Russian River (California)

The Russian River (Southern Pomo: Ashokawna, Spanish: Río Ruso) (Russian: русская река) is a southward-flowing river that drains 1,485 mi² (3,850 km²) of Sonoma and Mendocino counties in Northern California. With an annual average discharge of approximately 1,600,000 acre feet (2.0 km³), it is the second-largest river (after the Sacramento River) flowing through the nine-county Greater San Francisco Bay Area, with a mainstem 115 mi (185 km) long.

Deriving its name from the establishment of colonial outposts by the Russian-American Company near its course, during the beginning of the 19th century, the river is today a significant body of water for recreation and agriculture and represents, as a result of its damming and the consequent creation of Lake Mendocino, a significant water source for several of the Northern California counties through which it runs.

Ecologically, the river is home to the Russian River tule perch, a distinctively endemic species of freshwater surfperch, as well as significant populations of steelhead trout, Coho and Chinook salmon. During its initial exploration, large numbers of otters and beavers were also identified, and subsequently hunted. Presently, toxic cyanobacteria of the genus Microcoleus have also represented a significant element of the Russian River ecosystem, including a species from that genus found only in the river as of yet.