Evaluating SWAT model for streamflow estimation in the semi-arid Okavango-Omatako catchment, Namibia

A semi-distributed hydrological model was used for runoff estimation in the Okavango-Omatako catchment Namibia. The configured a 31-year period from 1985 to 2015. Subsequently, calibration and validation processes followed using SUFI-2 algorithm. For evaluating simulation, two methods were used: i. prediction uncertainty measured by P-factor R-factor ii. Model performance indicators, that is, Nash-Sutcliffe Efficiency (NSE), Coefficient of determination (R2), Percent bias (PBIAS), Residual variation (RSR). achieved 0.77 0.68 while attained 1.31 1.82 validation, respectively. following indicators evaluate through results respectively; NSE with 0.82 0.80, R2 0.84 0.89, PBIAS achieving -20≤PBIAS≤-1.1 RSR performing 0.42 0.44. All indices very good ratings apart which rated as satisfactory. semi-arid characteristics together relatively flat terrain features justified need evaluation discharge data our study region. SWAT demonstrated reasonable modelling streamflow high low flows adequately captured. Consequently, this necessary further investigations into impacts climate change on scarce water resources highlighting challenges applications area climatic regime other similar regions globally improvements.   Key words: Stream flow, catchment, semi-arid, SWAT, SUFI-2, calibration, TanDEM-X, Okavango,