Numerical groundwater flow modelling under changing climate in Abaya–Chamo lakes basin, Rift Valley, Southern Ethiopia

Ongoing socio-economic developments and climatic change have been pressurizing the groundwater resource availability in the Abaya–Chamo lakes basin, Ethiopian Rift valley. The primary goals of the present study are: (1) to simulate the groundwater gradient and flow direction, (2) to calculate the groundwater balances and flux of the sub-major river basins under the water budget code of the MODFLOW, and (3) to predict the future groundwater levels of the lake's basin under a projected changing climate. The numerical groundwater flow of the Abaya–Chamo lakes basin aquifer system is simulated using the USGS three-dimensional finite-difference groundwater flow model MODFLOW-2005 with Block centered flow packages (BCF). The following datasets, such as aquifer properties, geology, recharge, discharge, topography, etc., were used to simulate the present model. The calibrated steady-state groundwater flow modeling simulation of the Abaya–Chamo lakes basin also confirmed the through-flow system in terms of groundwater gradient and flow direction, on which groundwater flow happens from the plateau toward the floor into the lakes from both directions with a high gradient exist in the escarpment. The present study provides a sound foundation for modern scientific direction in water resource evaluation by establishing integrated surface and groundwater models that change climatic conditions for sustainable water resources management.