Taking into account the role of neglected farmer groups in recharging groundwater

A new study by researchers at the Indo-French Cell for Water Sciences (IFCWS), Indian Institute of Science (IISc), introduces a new framework for water budgeting in agricultural regions that includes farmers’ social categories that are usually neglected.

Conventional water accounting methods often focus on how much water agriculture consumes, without adequately considering who extracts groundwater and whose farming practices help replenish it. This can obscure the links between groundwater depletion, agricultural livelihoods, and social inequality.

In the study, the team proposes a new indicator, the Blue Water Potential (BWP), to assess each farmer category’s potential to exploit or replenish groundwater resources. It estimates the difference between groundwater recharge and the amount of groundwater required for irrigation under assumed optimal farming conditions. A positive BWP indicates that a farming system potentially contributes more water to groundwater recharge than it requires for irrigation. A negative BWP indicates that its irrigation requirements exceed its estimated contribution to recharge.

Applied to the case of a village in the semi-arid region of Rayalaseema in southern Andhra Pradesh, the researchers found extremely large variations in BWP at the plot level. Perennial irrigated orchards – such as pomegranate, sweet lime, and grapes – exhibit heavily negative BWP on average, consuming roughly 1,000-1,200 mm/year more water than they return to the aquifer. In contrast, rainfed groundnut crops and grasslands have a positive BWP of 200-300 mm/year.

Aggregation at the village level reveals stark inequalities. A minority (26%) of wealthier farmers appear to exploit most of the groundwater resource for horticulture, while a large majority of poorer rainfed groundnut farmers and pastoralists replenish it. However, policymakers often ignore the critical contribution of these poor farmers to groundwater resources. The study therefore identifies a hidden interdependence: groundwater-dependent farmers rely, in part, on recharge generated by rainfed farms and grazing lands. These latter groups are often economically disadvantaged, despite contributing to a shared resource on which more profitable irrigated agriculture depends.

“The regional water balance so far seems positive, but our results suggest that small increases in the area of cropping systems with highly negative BWP such as fruit trees would suffice to induce groundwater overexploitation, especially if this increase happens at the expense of the area with positive BWP,” says Charlotte Hemingway, first author and researcher at IFCWS.

These findings are particularly timely, as the Andhra Pradesh government recently unveiled an ambitious Rs 1 lakh-crore project to transform the historically parched Rayalaseema region into the "Fruit Bowl of the World" by expanding the region’s horticultural area from 8.41 lakh hectares to 14.41 lakh hectares through major irrigation projects.

“A robust assessment is needed to determine the water that will be imported through canals to improve the current fragile water balance at the village scale against climate risks as well as to sustainably satisfy the future needs of altered crops,” says co-author M Sekhar, Professor at the Department of Civil Engineering, IISc.

The paper includes open-source software, led by co-author and IISc alumna Rutuja Chitra-Tarak, that lets users compute the BWP for any cropping system or region of interest, which the authors hope will help design sustainable agricultural development policies.