Banks Lake Banks Lake Banks Lake is a long reservoir in central Washington in the United States. Part of the Columbia Basin Project, Banks Lake occupies the northern portion of the Grand Coulee, a formerly dry coulee near the Columbia River, formed by the Missoula Floods during the Pleistocene epoch. Grand Coulee Dam, built by the United States Bureau of Reclamation on the Columbia River created Franklin D. Roosevelt Lake, the reservoir on the river behind the dam. The surface of Lake Roosevelt is several hundred feet above the original Columbia River, making it easier to pump water up and out of
Grand Coulee pumped from the Grand Coulee Dam, into Banks Lake to act as an Equalizing Reservoir and irrigation water source. Evidence of the waterfalls includes a plunge basin where the falls began, immediately south of Coulee City. It contains at least of gravel lower than the open flooring of the land. The river above the falls was shallow and much wider than the gorge. Thus, it wrapped around the lip of the main falls creating lateral falls. These flowed until the recession of the main falls denied them water. Northrup Canyon in Steamboat Rock State Park, contains a dry cataract as