Current exploitation rate to deplete Mekong Delta sand within 10 years: study

The study released last week by the World Wide Fund for Nature (WWF) in Vietnam said the volume of sand flowing down to the delta was less than four million cubic meters last year, much lower than the 6.8-7 million average in the past due to the construction of hydropower dams in the Mekong River's upstream areas.

Meanwhile, 35-55 million cubic meters of sand was extracted from its tributaries in the delta.

An author of the study, Sepehr Eslami, a senior researcher and advisor at Deltares, a Dutch consultancy, said at a conference held to release the study last Friday in Can Tho City that the sand bank reserve in the region is currently negative 42.3 million cubic meters.

The reserve must be positive or zero if there is to be no erosion.

"If the current exploitation speed continues, the sand reserve in the delta will only be enough to last until about 2035," Eslami said.

"If exploitation is reduced by 5% a year, the reserve can be maintained until 2040."

According to the study, the reserve is around 367-550 million cubic meters, accumulated over hundreds of years ensuring stability of water flow in rivers.

As of last year the delta had 595 eroded spots stretching almost 583 km along rivers and 48 spots running 222 km along the coast.

The research team predicted that if the sand reserves are fully depleted, the river depth will increase by 0.5-1 m, causing an additional 180-200 thousand hectares to be affected by salinity, and worsening erosion and subsidence in the delta.

But the study has a limitation: it was unable to calculate the volume of sand illegally mined at night.

It used satellite images to record the activities of sand mining barges between 7:00 a.m. to 5:00 p.m. to arrive at the data.

There is no indigenous research to provide data about illegal sand mining either.

To exploit sand sustainably, Ha Huy Anh, country manager of the WWF Vietnam's Sustainable Sand Management Project, said a regional agency should be set up to oversee it instead of having it done at the provincial level, which is the current modus operandi.

In the long run, Vietnam should limit the use of river sand for construction and work to replace it with other materials, he said.

He said the Netherlands and other upstream countries the Rhine Meuse Delta banned sand mining after realizing it is impossible to recover the sand in the rivers that had sediments deposited over centuries to create the delta.

For construction, they have used quarry dust and construction waste as substitutes for river sand or design buildings in such a way as to save construction materials.

The study by the WWF Vietnam is part of a project called "Drifting Sands: Mitigating the impacts of climate change in the Mekong Delta through public and private sector engagement in the sand industry" that is funded by the International Climate Initiative, one of the key instruments of the German government to support international climate action and biodiversity and managed by the WWF Germany.

It has been carried out with cooperation from Vietnam's Ministries of Agriculture and Rural Development, Natural Resources and Environment, and Planning and Investment.

Its goal is to help maintain key ecological functions and reduce socio-economic vulnerability to climate change in the Mekong Delta.

It began in 2019 and will go on until 2024.

Nguyen Van Tien, deputy head of the agriculture ministry's Department of Dyke Management and Natural Disaster Prevention and Control, said the results would work as the basis for the government to study sustainable socioeconomic development plans, protect the environment and prevent natural disasters.

The director of the Southern Regional Hydrometeorological Station, Le Ngoc Quyen, said monitoring sand movement throughout the delta is a difficult task and has never been done.

So this research is meaningful for overall and long-term sand management as it predicts annual sand movement to assess reserves, contributing to balancing resource exploitation with economic development, he said.