India's warming climate to triple groundwater depletion rates in the country: Study

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Rising temperatures may triple the rate of groundwater loss in India by 2080, further threatening the country's food and water security, according to a study. The study, published online in the journal Science Advances, showed that farmers in India have adapted to warming temperatures by intensifying the withdrawal of groundwater used for irrigation.

If the trend continues, the rate of groundwater loss could triple. Reduced water availability in India due to groundwater depletion and climate change could threaten the livelihoods of more than one-third of the country's 1.4 billion residents. "We find that farmers are already increasing irrigation use in response to warming temperatures, an adaptation strategy that has not been accounted for in previous projections of groundwater depletion in India," said Meha Jain, Assistant Professor at University of Michigan's School for Environment and Sustainability.

"This is of concern, given that India is the world's largest consumer of groundwater and is a critical resource for the regional and global food supply," Jain said. India is the second-largest global producer of common cereal grains including rice and wheat. The study analysed historical data on groundwater levels, climate and crop water stress to look for recent changes in withdrawal rates due to warming.

The researchers also used temperature and precipitation projections from 10 climate models to estimate future rates of groundwater loss across India. The new study also takes into account the fact that warmer temperatures may increase water demand from stressed crops, which in turn may lead to increased irrigation by farmers.

Previous studies have shown that climate change could decrease the yield of staple Indian crops by up to 20 per cent by mid-century. At the same time, the country's groundwater is being depleted at an alarming rate, primarily because of water withdrawal for irrigation. The research team also found that warming temperatures coupled with declining winter precipitation more than offset added groundwater recharge from increased monsoon precipitation, resulting in accelerated groundwater declines.

Across various climate-change scenarios, their estimates of groundwater-level declines between 2041 and 2080 were more than three times current depletion rates, on average. "Using our model estimates, we project that under a business-as-usual scenario, warming temperatures may triple groundwater depletion rates in the future and expand groundwater depletion hotspots to include south and central India," said lead author Nishan Bhattarai of the Department of Geography and Environmental Sustainability at the University of Oklahoma. Bhattarai, formerly a postdoctoral researcher in Jain's lab, suggested strong "policies and interventions to conserve groundwater", without which "warming temperatures will likely amplify India's already existing groundwater depletion problem, further challenging India's food and water security in the face of climate change".

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