Shasta Dam

Shasta Dam is a massive concrete gravity structure, 3,460 feet (1,050 m) long at its crest, with a volume of 6.5 million cubic yards (5.0 million m³).¹ Construction began in 1938 under the Bureau of Reclamation, employing up to 8,000 workers. The dam was built in stages, with the first concrete placed in 1940 and the final bucket in 1945.² The design includes a spillway with a capacity of 100,000 cubic feet per second (2,800 m³/s) and a river outlet works that can release up to 14,000 cfs.³ The dam's foundation is anchored in bedrock, with a grout curtain to reduce seepage.

The dam serves multiple purposes: flood control, irrigation supply, and hydroelectric generation. Its reservoir, Shasta Lake, has a storage capacity of 4.5 million acre-feet (5.5 km³), making it California's largest reservoir.⁴ Water releases are managed to meet downstream demands for agriculture and municipal use, while also maintaining river flows for salmon and other species. The powerplant, with five Francis turbines, has a generating capacity of 710 megawatts, providing renewable energy to the region. Operations are coordinated with other Central Valley Project facilities to optimize water supply and flood protection.

The dam's construction permanently altered the Sacramento River ecosystem, blocking fish migration and changing sediment flow. The Shasta Dam and its reservoir flooded the ancestral lands of the Winnemem Wintu tribe, displacing communities and submerging cultural sites. In recent decades, efforts have been made to mitigate impacts, including the construction of a temperature control device to release cooler water for endangered winter-run Chinook salmon. The dam also contributes to the decline of native fish populations, prompting ongoing debates about dam removal and fish passage.

Shasta Dam was the first dam to use a technique called 'pre-cooling' of concrete to control thermal cracking, a method later adopted worldwide. During World War II, construction was accelerated, and the dam was completed ahead of schedule despite labor shortages. The dam's design includes a unique 'glory hole' spillway, a bell-mouth intake that funnels water into a vertical shaft. Additionally, the dam's construction required the relocation of the Southern Pacific Railroad, which was rerouted along the reservoir's edge. The Winnemem Wintu have proposed adding a fish ladder to allow salmon to pass, but the idea remains controversial.

Gravity dam

A dam that relies on its own weight to resist water pressure.

Central Valley Project

A federal water management project in California.

Acre-foot

Volume of water covering one acre to a depth of one foot.