Grand Coulee Dam south, enclosed and created Banks Lake, which covered the northern of the Grand Coulee. Additional dams, such as the Pinto and O'Sullivan Dams, were constructed alongside siphons and canals, creating a vast irrigation supply network called the Columbia Basin Project. Irrigation began between 1951 and 1953 as six of the 12 pumps were installed and Banks Lake was filled. After World War II, the growing demand for electricity sparked interest in constructing another power plant supported by the Grand Coulee Dam. One obstacle to an additional power plant was the great seasonality of the Columbia River's streamflow. Today the flow
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