Canada holds vast reserves of water: its rivers discharge nearly 9% of the world’s renewable water supply, it contains a quarter of the world’s wetlands, and it has the third largest amount of glaciers (after Antarctica and Greenland). Because of extensive glaciation, Canada hosts more than two million lakes: of those that are entirely within Canada, more than 31,000 are between 3 and 100 square kilometers (1.2 and 38.6 sq. mi) in area, while 563 are larger than 100 km2 (38.6 sq. mi).
Canada’s two longest rivers are the Mackenzie, which empties into the Arctic Ocean and drains a large part of northwestern Canada, and the St. Lawrence, which drains the Great Lakes and empties into the Gulf of St. Lawrence. The Mackenzie is over 4,200 km (2,600 mi) in length while the St. Lawrence is over 3,000 km (1,900 mi) in length. Rounding out the ten longest rivers within Canada are the Nelson, Churchill, Peace, Fraser, North Saskatchewan, Ottawa, Athabasca and Yukon rivers.