensive modeling efforts and a discussion of environmental consequences are
presented i.n 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 on the morphology of the reservoir and its
opE,rational 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
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
condi tion will usually persist until Hay or June.During the summer,the
epilimnion will gradually warm with maximal surface temperatures of 10-13 C
occurring in August and September.Stratification will remain in place until
the turnover in November.Available forecasts indicate that a spring turnover
might also occur in June during unusually dry years (e.g.1974-75).
33RD3/001 -15 -
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Table 4.Selected morphometric and hydrologic features of the Watana and
Devil Canyon reservoirs .
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i
--
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 Drm.,rdown
Hat ana
48 mi (7~m)
1.25 mi
60 mi 2
9.5xl0 6ac ft (11.7xl0 9m3 )
735 ft (2110
250 ft 0t)
1.6%
.:ti-
183 mi (295fm)
6.7
1.65 yrs
#-
120 ft (36.+)
Devil Canyon
26 mi (42 km)
0.46 mi
12 mi 2
1.lxl06 ac ft (1.4xl0 9m3 )
565 ft 07l!>
140 ft (42FT
2.7%$;
76 mi (123~m)
6.2
60 days
50 ft 05.10
-
Based on:Acres P.~erican 1983.
(Sus.Hydro Project.Fed.Energy Reg.Comm.License App.Exhibit F.Supporting
Design Report.(Preliminary).Feb.1983.by Acres.)
33RCl/00lc -16 -
Model forecasts for downstream river temperatures show a general
dampening of the variations that occur naturally and this will affect
conditions as far dOw"'Ilstream as Talkeetna.Mean summer river temperatures
under \vatana only 1;'1Ould be approximately 1 C cooler than natural at river
miles (RM)150 and 130,and 0.6 C cooler at RH 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 1;'1Ould peak later in the summer with the greatest
deviation from natural temperatures occurring in September-October.Winter
releases would range from 0.4 to 6.4 C from October to April.Natural winter
temperatures are 0 C.These alterations in the natural temperature regime are
Hell within the tolerance limits for adult and juvenile salmon and are not
expected to significantly impact migration or spawning activity with the
exception of a posstble 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-project 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).
33RD3/001 -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).
-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.
3.Approximately 70-97 percent of the suspended sediment load carried into
the Ivatana reservoir by the inflow will settle,resulting in
I""",
significantly less turbid conditions in summer,but higher turbidity
levels in winter.
4.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.
6.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
existing oxygen demand is low.
8.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
33RD3/001 -18 -
middle river under with-proj ect 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 glacial surges which occurred in the 1950s,USGS gathered 'vater 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 an
inadequate assessment of a water quality condition.
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 project 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
33RD3/001 -19 -
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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.
33RD3/001 -20 -
U:lPACT 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 tine.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
depl2ndent 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
factors,combined with the high levels of suspended sediment that ~vill 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 ~vhile the morphology and glacial character of the Susitna
-~
River essentially eliminates 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!OOl -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 on questions relating to trace
metals.
The mitigable problem of gas supersaturation is treated thoroughly in the
license application and will not be discussed in detail here.Briefly~gas
supersaturation should not occur below the Devil Canyon dam unless spillway
releases become necessary which will occur only under 1 in 50 year flood
conditions.Under normal circumstances ~the lower flows sent through the
-
-
rapids in Devil Canyon under with-project conditions will lead to considerably
lower levels of dissolved gas supersaturation during the summer months and
higher levels during the lvinter months.These levels should not exceed 110%
(ADF&G Su Hydro 1983)which is well within the tolerance limits for aquatic
organisms (Fickerson and Schneider 1976)and complies with Alaska state water
quality standards (18 AAC 70.020).
POTENTIAL I}~ACT OF INCREASES IN 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,
especially for downstream salmon and resident fish populations since fish
densities in the reservoirs themselves are likely to be very low and largely
33RD3!001 -22 -
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 (Rg),nickel (Ni),and zinc (Zn),which 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,Rg,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,the 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
mercury (presumably methylmercury)(Tom Stuart,Rarza-Ebasco,pers.comrn.).
The meat in a can of tuna averages 250 ppb (EPA 1980).
