Subbasin Spatial Scale Effects on Hydrological Model Prediction Uncertainty of Extreme Stream Flows in the Omo Gibe River Basin, Ethiopia

Quantification of hydrologic model prediction uncertainty for various flow quantiles is great importance water resource planning and management. Thus, this study designed to assess the effect subbasin spatial scale on hydrological different quantiles. The Soil Water Assessment Tool (SWAT), a geographic information system (GIS) interfaced model, was used in study. Here, variations within sub-basins Omo Gibe River basin Ethiopia’s Abelti, Wabi, Gecha watersheds from 1989 2020 were examined. results revealed that (1) watersheds, SWAT able reproduce observed hydrograph with more than 85%, 82%, 73% accuracy terms Nash-Sutcliffe efficiency coefficient (NSE), respectively; (2) variation size had no overall simulations. However, reproduction considerably influenced by scales; (3) coarser resulted coverage most observations. finer provided best simulation closer stream pattern; (4) performed much better recreating moist, high, very-high flows it did replicating dry, low, very-low studied watersheds; (5) smaller (towards distributed model) may replicate low flows, while larger lumped enhances high replication precision. crucial investigate peak flows; (6) study, scales found be 79–98% 29–42%, respectively. Hence, worthwhile proper reproducing toward sustainable management floods drought.