Very strong El Nino to bring early saltwater intrusion to southern Vietnam from December

El Nino is a climate phenomenon marked by the periodic warming of surface waters in the central and eastern equatorial Pacific Ocean, which can disrupt weather patterns worldwide, affecting rainfall and temperatures in Vietnam.

Ta Thi Hong An, a forecaster at the Climate Forecasting Division of the National Center for Hydro-Meteorological Forecasting, said on Saturday that El Nino had begun to noticeably affect weather conditions in Vietnam.

Temperatures nationwide were generally 1-2 degrees Celsius above the multi-year average in September and the first half of October, with 59 meteorological stations recording daily maximum temperatures that equaled or exceeded historical highs for the same period in the first half of October.

El Nino is forecast to remain very strong until January 2027 before gradually weakening, with its effects potentially continuing into early summer next year, An said.

Rainfall in central Vietnam is expected to remain below the multi-year average through the end of this year, while the rainy seasons in the Central Highlands and southern Vietnam may end early.

As a result, river flows in central and southern Vietnam are expected to fall below average, raising the risk of earlier and more severe saltwater intrusion in the Mekong Delta than in previous years and the same period in 2026.

In a dispatch sent to Mekong Delta localities on October 16, the agriculture and environment ministry said upstream reservoirs in the Mekong River basin had stored more than 52 billion cubic meters of water by mid-October, equivalent to nearly 80 percent of their total designed usable capacity.

However, water availability is expected to decline toward the end of the flood season, with flows into the Mekong Delta during the 2026-27 dry season forecast to be among the years with the lowest water availability.

Saltwater intrusion could begin as early as December 2026, reaching 10-20 km farther inland than the multi-year average at river mouths across the basin, the ministry warned.

The ministry urged Dong Thap, Vinh Long, Tay Ninh, Can Tho, An Giang and Ca Mau to update safe water supply plans for centralized systems, prepare backup supplies for urban and other areas at high risk of shortages, and ensure sufficient freshwater for household use, agriculture and aquaculture.

Local authorities were also asked to develop water regulation plans for the 2026-27 dry season, store freshwater in canals, reservoirs, ponds and enclosed fields, and expedite the completion of inter-regional water transfer systems and water storage projects.

The ministry recommended adjusting crop choices and planting schedules in areas vulnerable to water shortages and saltwater intrusion, including northern Ca Mau, Long Phu-Tiep Nhat and Go Cong, as well as areas served by the Nam Mang Thit irrigation system.

Agricultural production plans for the winter-spring and summer-autumn crops should be reviewed to avoid periods of severe saltwater intrusion and freshwater shortages.

Planting areas without reliable water supplies may need to be reduced, while priority should be given to storing freshwater for concentrated fruit-growing areas and other high-value crops sensitive to saltwater, particularly durian and ornamental plants.