Theme 2-17-Identification of aquifer recharge sources and zones in parts of Ganga-Yamuna Doab using environmental isotopes

Abstract

Environmental tritium has been used to identify the recharge zones and sources to groundwater, in parts of Ganga - Yamuna Doab, western Utter Pradesh, India. The study area is characterized by thick alluvial deposits and has been a challenging area due to the complex hydrogeologic setting. In spite of several studies in the past, by several investigators who used conventional techniques, information on the groundwater flow regime is very less. The study reveals that rainfall actively recharges the local aquifers (extended over an area about 800 km2) in the Saharanpur district where, the aquifers upto a depth of around 100m are well interconnected to form a single unit. This is in stark contrast to the conditions in Hardwar district (mainly the area falling in the river Solani - river Ganga interfluve) where, the recharge is mainly taking place at higher altitudes, and the unconfined aquifer is poorly or not connected to the deep seated aquifers in the multi-aquifer system. In addition, the mean transport rate for the deep-seated aquifer has been evaluated as about 1.1 m/d, which is marginally lower than the values considered by other investigators. In general, it is found that the area characterized by sand-bars developed in the paleo-channels act as local recharge zone in the plains, while the Bhabhar and Siwalik Hills (above an altitude of 400 m above m.s.l.) act as regional recharge zones. The area close to the major rivers viz., river Ganga and river Yamuna act as discharge zones for the regional groundwater system. Further studies to correlate the water chemistry will help to identify those recharge zones that are to be preserved, in order to protect the groundwater from being polluted.