A new kind of problem may be on the horizon for the residents of the national capital region. Around 100 square kilometres (over 24,700 acres) of land in parts of Delhi-NCR is sinking in a phenomenon called land subsidence, as per a new study based on satellite data and conducted by researchers from German Research Centre for Geosciences, Cambridge, the Southern Methodist University in US and IIT Bombay. The reason behind this is the depletion of groundwater at an alarming rate.
As per the study titled ‘Tracking hidden crisis in India’s capital from space: implications of unsustainable groundwater use’, the speed of this sinking was around 11 cm per year between 2014 and 2016 and rose to 17 cm per year over 2017-2018.
This land reportedly includes 12.5 square kilometres of land in Kapashera region in southwest Delhi, which is the most vulnerable and less than a kilometre away from the city’s Indira Gandhi International. The extremely high sinking here is accelerating and expanding towards the airport. Land subsidence can cause cracks on taxiways, runways and waterlogging inside airports. Shagun Garg, a doctoral researcher at the University of Cambridge, who was among researchers explained, “Airport requires stable ground because of the risk of major disruption if there’s significant ground movement. Kuala Lumpur airport is an example to understand the implications of land subsidence where cracks on taxiways, and waterlogging emerged due to soil settlement. Continuous monitoring of IGI (Indira Gandhi International) airport and its connecting roads is therefore crucial.”
Why does land sink?
This happens when excessive amount of groundwater is extracted from some types of soil and rocks under the surface. Unlike sinkholes and when land caves in, subsidence happens gradually over an elongated time. As per a survey in the US, around four-fifth of land subsidence globally is the result of excessive groundwater being taken out.
Which parts are most vulnerable?
In Delhi, the study cautions about areas including Kapasehra, Samalkha, Bindapur, Mahavir Enclave and Bijwasan. In Gurgaon, areas under threat are Sector 22A and Block C, Dundahera. In Faridabad, Sanjay Gandhi Memorial Nagar’s A, B and C pockets are most vulnerable.
