Positive signs regarding water flow are opening up opportunities to improve water resources for the Mekong Delta  , but they also come with many challenges, especially the risk of flooding due to high tides.

According to forecasts from the National Center for Hydro-Meteorological Forecasting and the International Mekong River Commission, total rainfall across the basin in May 2026 will range from 15% lower to 10% higher than the multi-year average. Currently, reservoirs on the Lancang River are storing approximately 50% of their usable capacity, while those downstream are at 20-35%. This creates favorable conditions for hydropower reservoirs to begin accumulating water when the first heavy rains of the season arrive.

Water flow from upstream into the Mekong Delta has begun to increase after a long period of decline during the dry season. Photo: NNMT.

The total flow through the Krache station is projected to reach 11.5 to 13.5 billion cubic meters, 11% to 25% higher than the multi-year average. However, water levels in Tonle Sap Lake remain low and do not contribute significantly to the main flow unless heavy rainfall occurs in the area.

In the upstream area of ​​the Mekong Delta, the flow through the Tan Chau and Chau Doc stations is forecast to increase significantly compared to April 2026. Specifically, at the Tan Chau station, the highest daily water level will fluctuate from 0.9 to 1.5 m, with an average daily flow rate of 3,500 to 7,000 m³/s. The total flow volume for the month is estimated to reach 11.4 to 12.8 billion m³, equivalent to or higher than the multi-year average by about 13%, and an increase of 10-25% compared to the previous month.

Meanwhile, at the Chau Doc station, the highest daily water level fluctuates from 1.1 to 1.6 m, with an average daily flow rate of 400 to 1,000 m³/s. The total flow volume here is generally close to the multi-year average, fluctuating from 6% lower to 15% higher. These figures indicate a gradually improving water resource trend, clearly reflecting the transition from the dry season to the rainy season throughout the basin.

Along with the increase in water flow, saltwater intrusion in May 2026 is expected to gradually decrease. However, the salinity boundary still penetrates quite deeply into the inland areas. On the Tien and Hau rivers, the 1g/l salinity boundary can penetrate from about 39 to nearly 50 km, while on the Vam Co Tay river it can reach 60-68 km. With a salinity threshold of 4g/l, the intrusion range is commonly from 31 to over 60 km, depending on the area. Although the salinity level has decreased compared to before, it still poses risks to agricultural production and domestic water supply if appropriate management measures are not implemented.

Notably, while water resources are showing signs of improvement, high tides in May 2026 are forecast to remain quite high. This increases the risk of localized flooding in low-lying areas, especially in the coastal regions of the Mekong Delta. The combination of high tides and low-lying terrain could directly impact production, infrastructure, and people's lives.

In this context, experts believe this is a "golden opportunity" for localities to proactively stockpile and efficiently utilize freshwater resources. At the same time, it is necessary to closely monitor water levels, saltwater intrusion, and tides to promptly adjust production plans and operate irrigation systems appropriately.

Besides taking advantage of opportunities to improve water resources, localities also need to proactively develop plans for flood prevention and control, especially in high-risk areas. A flexible combination of freshwater storage, salinity control, and tidal surge response will be key to helping the Mekong Delta minimize risks and ensure stable production and livelihoods during this volatile transitional season.