Depleting groundwater imperils safety of buildings and infrastructure along the Ganga river. Credit: David Clapp/DigitalVision/Getty Images
Excessive use of groundwater for irrigation and domestic purposes is leading to land subsidence in and around Varanasi city, particularly along the banks of the Ganga1.
Diminished groundwater leads to compaction of the aquifer system, causing land to cave in. This manifests as deformed and undulating stairs and platforms on the banks of the Ganga, where people bathe and worship. An international research team says it threatens the safety of buildings and infrastructure near the river.
Scientists assessed groundwater storage in Varanasi by analysing images of the Earth’s surface from satellite Sentinel-1, and groundwater level and rainfall data between 2002 and 2023.
The team, which included researchers at the Banaras Hindu University in Varanasi and Chapman University in the USA, found that groundwater storage had declined significantly, at a rate of 14.6 mm a year which was linked to major droughts in 2004, 2012, 2017 and 2021, and extreme droughts between 2009 and 2014.
A warming climate, evapotranspiration, rainfall deficits and rapid urbanisation contribute to groundwater shortages in Varanasi. A fifth of the world's population, mostly in Asia, faces a similar risk.
In this city, groundwater depletion has created a subsidence zone that spans 1 to 1.5 km inland. Analysis shows the river banks and places nearby have been sinking at a rate of 2.4 to 8 mm a year.
The researchers say the issue of groundwater levels and land subsidence must be included in future water management policies.
