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
Grand Coulee Dam interest in irrigation projects. The Bureau of Reclamation, desirous of a major project that would bolster its reputation, was focusing on the Boulder Canyon Project that resulted in the Hoover Dam. Reclamation was authorized to conduct a study in 1923, but the project's cost made federal officials reluctant. The Washington state proposals received little support from those further east, who feared the irrigation would result in more crops, depressing prices. With President Coolidge opposed to the project, bills to appropriate money for surveys of the Grand Coulee site failed. In 1925, Congress authorized a U.S. Army Corps of Engineers study