Glacial Lake Columbia was a prehistoric lake in central Washington, created during the Wisconsin glaciation when the Okanogan lobe of the Cordilleran Ice Sheet blocked the Columbia River across the Waterville Plateau west of Grand Coulee. As the ice dam shifted, the river overflowed successively through Foster Coulee, Moses Coulee, and Grand Coulee. This lake was part of a broader glacial system that included Glacial Lake Missoula in Montana. When Missoula’s ice dam failed, immense floods crossed eastern Washington, carving landforms such as Grand Coulee, Dry Falls, Palouse Falls, and the Channeled Scablands. Sediments from the former lake preserve evidence that these major floods often recurred about every 35 to 55 years.