NEW DELHI: A study has found that consistent weaker summer monsoons and warmer winters — the fallout of global warming-induced climate change — have led to a massive loss of groundwater in North India in last two decades.
The groundwater depletion rate of 1.5 cm a year resulted in a net loss of 450 km3 of the groundwater during 2002-2021. This subsequently increased the irrigation water demands and reduced the groundwater recharge.
The trend may be a significant threat to India’s food security as groundwater plays a pivotal role in North India’s food production and the country’s food security for more than one billion people. For instance, current cropping intensity could decline by 68% due to groundwater depletion.
A batch of Indian scientists led by Dr Vimal Mishra from IIT Gandhinagar conducted research “Summer Monsoon Drying Accelerates India’s Groundwater Depletion Under Climate Change” and examined the role of summer monsoon drying and winter warming on groundwater storage in India. The study was published in Advancing Earth and Space Sciences.
According to the study, summer monsoon precipitation has significantly declined by around 8%, while winters have become warmer in north India from 1951 to 2021.
Analysis shows that if the warm winter rises by (+1°C), the irrigation water demand rises by about 9% regardless of whether the summer monsoon is normal, dry or wet.
“Summer monsoon drying coupled with winter warming climate will increase irrigation water demands and reduce groundwater recharge,” said Mishra. “This necessitates the implementation of groundwater sustainability measures to ensure future agricultural production during monsoon droughts,” he further adds.
The study used in-situ observations, satellite data, and a hydrological model that considers the role of irrigation and groundwater pumping.
“We show that summer monsoon drying and winter warming accelerate groundwater depletion in north India during the observed climate, which will continue in the projected future climate,” said Mishra.
For instance, summer monsoon drying (10-15% deficit for near-far periods) followed by substantial winter warming (1-4°C) in the future will accelerate groundwater depletion by increasing (6-20%) irrigation water demands and reducing groundwater recharge (6-12%).
The study emphasises groundwater sustainability measures to reduce the threat of the future. It suggests that lesser extraction and enhancing recharge of the groundwater during the summer monsoon seasons are needed to ensure future agricultural production.
Weaker monsoon, warmer winter
Weak summer monsoon followed by warmer winter has created massive loss of groundwater in last two decades in North India as groundwater extraction rose
North India’s groundwater depletion rate of 1.5 cm per year between 2002-2021 poses a great threat to the country’s food security