Assesment of Physiographic Characteristics Effect on SWAT Model Performance: A Case Study of Haraz Catchment, Amol, Iran

SWAT model is used to predict the effects of management methods on water cycle, erosion simulation and agricultural chemicals transfer in vast and complex catchment areas. The main objective of this study was to test the SWAT model performance and usage in simulating the runoff flow in areas with different scales. In distributed and semi- distributed models such as SWAT,before calibration, it is necessary to identify parameters that are sensitive to obtain a better output. Therefore, sensitivity analysis was performed using SUFI2 method. In order to evaluate the performance of the model in simulating the runoff flows of different catchment scales, the calibration model was conducted for four stations: Karehsang, Razan, Chelav and Panjab from 1995 to2004 and the model was evaluated from 2005to 2009. To evaluate the ability of the SWAT model in simulating runoff, 3 indices, namely R2, NS, and MSE were used. The results of calibration and validation showed that Karehsang station with an area of 3285 km2. and the coefficients of 0.80-0.87, 0.77-0.75 and 93.20-71.10 had the highest accuracy, respectively. Also, Panjab station, with an area of 130 km2 and the coefficients of 0.68-0.75, 0.55-0.70 and 7.2 67.0 had the lowest accuracy, respectively. The overall results showed that the model has good performance for estimating the runoff.