Simulation of streamflow using TOPMODEL in the Upper Save River catchment of Zimbabwe

This paper demonstrates the application of TOPMODEL, a rainfall-runoff model to simulate streamflow of Upper Save River catchment of Zimbabwe based on 2003–2007 hydrometeorological data. The key driver in TOPMODEL, the topographic index was determined using the satellite derived ASTER 30 m DEM. The calibration process (2003–2005 period) gave a Nash-Sutcliffe model efficiency (NS) of 0.77 and a Relative Volume Error (RVE) of 6.2%. Sensitivity analysis of the model showed that the parameters most critical for accurately simulating streamflow were: the soil hydraulic conductivity decay parameter (m), the soil transmissivity at saturation (T0) and the root zone available water capacity (SRmax). The model was validated using 2006–2007 hydrometeorological dataset and a satisfactory model performance was obtained (NS = 0.73, RVE = −8.6%). We deduce that the ASTER DEM can be used to estimate model parameters for simulating streamflow using TOPMODEL in this catchment.