Determining the best management practices of non-point pollutants using ArcSWAT model (Case study: Dashte Bozorg catchment)

Document Type : Research Paper


1 Department of Soil Science and Engineering, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran.

2 Associate Professor, Department of soil science, Faculty of Agriculture , Shahid Chamran University of Ahvaz, Iran


The best management practices are solutions to reduce non-point pollution in catchments. In many cases, the use of these solutions requires knowing the features of the watershed and investing in this sector. Accordingly, the use of computer models to simulate real catchment conditions can be an effective way to reduce time and cost. This research aimed to investigate the effect of different management scenarios on non-point source pollution losses in Dashte Bezorg catchment in Iran using the ArcSWAT model. To collect observational data, river water was sampled from September 2020 to June 2021. Calibration data were selected from September to March and validation data from April to June. After identifying critical areas, three non-structural scenarios and five structural scenarios were simulated using the model. The results revealed that the ArcSWAT model provides a good prediction in estimating non-point source pollution loads (nitrate, total nitrogen, and total phosphorus). The "wheat-potato-tomato" and "wheat, rice-wheat, mung bean-wheat" rotation scenarios showed the highest total nitrate and nitrogen loss, while the lowest total phosphorus loss was observed in the "wheat-potato-tomato" rotation. The terracing and buffer strip methods were recognized as the best methods of reducing the load of non-point pollution. The findings showed that the application of management practices in dominant land use and reduc the degree of slope can significantly reduce the non-point source pollution loads.


Main Subjects



The best management practices are methods to reduce non-point source pollution in catchments. The use of these methods requires knowing the features and investing in catchments. Accordingly, the use of computer models to simulate the actual condition of catchments effectively helps to reduce time and cost. The Soil and Water Assessment Tool (SWAT) is a semi-distributed model to estimate nutrient losses in large watersheds.This research has aimed to investigate the effect of different management scenarios on the loss of non-point source pollutions (nitrate, total nitrogen, and total phosphorus) in Dashte Bezorg catchment in Iran using the ArcSWAT model.


Materials and Methods

To collect observational data, river water was sampled from September 2020 to June 2021. Calibration data were selected from September to March and validation data from April to June. SUFI-2 algorithm was applied to sensitivity analysis, calibration, validation, and uncertainty analysis. Critical areas of non-point source pollution loads were also identified, and three agricultural scenarios including residue management, tillage, and crop rotation were applied. Furthermore, five structural scenarios were simulated including grassed waterway, vegetated buffer strip, strip cropping, contouring, and terracing. The effect of different scenarios on nitrate, total nitrogen, and total phosphorus losses in the catchment was investigated.



The values of R2, NS, and BIAS statistical indices for the monthly nitrate were 0.82, 0.82, and -3.8 for the calibration period and 0.99, 0.99, and -2.9 for the validation period, respectively. For total nitrogen, R2, NS, and BIAS were 0.92. 0.9 and 4.3 for the calibration and 0.9. 0.7 and -18.3 for the validation, respectively. For total phosphorus, R2, NS, and BIAS were 1.00, 1.00, and -1.8 for the calibration; and 1.00, 1.00, and 0.5 for validation, respectively. The results showed that the ArcSWAT model provides a good prediction in estimating non-point source pollutant loads. The "wheat-potato-tomato" and "wheat, rice-wheat, mung bean-wheat" rotation scenarios showed the highest nitrate and total nitrogen loss, while the lowest total phosphorus loss was observed in the "wheat-potato-tomato" rotation. The highest reduction of nitrate loss in the no-tillage and minimum tillage scenarios were obtained under rotation number 3 by 2.76 and 2.61 percent, respectively. The amount of total nitrogen loss in no-tillage and minimum-tillage scenarios under rotation number 3 was reduced to 2.21 and 2.08%, respectively. The methods of terracing and vegetated buffer strips were recognized as the best strategies for reducing non-point pollution loads. However, other structural methods were also effective.



This study has shown that identifying critical areas can be a suitable strategy for implementing management practices in those areas. The application of management practices in dominant land use can significantly reduce the non-point source pollution loads.

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