Saline intrusion in Mekong Delta leaves farmers and scientists at odds

Vinh Long, VIETNAM — Khanh Chi tends a small apricot blossom orchard in Nhuan Phu Tan, a commune in southern Vietnam’s Vinh Long province by the Co Chien River, one of the Mekong River’s final distributaries before reaching the ocean. Her orchard is 55 kilometers (34 miles) inland.

According to the provincial hydrometeorological observatory, Chi’s commune is the furthest point along the Co Chien River where, this year, salinity levels hit 4 parts per thousand (ppt) — the threshold at which rice farming is damaged.

As saltwater pushes deeper and less predictably into the delta in recent decades, Vietnam has responded with canals, dikes and sluice gates to keep it out. For farmers, such projects offer the most explicit and immediate relief.

Scientists say that might be a problem. Instead of engineering its way out of the salinity crisis, scientists argue, the region must adapt to it.

“I buy freshwater, bring it back by truck, and just spray it like a mist,” Chi says, describing how she waters the apricot during dry season, when the river is saline. She used to grow fruit seedlings, durian and jackfruit but made the switch to ornamental plants as they are more resilient to saltwater.

A few years ago, Chi dug a small pond in her orchard to store water when it rains or the river runs fresh. She uses it sparingly, enough to stretch through a few worst days of an intrusion.

“The bigger the orchard, the larger the lake,” she says. “My orchard is small, so I don’t need much.”

Chi and her neighbors have a group chat on Zalo, Vietnam’s native messaging app. Every morning, including weekends, a local official posts salinity data aggregated by the province’s hydrometeorological observatory. Many farmers, including Chi, still double-check with their own salinity-measuring pens.

Last year, the people of Nhuan Phu Tan celebrated the inauguration of a new sluice gate. Stretching 30 meters (98 feet) wide, Cai Hang gate is a $5.7-million investment designed to guarantee freshwater for 5,200 hectares (12,850 acres) of orchards and farmland through drought and peak saline season.

“This is the first dry season with the gate,” a farmer inside the gate tells Mongabay. “Things are so much better.”

Scientists, however, warn against that immediate reassurance.

“Sluice gates are like a pill that gives immediate calm,” says Nguyen Thanh Phong, a scientist at the IUCN Vietnam. “But they are not a long-term remedy.”

The most alarming threat

Salinity intrusion is not new in the Mekong Delta. And for much of the delta’s history, it was not feared.

“If you go back 200 years, no one in the Mekong was afraid of saltwater,” says Duong Van Ni, a scientist at Can Tho University, Vietnam, who has spent more than three decades studying climate adaptation in the delta. Early settlers understood the river’s shifting salinity and adjusted what they fished and planted with the seasons.

That relationship has since shattered. Saltwater is now widely agreed to be the delta’s most alarming environmental threat, with effects that reach beyond crop damage.

A 2024 World Bank survey found that households exposed to severe saline intrusion earn 17% less per capita than those in unaffected areas. Unlike floods or heatwaves, salinity leaves lasting damages by degrading soil quality and reducing freshwater availability for years.

The cohesive system of natural forces that once protected the delta is gradually being dismantled. Upstream dams in China and Laos trap sediment and dampen freshwater flow needed to push saltwater out during the dry months. Sand mining cuts deeper channels that bring saline water further inland while groundwater extraction causes the delta to sink. Researchers estimate these human pressures alone could expand salinity-affected areas by 10-27% by 2050, with sea level rise adding another 5-19%.

El Niño worsens the effects. In 2016, saltwater pushed more than 90 km (56 mi) inland, destroying nearly 240,000 hectares (593,000 acres) of rice crops and causing an estimated $450 million in losses. Another severe intrusion followed in 2020. The aftermath of the two events, the World Bank report found, reversed years of poverty reduction across the delta.

Nonetheless, as the salinity intrusion intensifies, scientists and development partners are shifting the solution narrative. The delta, they say, cannot rely on infrastructure alone; it must learn to live with saltwater.

On the ground, people fight their own fights

This year’s dry season was forecast to be far less severe than 2016 or 2020.

But in Vinh Long province, where Mongabay visited, authorities still approach the dry season with caution. Since late 2025, the province has devised different response scenarios. In all cases, sluice gates are the primary weapons to fight saline water.

The province also had plans to dispatch barges carrying 40,000 cubic meters (1.4 million cubic feet) of freshwater from upstream to water treatment plants in saline water areas, in case their reservoirs ran dry.

On the ground, however, people don’t rely on the government.

In Huong My commune, about 25 km (15 mi) from the estuary, few households are connected to the utility water network.

Ba Hung, a resident in his 60s, shows his water tanks — standard household necessities here — and a small packet of water treatment agent he bought for 20,000 dong, less than a dollar.

“We store enough rainwater during the rainy season and use it for months,” he says. Underground water in this area is saline, while connecting to the utility network costs money that many deem unnecessary.

Hung, who has lived with saltwater his entire life, navigates it entirely on personal knowledge and experience. Yet, saltwater has become more unpredictable.

