Excessive groundwater extraction can cause subsidence

Subsidence is a global phenomenon seen not just in coastal regions, but also in inland areas. Natural subsidence progresses slowly, but anthropogenic activities, like excessive groundwater extraction, can significantly accelerate the rate, says LEONARD OHENHEN, assistant professor, department of earth system science, University of California, Irvine, US. In an interview with SUSHMITA SENGUPTA, Ohenhen says that climate change intensifies the problem through multiple pathways.

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Which cities in the world are prone to subsidence?

Most coastal cities are prone to subsidence because coastal areas naturally sink over time due to natural compaction of sediments. However, in some cities where intensive groundwater extraction occurs, the rates are dramatically accelerated. Notable examples include cities like Jakarta, Mexico City, Tehran, Bangkok, Tokyo, Ho Chi Minh City, Dhaka and Lagos. In the US, subsidence has been documented in cities including Houston, New Orleans, Norfolk and Los Angeles. The common thread is the combination of natural coastal vulnerability or intense groundwater pumping, often in areas with clay-rich sediments.

Will climate change make these cities more vulnerable to land subsidence?

Absolutely. Climate change intensifies the problem through multiple pathways. Increased drought frequency drives greater groundwater demand, while rising temperatures increase water consumption. This creates a dangerous feedback loop where climate adaptation efforts often increase groundwater dependence, accelerating subsidence that makes communities more vulnerable.

What are the natural and anthropogenic reasons for such land subsidence?