Tonlé Sap
Inflow starts in May or June with maximum rates of flow of around by late-August and ends in October or November, amplified by precipitation of the annual monsoon. In November the lake reaches its maximum size. The annual monsoon coincides to cease around this time of the year. As the Mekong River is at its minimum flow around this time of the year and its water level falls deeper than the Tonlé Sap Lake, the Tonlé Sap River and surrounding wetlands, waters of the lake's basin drains via the Tonlé Sap River into the Mekong. As a result, the Tonlé Sap River flows six months a year from southeast (Mekong) to northwest (lake) and six months a year in the opposite direction. The mean annual reverse flow volume in the Tonlé Sap is , or about half of the maximum lake volume. A further 10 percent is estimated to enter the system by overland flow from the Mekong. The Mekong branches off into several arms near Phnom Penh and reaches Vietnamese territory south of Koh Thom and Loek Daek Districts of Kandal Province.