Identification of Recharge Sources Using Environmental Isotopes in Piedmont Zone of Himalaya, Hardwar District, India

The environmental tritium contents and chemical composition of twenty-one groundwater samples collected from shallow and deeper aquifers were measured in the present study to identify the recharge sources of various aquifers, and aquifer-aquifer interaction in the Piedmont zone of Himalaya, India. Tritium concentrations in the shallow aquifers varied from 4.2 to 11.24 Tritium Units (TU), whereas in the deeper aquifers, tritium varied from 0.9 to 12 Tritium Units (TU). The tritium concentration map in relation to ground elevation shows that high concentrations of tritium (above 10 TU) are observed at higher altitudes (300-400 m AMSL) in the Bhabhar region (Upper Piedmont), which suggests that the existence of youngest water acts as a groundwater recharge area. The chemical composition of the collected groundwater samples indicates the presence of two water types, which suggests the presence of different sources of recharge to the shallow and deeper aquifers in the region. The Electrical Conductivity (EC) values of the shallow aquifers especially in the Bhabhar zone (Upper Piedmont) were high indicating that the shallow aquifers have a recharge source other than that of the deeper aquifers, and that the interconnection between the shallow and deeper aquifers is poor to moderate.