According to a new study by the University of Michigan, farmers in India have adapted to rising temperatures by increasing groundwater extraction for irrigation. If the current trend persists, the rate of groundwater loss could triple by 2080, posing an even greater threat to India’s food and water security.
Reduced water availability in India due to groundwater depletion and climate change could endanger the livelihoods of more than one-third of the country’s 1.4 billion inhabitants and have global repercussions. India recently surpassed China as the world’s most populous country, and it is the second-largest producer of cereal grains, including rice and wheat.
According to Meha Jain, an assistant professor at the University of Michigan’s School of Environment and Sustainability and the study’s lead author, farmers are already increasing irrigation use in response to rising temperatures, a strategy not accounted for in earlier projections of groundwater depletion in India. This is concerning, as India is the world’s largest consumer of groundwater and a vital resource for regional and global agricultural production, she said.
The main author is Nishan Bhattarai of the Department of Geography and Environmental Sustainability at the University of Oklahoma. He was a postdoctoral researcher in Jain’s laboratory at the University of Michigan.
The study published online on September 1 in Science Advances, analysed historical data on groundwater levels, climate, and crop water stress to identify recent variations in withdrawal rates caused by global warming. In addition, the researchers used temperature and precipitation projections from ten climate models to estimate future groundwater loss rates in India.
Previous research has focused on the separate effects of climate change and groundwater depletion on India’s agricultural production. These studies did not account for farmers’ decision-making, including how farmers may adapt to a changing climate by modifying their irrigation decisions.
The new study considers the possibility that higher temperatures may increase the water demand of stressed crops, leading to an increase in irrigation by farmers.
According to the study, under a business-as-usual scenario, rising temperatures may treble groundwater depletion rates in the future and expand hotspots of groundwater depletion to include southern and central India. Without policies and interventions to conserve groundwater, warming temperatures will likely exacerbate India’s already-existing groundwater depletion issue, further threatening India’s food and water security in the face of climate change.
Previous research indicates that climate change could reduce the yield of Indian staple commodities by up to 20 per cent by mid-century. Simultaneously, the country’s groundwater is being depleted at an alarming rate, primarily due to irrigation water withdrawals.
For the recently published study, the researchers compiled a database of groundwater depths from thousands of wells in India, high-resolution satellite observations that measured crop water stress, and temperature and precipitation records.
In the coming decades, most climate models predict that India will experience an increase in temperature, monsoon (June to September) precipitation, and a decrease in winter precipitation. The research team led by the University of Michigan discovered that rising temperatures and a decline in winter precipitation more than offset the increased groundwater recharge from increased monsoon precipitation, resulting in accelerated groundwater depletion.
Their estimates of groundwater level declines between 2041 and 2080 were, on average, greater than three times the current depletion rate under various climate change scenarios.