Map of the Eel River Watershed
The Eel River Watershed covers over 3,500 square miles. The Counties of Humboldt, Trinity, Tehama, Glenn, Colusa, Lake and Mendocino share this diverse river system. The main tributaries of the Eel River include the Middle Fork, North Fork, Van Duzen, South Fork and the Upper Mainstem. The Potter Valley Project is located in the very highest reach of the Upper Mainstem of the Eel River.
Map of Potter Valley Project
The Potter Valley Project is located on the Upper Mainstem Eel River. The Project consists of Cape Horn Dam, which was built in 1908, forming Van Arsdale Reservoir. This is the area where the actual diversion, fish ladder and fish screen facilities are located. Twelve miles upriver from Cape Horn Dam is Scott Dam. Scott Dam was built in 1922 to store winter rainfall and snow melt that is released in the summer. Scott Dam is over 170 river miles from the estuary and the mouth of the Eel River at Fortuna. Lake Pillsbury was formed by Scott Dam and it is in the Mendocino National Forest. It attracts thousands of visitors every year for camping, fishing and boating. The map also shows the relationship between the diversion tunnel at Van Arsdale Reservoir, the Powerhouse in Potter Valley, the East Branch of the Russian River and Lake Mendocino.