Cambodia’s life-giving Tonle Sap lake in peril

Tonle Sap was once renowned for its abundance of fish and wildlife -- 43-year-old Leng Vann recalls catching hundreds of kilos a day in his nets.

Koh Chivang: As night falls over his floating village, fisherman Leng Vann puffs on a cigarette and heaves a sigh for Tonle Sap, the great inland lake that has sustained Cambodia for centuries.

More than a million people live on or around the lake, the world’s largest inland fishery, but water levels have plummeted and fish stocks dwindled because of climate change and dams upstream on the Mekong.

Tonle Sap was once renowned for its abundance of fish and wildlife — 43-year-old Leng Vann recalls catching hundreds of kilos a day in his nets.

“We fishermen survive by water and fish. When there is no water and fish, what else can we hope for?” said Leng Vann.

The lake, a world heritage ecological reserve, depends on an unusual seasonal reversal — in the dry season, it drains into the Mekong via a fast-flowing river artery.

But when the rains come from May to October, the mighty Mekong is so powerful that the water flows backwards, replenishing the lake.

But lately the reverse flows have been seriously delayed. Last year the amount of water that flowed into the lake was down around a quarter from the average levels seen around the turn of the century.

The reverse flow effect has been at its lowest since 1997, leading to “extremely dry conditions”, the MRC says.The change in water levels is having a major effect on surrounding wetlands, precipitating a decline in endangered species living around the lake.

Nearly one-third of the Tonle Sap’s natural habitats vanished in the 25 years to 2018 and half of the lake floodplain was now under rice cultivation, according to a recent study by the Wildlife Conservation Society.