Exhaustion of groundwater levels causing parts of Delhi-NCR to sink

NEW DELHI: Researchers have discovered that over 100 square kilometers of land in the national capital region is at risk of ground displacement, with the greatest of these around 12.5 sq km in south-west Delhi’s Kapashera, just 800m from the airport, according to satellite data.

The capital’s worrisome pace of groundwater depletion may be leading to a different kind of slow-moving crisis: portions of the city’s surface are sinking, a phenomenon known as land subsidence, which could damage the international airport. According to researchers from Indian Institute of Technology (IIT) Bombay, the pace of “sinking of land” in the vicinity of the airport is increasing, and the subsidence characteristic is swiftly moving towards the airport, potentially endangering it. “During the years 2014–2016, the subsidence velocity was estimated to be around 11 cm/year, but it increased by nearly 50% over the next two years to roughly 17 cm/year.” During 2018–2019, the trend stayed nearly unchanged, according to the report.

Land subsidence is a common global issue that occurs when substantial volumes of groundwater is drained from certain types of rocks and subsurface soil. When water is taken from aquifers, the clay between pockets of water progressively collapses, causing the ground beneath to deflate. It’s not like a sinkhole or a cave in, when the effects are immediate, rather it happens gradually across a broad region.

Water-stressed Delhi has a demand-supply mismatch of 300 million gallons per day (MGD) with a forecast demand of 1236 MGD. This demand is expected to rise to 1746 MGD by 2031, according to the Draft Master Plan 2041. Excessive groundwater extraction could cause land subsidence, according to Vikram Soni, Conservationist and Retired Professor, Jawaharlal Nehru University, who has worked on water-related issues in Delhi. The Delhi government implemented a number of stringent rules to enhance the state of the groundwater in the city.