Nespelem River before the river empties into the Columbia River. This reach of the Columbia River is several miles below Grand Coulee Dam and many miles above Chief Joseph Dam. The impounded Columbia River behind Chief Joseph Dam, into which the Nespelem River flows, is called Rufus Woods Lake. Nespelem River The Nespelem River is a northern tributary of the Columbia River, in the U.S. state of Washington. It is completely contained within Okanogan County and the Colville Indian Reservation. The name "Nespelem" is said to come from the Indian word "nesilim", meaning "flat land". The Nespelem River originates in eastern Okanogan
Grand Coulee Dam of electricity. Each generator is supplied with water by an individual penstock. The largest of these feed the Third Powerplant and are in diameter and can supply up to . The dam's power facilities originally had an installed capacity of 1,974 MW but expansions and upgrades have increased generation to 6,809 MW installed, 7,079 MW maximum. Grand Coulee Dam generates 21 TWh of electricity annually. This means the dam generates about 2,397 MW of power on average, which results in a total plant factor efficiency of 35%. In 2014, 20.24 TWh of electricity was generated. Grand Coulee Dam's spillway is