Kinematic runoff and erosion model efficiency assessment for hydrological simulation of semi-arid watersheds

Abstract

Hydrologic modeling of semi-arid watersheds is imperative for the development of appropriate water and soil conservation plans. In the current study, the efficiency of Kinematic Runoff and Erosion model-version 2 (K2) model was used to evaluate water discharge and sediment load simulation of Bar watershed, located in the north-eastern part of Iran. The K2 model relies on the kinematic wave approach to route surface flow. The drainage network and planes are discretized to represent the watershed. In order to evaluate the model, 3 and 2 reported rainfall incidents in various dates were selected for K2 calibration and validation, respectively. The multiplier approach was employed for model calibration. The results of sensitivity investigation revealed that the soil parameters Ks-CH, n and G had the highest impact on flow discharge. Through the calibration process, the Nash-Sutcliff Efficiency and the coefficient of determination as fitting metrics for water discharge simulation (based on event #2, dated 16 March 1992) were estimated to be 0.78 and 0.88, respectively. According to the aggregated measure, the highest K2 efficiency was obtained during the calibration process based on event #2. Other storm events were resulted in a good simulation, as well. During the validation process, K2 simulation (based on event #4, dated 07 March 1991) led to the Nash-Sutcliffe Efficiency and R² of 0.77 and 0.71, respectively. The K2 calibration for sediment load simulation was performed through the alterations of the Pave and Rainsplash parameters. The bias percentages between simulated and observed total sediment loads based on events #2 and #4 were 5% and 16%, respectively. Conclusively, the K2 model showed an acceptable robustness in the hydrological simulation of Bar watershed as a representative semi-arid watershed in northeast of Iran.