A Coupled Boussinesq-McCarthy-Muskingum Modelling Framework for Assessing Stream-Aquifer Dynamics Under Synergistic Impacts of Land Use and Climate Change

As groundwater buffers the impacts of land use and land cover (LULC) and climate change, to alleviate the future water crisis, there is a need to assess the corresponding future impacts. This study advocates a modelling framework based on the coupled Boussinesq-McCarthy-Muskingum model to evaluate the future implications of LULC and climate change on groundwater, surface water, stream-aquifer interaction, and the resulting streamflow regimes. This framework is applied in a data-limited Baitarani River basin in eastern India as an example. The impact assessment was carried out considering three typical scenarios with the model forcings of (i) future climate, based on the eight COREDX experiment-derived regional climate model (RCM) datasets and the static LULC of the base year; (ii) average climate of the base period and future LULC, predicted by the Dynamic Conversion of Land Use and its Effects (Dyna-CLUE) model; and (iii) RCM-derived future climate and the Dyna-CLUE model-predicted future LULC. The results reveal that by 2085, climate change alone would result in an increased water table, whereas the integrated effect of LULC and climate change would decline the water table, and their synergism would also result in a declined water table. The high- and medium-streamflow regimes with the probability of exceedance (POE) ≤ 35% would increase with the increase in the built-up and barren land covers in the future, whereas the low flow (POE ≥ 90%) would decrease by 50% due to the integrated effect of LULC and climate change. The proposed framework can be used in other world-river basins to assess aquifer and river sustainability under future climate and land use scenarios.