Grand Coulee on through and beyond Quincy Basin. The Ephrata Fan is a gravel fan formed when floodwaters from the lower Grand Coulee entered the Quincy Basin during the formation of the Scablands. The area surrounding the Grand Coulee is shrub-steppe habitat, with an average annual rainfall of less than . The Lower Grand Coulee contains Park, Blue, Alkali, Lenore, and Soap lakes. Until recently, the Upper Coulee was dry. The Columbia Basin Project changed this in 1952, using the ancient river bed as an irrigation distribution network. The Upper Grand Coulee was dammed and turned into Banks Lake. The lake is
Coulee Dam, Washington Coulee Dam, Washington Coulee Dam is a town in Douglas, Grant, and Okanogan counties in the State of Washington. The Douglas County portion of Coulee Dam is part of the Wenatchee–East Wenatchee Metropolitan Statistical Area. The population was 1,098 as of the 2010 census. Coulee Dam was founded by the U.S. Bureau of Reclamation in 1933, to serve as headquarters for the construction of the Grand Coulee Dam. The Okanogan County portion was known as Mason City, location of the head contractor. The Portions in Douglas and Grant Counties was known as Engineers Town and was government owned. In 1942