Use of stable water isotopes to identify and estimate the sources of groundwater recharge in an alluvial aquifer of Upper Jhelum Basin (UJB), western Himalayas

Abstract

In the present study, we used stable water isotopes (δ18O and δD) of source waters (rain, snow, and glacier melt) and groundwater to identify and estimate the sources of recharge in alluvial aquifer(s). The stable water isotopic composition of source waters showed a significant correlation with altitude (R2 = 0.75). Unlike source waters, the groundwater did not show significant spatio-temporal variation. The attenuation in the isotopic signal of groundwater may be due to lag and mixing of different waters recharging from different altitudes. The results revealed that snowmelt (44 ± 0.9% to 68 ± 2.7%) predominantly recharges the groundwater. The glacier melt contribution to groundwater recharge (2 ± 0.1% to 14 ± 0.9%) in Upper Jhelum Basin (UJB), although limited to some summer and autumn months, has tremendous significance in sustaining the groundwater recharge. The early and rapid melting of winter-accumulated snow due to climatic variability may disturb the seasonal water balance and decrease the annual groundwater recharge.