Moses Coulee through Foster Coulee to rejoin the Columbia River. As the glacier moved further south, Foster Coulee was cut off and the Columbia River then discharged through Moses Coulee, which runs southward slightly to the east of the ancient and current course of the Columbia. As the Okanogan lobe grew, it blocked Moses Coulee as well; the Columbia found the next lowest route through the region which was eroded to become the modern Grand Coulee. Flowing across the current Grand Coulee and Dry Falls regions, the ice age Columbia then entered the Quincy Basin and joined Crab Creek, following Crab Creek’s
Grand Coulee, Washington Grand Coulee, Washington Grand Coulee is a city in Grant County, Washington, United States. The population was 988 at the 2010 census. Grand Coulee was officially incorporated on November 6, 1935. It is located above the Grand Coulee Dam and next to North Dam. Grand Coulee is located at (47.939706, -119.001597). According to the United States Census Bureau, the city has a total area of , of which, is land and is water. As of the census of 2010, there were 988 people, 474 households, and 246 families residing in the city. The population density was . There were 554