“Back then, saltwater drained out in February or March. Now, you just can’t tell,” Hung says.

The government’s infrastructure response

“For a long time, Vietnam employed an irrigation-first approach,” says Duong Van Ni, the scientist at Can Tho University. What that translated to, he says, was that infrastructure was built first to control the water, and agriculture was subsequently forced to adapt to it, regardless of what the land was actually suited for.

The numbers are considerable. By 2014, the Mekong Delta had over 90,000 km (almost 56,000 mi) of canals of all sizes, along with 13,000 km (8,078 mi) of embankments and dikes. The delta now has more than 1,143 sluice gates wider than 4 m (13 ft), with more being built every year.

At Vung Liem sluice gate, one of the most modern in the region and part of the larger Nam Mang Thit system, completed in 2020, Mongabay spoke with two workers and received different accounts of the gate’s operation.

A lower-level operator simply describes the mechanism as keeping salinity on the inside below 0.5 ppt, closing before that threshold is crossed.

The station manager, Hoang Hiep, presents a more formal procedure, coded in a written operational procedure governing the entire Nam Mang Thit system, and a monthly operational plan specifically for Vung Liem gate.

When the salinity level falls below 1 ppt, the gate opens. Above that, it closes to retain freshwater, reopening briefly at low tide to let river traffic through and drain trapped wastewater. In practice, during high salinity intrusion, workers constantly check readings of the saline level along the river every hour, sometimes every 10 minutes, closing the gate preemptively when tidal patterns suggest a surge in salinity.

Both, however, have limited information about how other gates along the Co Chien River work.

This, according to Le Anh Tuan, a senior lecturer at Can Tho University’s College of Environment and Natural Resources, is part of the problem.

‘Sluice gates are not the answer’

“Imagine plugging a leaky water pipe,” Tuan says. “When you plug these holes, the water at the nozzle shoots much deeper. When you close the gates here, the salt is just pushed into other areas.”

Without coordination across the full network, each gate’s gain becomes its neighbor’s problem.

Then there are the quieter ecological costs. “A river has three zones: saline, brackish, and fresh,” Tuan says. “When you install these gates, you completely eradicate the brackish water ecosystem.” Nurseries for many species of marine life, and an important transition zone between land and sea, brackish zones are dynamic and highly productive ecosystems.

Researchers and international partners have been advocating for less concrete-reliant approaches.

In 2013, a Dutch-led consortium drafted the Mekong Delta Plan (MDP), a 100-year vision for the region built around a core idea: Instead of fighting the water, find ways to live with it. After years of institutional stall, by 2017, the Vietnamese government formally embraced the MDP’s principle in the country’s Resolution 120.

The resolution conceded that saline water was a condition that the delta should plan around, not fight against. In practice, it meant diversifying away from rice monoculture where needed, recognizing brackish- and salt-water as productive resources, and promoting natural hydrology. Importantly, it delegated specific tasks for different ministries, bridging MDP and reality.

International development partners rallied behind the resolution. In 2022, Vietnam adopted the Mekong Delta Integrated Regional Plan (MDIRP), developed by Royal HaskoningDHV and GIZ. If Resolution 120 was a formal basis for change, the integrated regional plan is a comprehensive, unified strategy involving different provinces to get there, says Phong of IUCN.

Four years after the plan was ratified, little has been done.

A region waiting for change

In 2025, Vietnam carried out a large-scale administrative reform, consolidating ministries and merging the delta’s 13 provinces into five. The national restructuring made the regional plan a second thought.

In early April 2026, a revised version of the integrated regional plan, adapted to the five consolidated provinces, was approved.

The restart is expected to come with obstacles. Phong says one of the biggest is human capacity. The provincial officials who had supported integrated planning were reassigned or dispersed during the reform, taking much of that expertise with them.

Funding and bureaucracy pose another concern. “Think of the regional plan as a development orientation,” Le Anh Tuan says. Each of the delta’s former 13 provinces then had to develop its own plan before being integrated into a broader regional framework. The process required time, coordination and funding, previously approved by the now-dissolved Ministry of Planning and Investment (MPI). Those plans now need to be reconfigured to fit the new administrative reality.

Implementation, Phong says, will likely require renewed support from development partners as well. “Vietnam just has to reach out, and partners would most likely help,” he adds.

In the meantime, international partners say their role remains advisory.

“The Mekong Delta is not the Netherlands,” says Raïssa Marteaux, Consul General of the Netherlands in Ho Chi Minh City. “Introducing Dutch knowledge and technology is not a one-way transfer, but a process of mutual learning.”

Marteaux also refrains from framing the issue as a simple rejection of infrastructure. “In practice, a mix of solutions is needed,” she says.

Scientists know change will not come easily. For now, hard infrastructure, appreciated by farmers for its immediate effect and supported by political incentives, will likely continue to be built.

A nature-based solution to save the Mekong Delta’s water future (commentary)

Banner image: Most of Chi’s annual income comes from selling apricot blossoms — a symbol of luck and prosperity in Vietnam — around Lunar New Year. Image by Minh Tran for Mongabay.

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