Effectiveness of Irrigation Tanks for Enhancing Groundwater Recharge

Abstract

India's agricultural sector increasingly relies on groundwater for irrigation, leading to depleting groundwater resources in various parts of the country. Historically, surface water storage structures known as ‘tanks’ were used for millennia in India to store rainwater for irrigation. Their use declined over time and due to the increased groundwater pumping in the 20th century, but recent revitalisation efforts aim to improve water availability and support sustainable livelihoods. Despite this resurgence, the role of irrigation tanks in recharging groundwater is not yet fully understood. This study aims to evaluate the effectiveness of tanks in facilitating groundwater recharge using numerical modelling with Hydrus 2D. Time series for tank water levels were reconstructed using satellite images from Planet Labs. The findings confirm that irrigation tanks contribute to groundwater recharge, particularly when constructed in a cascade system. As the cascade of tanks, where water flows from upstream to downstream tanks, is supplied by rivers, both tanks are almost constantly filled with water. This causes recharge throughout the year, except on some days in the dry season. Recharge rates strongly depend on both the aquifer's hydraulic conductivity and the characteristics of the tank floor. The results show the effect of measures such as the removal of accumulated sediments and thus provide insights to optimise the tanks' dual function as reservoirs for irrigation as well as aquifer recharge structures.