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.