is built on an abandoned meander of the river. Near Guerneville, another meander cut short Smith Creek. The Mendocino Plateau is a part of the Franciscan Assemblage. History The river was originally known among the Southern Pomo as Ashokawna (ʼaš:oʼkʰawna), "east water place" or "water to the east", and as Bidapte, "big river". Juan Rodríguez Cabrillo and his expedition may have made it as far north as the Russian River in November 1542, before storms forced them to turn back south towards Monterey. The earliest Slavic name for the river, Slavyanka, appears on a Russian-American Company chart dated 1817. In 1827 the Spanish called it the San Ygnacio, and in 1843 the Spanish land grant referred to it as Rio Grande. The river takes its current name from Russian Ivan Kuskov of the Russian-American Company, who explored the river in the early 19th century and established the Fort Ross colony northwest of its mouth. The Russians called it the Slavyanka River, meaning "Slav River". They established three ranches near Fort Ross, one of which, the Kostromitinov Ranch, was along the Russian River near the mouth of Willow Creek. The redwoods that lined its banks drew loggers to the river in the late 19th century. According to the USGS, variant names of the Russian River include Misallaako, Rio Ruso, Shabaikai, and Slavyanka. River modifications A portion of the Eel River is diverted to headwaters of the Russian River in Potter Valley, via a scheme known as the Potter Valley Project. The Sonoma County Water Agency draws drinking water from the Russian River for sale to several hundred thousand residents of Sonoma, Mendocino, and northern Marin counties. Santa Rosa's Laguna Wastewater Treatment Plant treats sewage from several communities to tertiary standards and returns some of it to the river by way of the Laguna de Santa Rosa. Water transferred from the Eel River and released from Lake Mendocino flows through the Russian River channel to withdrawal points in Sonoma County. Although this method of transport supports aquatic and riparian zone habitats, it is vulnerable to chemical contamination from transportation accidents where the river is in close proximity to highway 101 and Northwestern Pacific Railroad transportation corridors in locations like the canyon between Cloverdale and Hopland. This vulnerability was demonstrated in March 1982 when a tank car of formaldehyde was vandalized in Ukiah. Emergency response personnel were able to clean up approximately half of the spilled, and a fortuitous combination of Lake Mendocino reservoir inventory and late winter storms helped flush the remainder through the river and into the ocean before local water storage inventories were exhausted. The Russian River reached flood stage of at Guerneville about five times per decade through the last half of the 20th century. Historic flood peaks were in February 1986, in January 1995, in December 1955, in December 1964, and in February 1940. Through effective use of Lake Mendocino and Lake Sonoma flood capacity the river has exceeded flood stage at Guerneville less frequently in the 21st century, but in late February 2019 it flooded to levels comparable to 1986. Ecology The river provides wildlife habitat including warm and cold freshwater habitat for fish migration and spawning. Historically it is interesting as one of two Northern California coastal rivers mentioned in the early nineteenth century by Russian explorer K. T. Khlebnikov as hosting sturgeon, presumably White sturgeon (Acipenser transmontanus), along with the Pajaro River. Khlebnikov stated in his "1820 Travel Notes", "Mr. Kuskov had sent two baidarkas to the Slavianka River to catch sturgeon, and they returned today with ten fish...the largest one exceeding two arshins (4.67