33RD3/001 -23 -
-
Of the four heavy metals of concern here,biomagnification has been
doeumented only for Hg as a direct result of impoundment (Bodaly et al.1984,
Abernathy and Cumbie 1977,Cox et al.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/1.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
transformation of elemental Hg to mercuric ion-
(chelation).This mobilization of Hg by organic matter facilitates the
+2(Rg )which in turn is the
most toxic.
substrate for microbial methylation.It is in the methylated form that Hg is
+2AvarietyofbacteriaandfungiarecapableoftransformingHg
(both in organic and inorganic form)to methylmercury even in well oxygenated
water (Forstner and Wittmann 1979)thus releasing it to the water itself and
into the food chain.
33RD3/001
Fish become contaminated with methylmercury either
-24 -
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 ~vatana and Devil Canyon reservoirs will increase by an
unquantifiab1e amount within one to three years after closure of the dams
(Abl~rnathy and Cumbie 1977,Boda1y et al.1984).With aging of the
resl~rvoirs,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
extl~nt (perhaps as
temperatures (Wright
much as 50%)by the prevailing cold (4 C)water
and Hamilton 1982)and by the blanketing action of
inflowing sediment settling to the reservoir bottoms (L.A.Peterson and Assoc.
reservoir aging process compared to reservoirs located in warmer regions
(Boda1y 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 bioaccumu1ation in fishes (Rudd and Turner
-
-
1982).The cold temperatures may also act to extend the length of the
1983b).
No information is available in the literature concerning Hg enrichment in
fish downstream of newly impounded reservoirs.Whether or not this process
will be enhanced downstream of the Susitna reservoirs depends largely on which
form of Hg is exported from the reservoirs and in what concentrations.
33RD3/001 -25 -
Another important factor ""ill 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 absorbed to suspended sediment particles in an inorganic form.Some
surface area for adsorption in proportion to their mass than the
-
-
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
av
1Q.Rger
particles (>5-10~)that will settle out in the reservoirs.
The concentrations of methylmercury that might be released by the
resle.rvoirs 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 proj ect.Concentrations downstream,
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 -26 -
.....
-
CADHIUM
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 ~g!l have never been recorded (R&H 1982).The global average for
dissolved Cd in freshwater is 0.07 ~g!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 do,"mstream habitats will be significantly
accelerated under with-project conditions.If acceleration does occur for Cd,
it lidll most certainly occur for Hg as well.
COPPER
Copper (Cu)is an essential macronutrient for plants which performs
sevleral vital enzymatic functions and plays a major 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 ~!l to 190 ~g!l;dissolved concentrations range from 0 to
121lg!1 (R&M 1982).The average concentration of soluble Cu in U.S.
freshwater is 15 ~g/l (EPA 1976).Holland (1960)reports a dissolved Cu
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!OOl -27 -
-
hydroxocopper.No studies have revealed any biomagnification of Cu following
impoundment so the risk of negative impacts to Susitna River fish stocks is
lm-T.It is possible that increases in Cu concentrations might be offset to
some extent by increased uptake by a more productive,with-proj ect benthic
algal community.
ZINC
Zinc (Zn)is also a macronutrient which becomes toxic when present in
exc:ess concentrations.Total Zn levels in the Susitna River vary from 10 to
200 ~g/l;dissolved levels from 0 to 30 ~g/l.The world average for
freshwater is 10 Jlg/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
(1964)as 910 ~g/l for juvenile rainbow trout tested in water of comparable
summertime alkalinities and pH levels to the Susitna River (although water
temperature 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
grmvth and propagation of aquatic organisms.As in the case of Cu,almost all
of the dissolved Zn would be chelated or otherwise bound to humic substances •
33RD3/001 -28 -
--
.-
.....
SUMMARY
(To be written)
33RD3/001 -29 -
.J._!f!!I!!§;!r~~,.._..__:;:q.............----_
-,
-
.....
f-<if-=r r<-£~e (.S
~
AbE!rnathy,A.R..and P.M.Cumbie.1977.Mercury accumulation by largemouth
bass (Micropterus salmoides)in recently impounded reservoirs.
Environ.Contam.Toxicol.17(5):595~602.
Bull.
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 •
Ala.ska Dept.of Fish &Game/Su-Hydro.1981.Subtask 7.10,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.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
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 ~.;ratana and Talkeetna reach.
Alaska Power Authority.
33RD3/001 -30 -
--------------------------.--------------------------
Alaska Power Au thori ty .1984.Comments on the Federal Energy Regulatory
Commission draft environmental impact statement of May 1984.Vol.6,
Appendix IV,temperature simulations,Watana and Devil Canyon Reservoirs.
