LAUSR

Abstract Study Region Lake Basaka is a volcanically dammed closed basin-type lake located within Matahara plain area, northern part of the Main Ethiopian Rift Valley (MERV) region. The MERV is situated within the Great East African Rift Valley (GEARV) region, which is hydrgeologically unstable and complex. Study Focus In the current study, a conceptual lake GW flux model was systematically formulated, solved, calibrated and validated. Then, the surface water-groundwater interaction was quantified and a mathematical relationship developed. New Hydrological Insights for the region The predictive performance of the developed GW flux model was very good both during the calibration and validation periods, which confirms the validity and acceptability of the developed GW flux model and the simulated time-series lake level. The net GW fluxes to the lake were variable during the different hydrologic periods considered. The GW flux to the total inflow increased from 15% (1960s) to about 54% (2000s). Overall, GW flux plays a leading role in the hydrodynamics, existence and expansion of Lake Basaka.