Environment

In India's West, What Explains Groundwater Shortage After Years of More Rain?

The answer could lie in the power sector.

Between 1996 and 2016, western India received more rainfall with each passing year. In this time, groundwater storage in Gujarat improved – but not so in Rajasthan, its neighbour, where levels were falling.

This difference is hard to explain. There’s no reason only one of two states that received more and more rain each year should simultaneously have less and less groundwater – until you look at electricity subsidies.

Specifically, a team of researchers from IIT Gandhinagar have found that the answer to Rajasthan’s situation lay in unrestricted access to groundwater subsidies.

In 2006, the government of Gujarat installed a separate electricity grid for farmers. Under the scheme, called the Jyotigram Yojana, farmers would receive free electricity supply for eight hours a day, according to a predeclared schedule. The aim: to ensure judicious use of water.

But no such restrictions are in place in Rajasthan, where farmers enjoy unlimited access to electricity and huge subsidies. Today, Rajasthan is facing a severe water crisis.

“We wanted to understand if the policies implemented in the neighbouring states had a role to play in their water fates,” Vimal Mishra, an associate professor in the Water and Climate Lab at IIT Gandhinagar told The Wire.

This is not the first time Mishra and his team are studying this issue. In a previous effort, they had examined changes in groundwater levels of shallow wells in the region.

And therein lay the flaw.

Shallow groundwater wells don’t properly reflect the influence of groundwater pumping on deeper aquifers. Rainwater can recharge shallow wells but not deeper aquifers, and about 55% of wells used for irrigation in Rajasthan are shallower than 40 m. In Gujarat, 85% of all wells are shallower than 40 m.

In their previous study, Mishra and co. noticed that groundwater levels increased more rainfall. “But that does not tell us if policy implementation has had an effect on groundwater recharge,” Mishra said.

To fix the problem, the team needed a way to assess the water storage at greater depths. Enter the twin GRACE satellites, whose name stands for ‘Gravity Recovery and Climate Experiment’. It’s a joint mission of NASA and the German aerospace agency. The two identical satellites record changes in Earth’s gravity at different points on its surface, and using that determine the composition of water in those places. Scientists have used these satellites to determine, for example, that the Indus-Brahmaputra basin is drying faster than then expected.

The IIT Gandhinagar team estimated groundwater storage using GRACE data, charting how it changed between 2002 and 2016. Then they compared the numbers with data from 406 wells in Gujarat and 234 wells in Rajasthan.

The GRACE records represent all sorts of water, including groundwater, soil moisture and surface water. Because India’s Central Groundwater Board (CGWB) assesses groundwater levels each quarter, scientists also collected GRACE data for the same periods, as well as rainfall and air temperature data for western India.

The effect of temperature and the weather on groundwater is nuanced. For example, the soil loses more water when it’s warmer. “Then, farmers pump more water as they need more water for irrigating the field,” Mishra said.

So when scientists accounted for this and all other factors in their model, they found that even though it had rained more, the state’s total groundwater storage fell in Rajasthan at 3.67 cubic km per year. But starting in 2002, Gujarat’s water storage has improved at the rate of 1.93 cubic km per year.

But these trends aren’t in sync with observations from groundwater wells in Rajasthan. GRACE data shows declining water storage but groundwater levels in shallower wells have been improving with more rainfall.

Both Gujarat and Rajasthan, temperature and the area under irrigation have changed in similar ways. So the differing trends could only pointed at one thing: policy measures.

Also read: India’s Groundwater Crisis: Well Water Levels Fall 65% In A Decade

However, Alok Bhargava of the Maryland School of Public Policy has some concerns. In a study of his own, published earlier this year, Bhargava had shown that satellite data doesn’t accurately assess groundwater storage.

“Variations in aquifer thickness as measured by GRACE satellite data are large and may not facilitate policy decision-making,” he told The Wire.

He also said Mishra and co. had disregarded changes in population size, which is an important aspect of groundwater use. With more people in a given region, there are more mouths to feed and the demand for water is higher. So policy isn’t the only thing able to explain poor groundwater recharge.

According to the 2011 Census, Rajasthan’s and Gujarat’s populations increased by 21% and 19%, respectively, in the decade since 2001.

However, Bhargava agreed that unregulated subsidies are part of the problem by triggering the vicious cycle of groundwater overuse, groundwater depletion and water stress.

Other states like Punjab, Haryana, Delhi and Bihar are also reeling from similar stresses, and have unregulated subsidies for farmers.

Baseline groundwater stress. Source: Central Groundwater Board/WRI

For Mishra, the most important finding is that deeper aquifers aren’t affected much by weather or rain.

“While it is important to safeguard the interests of farmers, granting subsidies without proper control does much harm than good in the long-term,” Mishra said. When groundwater is depleted, farmers either have to buy water or dig deeper, and neither is good news for their already strained finances.

Also read: Groundwater in Northwest India Has a Uranium Contamination Problem

Unhindered subsidies have also allowed farmers to cultivate crops that aren’t suited to their states’ needs. For example, farmers used to grow rice along the coast and in West Bengal – all places that experienced seasonal floods. But after Punjab rolled out subsidies, farmers could pump all the water they needed to submerge the rice crop. Punjab quickly became the country’s top rice producer, at the cost of incurring a severe water shortage.

The silver lining, if that, is that this isn’t a climate emergency problem – which means policymakers don’t get to throw their hands up. It’s an eminently solvable problem, as Gujarat is attempting to do, and cogent policy measures can lead the way.

“What we need now is long term data from deeper aquifers, more hours of study, and science backed policy, not appeasement politics,” Mishra said.

Sarah Iqbal is a freelance science writer.

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