for agricultural uses downstream during the dry season. The dam is the principal feature for the California State Water Project, storing water for more than 23 million people and of farmland in Central and Southern California Directly downstream from Oroville Dam lies the Oroville-Thermalito Complex, which consists of two reservoirs, a Forebay and Afterbay, both used for hydroelectricity generation. Although the water diverted from the Feather for this purpose is returned to the river, the water of downstream canals do not, except in the form of irrigation return flows (agricultural waste water). Downstream of Oroville, the river's flow is sucked away by numerous irrigation canals that supply water to the agricultural businesses of the lower Feather River valley. The heavy usage of water from the river has reduced its flow significantly. The Feather's main tributaries, the Yuba and the Bear, are also impounded by large dams that provide irrigation water and flood control. New Bullards Bar Dam and Englebright Dam are located on the Yuba, and Rollins Dam and Camp Far West are situated on the Bear. Smaller dams now also block other tributaries, including the Middle, South and North Forks of the Feather. The watershed's high mountain streams are often utilized in complex schemes for hydroelectricity generation, including the Pacific Gas and Electric Canyon Power Project on the North Fork, which uses water from Lake Almanor, and the Yuba Hydroelectric Project which taps the Middle and South Forks of the Yuba River. Water diversions, especially from Lake Oroville, has reduced the streamflow of the Feather River. The USGS has operated a stream gage downriver of Oroville Dam since 1902. The river's average annual discharge between 1902 and 1967, before the dam was built, was . From 1969 to 2009 the average flow is , mainly due to diversion for power generation at the Thermalito pumped-storage plant. Most of this water is returned to the river further downstream via a tailrace canal. The maximum discharge at this stream gauge was , recorded on March 19, 1907. The minimum was , recorded on September 19, 1972. Ecology The riparian area of the Feather River supports a rich biodiversity of native flora and fauna. The Sierra Nevada reaches have considerable wild river features and steep gradients. In lower reaches, after joining of the forks, there is also significant habitat; near Yuba City, for example, there are extents of the river with numerous