The Upper Sacramento River remains one of the most promising sites for increased natural salmon spawning and rearing in the entire Central Valley. Historically, this area supported more production than any other zone. However in too many years, overly warm water released from Lake Shasta when salmon eggs are incubating kills the eggs. In some years there’s enough cold water for winter run but not the early and middle part of the fall run spawn until the shorter late fall days and ambient air temperatures naturally cool the river.
This project is designed to restore a significant portion of this area’s spawning productivity through strategies that provide colder water needed for all runs. Water storage and release practices that will conserve and better utilize the cold water storage behind Shasta Dam are needed. That includes repairs to the Shasta temperature curtain to fix warm water leaks.
Each winter and spring the Bureau of Reclamation forecasts its Lake Shasta water supply, including temperatures, for the coming year and produces a plan which is then submitted to the State Water Resources Control Board for approval. In spite of state board approval, in 2014 and 2015, not enough cold water was retained to avoid a massive temperature-caused die off of the eggs of both winter and fall run. When water temperatures exceed 56ºF, some of the eggs are lost. When the temperatures reach 62º, 100 percent of the egg perish. In those two years, the fish agencies estimated that 95 percent of the eggs were lost, due to elevated temperatures. Returns of both runs have been low since then.
Because of these heavy losses, NMFS attempted to put in place stronger requirements for colder water but the Bureau of Reclamation resisted.
In October of 2019 the federal government proposed new rules governing operation of Shasta Dam that would allow water temperatures to soar to levels that can kill all of the winter run salmon, and likely a significant portion of the fall run. These losses could occur for three years in a row before the Bureau would be called to reconsider its actions. These new rules will be challenged in court.