The News
The warming climate could drive India to use up its groundwater much more rapidly in the coming decades, according to projections published Friday in the journal Science Advances.
India already pumps up more underground water than any other country, largely to irrigate staple crops like wheat, rice and maize. But hotter temperatures are drying out fields and leaving less moisture to soak into the soil and replenish the aquifers below. Unless big steps are taken to promote water efficiency, underground supplies could shrink between 2041 and 2080 at three times the present rate, the new estimates suggest.
Why It Matters: Farmers in India depend heavily on groundwater.
Groundwater is vital for farming in India, supplying 60 percent of all irrigation. But growers in parts of the country are already starting to exhaust aquifers — layers of water-soaked dirt and rock — that could take centuries to refill. And, at the moment, India doesn’t have the dams and other infrastructure needed to significantly increase its river-fed irrigation.
“If you run out of groundwater, there aren’t other quick fixes, like providing canal irrigation, that can get you to the same level of production,” said Meha Jain, an assistant professor at the University of Michigan’s School for Environment and Sustainability, who contributed to the new research.
Background: Stronger monsoon rains, but more evaporation, too.
The researchers first looked at the relationship between groundwater levels, climate and crop water stress in India between 2004 and 2013. They then estimated how groundwater use might respond to three major effects of global warming: greater evaporation, increased rainfall during the summer monsoon season and decreased rain in winter.
The researchers found that the additional summertime rain could help refill aquifers, though not by enough to offset increased evaporation from warmer temperatures and increased irrigation needs during the drier winters.
“When the temperature is warming, this recharge is actually decreasing in monsoon season,” said Nishan Bhattarai, an assistant professor of geography and environmental sustainability at the University of Oklahoma, who led the new research.
So far, India’s groundwater overuse has been most severe in the northwestern breadbasket states of Punjab and Haryana. But the researchers’ modeling suggests that problems could arise by 2050 in the country’s southwest, where aquifers of hard rock can’t hold as much water as those in other areas.
In their projections, the authors didn’t try to predict the effects of water-saving changes that haven’t yet occurred on a large scale in India. These include shifts to less thirsty crops like millet, use of more efficient watering techniques like drip irrigation and results from changes in government policy, such as free or cheap electricity in rural areas, which have increased groundwater extraction by enabling poor farmers to run electric pumps.
They also didn’t try to account for the possible physical limits to water pumping — in other words, the very real likelihood that wells in parts of India will go completely dry.
What’s Next: Monitoring farms’ water use from space.
Many growers in India work on small plots, not industrial farms, so it can be hard to determine how many of them are adopting more environmentally sustainable methods. Dr. Jain is involved in research projects that use satellite-mounted sensors to map agricultural practices at the level of individual fields.
“We’re in the golden age of satellite data,” she said. “That’s allowing us to answer these questions at scales that just historically have not been possible.”
