Science activity

This project examined cold water storage and regulation in Shasta Lake through the Shasta Dam Temperature Control Device (TCD). The TCD is a 300-foot structure with multiple gate openings, allowing water from different depths - and thus different temperatures - to be selectively released to manage water temperature in the river downstream. River water temperature is managed to support the imperiled Chinook salmon, a species of fish that is native to California. This capability is becoming increasingly important because low water years generally mean warmer river water temperatures that compromise habitat suitability for different species. In particular, cold pool management is essential for downstream spawning and rearing habitat for winter-run Chinook salmon that rely on cooler water temperatures to survive and reproduce. When the water is too warm, oxygen availability is limited for Chinook salmon and their eggs, which contributes to their mortality. Although the TCD allows reservoir managers to control water release and downstream water temperature, flow contributions into the TCD under day-to-day operations for different gate openings, operations, and thermal conditions within the reservoir are largely unquantified. Further complicating temperature management, TCD leakage (whether within the structure itself or through malfunctioning gates) needs to be better quantified in location and magnitude. This information will improve operational strategies for cold water performance especially during summer and fall months to manage cold water supply for downstream Chinook salmon habitat.