Mekong Delta faces intensifying saltwater intrusion amid declining dry season flow

Hydrological forecasts from the National Centre for Hydro-Meteorological Forecasting and the Mekong River Commission suggest that total rainfall across the Mekong Basin in March will remain close to the long-term average, with variations of 5-20 per cent across different sub-basins.

The Mekong Delta is bracing for heightened saltwater intrusion, as dry season water flows continue to decrease, according to the latest report from the Việt Nam Mekong River Commission.

The phenomenon threatens agricultural production and freshwater supplies in one of the country’s most important rice-producing regions.

Authorities have urged localities to optimise saltwater prevention measures and proactively store freshwater to mitigate the impact on farming and daily life.

Hydrological forecasts from the National Centre for Hydro-Meteorological Forecasting and the Mekong River Commission suggest that total rainfall across the Mekong Basin in March will remain close to the long-term average, with variations of 5-20 per cent across different sub-basins.

While upstream areas are expected to receive rainfall at levels similar to previous years, the Mekong Delta and northeast Thailand may experience a slight increase.

Reservoirs along the Lancang River are currently at approximately 75 per cent of their total capacity, while those in the lower Mekong Basin are at about 60 per cent.

Hydroelectric generation is expected to continue, further influencing downstream water levels.

At Kratie Station in Cambodia, flow is estimated to decline, with total discharge in March estimated at 6.4-8.2 billion cubic metres. Meanwhile, the Tonle Sap Lake, which plays a critical role in regulating water levels, currently holds about 2.2 billion cubic metres, limiting its contribution to the main Mekong River.

According to the Việt Nam Mekong River Commission, water levels in key monitoring stations will fluctuate but remain below average.

At Tân Châu Station in Tây Ninh Province, peak daily water levels in March are expected to range from 1.1 to 1.6m. The average daily discharge is estimated between 3,000 and 4,500cu.m per second, which is comparable to historical averages, but five per cent lower than in 2024.

At Châu Đốc Station in An Giang Province, water levels are forecasted to range from 1.2 to 1.6m. The average daily discharge is expected to be between 250 and 480cu.m per second, representing a 24 per cent drop from historical averages and a six per cent decline from last year.

Flow levels at Châu Đốc in March are projected to fall between 1.0 and 1.1 billion cubic metres, down by 18-29 per cent from historical norms and 0-11 per cent lower than the same period in 2024.

Based on flow and tidal projections, the one gramme per litre salinity boundary is expected to push 3-13 kilometres further inland along the Hậu, Tiền, and Vàm Cỏ Tây rivers, compared to the averages in the past. The four grammes per litre salinity boundary, a critical for agriculture, is also forecasted to extend 3-10km deeper inland.

Local areas are being urged to closely monitor water sources, store freshwater and implement proactive measures to counteract the worsening saltwater intrusion. Areas at high risk should stay updated on salinity monitoring and forecasts to adjust their mitigation strategies accordingly.

According to the Head of the Central, Central Highlands, and Southern Hydrological Forecasting Division at the Ministry of Agriculture and Environment, Phùng Tiến Dũng, the 2024-2025 dry season is expected to see above-average saltwater intrusion, although not to the extreme levels experienced in 2015-16 and 2019-20.

Saltwater intrusion is shaped by upstream flows, tidal patterns and shifting environmental factors. Peak intrusion at the Mekong River’s estuaries, Vàm Cỏ and Cái Lớn rivers is anticipated this month and across April.

Several districts are particularly vulnerable to saltwater intrusion, including Long An, Tiền Giang, Bến Tre, Trà Vinh, Sóc Trăng, Bạc Liêu, Kiên Giang and Hậu Giang provinces.