South Fork American River
| South Fork American River | |
|---|---|
 | |
| Physical characteristics | |
| Mouth | Folsom Lake 36°46′24″N 121°02′24″W / 36.77333°N 121.04000°W[1] |
• elevation | 466 ft (142 m) |
| Length | 87 mi (140 km)[2] |
| Basin features | |
| Progression | American–Sacramento |
The South Fork American River is a major tributary of the American River in El Dorado County, California,[1] draining a watershed on the western slope of the Sierra Nevada east of Sacramento. The river at Coloma was the site of James Marshall's discovery of gold at Sutter's Mill on January 24, 1848, which started the California Gold Rush.[5]
Geography
The river begins at Nebelhorn near Johnson Pass about 10 mi (16 km) south of Lake Tahoe. From there it flows west for 87 mi (140 km),[2] past the towns of Kyburz, Pollock Pines and Coloma, before emptying into Folsom Lake, the reservoir formed by the Folsom Dam. The North Fork American River also flows into the lake, and the combined rivers form the American River proper, which flows from the dam southwest to a confluence with the Sacramento River.[6]
The South Fork drains an area of 840 sq mi (2,200 km2),[4] or about a third of the 2,150 sq mi (5,600 km2) American River watershed. Major tributaries include Silver Creek, Rock Creek, Weber Creek, and Caple Creek. Most of the watershed consists of high, forested mountains and steep-sided valleys that receive up to 40 in (1,000 mm) of annual precipitation, except for the westernmost section which consists of drier foothill country. The river also contributes about a third of the total outflow of the American River system.[4]
Discharge
According to a U.S. Geological Survey stream gage at Lotus, about 5 mi (8.0 km) above Folsom Lake, the average discharge was 1,458 cu ft/s (41.3 m3/s) from 1951 to 1995.[3] The highest recorded flow was 90,000 cu ft/s (2,500 m3/s) on January 1, 1997 (see New Year's Flood),[7] and the lowest monthly mean was 86.8 cu ft/s (2.46 m3/s) in July 1977.[3]
Dams
There are two dams on the South Fork proper: Slab Creek Dam, which forms Slab Creek Reservoir near Camino, and Chili Bar Dam, located north of Placerville. Both are run-of-the-river dams serving mainly for hydroelectricity production. Other major dams in the South Fork basin include ones at Union Valley Reservoir and Ice House Reservoir on the Silver Creek drainage. Most of the dams and reservoirs in the basin are operated by the city of Sacramento as part of the 688 megawatt Upper American River Project[8] and Pacific Gas and Electric as part of the Chili Bar Project.
References
- ^ a b c "South Fork American River". Geographic Names Information System. United States Geological Survey, United States Department of the Interior. 1981-01-19. Retrieved 2013-04-14.
- ^ a b U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National Map, accessed 2011-03-10
- ^ a b c "USGS Gage #11445500 on the South Fork American River near Lotus, CA: Monthly Streamflow". National Water Information System. U.S. Geological Survey. 1951–1995. Retrieved 2013-04-14.
- ^ a b c "South Fork American River Watershed Stewardship Strategy" (PDF). El Dorado County and Georgetown Divide Resource Conservation Districts. May 2004. Retrieved 2013-04-14.
{{cite web}}: Cite uses deprecated parameter|authors=(help) - ^ "South Fork of the American River". The American River: California's favorite whitewater river. Retrieved 2013-04-14.
- ^ USGS Topo Maps for United States (Map). Cartography by United States Geological Survey. ACME Mapper. Retrieved 2013-04-14.
- ^ "USGS Gage #11445500 on the South Fork American River near Lotus, CA: Peak Streamflow". National Water Information System. U.S. Geological Survey. 1951–1997. Retrieved 2013-04-14.
- ^ "SMUD projects awarded grants totaling nearly $6.5 million to advance hydropower technologies". Sacramento Municipal Utility District. 2012-09-12. Retrieved 2013-04-14.