A local man tested water from it and using a salinity meter on Monday and got a reading of 1.45 parts per thousand (ppt). Fresh water has a salinity of 0.5 ppt or less.

Vo Thi Thuy lives a kilometer from the reservoir in Ba Tri District, but now uses rainwater stored in large jars and freshwater she buys to cook instead of using tap water as usual.

She said: "My family used tap water from Kenh Lap reservoir. But for a month now, with the water becoming salty, we can only use it to shower, do laundry and wash vegetables. We have to buy filtered water or freshwater elsewhere to cook which costs VND70,000-80,000 ($3-3.4) a cubic meter." The price is 10 times what she pays for tap water.

Locals are aware of the saltwater intrusion but use tap water anyway since it is still only half as salty as water sourced from other canals.

Except for households that use rainwater they have stored, a family now spends a couple of million dong (VND1 million = $43) a month on water instead of the few hundred thousand they spent earlier.

Kenh Lap, which is nearly five kilometers long and 40-100 meters wide, is the Mekong Delta’s largest manmade freshwater storage and was 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.

It currently supplies water to around 500 families in five communes, and pipes are planned to be laid next year to expand the number 100 times.

Nguyen Dinh Dung, manager of the Kenh Lap water pumping station, said the saltwater intrusion has halved the water level in the reservoir to 500,000 cubic meters.

"The water is not good enough for use due to the saltwater intrusion, but it meets the basic needs of locals. The water left in the reservoir is enough to sustain them through the [ongoing] dry season." The rainy season in the area begins in May.

The saltwater has also affected most of the 4,500 hectares of winter-spring rice in Ba Tri District. A part of the crop has died while the rest is of much lower quality than before.

Nguyen Van Lan, 51, a farmer in Ba Tri, has brought a sickle to the 4,000-square-meter field in which he planted rice nearly two months ago. He has come to remove the plants damaged by the saltwater.

Nguyen Van Lan, a Ba Tri District farmer, removes saltwater-affected rice plants
to feed his cattle. Photo by VnExpress/Hoang Nam.

"I know for a fact some plants won't grow panicles, so I cut them off to feed our 100 goats and four cows because straw and grass are in short supply," he said.

Duong Van Chuong, vice chairman of the Ba Tri District People's Committee, said the water salinity levels in the district range between 1.8 to 3 ppt, posing a big challenge to farming and husbandry.

Workers have been deployed to remove the saltwater, but they have only done so from the surface, and saltwater beneath the surface accumulated over many years still remains.

Chuong added: "Local authorities will soon ask the reservoir management unit to take advantage of the [next] rainy season and freshwater season to continue pumping out the saltwater and bring freshwater into the reservoir to remove the saline water. It is expected that all saltwater will be kept out by next year."

According to the Ben Tre meteorological station, the salinity levels in the estuaries of the Co Chien and Ham Luong, the province’s main rivers, range between 25 to 30 ppt.

Areas situated 48-68 kilometers up the rivers have levels of 4 ppt. A lower level of 1 ppt is found 20 km further inland.

The province has declared the saltwater intrusion a natural disaster level two, or medium intensity, on a rising scale of one to five.

Recently Ben Tre has launched a VND6 trillion ($259 million) water management project. Eight saltwater prevention sluices and pumping stations will be built across the province. The project seeks to generate freshwater and prevent salinity on more than 200,000 hectares of land. The water will be used to irrigate around 90 percent of its agricultural lands.

Work will begin next year and run until 2025.