Hydrological responses to land use and land cover change and climate dynamics in the Rift Valley Lakes Basin, Ethiopia

Abstract

Due to the rapid socio-economic development in the Ethiopian Rift Valley basin, the pressures on water resources are increasing. To understand the change of spatio-temporal water fluxes, the hydrologic model SWAT+ (Soil and Water Assessment Tool+) was applied to five selected watersheds within the basin. With regards to the objective functions, Kling–Gupta efficiency (KGE: 0.68–0.84), the Nash–Sutcliffe efficiency (NSE: 0.61–0.73), percent bias (PBIAS: 3.4 to 1.4), and RMSE-observations standard deviation ratio (RSR: 0.52–0.69), the SWAT+ model performed very well for daily streamflow in all watersheds. The change in water balance components indicated a considerable spatial variation of water fluxes in the watersheds. Precipitation, evapotranspiration, and infiltration have generally decreased, but surface runoff has increased in the interference period compared to the baseline period. The spatial distribution of rainfall (40 to 10%), evapotran-spiration (20 to 5%), surface runoff (7.8–13.1%), lateral flow (4.47 to 16.5%), and percolation (3.3 to 10.2%) varied. The changes in the hydrologic system within the basin are greatly attributed to the combination of land use and land cover change due to rapid population growth and climate variability.