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Assessing flows for fish below dams: A systematic approach to evaluate compliance with California Fish and Game Code 5937

Publication Date
Sep 30, 2014
Center for Watershed Sciences John Muir Institute of the Environment


Scientists have identified 181 California dams that may need to increase water flows to protect native fish downstream. The screening tool, developed by the Center for Watershed Sciences at the University of California, Davis, to select \textquotedbllefthigh-priority\textquotedblright dams may be particularly useful during drought years amid competing demands for water. The study evaluated 753 large dams in California and screened them for evidence of altered water flows and damage to fish. About 25 percent, or 181, were identified as having flows that may be too low to sustain healthy fish populations. The \textquotedbllefthigh-priority\textquotedblright list includes: \textbullet Some of the state\textquoterights biggest dams: Trinity Dam on the Trinity River, New Melones Dam on the Stanislaus River, Pine Flat on Kings River, and Folsom Dam on the American River \textbullet Dams on rivers with the greatest richness of native species: Woodbridge Diversion Dam on the Mokelumne River, Nash Dam in Shasta County, and three rubber dams on lower Alameda Creek \textbullet Dams affecting the greatest number of native species with sensitive population status: Keswick and Anderson-Cottonwood dams on the Sacramento River, and Woodbridge and Nash dams. A state law, California Fish and Game Code 5937, requires dam operators to release \textquotedblleftsufficient water\textquotedblright to keep fish downstream \textquotedblleftin good condition.\textquotedblright But, with thousands of dams in the state and limited resources to assess each one, the law is rarely enforced without a lawsuit behind it. For example, a series of lawsuits in the 1980s led to higher flow releases for native fish in Solano County\textquoterights Putah Creek. Section 5937 was also invoked in the 2006 San Joaquin River settlement agreement to restore flows to that river below Friant Dam. Such lawsuits do not always indicate which dams are in most need of attention to protect native fish. The new study provides a scientific basis for dam operators, natural resource managers and policymakers to perform water \textquotedbllefttriage\textquotedblright — setting management priorities for dams requiring the most urgent attention. Inclusion on the list does not necessarily mean the dams are out of compliance with the state law.

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