Moses Coulee the southern portion of the plateau. These streams had combined into a canyon that drained to the Columbia near the current mouth of Moses Coulee. These side drainages are still visible today along the coulee walls as truncated streambeds, interspersed with gable-like highlands. The Okanogan lobe of the Cordilleran Glacier moved down the Okanogan River valley, covering 500 mi² of the Waterville Plateau and blocked the ancient route of the Columbia River, backing up water to create Glacial Lake Columbia and Lake Spokane. Initially water discharged from Lake Columbia by running up through the head of Grand Coulee and down
Grand Coulee, Washington 100 females age 18 and over, there were 80.5 males. The median income for a household in the city was $21,818, and the median income for a family was $29,375. Males had a median income of $25,625 versus $18,125 for females. The per capita income for the city was $13,639. About 11.7% of families and 19.3% of the population were below the poverty line, including 25.3% of those under age 18 and 17.6% of those age 65 or over. Grand Coulee, Washington Grand Coulee is a city in Grant County, Washington, United States. The population was 988 at the 2010