Lake Roosevelt National Recreation Area
Lake Roosevelt stretches about 150 miles from Grand Coulee Dam upstream to the Canadian border, making it among the largest lakes in Washington State with over over 630 miles of shoreline, making it ideal for motor boating, water skiing, canoeing, kayaking, wind surfing sailing, swimming and fishing. Lake Roosevelt is the result the flooding of the Columbia River and the creation of the reservoir behind Grand Coulee Dam once it was built so historically, its creation also had a major impact on the region in that it resulted in several communities relocating to their current locations as the waters rose.
The lake level may vary 60 to 80 feet throughout the year and tends to peak in early- to mid-July, meaning less beach then. The lake drops to its lowest level in May to make room for spring snowmelt from faraway mountains that drain to the Columbia River.
Depending on how full it is, the reservoir reaches upriver about 150 miles. It averages 4,000 feet in width and 375 feet in depth. When full (elevation 1,290 feet above sea level at the dam), Lake Roosevelt impounds 9 million acre-feet (11.1 billion cubic meters) of water. That amount would cover a land mass the size of the state of Washington (71,303 square miles, or 184,674 square kilometers) with 2.3 inches of water. 
Lake Roosevelt National Recreation Area is managed by the National Park Service (http://www.nps.gov/laro/) and is ideal for motor boating, water skiing, canoeing, kayaking, wind surfing sailing, swimming and fishing. Two Walleye fishing tournaments are held annually, the Governor's Cup Walleye Tournament is held in June and in July the Spokane Valley holds its championship.
Lake Roosevelt National Recreation Area Map (click for larger view)