A farmer in her rice field in southern India. Photo: Meena Kadri/Wikimedia Commons

The severe and ongoing depletion of underground water supplies in India poses a growing threat to the nation’s food security. Without serious efforts to stem the mining of groundwater, food production will decline, unleashing painful social and economic consequences for this nation of 1.25 billion people.

All four of the world’s top irrigators – China, India, Pakistan and the United States – are pumping groundwater faster than it is being replenished in crucial crop-producing areas. But the problem is most serious in India, where 60 percent of irrigated farming depends on groundwater.

Scientists have estimated that northern India, which includes the nation’s breadbasket of wheat and rice production, is depleting groundwater at a rate of 54 billion cubic meters per year, a volume that could support a subsistence-level diet for some 180 million people.

In addition to the breadbasket states of Punjab and Haryana in the northwest, groundwater levels are falling extensively in Andhra Pradesh, Gujarat, Maharashtra, Rajasthan and Tamil Nadu.

More than 15 percent of India’s food is being produced by mining groundwater.

In the southern state of Tamil Nadu, irrigated land has dropped by half over the last decade due to the depletion of groundwater, according to a new study by the International Water Management Institute (IWMI), based in Colombo, Sri Lanka, and published recently in the journal Water Resources Management. Some 95 percent of open wells in the state are dry.

Tamil Nadu’s production of rice, bananas, groundnuts and other dietary staples is threatened, as are the livelihoods of the farmers who produce them.

“It’s a precarious situation,” said the IWMI study’s leader, Pennan Chinnasamy, in a press release. “This is one of the most important agricultural states in India, and largely depends on groundwater to produce food. Without groundwater, the sector could collapse, wiping out the benefits of agricultural development achieved in recent years.”

Groundwater depletion has long been a problem in India, driven by the availability of inexpensive motorized pumps and heavy subsidies for electricity and fuel. With flat rates for electricity, for example, the marginal cost of pumping additional water is effectively zero. As a result, farmers race to pump as much as they can before their neighbors get the last drop.

Although the widespread drilling of groundwater wells helped spur the Green Revolution, the benefits of that revolution are now at risk as those wells run dry.

As underground water levels drop, rivers and wetlands that depend on groundwater for base flows can dry up as well.

The researchers used data from a US National Aeronautics and Space Administration mission called GRACE (for Gravity Recovery and Climate Experiment), which uses a pair of satellites to measure changes in the Earth’s gravity field caused by changes in water storage.

Over the period 2002-2012, the research team found that farmers were pumping out 8 percent more water on average than was being replenished, causing water tables to drop at an average rate of 1.4 meters (4.6 feet) per year.

Without strong regulations or economic incentives to slow the pumping, and active efforts to recharge the depleted aquifers, India faces a future of food insecurity and declining rural economies.

Sandra Postel is director of the Global Water Policy Project, Freshwater Fellow of the National Geographic Society, and author of several books, including Pillar of Sand: Can the Irrigation Miracle Last?, and numerous articles on global water issues. She is co-creator of Change the Course, the national freshwater conservation and restoration campaign being piloted in the Colorado River Basin.