降雨和土地利用对流域非点源污染的影响——以滇池流域为例

Study on effects of rainfall and land use on watershed non-point source pollution:case of Dianchi lake basin

基于污染排放负荷计算的非点源污染特征识别是开展滇池流域非点源污染控制的重要基础,并在当前流域气候变化和城镇化用地扩张的背景下显得尤为重要。基于流域分布式非点源模型IMPULSE,选择2008年和2014年开展滇池流域入湖非点源污染排放负荷模拟,从负荷量和负荷组成2个方面对比分析降雨和土地利用变化对流域非点源污染负荷排放特征的影响,并比较了4种水土流失控制措施的污染负荷削减效果。结果表明:(1)2014年流域TN、TP和COD入湖排放量比2008年分别增加23.87%,29.19%和1.65%。(2)各因子对入湖非点源污染负荷的影响排序为降雨>土地利用>农业结构及农村人口。降雨和农业结构及农村人口的变化均使入湖非点源污染负荷增加,而以城镇用地扩张为主要特征的土地利用变化减少了入湖非点源污染负荷。(3)水土流失是流域入湖非点源污染负荷贡献率最高的污染源,2014年TN和TP入湖负荷中城市面源比重略有提升,COD入湖负荷中城市面源的比重由16.44%提高至38.63%。(4)退耕还林在3种单项措施中的负荷削减效果最好,而退耕还林和坡地改梯田组合措施的TN,TP和COD负荷削减率分别为37.20%,37.73%和11.91%。研究结果对于科学制定流域非点源污染控制策略具有重要的支撑意义。

The identification of non-point source pollution characteristics based on the calculation of pollution emission load is the basis for non-point source pollution control in Dianchi Lake Basin,and is particularly important under the background of climate change and the expansion of urban land use. Based on IMPULSE,a distributed watershed non-point source pollution simulation model,this study carries out the simulation of total non-point source pollution emission load into Dianchi Lake in 2008 and 2014,respectively. The total non-point emission load and the composition of load are compared to identify the effects of rainfall and land use change on non-point source pollution characteristics. The effects of 4 soil erosion control measures on emission load reduction are analyzed. The results show that compared with 2008,the discharge of non-point source TN,TP and COD into the lake in 2014 increased by 23. 87%,29. 19% and 1. 65%,respectively. The ranking of contribution level of each factor to the change of non-point source pollution load in the lake was： rainfall 〉 land use 〉 agricultural structure and rural population. Both of the changes in rainfall and agricultural structure and rural population increased the non-point source load into the lake,while the expansion of urban land use reduced the pollution load. Soil erosion is the most significant pollution source contributing to the non-point source pollution load in the lake. The proportion of urban non-point source in TN and TP load in2014 increased slightly,while the proportion of urban non-point source in COD load increased from 16. 44% to 38. 63%. The simulation results of 4 control measures showed that the load reduction effect of the conversion of cropland to forest performed the best among the three single measures,and TN,TP and COD load reduction rates of the combination of the conversion of cropland to forest and slope land to terraced fields were 37. 20%,37. 73% and 11. 91%,respectively. The research results can provide an important support for the formulation of scientific and effective non-point source pollution control strategies in the basin.