page_title: Nimbus Dam
section_title: Impact on Fish and Wildlife
hierarchical_section_title: Nimbus Dam / Impact on Fish and Wildlife
caption_attribution_description: Am. River at Nimbus Dam 969
context_page_description: The Nimbus Dam is a base load hydroelectric dam on the American River near Folsom, California. Approximately 8,700 acre feet of water is retained by the dam. It is responsible for the impoundment of water from the American River to create the Lake Natoma reservoir. The dam stands 87 feet and spans 1,093 feet. The Nimbus powerplant consists of two generators. Each generator produces enough electrical power to power over 200,000 100-watt light bulbs, about 15,500 kilowatts of electrical power. Nimbus Dam consists of 18 radial gates, each with their own gate bays. These 18 gates today are the ones that were completed in 1955 along with the rest of the dam. Of the eighteen gates, four of them have had their coating system replaced. This protects the gates from a faster rate of corrosion. The other fourteen gates have the original coating.
  As part of the Central Valley Project, a federal water project that provides irrigation and municipal water to much of California's Central Valley, it was authorized in 1949 as a regulating reservoir for Folsom Dam, and a diversion pool for the Folsom South Canal. Construction began in 1952, and it opened in 1955.
context_section_description: The water in Lake Natoma, which is the lake created by Nimbus Dam, is too cold for warmwater production of fish, and never has the lake been a natural producer of fish. The rapid water exchange from Nimbus Dam sharply decreases the production of plankton, which inhibits trout growth. The Department of Fish and Game annually plants Lake Natoma with 20,000 to 30,000 catchable-sized trout. The water exchange in the lake during the summer season increases with the operation of the Auburn-Folsom South Project. This ultimately lowers water temperatures. 
  125 miles of habitat for Chinook and steelhead salmon were accessible in the American River Watershed before the construction of Nimbus Dam. When the dam was constructed in the 1950s, this habitat area was dramatically decreased in size, as the salmon were not able to pass through the dam. To make sure the salmon had a place to spawn, through the California Department of Fish and Game, the Bureau of Reclamation opened the Nimbus Fish Hatchery in 1958 downstream from Nimbus Dam. The purpose of the hatchery was to provide the salmon with an artificial spawning habitat before they are let back out into the wild.
  Fishing has been a popular recreational use of the waters below Nimbus Dam since the Nimbus Fish Hatchery was built in 1958. However, the amount of fishing that was being done severely impacted the spawning locations of fish once passed the fish ladder at the hatchery. On March 1, 2018, the Nimbus Basin became permanently closed to all fishing. The closure of the basin is an effort to reorienting the fish ladder as part of the Nimbus Hatchery Fish Passage Project, which would create a system of collecting steelhead and adult salmon for the hatchery. The project would also include changes that would minimize flow fluctuations in the river associated with the weir of the hatchery, as well as eliminate safety concerns associated with the existing weir.
caption: The fish ladder at the Nimbus Hatchery downstream from Nimbus Dam, provides Chinook and steelhead salmon a path to their spawning grounds.
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