The Everglades are part of a very large watershed that begins in the vicinity of Orlando. The Kissimmee River drains into Lake Okeechobee, a 730-square-mile (1,900 km2) lake with an average depth of 9 feet (2.7 m). During the wet season when the lake exceeds its capacity, the water leaves the lake in a very wide and shallow river, approximately 100 miles (160 km) long and 60 miles (97 km) wide.[4] This wide and shallow flow is known as sheetflow. The land gradually slopes toward Florida Bay, the historical destination of most of the water leaving the Everglades. Before drainage attempts, the Everglades comprised 4,000 square miles (10,000 km2), taking up a third of the Florida peninsula.[5]