A Watershed Approach for the Determination of Groundwater Recharge in Rajasthan, India

The determination of groundwater recharge is imperative for sustainable water management, particularly in semi-arid regions where mitigation and adaptation strategies are needed. Two-thirds of India is underlain by hard rocks, and appropriate techniques for the estimation of groundwater recharge are currently problematic in such areas. Chloride mass balance (CMB) has been employed in this study to determine recharge rates from groundwater collected from a monsoon dependent area in the Aravalli Hills in Rajasthan, India. A monitoring program was established in the summer of 2009 in the Gangeshwar Watershed with local participation for the collection of rainfall and groundwater samples. Groundwater recharge estimation was spatially determined over a 3-year period with pre-monsoon and post-monsoon datasets. Irrigation return flow was likely to impact 90% of the samples, and has thus required stable isotope analysis using hydrogen (δ2H) and oxygen (δ18O) to corroborate nitrate and other anionic chemistry to determine sources of groundwater recharge. The possibilities of using total dissolved solutes (TDS) as an alternative for chloride have also been addressed as a way to simplify the determination of groundwater recharge at the user-level.