Simulation of runoff and sediment using the WetSpa model

Since catchment scale measurement of meteorological and hydrological factors affecting on the basin response in the form of runoff generation and sediment production is not feasible, study of governing processes under a rainfall-runoff modeling framework is necessary. In this reaserch, to understand the relationship between runoff and sediment production in Beheshtabad Basin, and generalizing the results to Alej Watershed a six years daily simulation was performed using a distributed model called WetSpa. For this purpose the basic maps and hydrologic data including peak discharge and hydrographs were used. Spatial distribution of hydrological processes was taken into account in the modeling. Moreover, another 6-years time series (unused for parametrization), were used for model validation. The simulation results showed a satisfactory good agreement between modeled both simulated runoff and sediment against observations. The Nash-Sutcliffe model efficiency57.6 for runoff and coefficient of determination 0.59 mean that the sediment-runoff relationship for any rainstorm depends on the dynamic of hydrologic processes. The results of sensitivity analysis for WetSpa model showed that ksnow, ki, kg and kss were ranked as the most sensitive parameters correspondingly. While Krain and Pmax parameters were identified as less influential parameters on the simulated hydrograph. Sensitivity of ksnow and g0 parameters is an indication for the importance of baseflow in Beheshtaba basin and the necessity of paying special consideration for its key role in hydrological modeling.