The surface area of Lake Tonle Sap varies greatly by season. Data sources report surface areas of from 2,569.9 km2 to 30,000 km2. Furthermore, as the main Mekong flood level heightens each year during the southwest monsoon every June or July, the direction of flow of the Tonle Sap River reverses, creating the exceptional water regime with huge changes in the lake water level (from about 1m up to 10 meters) and water volume (from about 2,500 km2 to approximate 11,000 km2) between seasons