Manitoba.Can.J.Fish.Aquat.Sci.41(4)~682-691.
levels in lakes flooded by the Churchill River diversion,northern
f"'"
I
I
I
,....
!
Bodaly,R.A.,R.E.Reeky,and R.J.P.Fudge.1984.Increases in fish mercury
of mercury in fish in new impoundments.Bull.Environ.Contam.Toxicol.-
Cox,J.A.,J.Carnahan,J.DiNunzio,J.McCay,and J.Meister.
23:779-783.
1979.Source
E.Woody Trihey and Assoc.and I-Joodward-Clyde Consultants.1984.
.",.
Preliminary draft,instream flow relationships report.Vol.1.Prepared
for Rarza-Ebasco Susitna Joint Venture.203 pp .
Environmental Protection Agency (EPA).
EPA-440!9-76-023.Washington,D.C.
EPA (Environmental Protection Agency).
mercury.EPA 440-5-80-058,136 pp.
1976.
1980.
Quality criteria for water.
Ambient water quality for
Forstner,V.and G.T.W.Wittmann.1979.Hetal pollution in the aquatic
environment.Springer-Verlag.Berlin.,+86 pp.
Rarza-Ebasco Susitna Joint Venture.1985.Water quality issue paper.
33RD3!OOl -31 -
Herbert,D.W.M.and D.S.Shurben.1964.The toxicity to fish of mixtures of
poisons.I.Salts of ammonia and zinc.Ann.Appl.Bioi.53:33.
Holland,G.A.1960.Toxic effects of organic pollutants on young salmon and
trout.State of Washington Dept.of Fisheries Res.Bull.No.5.264 pp.
Jackson,K.S.,I.R.Jonasson,and -G.B.Skippen.1978.The nature of
metals-sediment-water interaction in freshwater bodies,with emphasis on
the role of organic matter.Earth-Sci.RE~V.14:97-146.
effects resulting from impoundment of the Susitna River.
Acres American Inc.39 pp.
L.A.Peterson and Assoc.and R&M Consultants,Inc.1982.Water quality
Prepared for
Lockwood.R.A.and K.Y.Chen.1973.Absorption of Hg (II)by hydrous
manganese oxides.Environ.Sci.Technol.7(11):1028-1034.
Meister,J.F.,J.DiNunzio and J.A.Cox.1979.Source and level of mercury
in a new impoundment.J.Amer.Hat.Wrks.Assoc.1979:574-576.
Moore,J.W.,and S.Ramamoorthy,1984.Heavy metals in natural ,vaters:
r Applied Monitoring and Impact Assessment.Springer-Verlag.New York.
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 .
33RD3/001 -32 -
-
R&M Consultants,Inc.1981.Water quality c:mnual report -1980.Prepared
for Acres American Inc.39 pp.
R&M Consultants,Inc.1982.Water quality annual report -1982.Prepared
for Acres American Inc.53 pp.+App.
R&M Consultants,Inc.1981.Water quality c:mnual report -1981.Prepared
for Acres American Inc.99 pp.+App.
R&M Consultants,Inc.and L.A.Peterson and Assoc.1981.Subtask 3.03 -
Water quality.Review of existing Susitna River basin water quality
data.Prepared for Acres American Inc.96 pp.
R&M Consultants,Inc.and L.A.Peterson and Assoc.1982.Water quality
-~
interpretation -1981.Prepared for Acres American Inc.109 pp.
Reuter,J.R.and E.M.Perdue.1977.Importanee of heavy metal-organic matter
interactions in natural waters.Geochim.Cosmochim.Acta 41:325-334.
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The English-Wabigoon River System:I.A synopsis of recent research with
....
-
a view towards mercury amelioration.
2206-2217 •
Can.J.Fish.Aquat.Sci.40:
33RD3/001 -33 -
v.Mercury and selenium bioaccumulation as a function of aquatic primary-Rudd,J.W.M.,and H.A.Turner.1983b.The English-Wabigoon River system:
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Schnitzer,H.and S.U.Khan.1972.Humic Substances in the Environment.
.....
I
Mercel Dekker,New York.344 pp .
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Vollenweider,R.A.1976.Advances in definJLng critical loading levels for
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....
phosphorus in lake eutrophication.Mem.1st Itol.Idrobiol.33 pp.
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Press.Cambridge.337 pp .
33RD3/001 -34 -
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