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Uttarakhand is witnessing a drastic decrease in spring discharge which leads to scarcity of drinking water for Himalayan inhabitants. This study uses a novel approach to assess the surface-subsurface interaction of water, pivotal for estimating the status of spring discharge. Hydrological modelling has been used to quantify the diminishing discharge of spring and their associated factors, including changes in land practises and precipitation patterns. The coupling of the soil water assessment tool (SWAT) and MIKE hydro NAM model was proposed in the study to assess the decreasing discharge for an ungauged watershed. The model performance evaluated between the SWAT and the MIKE hydro NAM model indicated a very good index of agreement (d = 0.81). Field-based spring discharge investigations were conducted in almost all watersheds in the study area. The MIKE hydro NAM model showed a good index of agreement (d = 0.79) with the observed spring discharge. Further, the geographically weighted regression (GWR) technique was applied over 17 driving factors based on hydrological parameters including topography, structural geology, land use/land cover and future annual precipitation (till 2030) under the RCP 4.5 scenario to understand the status of diminishing discharge of springs. The accuracy between the observed spring discharge and the GWR indicated a good index of agreement (d = 0.86). The results indicate that annual spring discharges will be significantly reduced up to 50% from 1975 to near future (2030), posing a threat to the drinking water supply. The proposed approach is replicable and scalable for ungauged river systems of the Himalayas. The study demonstrates the methods such as trend analysis of precipitation behaviour, land use change dynamics using remote sensing techniques, structural geological investigation through field measurements and hydrodynamic modelling are important for understanding surface-subsurface interaction. The findings of the study help to identify the critical recharge zones for implementing the spring revival and rejuvenation programmes.
https://onlinelibrary.wiley.com/doi/abs/10.1002/hyp.14582
