East Fork Russian River is a 15 mi (24 km) long tributary of the Russian River in Mendocino County, California artificially connected to the Eel River via an interbasin diversion at the Potter Valley Project hydroelectric facility. It forms in the north of Potter Valley, flows south through this valley, then southwest through a mountain pass to Lake Mendocino, an artificial reservoir that empties into Russian River.At one time Clear Lake to the east drained through Cold Creek then along the lower part of East Fork Russian River through Coyote Valley to the Russian River proper.A few hundred years ago a massive landslide blocked this channel, and Clear Lake found a new outlet to the Sacramento River.