Rain and snow melt runoff from 63 tributaries in the 312 square-mile watershed adds 65% of the water. Another 35% falls as precipitation directly on the Lake. Typically, 212 billion gallons of water enter the Lake this way each year. In a normal year, Lake Tahoe will rise 15 inches from spring runoff, assuming the outlet gates are closed.
Fact credit: TahoeFacts.com