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This study aims to evaluate water availability under changing climate scenarios in the Woybo catchment, Ethiopia. The bias-corrected outputs of multiple climate models’ ensemble mean were employed for the 2050 and 2080s against the reference period (1976–2005) under representative concentration pathways (RCPs) for both RCP4.5 and RCP8.5 scenarios. A semi-distributed physically based Hydrologic Engineering Center of Hydrologic Modeling System (HEC-HMS) was used to perform rainfall–runoff simulation. The projected rainfall and temperatures of the watershed will increase in the far future. The predictions from ensemble means of multiple climate models indicated that rainfall of the watershed will likely increase by 25% in the 2050s and 19% in the 2080s under RCP4.5 and RCP8.5, respectively. The discharge projection for the ensemble mean of all climate models shows an increment up to 20 and 19% under RCP 4.5 and RCP8.5, respectively, in the 2050s, whereas it will decline up to 15 and 28% in 2080s, under RCP4.5 and RCP8.5, respectively. This research plays a great role to reduce the impacts of changing climate for sustainable water resources management.

Adopting the appropriate method to separate baseflow from stream flow is desirable for future low flow prediction, planning, management of water resources, and nourishing the environment as well. Thus, comparing the baseflow separation method is inevitable unfortunately not studied within the basin. Therefore, in this study, seven recursive digital filters (RDF) and two digital graphical (DGM) methods were compared in rift valley lakes basins. All the methods were calibrated manually with the help of BFI 3.0 tool; the performance of each method was checked by R2 and RMSE, taking the separation with maximum R2 and minimum RMSE were taken as appropriate separation method and (Baseflow Index) BFI was calculated by using the baseflow from the suitable method for each catchment. The outcomes of baseflow separation indicate that two methods (exponentially weighted moving average (EWMA) and Lynie-Holick) performed better than the other seven methods; unlikely, local minimum and one parameter methods perform less by both R2 and RMSE. Therefore, these comparisons could possibly elucidate the baseflow prediction in the majority of catchments. Subsequently, existing and forthcoming water resource improvement attempts may employ this estimation approach for low flow forecasting, baseflow trend analysis, as well as planning and designing water resources projects.