Quantification of groundwater recharge and its spatio-temporal variability in the Ganga river basin

The reliable quantification of Groundwater Recharge (GR) is essential for efficient and sustainable groundwater resource practices. In this study, the spatio-temporal GR over the Ganga River Basin (GRB) was calculated using six different methods during 2003-2016. The Gravity Recovery and Climate Experiment (GRACE) and water fluxes were utilized as inputs to the GR methods. The GR of individual methods were validated with in-situ measurements, indicating a higher correlation ranged from 0.64 to 0.77. Overall, the GR trend shows an insignificant declining trend with a mean of -0.09 cm yr(-1) for all selected methods. The spatial distribution of GR indicates large heterogeneity in the GRB with a higher recharge in the eastern than the western part. The uncertainty of each method and sensitivity of water fluxes were analyzed. Further, the possible causes of GR change through hydro-climatic variables as well as anthropogenic activities related to irrigation and urbanization were evaluated.