The Mekong River Commission (MRC) said Tuesday that the annual reversal in the flow of the Tonle Sap River remained delayed, causing “very low” water levels on the Tonle Sap Lake.
In a weekly situation report, the MRC said low inflows from the Mekong and low rainfall in the Tonle Sap’s upper-catchment areas had “resulted in a very critical situation” for the lake.
“More than half of the annual inflow to the lake originates from the Mekong mainstream. Thus, flow alterations in the mainstream would have direct impacts on the Tonle Sap water levels and hydrology,” it said.
The report — by the MRC Flood and Drought Management Centre in Phnom Penh — said Mekong water levels in Stung Treng, Kratie, Kampong Cham and Neak Luong had risen from the previous week.
But they were “still below their minimum levels” recorded between 1960 and 2019, it said.
Water levels on the Bassac River at Chaktomuk and Koh Khel as well as the Tonle Sap River at Phnom Penh Port and Prekdam had also risen. But they too were below minimum levels seen over the past 60 years.
The MRC reiterated that low waters in the Tonle Sap Lake could affect fish spawning in the surrounding floodplain and lead to water shortages for agricultural production.
The report noted that a prolonged El Nino — usually causing extreme heat and insufficient rain in the region — was “a cause of low water levels in the Mekong mainstream” in June and July this year.
But it added that “the contribution from major tributary dams” was “another potential important reason” for low flows in the Mekong between January and July.
“However, we do not have any official data to quantify their amount,” the report said.
Over the next five days, Mekong water levels are forecast to rise by between 6 and 45 cm from Stung Treng to Neak Loung.
Tonle Sap water levels are forecast to rise by 5 to 35cm and Bassac water levels by 30 cm over the same period. Sao Da – AKP