About 450 cubic kilometres of groundwater was lost in northern India during 2002-2021 and climate change will further accelerate its depletion in the years to come, according to a new study.This is about 37 times the quantity of water the Indira Sagar dam -- India’s largest reservoir -- can hold at full capacity, lead author Vimal Mishra, Vikram Sarabhai Chair Professor of Civil Engineering and Earth Sciences at IIT Gandhinagar, said.
Using on-site observations, satellite data and models, researchers found that across north India, rainfall in the monsoon season (June to September) has reduced by 8.5 per cent during 1951-2021. Winters in the region have become warmer by 0.3 degrees Celsius over the same period, they found.
The team, comprising researchers from the National Geophysical Research Institute (NGRI) in Hyderabad, said lesser rainfall during the monsoons and warming of winters will increase irrigation water demand and reduce groundwater recharge, further stressing the already depleting groundwater resource in north India.While a drier monsoon leads to more reliance on groundwater to sustain crops during rainfall-deficit periods, warmer winters result in relatively drier soils, again requiring more irrigation -- something the researchers observed during the unusually warm winter of 2022, the fifth warmest for India since the India Meteorological Department started records in 1901.
“The accelerating trend of depleting groundwater is expected to continue as the planet warms because even though climate change causes more rainfall, most of it is projected to occur in the form of extreme events, which does not support groundwater replenishment,” Mishra told PTI.
The shortage of rainfall in the monsoons followed by warming winters, both driven by climate change, is projected to cause a “substantial decline” by about 6-12 per cent in groundwater recharge.