Estimation of Groundwater Recharge Potential using Rooftop Rainwater Harvesting: Case Study from Pune Urban Area, India

Abstract

Water scarcity is increasingly being felt in most nations includes highly developed countries. It is especially acute in urban growth centres as the demand for water increases rapidly while the supply of fresh potable water is decreasing. Ground water is increasingly being used as a source of fresh water in many cities across the world and causing depletion of the scarce resource. Groundwater recharge practices using rainwater harvesting contribute to restoring the water balance. Recharge to groundwater from rainfall has been studied extensively and numerous methods have been proposed for estimation of natural and artificial recharge of groundwater. However, most of these studies pertain to the recharge of surface aquifers. The present study covers the use of Rooftop Rainwater harvesting for recharge through direct injection to confined aquifers or deep-seated aquifers and a part of the larger study to understand the recharge potential from rooftop rainwater harvesting for Pune city. The recharge potential of roof rainwater harvesting is the capacity of a particular roof to harness the water that falls on it annually. The result of the study suggests that there is a large scope for supplementing the existing groundwater reserves of Pune city by direct injection using rooftop rainwater harvesting. The total water availability (run-off) per annum was estimated to be 49.05 million cubic metres (MCM). Even if half of this total rainwater is harvested, the recharge can supplement the groundwater annually by about 22 - 25 MCM (0.7 to 0.88 TMC) and can cater to nearly 70 % of the annual groundwater requirement of the Pune city.