The Middle Fork American River is one of three forks that form the American River in Northern California. It drains a large watershed in the high Sierra Nevada west of Lake Tahoe and northeast of Sacramento in Placer and El Dorado Counties, between the watersheds of the North Fork American River and South Fork American River. The Middle Fork joins with the North Fork near Auburn and they continue downstream to Folsom Lake as the North Fork, even though the Middle Fork carries a larger volume of water.
The Middle Fork was one of the richest gold mining areas during the California Gold Rush of the 1850s, and is still recreationally mined today. The river is dammed extensively to produce hydroelectricity and provide domestic water supply. Although long stretches of the Middle Fork have been dewatered by diversions, the portion of the river and canyon in the Auburn State Recreation Area is one of the state's most popular whitewater runs. Professional whitewater rafting companies offer guided trips on the Middle Fork American river from May to October. The Middle Fork canyon also has an extensive system of hiking and riding trails including the Western States Trail, which stretches from Auburn to Lake Tahoe.
Course
The Middle Fork begins at an unnamed spring in the Granite Chief Wilderness, above sea level, in eastern Placer County, west of the Palisades Tahoe Ski Resort, and about west of Lake Tahoe. The headwaters are in a rugged granite basin fed by multiple streams including one flowing from Little Needle Lake. The river flows west, turning southwest where it receives Talbot Creek from the right, through the high mountain valley of French Meadows. Several campgrounds and numerous public trails are located along this upper reach of the river. About from its source, it enters French Meadows Reservoir, above sea level, formed by the rockfill L.L. Anderson Dam. Almost the entire flow of the river at this point is diverted for hydroelectric generation, to be returned much farther downstream, with the consequence that the river immediately below the dam is reduced to a trickle except during periods of heavy snowmelt.
Below Anderson Dam the Middle Fork begins to form the boundary between the Tahoe National Forest on the north and the Eldorado National Forest on the south, almost to its confluence with the North Fork. It turns south-southwest, flowing through an extremely steep canyon, descending about in to its confluence with Duncan Creek at above sea level. The Middle Fork's canyons, often exceeding in depth, are bounded by extensive high ridges on either side, with Red Star and Chipmunk Ridges to the north and south of the river, respectively, between French Meadows and Duncan Creek. From there downstream to the El Dorado County line the canyon is bounded by Mosquito Ridge to the north, and Ralston Ridge to the south.
At the confluence with Duncan Creek the Middle Fork begins to turn west, winding through its rugged canyon, and flows through the small Interbay Reservoir where more water is diverted for power generation. It receives Big Mosquito Creek from the right and makes a large bend around the north side of Tanner Point. The Middle Fork continues west towards the western end of Ralston Ridge, north of Balderson Station, where it is joined by its largest tributary, the Rubicon River. The Rubicon is significantly longer than the Middle Fork above their confluence, and its drainage basin is also larger, extending to the Desolation Wilderness and draining a large part of northern El Dorado County. Like the upper Middle Fork, the Rubicon is almost entirely diverted for power generation. The diverted water is returned to the Middle Fork at Ralston Afterbay (Oxbow Reservoir), located directly below the confluence of the Middle Fork and Rubicon River at an elevation of .
A short distance below the dam the Middle Fork is joined by its second largest tributary, the North Fork Middle Fork American River, which drains an extensive area along the Forest Hill Divide, though lower in elevation than the upper Middle Fork or Rubicon Rivers. The North Fork Middle Fork is free-flowing with no significant dams or diversions. Just downstream, the Middle Fork flows through Tunnel Chute, where the river races through a man-made tunnel blasted out during the California Gold Rush, in order to dewater part of the river bed for mining. The Middle Fork delineates the Placer County (north)–El Dorado County line from Oxbow Dam all the way until its confluence with the North Fork.