SWAT模型在三峡库区流域非点源污染模拟的适用性研究

将SWAT(Soil and Water Assessment Tool)模型应用于库区大尺度流域的污染模拟研究,对其进行适用性评价及模拟应用分析。模型校验采用的是2002—2008年的水文月数据及水质水期数据,径流模拟效果最好,评价指标ENS(Nash-Suttclife Efficiency)均在0.9以上;泥沙模拟评价指标ENS在0.46~0.9;营养盐模拟评价指标ENS个别出现了<0.36的情况,但总体模拟效果满足要求。应用SWAT模型对库区降水与地表产流、产沙、营养盐负荷进行了研究。结果表明:库区地表产流与降水的相关性趋势最好;地表产沙与产流、降水的总体趋势一致,但偶尔出现4、5月份地表产沙先于产流出现峰值的情况,这可能是由于春耕对地表扰动后又逢较强降水引起的水土流失;营养盐污染负荷尤其是TP的峰值趋势与地表产流相比,更接近地表产沙趋势。本文还对库区不同土地利用类型的污染负荷做了分析,得到各类土地利用类型的年均污染负荷总量排序及单位面积污染负荷,再次验证了SWAT模型在三峡库区流域的适用性。根据分析结果,库区耕地为非点源污染产出的主要源头,可将耕地耕种措施转变及土地利用类型转换作为库区非点源污染削减的重要手段。

On the applicability of SWAT model to the nonpoint source pollution in the watershed of the three-gorge reservoir

This paper intends to study the applicability of SWAT model to the non-point Source pollution in the watershed of the Three-Gorge Reservoir.The so-called SWAT(Soil and Water Assessment Tool) model is a model we have developed in hoping to be applied and adapted to the macro-scale watershed,in the TGR area as a case study.The said model has been established under the support of the Geographic Information System(ArcGIS) as well as the spatial dataset such as DEM(digital elevation model),land-use map and so on.In our research,we have studied the data of hydrological and water quality in the TGR area from 2002 to 2008 for simulated calibration and validation.On the whole,our simulation proves to be successful,for the indicator ENS(Nash-Suttclife efficiency) for stream flow in most cases was above 0.9,whereas the ENS for sediment was from 0.46 to 0.9 though the ENS for nutrient in some individual cases was less than 0.36.We have also studied the correlation between the precipitation and the surface runoff,sediment load,nutrient load in the TGR area,too.The results of our simulated investigation have shown that the surface runoff and sediment load were both closely related with the precipitation,except that the peak of sediment load took place earlier than that of surface runoff in April or May occasionally.The reason for the sediment situation is perhaps that it is because of the large amounts of the soil loss caused by the tillage and precipitation activities during the season.As to the nutrient load,especially,the TP,the consequence seems also relevant to the sediment load in comparison with the surface runoff.And,finally,we have also analyzed the pollution loads generated by the different landuse types in the area.When we worked out the order of the average pollution load for different landuse situations,we have found that the most serious non-point sources of pollution are the crop fileds in the TGR area.So it is urgent to improve the cultivation measures and change the landuse types so as to reduce the pollution situation.Further studies of the pollutant loads per area of landuse types were also evaluated later,which prove the applicability of SWAT model to the pollution situation research in the TGR area.Thus,it can be concluded that the given model enjoys the scientific support for non-point pollution control in the area.