Mekong Delta braces for drought, salt intrusion

Early March, Huynh Huu Loc, 62, comes to check the water level in canals around his family’s durian farm, which stretches 1,000 hectares (2,470 acres) on the islet of Ngu Hiep in the eponymous commune of Cai Lay District, Tien Giang Province.

Under the scorching sun of southern Vietnam’s dry season, the canals of two meter wide each are filled with water of one meter deep, running in between lines of durian, which is often dubbed Vietnam's king of fruit for its special and possibly addictive taste.

"Since the dry season kicked in, I have hired people to dredge the canals and let water in so if any drought or salinity strikes as bad as last year, the farm could still hold up," he said.

Around the root of each tree, Loc lets wild grass grow freely and covers the roots with straw and sacks to retain moisture.

Huynh Huu Loc holds a durian tree on his farm in Tien Giang Province, March 2021. He expects to harvest the crop in April for sale. Photo by VnExpress/Hoang Nam.

Loc is growing 200 durian trees aged from 13 to 15. In previous years, he usually collected 20 tons of durian fruits per crop and earned a profit of around VND40,000 per kilo on average.

That story changed last year all thanks to historic drought and salinity.

During the last dry season, which normally lasts from late November of the previous year to May the next year, the delta, home to 12 provinces and Can Tho City, was hit by the worst drought ever that caused historic levels of salinity in its rivers as water flowed inland from the sea.

The rainy season arrived late in 2019 and was shorter than usual, resulting in 8 percent less rainfall than normal at 1,240 millimeters, according to the Ministry of Agriculture and Rural Development.

A series of upstream dams in China is seen as preventing the natural flow of water, while the sea level rise and gradual subsidence of southern Vietnam are also blamed for salt intrusion in the delta.

By mid-March last year seawater had intruded 50-110 kilometers into major rivers and all branches of the Mekong, two to eight kilometers more than in 2016 when the region had suffered the worst drought in a century.

In all, the lack of freshwater damaged 41,900 hectares of rice and 6,650 hectares of fruit orchards, while 96,000 families struggled to obtain water for their daily needs last year.

Due to the serious drought and salinity, Tien Giang Province had to spend VND37 billion ($1.6 million) buying freshwater to provide for its people aside from the sum farmers had paid to save their farms on their own.

Despite such efforts, Ngu Hiep Commune had still lost more than 400 hectares of durian trees out of a total 1,500.

Loc himself lost 40 trees while other trees that had still been alive could not produce qualified fruits. As a result, he could not sell a certain amount of durian fruits and for those that could still be sold, the prices were much lower than normal. Loc ended up suffering a loss.

After the disaster, Loc had to spend VND300 million ($13,000) on fertilizers and other chemicals to recover the trees and buy seedlings to grow new trees and replace the dead.

Next door, his neighbor has already switched to cultivating jackfruit after losing his entire 12-year-old durian farm to last year’s drought and salinity.

Suffering from such serious damages, Mekong Delta inhabitants have, since the beginning of this year’s dry season, geared up for the worst, as meteorologists forecast salt intrusion would be higher than normal this year, though not as bad as last year’s record levels.

The salinity level along the Tien River, a branch of the Mekong, currently measures at 0.1 grams per kilogram of water, or just 0.1 ppt compared to 7 ppt in the same period last year.

These days in Ngu Hiep Commune, six groundwater wells have been put in operation. All of them have been approved by Tien Giang authorities to run only when drought and salinity become severe. At all other times they would remain sealed to protect groundwater sources.

Around 20 kilometers (12.4 miles) from the commune, a dam of 65 meters wide along a canal of 19 kilometers in length has been built to reserve water. Along with this dam, Tien Giang has invested VND45 billion building seven other dams of smaller scale along canals to ensure water for 1.1 million people and 128,000 hectares of farm land.

Meanwhile, Ben Tre Province has finished dredging Kenh Lap, the largest reservoir of Mekong Delta to store fresh water.

Kenh Lap stretches nearly five kilometers in length and 40-100 meters in width, built at a cost of VND85 billion ($3.6 million). With a capacity of nearly one million cubic meters, it is designed to supply water to more than 200,000 people living in 24 communes and towns for household, industrial and irrigation purposes.

Given its scale, even the reservoir ran dry when the dry season reached its peak in southern Vietnam last year.

Nguyen Thi Lan, 43, a local in Phuoc Ngai Commune of Ba Tri District, said her family of four is using water pumped from the reservoir for their daily activities and that she has prepared eight concrete tanks storing rainwater from the earlier rainy season for cooking and drinking.

Many other people in Ba Tri District as well as Giong Trom and Thanh Phu districts have prepared plastic bags that could store 7-30 cubic meters of water each.

Nguyen Thi Thu Lai stands by a plastic bag storing water at her home in Ben Tre Province, March 2021. Photo by VnExpress/Hoang Nam.

They have either used the bags to keep water for family use in case freshwater runs dry in nearby canals or suffers salt intrusion.

"These bags are less costly than building a concrete tanks and we can fold them and put them away when we finished using them," said Nguyen Thi Thu Lai in Giong Trom.

Lai’s family has prepared water enough for three months, stored in both bags and concrete tanks.

As for this year’s dry season, Mekong Delta, the nation’s agriculture and aquaculture hub, should expect the worst during March 12-16 and 25-29 period, and April 14-19 and 24-28 before saltwater gradually retreats, according to the National Center for Hydro-Meteorological Forecasting.

Last year, El Nino caused scanty rainfall in southern Vietnam while upstream Chinese dams held back water and sediments that traditionally fertilize downstream agricultural lands, experts have said.

The Mekong flows 4,880 kilometers through six countries, 2,130 kilometers in China. Of the 19 hydropower projects China plans along the river, it has completed 11.

As for this year, Nguyen Huu Thien, an independent expert on Mekong Delta ecology, said the situation will be less severe as El Nino had ended last September and the rainy season of 2020 had brought more rainfall compared to 2019.