A recent study in Nature reveals a concerning situation: over half of India’s major deltas are sinking faster than the sea is rising, including the Ganga-Brahmaputra, Brahmani, Mahanadi, and Godavari deltas. Over 236 million people around the world reside in these low-lying delta areas, which are now at higher risk of floods, saltwater entering freshwater supplies, and coastal land loss.

From 2014 to 2023, parts of these areas sank by more than 3 mm each year, and the Brahmani and Mahanadi deltas are sinking even faster, at over 5 mm annually, means that more than half of the world’s 40 major deltas, which include important parts of India’s coast, are losing land faster than shorelines are rising due to climate change.

Why Indian Deltas Are Sinking: Causes and Context

The main reason is that too much groundwater is being used, and when water is pumped out of the ground quicker than it can be refilled by rain, the soil gets compacted, and the land sinks- known as land subsidence. India is one of the world’s biggest users of groundwater, accounting for about 25% of all groundwater taken globally, and agriculture depends on it heavily, using it for over 60% of irrigated crops and 85% of drinking water in some areas. This overuse makes the sinking problem worse in delta areas, whose sediments are already prone to compression.

The situation is also worsened by:

• Less sediment is reaching the deltas because of dams and other river controls upstream. Sediment has been used to help build up the land and balance out the sinking for years.
• City growth and infrastructure are putting more strain on water resources and changing how land is used in these fragile delta areas.

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Key Impacts of Subsidence on Indian Deltas

As over half of India’s major deltas are sinking and the sea is rising, these delta areas, already low-lying, are experiencing more frequent flooding, even during normal high tides. As the land sinks, saltwater moves inland, contaminating the freshwater supplies that people rely on for drinking and farming.

Here’s a quick look at some data:

Note: These numbers cover 2014 to 2023 and are based on satellite and other data.

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Human and Ecological Costs

The human and environmental costs of this are significant:

• Millions face higher flood risks, especially during monsoons and cyclones.
• Farmland is becoming ruined because of saltwater and waterlogging.
• Roads, railways, and homes are getting damaged more often, costing more money to repair.
• Natural environments, like mangroves, are struggling to survive because of the changing land and water conditions.

Cities like Kolkata are seeing more severe flooding because over half of India’s major deltas are sinking, which is adding to sea-level rise and putting stress on city services. While some sinking is natural, human actions have made it happen much faster.

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What Can Be Done?

Solutions need to address multiple aspects:

• Limit how much groundwater is used, especially in farming and industry.
• Allow more natural river sediment to flow by changing how dams are operated.
• Develop stronger measures to adapt, like building flood defenses and planning resilient infrastructure.
• Involve communities to support the careful use of water.

Some of these actions need policy changes, while others, like collecting rainwater and using irrigation, can be done locally right away.

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The Ground Beneath Our Feet

The fact that over half of India’s major deltas are sinking because of groundwater use is a serious environmental warning that needs to be taken into account when planning for the future. These fertile plains are important for agriculture and are home to millions of people whose lives depend on the stability of the land.

To address this, we need urgent policy action, public awareness, and careful water management at all levels. If we don’t take action, the continued sinking of river deltas will make sea-level rise worse, displace communities, and harm India’s environment.

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FAQs

1. Why are river deltas important?

Deltas are fertile areas where rivers meet the sea, which are good for farming, fishing, transportation, and supporting large populations.

2. Can the sinking of deltas be reversed?

It’s hard to completely reverse it, but we can slow down or stop subsidence by managing water sustainably and restoring sediment flow.

3. Is sea-level rise more important than sinking?

In many Indian deltas, the local land sinking is happening faster than sea-level rise, making subsidence a more immediate problem.

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