| چکیده انگلیسی مقاله |
Soil and water degradation has been recognized as one of the most serious environmental degradation problems that threatens land productivity and sustainable development. Planning and implementation of appropriated soil and water conservation practices is essential for sustainable utilization of soil and water resources. A suitable method for this task should be fast, economical and accurate and can consider the most important factors and processes affecting hydrology and pollutants’ transport within a watershed. In this study an integrated simulation-optimization framework is developed by coupling the process-based SWAT model and Genetic algorithm for optimal selection and placement of Best Management Practices (BMPs) in the Gharesou River watershed, north-eastern Iran. After model calibration and uncertainty analysis, three pollution quantifying indices including a Load per Unit Area Impact Index (LUAII), a Concentration Impact Index (CII) and a Load Impact Index (LII) were computed for identifying critical areas within watershed. Then, eight BMPs were chosen (following consultation with local experts) for modelling and placement in the critical areas of the watershed. To optimally allocate BMPs (in terms of type and location), a simulation-optimization framework was created in the R programming environment by integrating the SWAT model as BMPs impact predictor and multi-objective genetic algorithm, NSGA-II, as the optimizer. The results of the study indicated that, SWAT performance for hydrologic simulation of the Gharesou watershed is good and for monthly sediment prediction is acceptable. Pollution impact indices identified critical areas that are the source of disproportionately large amount of pollution and so desperate for management interventions. The results of BMPs’ spatial optimization in the critical areas suggest that, cropland conversion to pasture, terracing and grassed waterways are the most effective practices for sediment and nutrient reduction. By implementing BMPs in the optimal areas (or streams) suggested by the simulation-optimization program, the sediment and nutrients loss from upland would reduce by about 25 percent and in the watershed outlet by about 57 percent. The outputs of this study may serve as a quick and accurate guide for targeting soil and water conservation practices in the watershed. The approach and the program developed in this study are easily extendable to other watersheds. |
