Evaluating Head-of-Reservoir Water Temperature for Juvenile Chinook Salmon and Steelhead at Shasta Lake with Modeled Temperature Curtains

摘要

Loss of historical spawning and rearing habitat in the rivers and tributaries of California's Central Valley is one of the factors that led to the listing of Chinook Salmon Oncorhynchus tshawytscha and steelhead O. mykiss under the Endangered Species Act. To recover these salmonid populations, an interagency committee is developing a plan to reintroduce fish to tributaries upstream of Shasta Dam and provide juvenile fish passage downstream past the dam. One downstream fish passage alternative involves the collection and transport of juvenile fish from head-of-reservoir locations. A hydrodynamic and water quality model (CE-QUAL-W2) of Shasta Lake and its main tributaries was used to assess where and when water temperatures were favorable for juvenile salmonid collection on the McCloud River arm of the lake under different hydrologic scenarios. The application of anchored and floating temperature curtains (i.e., flexible fabric flow barriers) was examined to assess whether they could be used to improve temperature conditions for juvenile fish by reducing temperatures to within an optimal range. Model results indicated that head-of-reservoir conditions without a temperature curtain were suitable for spring-run Chinook Salmon, fall-run Chinook Salmon, and steelhead but not for winter-run and late-fall-run Chinook Salmon. However, permanent or temporary use of temperature curtains, especially a long floating curtain, may improve conditions for juvenile winter-run and late-fall-run Chinook Salmon by reducing or eliminating lethal water temperatures.