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
Laser light show (Grand Coulee Dam) in 2014. It will replace the current laser show "Water and Life" which has been running for the past 24 seasons. The new show is being prepared by LumaLaser of Eugene, Oregon. Laser light show (Grand Coulee Dam) "The laser light show" at Grand Coulee Dam, which began in 1989, is one of the largest light shows in the U.S.. The 37 minute show runs daily from Memorial Day through September 30. An addition of fireworks lights up the sky above the dam each Memorial Weekend Sunday and July 4. The Grand Coulee Dam premiered its first non-laser light show