Groundwater depletion could affect winter harvests
doi:10.1038/nindia.2021.36 Published online 10 March 2021
The land area that Indian farmers can sow on in winter may decrease significantly in regions facing the most severe aquifer depletion, leading to a 20% fall in harvests nationwide by 2025, says a study1 by a team of researchers from India, the US and Israel.
While the monsoon rains in India enable cultivation during the fall and spring seasons, agriculture during winter, depends primarily on groundwater. Global groundwater reserves — the source of irrigation for 40% of the world’s agricultural production — are rapidly depleting, and the problem is particularly acute in India, the world’s largest consumer of groundwater, the researchers say.
The researchers used satellite data to measure winter cropped area across the country. They then linked this data to census information on three main types of irrigation infrastructure in 500,000 villages in India — shallow dug wells, deeper tube wells and canals that divert surface water. Linking the datasets allowed them to determine the relative efficacy of each irrigation method which, in turn, helped estimate potential future acreage losses.
"If access to all groundwater is lost in critically depleted regions, and if that irrigation water is not replaced from another source, villages in those regions may lose 68% of their winter cropped area, causing a 20% loss nationally," they report. Switching to canal irrigation, which the Indian government is promoting widely, is not the solution, the researchers say.
Even if all regions currently using depleted groundwater switch to canal irrigation, winter cropped acreage could still decline by 7% nationwide and by 24% in the most severely affected locations, their analysis shows.
“Simply providing canal irrigation as a substitute irrigation source will likely not be enough to maintain current production levels in the face of groundwater depletion," lead author Meha Jain from the University of Michigan told Nature India.
The data could help inform adaptation strategies that may include switching over from winter rice to less water-intensive cereals, increased adoption of sprinklers and drip irrigation to conserve water in the fields, and policies to increase the efficiency of irrigation canals.
1. M. Jain et al. Groundwater depletion will reduce cropping intensity in India. Sci. Adv. (2021) doi: 10.1126/sciadv.abd2849