Mendocino County Russian River Flood Control & Water Conservation Improvement District (also known as RRFC) holds License No. 13898 authorizing RRFC to appropriate up to 7,940 acre-feet annually from the East Fork Russian River, including storing water in and rediverting water from Lake Mendocino.

Lake Mendocino is the reservoir impounded by Coyote Valley Dam on the East Fork Russian River in Mendocino County. Sonoma Water and Mendocino RRFC each hold appropriative water rights to divert and use water stored in Lake Mendocino. Sonoma Water’s relevant water right is reflected in Permit No. 12947A. Mendocino RRFC’s relevant water right is reflected in License No. 13898.

 Sonoma Water was the local sponsor for the U.S. Army Corps of Engineers’ construction of Coyote Valley Dam. Sonoma Water therefore operates Coyote Valley Dam and Lake Mendocino. Permit No. 12947A’s terms require that Sonoma Water maintain certain minimum streamflows below the dam in the East Fork Russian River and downstream on the mainstem of the Russian River. Seasonally over the summer and longer during dry years, Sonoma Water maintains those streamflows by releasing stored water from Lake Mendocino. Permit No. 12947A’s priority date is January 28, 1949.

RRFC's License No. 13898 does not contain minimum streamflow requirements, but Sonoma Water’s need to release stored water to meet such requirements under Permit No. 12947A physically affects the volume of water available to Mendocino RRFC under License No. 13898. License No. 13898’s priority date also is January 28, 1949.

There are thousands of diversions from the Russian River system downstream of Coyote Valley Dam. Some of these diversions occur under claimed riparian rights. Some occur under claimed appropriative water rights. Some of those claimed appropriative water rights are associated with claims that have priorities older than Permit No. 12947A and License No. 13898. In addition, groundwater pumping occurs along the Russian River at wells whose operations may affect the river’s streamflows.

Some of the appropriative permits and licenses under which diversions from the Russian River occur do so under the “10,000 acre-foot reservation” established originally by the State Water Rights Board in Decision 1030 with the approval of Application A012920A and referenced in Permit No. 12947A’s Term 23. Under that term, Sonoma Water’s right to appropriate water into storage at Lake Mendocino is subject to up to 10,000 acre-feet of depletion by permits and licenses within the Russian River Valley in Sonoma County with priority dates that are later than January 28, 1949. Those post-1949 permits and licenses, however, do not authorize diversions that would threaten Sonoma Water’s ability to comply with Permit No. 12947A’s minimum instream flow requirements. That permit’s Term 23 states, in relevant part, that these junior rights are subject to the “retention of stored water [that] is necessary to insure satisfaction of the minimum streamflows required by permit.”