Electrical Power for Valdez and the Copper River Basin-1981

outlet from the lake; however, the CE expects· natural seepage throughglacial deposits to provide some flow into the upper creek. Also,tributary flow will provide some stream flow to lower portions ofthe creek.Water for hydropower production would be drawn from deep in the lakeand, based upon available information, will be warmer than AllisonCreek water in the winter and colder than the stream's water in thesummer. Water at lake tap depth may also be deficient in dissolvedoxygen. A minimum dissolved oxygen concentration of 6.0 milligramsper liter (mg/l) has been recommended for coldwater fish (Doudoroffand Shumway, 1966). At the present time, dissolved oxygen data atthe depth of the proposed lake tap is not available. The passage ofwater through the powerhouse and energy dissipator is expected toaerate these waters, although the extent of this occurrence inrelation to the acceptable limits for fish is not known at present.Temperature has a major influence on the freshwater stages of salmon.Stream temperature data for Allison Creek has been collected by theU.S. Geological Survey and is now being collected by the ADF&G(APPENDIX B). The CE has also collected some temperature data forAllison Lake (APPENDIX B). The ADF&G has also taken intertidaltemperatures at Solomon Creek (three miles to the east) sinceSeptember, 1979, and this data would probably be consistent withsalt water temperatures off the mouth of Allison Creek (APPENDIX B).No intragravel temperatures have been taken~The effects of warm water discharges on developing eggs and alevinshave been studied in laboratory situations and at most major hatcheryfacilities. Increased mortality and abnormal embryonic developmenthave been shown to occur if the initial incubation temperatures fordeveloping pink salmon eggs is 4.SoC or lower. At 2.0°C or lower,complete mortality will occur (Bailey and Evans, 1971). Preliminarytemperature data from the lake (APPENDIX B) indicates that the waterthrough the powerplant would be 4°C or less. Based upon these data,the potential alteration of the temperature regime in Allison Creekcould have a significant adverse impact upon the fish resources ofAllison Creek.Low concentrations of dissolved oxygen and exposure to light canincrease incubation time, but temperature is the primary factor inregulating the duration and timing of incubation and hatching.Development is normally expressed in terms of temperature units. Atemperature unit is defined as one degree above freezing for aperiod of 24 hours. A given number of temperature units is requiredfor the eggs to hatch. The number of temperature units required isgenerally specific to the species of fish and even to the particularstock. Hatching and emergence is delayed in colder water temperaturesand accelerated in warmer temperatures. A minor temperature increaseor decrease could considerably advance or delay hatching. A changein the natural temperature regime of Allison Creek could change thetiming of pink and chum salmon fry emergence. The extent of thisimpact is difficult to assess with the data available; however,significant early development of eggs would result in early1'1