Middle Fork American River
|Middle Fork American River|
Middle Fork flowing through the Auburn State Recreation Area
|- left||Rubicon River, Otter Creek (California), Canyon Creek (California)|
|- right||Duncan Creek (California), North Fork Middle Fork American River|
|- elevation||8,399 ft (2,560 m)|
|Mouth||North Fork American River|
|Length||62 mi (100 km)|
|Basin||616 sq mi (1,595 km2)|
|Discharge||for near Foresthill|
|- average||1,111 cu ft/s (31 m3/s) |
|- max||310,000 cu ft/s (8,778 m3/s)|
|- min||35 cu ft/s (1 m3/s)|
The Middle Fork American River is one of the three main branches of the American River in Northern California. The river flows 62 miles (100 km) from its headwaters in the Sierra Nevada, in a generally southwest direction, to join the North Fork American River near Auburn.
The main stem of the river begins along the Sierra Crest, on the south flank of Granite Chief near Squaw Valley Ski Resort west of Lake Tahoe. It flows west than southwest into French Meadows Reservoir, which is impounded by the L.L. Anderson Dam. Below the dam the Middle Fork enters a rugged and inaccessible canyon more than 2,000 feet (610 m) deep. About 15 miles (24 km) downstream, the Middle Fork flows into the Ralston Afterbay, where it is joined from the east by the Rubicon River. Directly below this point, the North Fork of the Middle Fork American River joins from the north. The Middle Fork then flows southwest, past Foresthill, through the Auburn State Recreation Area, and into the North Fork directly below the Foresthill Bridge and above Highway 193. Below this confluence the North Fork flows a further 5 miles (8.0 km) to the Folsom Lake reservoir above Sacramento. Although nominally a tributary of the North Fork, the Middle Fork has a greater flow and drains a much larger watershed of 616 square miles (1,600 km2).
The Middle Fork is used heavily for water supply and the generation of about 1.03 billion kilowatt hours of hydroelectricity each year. The Placer County Water Agency operates the dams and power plants on the river, which are known collectively as the Middle Fork Project. The project consists of two major reservoirs, French Meadows on the Middle Fork and Hell Hole Reservoir on the Rubicon River, which can store 342,583 acre·ft (0.422570 km3) combined. The reservoirs store winter and spring runoff and release it during the summer and fall; in dry years, water supply takes precedence over power generation. The firm water supply provided by these reservoirs is about 120,000 acre·ft (0.15 km3). Water released from these reservoirs flows through the Middle Fork and Ralston Powerhouses and is returned to the river at Ralston Afterbay. As a consequence, the Middle Fork from LL Anderson Dam to Ralston Afterbay is often dry, as is the Rubicon River from Hell Hole Dam to its confluence with the Middle Fork.
The river is known for its challenging Class III and IV rapids. Both guided and solo whitewater rafting and kayaking tours are popular, with thousands of people making the trip each season. One of the Middle Fork's most notable features is Tunnel Chute, where the river flows through a tunnel blasted through a ridge during the California Gold Rush in order to allow gold mining in the adjacent riverbed. The Middle Fork is a heavily dam-controlled river and during the height of the summer rafting season, flows are highly dependent on electric power demand in the Sacramento area. However, this also guarantees steady flows in the river during dry years.
- "USGS Gage #11433300 on the Middle Fork American River near Foresthill, CA" (PDF). National Water Information System. U.S. Geological Survey. 2013. Retrieved 2015-08-20.