River diversion plan could combat Mekong Delta salt intrusion

Tran Ngoc Tam, chairman of the Ben Tre People's Committee, made the proposal on Tuesday.

Salt intrusion levels of 4/1,000 have been recorded at 52-64 km inland in major Ben Tre estuaries, the rough equivalent of levels seen in the 2016 dry season, according to the Department of Agriculture and Rural Development.

Salt intrusion in the river systems of Ben Tre has affected the lives of tens of thousands of families. Due to the salt contamination, the salinity levels at several water factories went up to 5.1/1,000, forcing over 10,000 families to make do with salty water.

Usual river salinity levels hover around 0.25/1,000 and such salinity level thresholds should not rise above 0.5/1,000.

Water with higher salinity levels should not be used for cooking, and once the salinity levels reach very high levels (around 3/1,000), the water should not be used for showering or laundry either as it can ruin washing machines and water heaters.

In Tien Giang, the Nguyen Tan Thanh Channel floodgate had to be closed down a week earlier than expected to prevent salt intrusion. In Kien Giang, the Cai Lon-Cai Be floodgate was closed down completely from March 14 to 17, due to forecasts saying salt intrusion level may reach 4/1,000 and go as far inland as 65 km.

In Ca Mau, around 340 cases of erosion and landslides at rivers and channels have been recorded over a span of 9 km. Rains ending early and severe droughts have caused the water to recede quickly, forcing people to pump water into their fields, which has dried up rivers and other water channels. The rising and dropping of water levels has thus also led to severe riverbank erosion problems.

Tam said the Mekong River is dependent on water sources upstream, so domestic river systems, like Saigon and Dong Nai can be utilized to meet the demands of Mekong Delta localities during dry seasons.

"The eastern area has a high terrain, so a channel can be made, or we can use a pipe system to bring water from this area to Long An, Tien Giang, and then Ben Tre, with the distances between each locality only spanning a few dozen kilometers," Tam said.

Tam also proposed that the central government continue investing its ongoing anti-salinity sluice gate system at certain areas. The system is part of the Ben Tre water management project JICA 3, with a total investment cost of over VND6.1 trillion (US$247.36 million). However, the project’s progress has been slow due to funding difficulties.

"For the long run, the central government needs to look into the creation of sluice gates on the Ham Luong river to help Mekong Delta localities deal with salt intrusion," Tam said.

Salinity levels have reached levels higher than in previous years and going 5-15 km deeper inland, according to the agriculture ministry. This year's dry season may include two waves of salt intrusion in late March and early April, though the salinity levels may drop, the ministry added.

Over 1.5 million ha of paddy fields in the Mekong Delta that were sowed a month ago will not be affected much. So far, over 600,000 ha of said paddies have been harvested.

Around 20,000 ha of paddy fields in Tra Vinh and Soc Trang, however, fell outside the sowing schedule, so they may be affected by water shortages. Droughts have also caused clean water access difficulties for around 30,000 families in the Mekong Delta.

Nguyen Hoang Hiep, deputy agriculture minister, said the ministry would help Ben Tre complete its sluice gate system. "By 2027 the locality will basically be able to prepare freshwater sources for the dry season," he said, adding that Ben Tre should continue to monitor the drought situation to prevent water shortages.

A historic drought period in 2016 caused 160,000 ha of soil to be contaminated with salt, resulting in total losses of over VND5.5 trillion. In 2020, droughts lasted over six months, damaging 43,000 ha of paddy fields and causing water shortages for 80,000 families. The government has since spent a total of VND530 billion combating this problem in eight Mekong Delta localities.