Eel River (California) - Watershed

Watershed

The Eel River drains an area of 3,684 square miles (9,540 km2), the third largest watershed entirely in California, after the San Joaquin River and the Salinas River. The Sacramento River and Klamath River are larger, but their drainage areas extend into neighboring states as well. Its major tributaries, the North Fork, Middle Fork, South Fork and Van Duzen Rivers, drain 286 square miles (740 km2), 753 square miles (1,950 km2), 689 square miles (1,780 km2), and 420 square miles (1,100 km2), respectively. The Middle Fork is the largest of the tributaries by drainage area, but the South Fork is longer, and carries more water because of its location closer to the coast.

Northwest-southeast ridges of the California Coast Ranges constitute the Eel River watershed, which is bordered on the north by the Mad River, on the east by the Sacramento River, on the west by the Mattole River, and on the south by the Russian River and Ten Mile River. Major cities on the river include Willits, Garberville, Redway, Scotia, Rio Dell, Fortuna, and Ferndale. The river's relatively large estuary/delta, which includes the soon to be restored Salt River tributary and related creeks, is located just one low ridge south from Humboldt Bay and 12 miles (19 km) south of Eureka, the main city for the entire region. Average flow of the Eel River varies widely due to its location, which places it as a major beneficiary of significant Winter storms. These storms produce enormous wet-season flows, while in the summer and early autumn provide only minimal precipitation, if any, allowing the sometimes mighty river to slow to a trickle. Reduction in flow occurs also in part due to deliberate water diversion from the Eel to the Russian River watershed by the Pacific Gas and Electric Company's Potter Valley Hydro-power Project at Potter Valley, located to the south in Mendocino County.

Since the 19th century, logging activity in the watershed has loosened soil and destabilized aquifers, reducing the river's base flow, although the river's watershed is slowly recovering. Logging and other resource exploitation activities are one of the primary causes of the river's massive surges and dry spells. In the 20th century, much of the watershed area became protected under state parks and national forest, including Six Rivers National Forest, Yolla Bolly-Middle Eel Wilderness, and Humboldt Redwoods State Park. Many tributaries and the mainstem Eel River have also been designated National Wild and Scenic Rivers.