Study: Replacing rice with other crops could help recover groundwater lost since 2000

New Delhi: Replacing about 40 percent of the area planted with rice with other crops could help reclaim 60 to 100 cubic kilometers of groundwater lost in northern India since 2000, a study shows.

Current farming patterns – which mainly focus on rice, which relies heavily on groundwater for irrigation – could lead to a loss of 13 to 43 cubic kilometers of groundwater if global warming continues, said a team of researchers including researchers from the Indian Institute of Technology Gandhinagar in Gujarat state.

The researchers suggested a shift from existing farming practices by limiting rice cultivation as a possible solution to conserve this rapidly depleting resource in a warmer world where food and water security are threatened.

“If 37 percent of the rice-growing area is replaced by other crops, 61 to 108 cubic kilometers of groundwater can be recovered under global warming of 1.5 to 3 degrees Celsius, compared to 13 to 43 cubic kilometers under current cultivation patterns,” the authors write in the study, which has been accepted for publication in the journal Proceedings of the National Academy of Sciences (PNAS) Nexus.

Compared with current cropping trends, the benefits of switching to other crops during the longer dry periods predicted due to global warming are greater in terms of groundwater conservation, the researchers said. According to the 2018 Intergovernmental Panel on Climate Change (IPCC) special report “Global warming of 1.5 degrees Celsius,” if current trends continue, global warming is likely to reach 1.5 degrees Celsius between 2030 and 2050, and could reach three degrees Celsius by 2100.

A change in cropping patterns could have a significant positive impact on groundwater sustainability and farmers’ profitability, particularly in the states of Punjab, Haryana and Uttar Pradesh, the authors said.

They also found that crop rotation had no significant impact on groundwater levels where recovery rates were low, such as in the states of Himachal Pradesh, Uttarakhand and Jharkhand.

The findings have policy implications for determining optimal cropping patterns to conserve groundwater in irrigated regions of northern India and ensure farmers’ profitability and income, it said.

Previous estimates suggested that about 300 cubic kilometers of groundwater were lost between 2002 and 2022 due to cultivation trends in northern India, where 80 percent of the cultivated area is planted with rice.

Parts of Punjab and the Ganges Basin are experiencing the world’s fastest groundwater depletion, the researchers said, adding that northern and northwestern India are among the global groundwater hotspots.

Studies have shown that switching to other crops has a positive impact on the environmental sustainability and income of farmers in China, the USA and India.

In this study, researchers examined current cropping patterns in regions where significant groundwater depletion has occurred. The team then used groundwater, well and satellite observations, as well as models, to estimate groundwater loss between 2002 and 2022.

To estimate the impact of a shift to crop cultivation on groundwater, the team examined two scenarios: in one scenario, the area under rice cultivation is reduced by five percent, and in the other scenario, a further 37 percent of the rice cultivation area is replaced by cereals, pulses and oilseeds, resulting in a total reduction in rice cultivation area of ​​42 percent.

The authors found that between 2002 and 2022, 45 cubic kilometers of groundwater could have been saved in the first scenario and 91 cubic kilometers of groundwater could have been saved in the second scenario in northern India, compared to current cultivation patterns.

They also found that in Punjab and Uttar Pradesh, under the two scenarios, the amount of groundwater saved over the past two decades could have been about one to four times the maximum storage capacity of India’s largest dam, the Indira Sagar.

In addition, the researchers estimated that farmers’ profits would increase by 13.5 percent in the first scenario while rice production remained the same.

In the second scenario, however, the authors expected farmers’ profits to increase by about 86 percent, but at the cost of a significant reduction in rice production by 45 percent.

The researchers suggested alternatives to rice cultivation: grains for Uttar Pradesh and oilseeds for West Bengal.