River deltas across the world, including the Ganga-Brahmaputra, are going under faster than oceans are rising, a new satellite study has revealed.
Here’s what that means for millions of Indians.
Scientists have found that Earth’s major river deltas are sinking faster than sea levels are rising, and the Ganga-Brahmaputra delta is among the worst affected.
The study, published in the journal Nature, used ten years of radar data from the European Space Agency’s (ESA) Copernicus Sentinel-1 satellite to track changes across 40 major river deltas between 2014 and 2023.
The results were alarming. More than half of the deltas studied are sinking at rates exceeding 3 millimetres per year, while the global sea level is rising at about 4 millimetres per year.
In other words, the river deltas, housing 5 per cent of the world’s population, are sinking faster than the sea level is rising.
WHAT IS HAPPENING TO THE GANGA DELTA?
More than 90 per cent of the Ganga-Brahmaputra delta area showed subsidence during the study period. This means that the ground is literally going down.
Subsidence is when land gradually sinks into the earth, often because too much water is being pumped out from below the surface.
It’s like deflating a sponge. Once the water is removed, the ground collapses inward.
Kolkata, located in the Ganga-Brahmaputra delta, is among the cities experiencing significant subsidence, putting its infrastructure, homes, and millions of residents at growing risk of flooding.
The study identifies excessive groundwater extraction as a primary cause of subsidence in the Ganga-Brahmaputra delta, largely driven by unsustainable use for agriculture, industry and domestic supply.
WHAT OTHER DELTAS ARE SINKING?
Ten of the world’s 34 biggest cities are built on river deltas. Cities like Bangkok, Shanghai, Ho Chi Minh City, Alexandria, and New Orleans face the same crisis.
The most severely impacted deltas are in Thailand, Indonesia, and China, with average sinking rates close to 8 millimetres per year.
The issue is acutely alarming because it’s happening right now, and it’s happening faster than most climate projections account for.
Land subsidence now exceeds climate-driven sea-level rise in many densely populated deltas, creating a double burden that hastens the relative sea-level rise beyond global averages.
When the ground sinks faster than the sea rises, floods reach further, more often, even without any storm or extreme weather event.
WHAT CAN BE DONE?
The issue requires immediate attention and action or millions are going to face the consequences of land sinking down into the water.
For now, experts have stressed the need for reducing groundwater extraction, restoring natural sediment flows in rivers which are often blocked by dams, and limiting heavy construction on fragile delta soils.
All of these need to be deterred as it would buy us time by helping to slow the sinking.
India’s deltas will face escalating risks from flooding, land loss and displacement in the coming decades without urgent action to regulate groundwater extraction, restore sediment flows and strengthen adaptation planning.
The Ganga has shaped India’s civilisation for millennia. Now, it needs protecting, before the ground beneath it disappears.
Tackling land subsidence in river deltas together with climate-driven sea-level rise will be essential for safeguarding some of the planet’s most at-risk and densely populated coastal regions in the coming decades.
This dual approach will better guide future management, adaptation strategies, and protection measures for vulnerable areas not just in India but around the world.
