‘Climate change worsened groundwater depletion’
◗ THE TEAM said lesser rainfall during the monsoons and warming of winters will increase water demand for irrigation and reduce groundwater recharge, further stressing already depleting groundwater resource in North India
New Delhi, July 7: 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, a new study said. 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, civil engineering and earth sciences, IIT-Gandhinagar, said.
Using on-site observations, satellite data and models, researchers found that across north India, rainfall in monsoons (June to September) has reduced by 8.5 per cent during 19512021. 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 water demand for irrigation 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 is getting warmer, because even though climate change causes more rainfall most of it is projected to occur in the form of extreme events that do not support groundwater replenishment,” Mr Mishra said.
The shortage of rainfall in the monsoons, followed by warm winters and both driven by climate change, is projected to cause a “substantial decline” of about 612 per cent in groundwater recharge. The study’s manuscript, accepted for publishing in the journal Earth’s Future, was shared exclusively with PTI.
“For groundwater to get recharged, we need lowintensity rainfall spread over more days,” Mr Mishra explained. Changes in groundwater levels are known to be largely dependent on rainfall received during summer monsoons and groundwater pumped out for irrigating crops during their respective growing seasons: June to September for Kharif crops and December to March for Rabi.