基于SWAT模型的三峡库区大流域不同土地利用情景对非点源污染的影响研究

非点源污染对三峡库区流域的水环境污染起到主导作用。本文将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中,以2005年土地利用现状为基准设定了6种土地利用情景,定量分析了不同土地利用措施对非点源污染的控制效果。首先采用三峡库区流域2002—2008年的水文、水质实测数据对建立的SWAT模型进行率定与验证,径流、泥沙、营养盐的评价指标ENS均达到令人满意的效果,表明SWAT模型应用于三峡库区流域是可行的。不同土地利用情景的非点源影响模拟结果表明,通过退耕还林措施将25°、15°、6°以上的耕地转化为林地可达到较好的非点源污染消减效果,考虑库区地处贫困山区,25°以上耕地退耕还林更为经济、可行;相同区域的草地转化为林地所产生的非点源污染要远远小于转化为耕地而产生的污染物,因此应严格控制自然植被退化为耕地的现象发生,否则会严重加剧库区污染状况;库区扩大林地范围的方案要有计划性、针对性,可在减少坡耕地的基础上进行,该措施能最大限度地减少库区非点源污染。本研究所得结论为政府科学合理的制定三峡库区流域非点源污染控制方案提供了重要科技支撑。

Research on Management of Non-point Source Pollution with Land Use Changing in Three Gorges Reservoir,Macro-scale Watershed Based on SWAT

This paper applied SWAT（Soil and Water Assessment Tool） model into the macro-scale watershed,with Three Gorges Reservoir（TGR） area as a case study.Effect of land use changes on non-point sources（NPS） pollution in TGR watershed was quantitatively analyzed on six scenarios designed with the baseline in 2005.Firstly,the SWAT model was calibrated and validated using the monitoring data during 2002—2008,with values of R2 and ENS（Nash-Suttclife efficiency） are satisfying,indicating this model performing well in simulating the runoff and yields of sediment and nutrients.After that,the calibrated SWAT model was used to simulate on six different land use scenarios and examine the effects of land use changes on the NPS pollution control in the watershed.The results showed that the slope farmland contribute dominantly to the NPS pollution in terms of yields of sediment,TN and TP.If the farmland,especially above the slope of 25,is changed into woodland,a better control and reduction of the NPS pollution could be achieved.On the contrary,the reverse process would aggravate NPS pollution seriously.This study provides a good understanding of the interactions between land use and NPS pollution,which is helpful for making sound decisions.It could help reducing the NPS pollution effectively and thus play a significant role in improving water quality of the TGR watershed to change the land use pattern and implement alternative management practices.