Shasta Dam forms the largest storage reservoir in the state, Shasta Lake, which can hold about 4.5 million acre-feet.
As the keystone of the federal Central Valley Project, Shasta stands among the world’s largest dams. Construction on the dam began in 1938 and was completed in 1945, with flood control as the highest priority.
Located 12 miles north of Redding, Shasta traps the cold waters of the Pit and McCloud rivers and the headwaters of the Sacramento River behind its 602-foot curved, concrete face.
In years of normal precipitation, it stores and distributes about 20 percent of the state’s developed water — about 7 million acre-feet —through its massive system of reservoirs and canals. Water is transported 450 miles from Lake Shasta in Northern California to the San Joaquin Valley. Along the way, the Central Valley Project has long-term agreements with more than 250 contractors in 29 of California’s total 58 counties.
Shasta Dam and Operations
Associated facilities include Shasta Powerplant, located just below the dam, with a generating capacity of 584,000 kilowatts, or enough power for 165,000 homes.
Ten miles downstream is Keswick Dam, reservoir and power plant. Keswick Dam creates an after bay for Shasta Dam and the Trinity River diversion facilities, stabilizing uneven water releases from the power plants.
As with most multi-purpose projects, the CVP’s operational priorities change with the seasons. From November to April, flood control is the top priority and reservoirs are filled to store winter runoff. From May to October, releases are timed to satisfy a variety of water-supply needs, and create room for flood flows. For example, at Shasta the reservoir typically is drawn down to between 1.2 million and 1.4 million acre-feet by early December, and maximum storage is normally reached in late May or June.
Similar to the Oroville Dam, construction of Shasta Dam blocked access to 187 miles of cold water streams, about half the available spawning and rearing habitat in the upper Sacramento River system.
During Shasta’s construction, the U.S. Fish and Wildlife Service worked with the Bureau of Reclamation to mitigate this habitat loss. Coleman National Fish Hatchery located near the mouth of Battle Creek where it joins the Sacramento River, was built in 1943 to offset the loss of anadromous fish that could no longer reach their spawning grounds upstream of Shasta.
Since Coleman and the Nimbus Salmon and Steelhead Hatchery, along with seven other hatcheries around the state, have helped sustain the commercial ocean salmon catch. However, the hatcheries alone cannot replace the wild salmon stocks that biologists consider essential for the survival of the species.
Today, there are three types of migratory barriers to anadromous fish within Battle Creek: natural waterfalls, hydroelectric diversion dams, and the Coleman Hatchery weir.
As part of this, an $80 million project to remove five dams in narrow canyons along the north and south forks of Battle Creek near Manton is underway and scheduled for completion by the end of 2014.
There are also efforts to restore and enhance the endangered winter-run for Chinook salmon.
Reclamation made numerous operational changes, including temperature control curtains and bypassing hydroelectric power generators at Shasta Dam in order to release deep, cold water from low-level outlets from mid-July to mid-October to improve spawning conditions. Other actions include closing the Delta Cross Channel gates for several months to keep migrating salmon in the river channel, and raising the gates of Red Bluff Diversion Dam to improve upstream and downstream migration.
Shasta Dam and the Future
Looking ahead, state and federal officials see a need for more water storage due to population growth and increasing demands for water. In consequence, Shasta Dam could be made larger.
Raising the dam 18.5 feet, for example, would mean an additional 636,000 acre-feet a year, enough water to sustain 2 million people a year. Opponents say the amount of water made available by raising the dam is not worth the ecosystem costs —flooding of canyons and endangering wildlife and habitat —and further loss of sacred tribal ground (an issue unresolved from the original construction).
At present, the Bureau of Reclamation is conducting the Shasta Lake Water Resources Investigation to evaluate enlarging Shasta Dam and Reservoir. As the SLWRI progresses, Reclamation plans to continue related work on environment, water rights, and Native American and cultural resources.