نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم و مهندسی خاک، دانشکدۀ کشاورزی، دانشگاه کردستان، سنندج، ایران
2 گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه کردستان، سنندج، ایران
3 سازمان جنگل‌ها، مراتع و آبخیزداری، اداره کل منابع طبیعی و آبخیزداری استان کردستان، سنندج، ایران
4 گروه آبخیزداری، دانشکده کشاورزی و دامپزشکی، دانشگاه آزاد اسلامی واحد سنندج، سنندج، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Soil erosion by water is a global threat to the environment which negatively affects soil and water quality. Soil erosion modeling is an efficient method to simulate soil erosion, to identify sediment source areas, and to evaluate soil conservation measures. In this study the Soil and Water Assessment Tool (SWAT) was used to model runoff and sediment in Gawshan dam watershed in west of Iran. For this purpose, climatic data obtained from a period of 11 years, from January 1, 2005 to the end of December 2015, from the stations of Bavale, Ravansar, Sanghor, Ghorve, Sanandaj, Kermanshah, Kangavar and Kamiyaran were used. We used two different approaches for estimating of model parameters. In the forward deterministic approach model parameters were independently derived from digital elevation model (DEM), soil and land use maps and climate data, whereas in the inverse stochastic approach model calibration were performed by sensitive model parameters using Sequential Uncertainty Fitting (SUFI-2), which is one of the programs interfaced with SWAT, in the package SWAT-CUP (SWAT Calibration Uncertainty Programs). Model performance was evaluated using the coefficient of determination (R2) and Nash-Sutcliff efficiency (NS) for forward approach and P factor and R factor for inverse approach. Results showed that in the forward approach, based on monthly data (2008-2013), the model performance was satisfactory for runoff (R2=0.66; NS=0.63) and fair for sediment (R2=0.42; NS=0.3). However, model prediction improved for both runoff (R2=0.94; NS=0.83) and sediment (R2=0.61; NS=0.53) when they were averaged on monthly basis. Calibration of the model parameters improved its performance for runoff (P factor>0.6; R factor<1) and sediment (P factor>0.4; R factor <1). These results demonstrated that the SWAT has the potential to be used as a decision making tool for Gawshan dam watershed management.
کلیدواژه‌ها [English]
Soil erosion by water is a global threat to the environment that negatively affects soil and water quality. Soil erosion modeling is a promising method to simulate soil erosion to identify sediment source areas and to evaluate soil conservation measures. The objective of this study was to use the Soil and Water Assessment Tool (SWAT) to model runoff and sediment in Gawshan dam watershed in west of Iran.
The input data required to implement the SWAT include digital elevation map (DEM), soil map, land use/land cover map and climate data. DEM was used to delineate the watershed boundary, divide it into different sub-basins, and prepare slope and flow network maps. It had a resolution of 30 meters which obtained from the United States Geographic Survey. Soil map was prepared from land survey and Landsat ETM remote sensing data. The soil physical and chemical parameters required to run SWAT were measured in the different soil units, and its spatial distribution was coincident with the soil unit boundaries. The climatic data obtained from a period of 11 years, from January 1, 2005 to the end of December 2015, from the stations of Bavale, Ravansar, Songhor, Qurveh, Sanandaj, Kermanshah, Kangavar and Kamyaran were used. The two different approaches for estimating the model parameters have been used. In the forward deterministic approach model, parameters were independently derived from digital elevation model (DEM), soil and land use maps and climate data, whereas in the inverse stochastic approach model, calibration were performed by sensitive model parameters using Sequential Uncertainty Fitting (SUFI-2), which is one of the programs interfaced with SWAT, in the package SWAT-CUP (SWAT Calibration Uncertainty Programs). Model performance was evaluated using the coefficient of determination (R2) and Nash-Sutcliff efficiency (NS) in the forward approach and P and R factor in the inverse approach.
Results showed that in the first approach, based on monthly data (2008-2013), the model performance was satisfactory for runoff (R2=0.66; NS=0.63) and fair for sediment (R2=0.42; NS=0.3). However, model prediction improved for both runoff (R2=0.94; NS=0.83) and sediment (R2=0.61; NS=0.53) when they were averaged on the monthly basis. Calibration of the model parameters improved its performance for runoff (P factor>0.6; R factor<1) and sediment (P factor>0.4; R factor <1). One of the reasons of the model weakness in simulating runoff is its uncertainty in simulating snow melting or the lack of information about water withdrawal from aquifers in the study area. Also, the lower efficiency of the model in simulating the sediment compared to the runoff can be attributed to the greater uncertainty of the measured data of the sediment compared to the runoff. Overall, these results demonstrated that the SWAT has the potential as a decision-making tool in the Gawshan dam watershed management.
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