基于面源污染削减的三峡库区小流域水塘系统空间配置

Non-point source pollution (NPS) in the Three Gorges Reservoir Area (TGRA) is serious environment problem. Pond system in TGRA cannot effectively reduce NPS load. In this study, Songjiagou watershed with area of 20 km2 is chose to be a research object. In order to reduce NPS load, place and storage capacity of ponds in the watershed should be optimized according to spatial distribution heterogeneity of NPS loss load and water demand. