Columbia Basin Project were built at the north and south ends of Grand Coulee, the dry canyon south of Grand Coulee Dam, allowing the coulee to be filled with water pumped up from the Columbia River. The resulting reservoir, called Banks Lake, is about long. Banks Lake serves as the CBP's initial storage reservoir. Additional canals, siphons, and reservoirs were built south of Bank Lake, reaching over . Water is lifted from Lake Roosevelt to feed the massive network. The total amount of the Columbia flow that is diverted into the CBP at Grand Coulee varies a little from year to year, and
Grand Coulee of Lower Grand Coulee. The Great Cataract forms the divide from the upper to lower coulees. The Lower Coulee tends along the monoclinal flexure to Soap Lake where the canyons end and the water flowed out into Quincy Basin. Quincy Basin is filled with the eroded gravels and silts from the Coulee. The Lower Coulee, also created its own path across the plains. Evidence of this is found in the tilted flows visible at Hogback islands in Lake Lenore and tilted flows along Washington 17 from Dry Falls to Park Lake. Numerous canyons acted as a distribution system for the