Feather River - River Modifications

River Modifications

Since 1967, the headwaters of the Feather River at the confluence of its four forks have been submerged under the waters of Lake Oroville, created by the construction of Oroville Dam in 1967. At about 770 feet (230 m) high, it is the tallest dam in the United States and wields nearly complete control over the flow of the Feather River by creating one of the largest reservoirs in California. The dam was built with the purpose of preventing the frequent floods that often inundated this part of the Sacramento Valley, and to store water for agricultural uses downstream during the dry season.

The Feather's main tributaries, the Yuba and the Bear, are also impounded by large dams serving similar purposes. 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.

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 river for this purpose, the water of downstream canals do not, except in the form of irrigation return flows. 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 to a fraction of its original size.

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 5,834 cubic feet per second (165.2 m3/s). From 1969 to 2009 the average flow is 1,086 cubic feet per second (30.8 m3/s). The maximum discharge at this stream gauge was 230,000 cubic feet per second (6,500 m3/s), recorded on March 19, 1907. The minimum was 222 cubic feet per second (6.3 m3/s), recorded on September 19, 1972.