Saltwater intrusion in the Mekong Delta intensifies as the 2025-2026 dry season begins

Saltwater intrusion in Vietnam’s Mekong Delta—an agricultural hub producing a large share of the country’s crops—is entering the peak of the 2025–2026 dry season with signs of rising salinity. Forecasts suggest the situation will not be as severe as in extreme years, but conditions on the ground indicate salinity is arriving earlier, moving farther inland, and persisting longer, creating major challenges for water security and the livelihoods of millions.

How far salinity is expected to push inland

Salinity intrusion varies not only by timing but also with tidal cycles. In late March, high tides coincided with the outlook for April 2026. At many river mouths, the 4‰ salinity front could extend 40–55 km inland, and in some locations reach 60–70 km, reducing the availability of fresh water for both production and domestic use.

Water supply risks for households and irrigation systems

Even if the dry season is not a historic drought year, the risk of freshwater shortages remains. In many coastal localities—especially downstream—shortages of groundwater or surface water can occur when salinity rises and stays elevated for extended periods.

Large irrigation networks are also exposed. Systems including the Go Cong network in Tiền Giang province (now adjacent to Đồng Tháp), Nam Mang Thít, and Long Phú – Tiếp Nhật (Vĩnh Long) face risks of unstable water supply during peak salinity.

Impacts on agriculture and local production

Saltwater intrusion affects daily life and directly harms agricultural production, a cornerstone of the region’s economy. As salinity moves into inland fields, irrigation for rice, fruit trees, and aquaculture becomes more difficult. Local authorities may need to adjust cropping calendars, shift crop structures, or suspend production in some areas to limit losses.

Key drivers: reduced upstream flow and climate pressures

One major cause of the worsening intrusion is reduced flow from the upper Mekong River. During the dry season, less water reaches the delta, weakening the delta’s ability to push back saltwater and allowing seawater to move further inland. Because the delta relies heavily on upstream water, fluctuations upstream can quickly affect the entire region.

Climate change is also increasing the frequency and intensity of extreme events such as prolonged heat, lower rainfall, and rising sea levels. These factors make salinity intrusion more frequent and harder to forecast. In particular, the combination of high tides and reduced river flow at the same time can cause salinity to spike beyond normal expectations.

Human factors: groundwater extraction and land subsidence

Beyond natural drivers, human activities contribute to the risk. Over-extraction of groundwater over many years has led to land subsidence in several areas, increasing vulnerability to saltwater intrusion.

Recommended responses

Experts recommend gradually reducing groundwater extraction, shifting toward surface water, and developing centralized water-supply systems to strengthen long-term water security.

Government and local measures

In response to the growing threat, the government and local authorities have implemented a range of measures. Salinity-control and freshwater-preservation projects continue to operate flexibly to protect production and ensure drinking water for residents. Forecasting and alert systems have also been strengthened so that people and authorities can adjust production plans.

Adaptation approaches beyond infrastructure

Alongside structural measures, many localities are promoting non-structural approaches, including adjusting production structures to suit saline and brackish conditions, encouraging water conservation, and storing freshwater during the rainy season. Early results from models such as brackish-water aquaculture and cultivation of salt-tolerant crops are cited as helping reduce losses from salinity intrusion.

Long-term outlook: “living with salinity”

Over the long term, experts suggest the Mekong Delta should shift its development approach toward “living with salinity.” Rather than focusing only on anti-salt measures, salinity should be treated as a natural factor to adapt to and, where possible, to exploit. Strengthening international cooperation in Mekong River management is also described as crucial for sustainable development.

Saltwater intrusion in the delta is no longer a rare event but an ongoing challenge amid climate change. Without coordinated, long-term solutions, risks of freshwater shortages, reduced production, and impacts on tens of millions of livelihoods are expected to become more pronounced. With proactive adaptation, the delta can still pursue a sustainable path as natural conditions change rapidly.