Glacial Lake Columbia was the lake formed on the ice-dammed Columbia River behind the of the Cordilleran Ice Sheet when the lobe covered 500 square miles (1,300 km2) of the west of Grand Coulee in central Washington state during the Wisconsin glaciation. Lake Columbia was a substantially larger version of the modern-day lake behind the Grand Coulee Dam. Lake Columbia's overflow – the diverted Columbia River – drained first through Foster Coulee, and as the ice dam grew, through first Moses Coulee, and finally, the Grand Coulee.