Scientists warn of global depletion of river sand reserves

Scientists have warned of the global depletion of river sand reserves, saying it is being extracted around the world far faster than natural processes can replenish it, according to a comprehensive review of 411 studies published in Reviews of Geophysics.

The researchers pointed to Vietnam's Mekong Delta as a striking example.

There, a dredger can extract 300 cubic metres of sand in just three hours, while current mining rates are nearly 12 times higher than the river's natural sediment replenishment rate of about 6.18 million tonnes per year.

Between 2015 and 2022, around 366 million cubic metres of sand were removed from the Vietnamese section of the Mekong, causing the riverbed to sink by nearly half a metre on average. The resulting riverbank erosion led to the collapse of more than 1,800 homes between 2018 and 2020. By 2023, researchers had identified 585 major erosion hotspots stretching a combined 741 kilometres along the river.

The changing riverbed has also intensified the backwater effect, allowing saltwater to penetrate farther upstream. If current extraction rates continue, researchers warn that sand reserves in Vietnam's section of the Mekong could be exhausted by 2035.

Similar trends have been observed at China's Poyang Lake, where landscape changes are visible from space, as well as along several rivers in India and Brazil's Paraná and Tocantins rivers.

River sand is particularly valued by the construction industry because its grain structure provides the friction required for concrete production. Unlike marine sand, it contains no salt, and unlike desert sand, it is not overly smooth. It accounts for more than 70% of the volume of concrete.

Hydrologist Dung Duc Tran of Singapore's Nanyang Technological University said extraction should be limited to carefully selected locations and volumes based on river sediment budgets and their natural replenishment rates.

By Bakhtiyar Abbasov