Over-reliance on groundwater threatens to drown Vietnam province

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 A family moving out of their house as it becomes submerged by seawater in the Mekong Delta province of Ca Mau. Experts say a majority of the southernmost province will be under water within the next few decades.

The rampant pumping of groundwater is one of the main reasons why the Mekong Delta province of Ca Mau's sinking and is at risk of becoming mostly submerged within the next few decades, according to a Norwegian study.

At a workshop held in the Mekong Delta City of Can Tho earlier this week, the Norwegian Geotechnical Institute (NGI) released its findings, which said that many places across the province have sunk 30-80 centimeters over the past 20 years.

Ca Mau will decline a further 90-150 centimeters in the next 25 years, and 120-210 centimeters within 50 years, it said.

According to the study's authors, the problem has been caused mainly by the rampant local practice of pumping groundwater.

They found that every day, 373,000 cubic meters of groundwater is pumped in Ca Mau, where nearly 110,000 wells are operating.

Statistics also showed that every Ca Mau person uses 310 liters of groundwater per day compared to the national average of 80-120 liters.

They said the network of groundwater wells was responsible for the region's decline of 1.9-2.8 centimeters a year, adding that it was worse at places with soft soil.

Most of Ca Mau will be under water in next few decades, if the groundwater pumping continues, Kjell Karlsrud, technical director of NGI, told the conference. 

Sinking has also led to other problems Vietnam's southernmost province has had to deal with over the years, including coastal erosion and the salinization of canal and river water, Norwegian experts said.

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For example, they cited figures obtained via satellite images as showing that the province's coastline has been reduced by 100-1,400 meters over the past 20 years.

They also warned that not only Ca Mau, but other provinces in the Mekong Delta also face the same threats.

Vietnamese experts who attended the workshop corroborated the Norwegian study's findings.

Le Anh Tuan from the Mekong Delta Institute for Climate Change Research said his organization has conducted survey trips to Nam Can and Ngoc Hien districts in Ca Mau, and found that many construction sites had been flooded.

The phenomenon can be explained by the increased sea level and the region's sinking, Tuan said.

It is a fact that local people use a lot of groundwater, and with the increasing number of shrimp farms they need more water and thus, have been digging more wells, he said.

While the entire Mekong Delta is sinking, Ca Mau is declining at an above average rate due to its "weak" foundation which has high levels of alluvium, or sediment deposited by rivers, the expert said.

It is time local authorities set up facilities to filter water from canals as a replacement for groundwater, Karlsrud said, warning that such facilities will require major funding.

Authorities were also advised to establish systems to observe the sinking and issue warnings accordingly.

Nguyen Truong Tien, chairman of the Vietnam Society for Soil Mechanics and Geotechnical Engineering, said another option is to use rain water, which can be made usable with advanced technologies.

In the meantime, the NGI will make a geological map of Ca Mau, and start programs to observe the sinking process, as well as provide a detailed analysis of the phenomenon in accordance with new figures during the second stage of its study.

The workshop was organized by the Ministry of Agriculture and Rural Development, and the Norwegian Embassy in Vietnam.

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