A geomorphology-based integrated stream-aquifer interaction model for semi-gauged catchments

Many of the existing stream-aquifer interaction models available in the literature are very complex with limited applicability in semi-gauged and ungauged catchments. In this study, to estimate the influent and effluent subsurface water fluxes under limited geo-hydrometeorological data availability conditions, a simple stream-aquifer interaction model, namely, the variable parameter McCarthy-Muskingum (VPMM) hillslopestorage Boussinesq (hsB) model, has been developed. This novel model couples the VPMM streamflow transport with the hsB groundwater flow transport modules in online mode. In this integrated model, the surface water-groundwater flux exchange process is modelled by the Darcian approach with the variable hydraulic heads between the river stage and groundwater table accounting for the rainfall forcing. Considering the exchange fluxes in the hyporheic zone and lateral overland flow contribution, this approach is field tested in a typical 48-km stretch of the Brahmani River in eastern India to simulate the streamflow and its depth with the minimum NashSutcliffe efficiency of 94% and 88%; the maximum root mean square error of 134 m3/s and 0.35 m; and the minimum index of agreement of 98% and 97%, respectively. This modelling approach could be very well utilized in data-scarce world-river basins to estimate the stream-aquifer exchange flux due to rainfall forcings.