“…Application of tritium to hydrologic problems was first proposed by Libby (Libby, 1953;Bergmann and Libby, 1957). Tritium analysis has been useful in many areas such as hydrogeology (Lloyd, 1981;Lehmann et al, 1993;Sanchez-Cabeza and Pujol, 1999), nuclear industry monitoring (Mundschenk and Krause, 1991;Castellano and Dick, 1993), dosimetry and healthrisk assessment (Okada and Momoshima, 1993;Murphy, 1993), and some special topics such as false labeling of alcoholic beverages (Schönhofer, 1992) and for estimating the groundwater residence time (Fontes, 1983;Yurstsever, 1983) as it is directly incorporated into water molecule. In the present study, an attempt has been made for first time to estimate tritium ( 3 H) in the groundwater samples from Varahi and Markandeya river basins, using low background liquid scintillation counting system (Wallac Quantulus 1220) to see whether the aquifer in the study area is getting modern recharge or not.…”