Parameter allocation approach for runoff simulation in an arid catchment using the KINEROS2 hydrological model

The KINEROS2 model was utilized for runoff simulation in the Dehgin catchment situated in the Hormozgan province of Iran. A parameter allocation procedure was used in lieu of parameter optimization. After parameter allocation, the model was able to adequately simulate hydrographs associated with high‐magnitude peak discharge events with the efficiency values between 0.011–0.83 for Nash–Sutcliffe and 0.36–0.98 for Kling–Gupta, but the model did not accurately simulate hydrographs corresponding to low‐magnitude peak discharge events. Although calibration after parameter allocation improved model performance with respect to the simulation of low‐magnitude discharge events, numerical values of the hydraulic conductivity and net capillary pressure as the most sensitive model parameters did not agree with parameters known to be reasonable in the region. So that the value of hydraulic conductivity was decreased from 61 to 55 mm/h in channels and from 3.7 to 1.7 mm/h in planes. The new values are physically reasonable but are not approximately the same as physical values associated with the regional and environmental context of the Dehgin catchment. In this case, the values of the evaluation criteria were obtained between −2.5 and 0.78 for Nash–Sutcliffe and 0.17 and 0.98 for Kling–Gupta. The results of using the HydroPSO package in R to automated calibration of the model, with the value of Nash–Sutcliffe between −0.63 and 0.43, indicated that autocalibration without intelligent and deliberate selection of parameters cannot accurately represent hydrological processes, and therefore should be avoided. Also, the results show that an understanding of the catchment environmental conditions and appropriate allocation of parameters is initially more effective as a first step of the modeling process and thereby contributes to a first‐order characterization of environmental conditions in the catchment.