Calaveras River Watershed


The Calaveras River Basin drains a total of 470 square miles above the foothill line in Calaveras and San Joaquin counties.  The watershed above New Hogan reservoir covers 363 square miles and average annual run-off is about 166,000 acre-feet.  The Calaveras River watershed is a tributary to the San Joaquin River Delta System and is located in the Calaveras, Stanislaus, and San Joaquin Counties of California.  The majority of the watershed lies in the northwestern region of Calaveras County; the westernmost portion of the watershed lies in San Joaquin County, and a small, southwestern area lies in Stanislaus County.  The most prominent manmade facility is New Hogan Dam and Reservoir at river mile (RM) 42 (as measured via the Mormon Slough route) which controls water flow on the lower Calaveras River.  


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The lower Calaveras River Mormon Slough area is below New Hogan Dam which encompasses approximately 115,000 acres and receives up to 90,000 acre feet of surface water supply from the lower Calaveras River. The four main tributaries below New Hogan are Cosgrove Creek, South Gulch, Indian Creek, and Duck Creek. Cosgrove Creek provides the largest run-off contribution to the Calaveras River, as much as 8,500 acre-feet in some years.


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Last updated: November 19, 2007.