Hillslope-storage Boussinesq model for simulating subsurface water storage dynamics in scantily-gauged catchments

Limited geo-hydro-meteorological data availability in most of the subsurface water catchments world-wide has constrained the effective surface and subsurface water management. For improved subsurface water modelling in real semi-gauged catchments, the direct-rainfall-recharge (DRR)-based low-dimensional hillslope-storage Boussinesq (hsB) model is enhanced by incorporating saturated phase processes of surface ponding (SP) in agricultural lands, unsaturated zone processes during non-monsoon (dry) period, bedrock leakage (BL) flux between the hillslope-aquifer and underlying confined aquifer, and root-zone water balance (WB) on the basis of precipitation forcing, catchment topography, and land-use/land-cover dynamics. The developed approaches are field-tested by considering the catchment as both semi-gauged regarding limited water table elevation (WTE) data and fully ungauged (no WTE data). The results reveal that the developed WB-SP-BL-based hsB model variant performed the best in reproducing the observed WTE in six experimental wells in the Kanjhari reservoir catchment (125.04 km2) in eastern India with the Nash-Sutcliffe model efficiency > 67%, root mean square error ≤ 0.28 m, and percentage bias of ±2.5% for both the gauged and ungauged scenarios. Conclusively, it is endorsed that accounting for all the hydrological fluxes in the hsB framework would make it amenable for useful prediction of subsurface flow in ungauged and semi-gauged catchments.