New Delhi: About 450 cubic kilometers of groundwater was lost in northern India between 2002 and 2021, according to a new study, and climate change will further accelerate its depletion in the coming years.
This is about 37 times the amount of water that the Indira Sagar Dam, India's largest reservoir, can hold at full capacity, said lead author Vimal Mishra, Vikram Sarabhai Senior Professor of Civil Engineering and Earth Sciences at IIT. Gandhinagar.
Using in situ observations, satellite data and models, researchers found that across northern India, monsoon rainfall (June to September) fell by 8.5 percent over the period 1951-2021. They found that winters in the region have become warmer by 0.3 degrees Celsius over the same period.
The team, comprising researchers from the National Geophysical Research Institute (NGRI) in Hyderabad, said decreasing rainfall during monsoons and warming winters will increase demand for irrigation water and reduce groundwater recharge, thereby which will further stress the already depleting groundwater resource in North India.
While a drier monsoon leads to greater reliance on groundwater to support crops during periods of rainfall deficit, warmer winters result in relatively drier soils, again requiring more irrigation, something the researchers noted during the unusually warm winter of 2022, the fifth warmest for India. since the Indian Meteorological Department began records in 1901.
"The accelerating trend of groundwater depletion is expected to continue as the planet warms because, although climate change is causing more rainfall, most of it is expected to occur in the form of extreme events, which does not support replenishment of groundwater," Mishra said.
Shortage of monsoon rainfall followed by warmer winters, both driven by climate change, is expected to cause a "substantial decline" of around 6 to 12 percent in groundwater recharge. The study manuscript, accepted for publication in the journal Earth's Future, was shared exclusively with .
"For groundwater to recharge, we need low-intensity rains spread over more days," Mishra explained. Changes in groundwater levels are known to largely depend on rainfall received during the summer monsoons and groundwater pumped to irrigate crops during their respective growing seasons: June to September for Kharif crops. and from December to March for those of Rabi.
Therefore, the combined effect of higher irrigation demand and lower groundwater recharge in the future may put more pressure on a resource that is already rapidly depleting, he said.
The findings challenge the optimistic perception that increased rainfall driven by climate change will solve our water problems, said the study's lead author.
In 2009, a monsoon drier by almost 20 percent, followed by an unusual winter that was one degree warmer, had "detrimental" effects on groundwater storage: it had shrunk by 10 percent, the authors found. .
Soil moisture loss during winters was also found to have increased significantly over the past four decades, suggesting the potential role of warming and increased irrigation demands.
The authors have projected that under continued warming, drier monsoons by 10 to 15 percent and warmer winters by 1 to 5 degrees Celsius will together increase irrigation water demand by 6 to 20 percent. hundred.
A warming of 1 to 3 degrees Celsius in northern India will also significantly hamper the replenishment of groundwater by 7 to 10 percent, they said.
"The findings have policy implications as the water crisis observed during this year's heatwave highlights the need for cautious and judicious exploitation of groundwater," Mishra said.
Groundwater, vital for food and water security in India, will become a more crucial resource in a warmer climate due to increased demand from both irrigation and industry, the author said.
"This is because surface water storage, such as in reservoirs and dams, is insufficient to meet demands during summer, as seen in cities like Delhi and Bengaluru. Failure to pay attention to the resource could pose water security challenges. in the future," Mishra said. aggregate.
This is about 37 times the amount of water that the Indira Sagar Dam, India's largest reservoir, can hold at full capacity, said lead author Vimal Mishra, Vikram Sarabhai Senior Professor of Civil Engineering and Earth Sciences at IIT. Gandhinagar.
Using in situ observations, satellite data and models, researchers found that across northern India, monsoon rainfall (June to September) fell by 8.5 percent over the period 1951-2021. They found that winters in the region have become warmer by 0.3 degrees Celsius over the same period.
The team, comprising researchers from the National Geophysical Research Institute (NGRI) in Hyderabad, said decreasing rainfall during monsoons and warming winters will increase demand for irrigation water and reduce groundwater recharge, thereby which will further stress the already depleting groundwater resource in North India.
While a drier monsoon leads to greater reliance on groundwater to support crops during periods of rainfall deficit, warmer winters result in relatively drier soils, again requiring more irrigation, something the researchers noted during the unusually warm winter of 2022, the fifth warmest for India. since the Indian Meteorological Department began records in 1901.
"The accelerating trend of groundwater depletion is expected to continue as the planet warms because, although climate change is causing more rainfall, most of it is expected to occur in the form of extreme events, which does not support replenishment of groundwater," Mishra said.
Shortage of monsoon rainfall followed by warmer winters, both driven by climate change, is expected to cause a "substantial decline" of around 6 to 12 percent in groundwater recharge. The study manuscript, accepted for publication in the journal Earth's Future, was shared exclusively with .
"For groundwater to recharge, we need low-intensity rains spread over more days," Mishra explained. Changes in groundwater levels are known to largely depend on rainfall received during the summer monsoons and groundwater pumped to irrigate crops during their respective growing seasons: June to September for Kharif crops. and from December to March for those of Rabi.
Therefore, the combined effect of higher irrigation demand and lower groundwater recharge in the future may put more pressure on a resource that is already rapidly depleting, he said.
The findings challenge the optimistic perception that increased rainfall driven by climate change will solve our water problems, said the study's lead author.
In 2009, a monsoon drier by almost 20 percent, followed by an unusual winter that was one degree warmer, had "detrimental" effects on groundwater storage: it had shrunk by 10 percent, the authors found. .
Soil moisture loss during winters was also found to have increased significantly over the past four decades, suggesting the potential role of warming and increased irrigation demands.
The authors have projected that under continued warming, drier monsoons by 10 to 15 percent and warmer winters by 1 to 5 degrees Celsius will together increase irrigation water demand by 6 to 20 percent. hundred.
A warming of 1 to 3 degrees Celsius in northern India will also significantly hamper the replenishment of groundwater by 7 to 10 percent, they said.
"The findings have policy implications as the water crisis observed during this year's heatwave highlights the need for cautious and judicious exploitation of groundwater," Mishra said.
Groundwater, vital for food and water security in India, will become a more crucial resource in a warmer climate due to increased demand from both irrigation and industry, the author said.
"This is because surface water storage, such as in reservoirs and dams, is insufficient to meet demands during summer, as seen in cities like Delhi and Bengaluru. Failure to pay attention to the resource could pose water security challenges. in the future," Mishra said. aggregate.
