Stable isotope hydrology of surface and groundwater from the Doon Valley: geometeorological processes and hydraulic linkages

Effective management of water resources requires an understanding of local hydrology and its links to precipitation. This study provides insights into geometeorological controls on precipitation and the hydraulic relationship between the water sources in the Doon Valley of the Indian Himalaya. Results suggest that inherent variance in isotopic characteristics of precipitation is closely associated with the evolution of different sources of moisture and topographic features. Back trajectories and d-excess suggest that precipitation is transported from the Arabian Sea, the Bay of Bengal, and the Mediterranean Sea. The differences in slopes and intercepts of delta O-18-delta H-2 regressions with space reveal that evaporation and local recycling regulate the compositional variation of precipitation. The study suggests a strong hydraulic connection between surface water and groundwater and recharge through flowpaths with higher permeability, where the Indian summer monsoon acts as the dominant replenishment input. Using the vertical isotopic gradient of precipitation, the groundwater feeding zones were also determined.