Tonle Sap Lake

Tonle Sap Lake is often referred to as the heart of Cambodia, it’s a giant, almost ocean-like, inland freshwater lake. The Tonle Sap River merges at Phnom Penh with the Mekong River and Tonle Bassac River. The flow of the river changes with the seasons and Cambodia relies on it for crops and fish in the different seasons. Siem Reap is the closest major town for visiting the Tonle Sap Lake.

Weather Cycles and Flow Reversal

Khmer New Year which occurs in April each year, signifies the end of the harvest season. It’s the time for Cambodian families to enjoy their harvest before the rainy season begins, around June. As the rain sets in, the water levels in the Mekong River rise and the flow from Tonle Sap is reversed.

Normally water from the Tonle Sap Lake flows along Tonle Sap River where it ultimately converges with the Mekong and Tonle Bassac River. When rainy season is in full swing, the higher water levels push the water back toward the lake. It’s quite a remarkable natural phenomenon. The lake essentially becomes a giant reservoir, swelling in size by up to 5 times and expanding through the surrounding wetlands. At this point, Tonle Sap transforms into the largest freshwater lake in Southeast Asia.

When the dry season arrives around November, the Tonle Sap Lake is full and everything is flourishing from. Water levels in the Mekong drop and the river flow goes back the other way again. Water Festival or Bom Om Touk (literally “boat festival”) symbolizes the end of the rainy season. Rice farmers have been working hard during the rainy season to cultivate one or two crops of rice and the water festival also indicated that the rice harvest is coming. There are ceremonies for pounding the rice, which is known as Ombok, and it is tradition to eat the pounded rice at this time of the year.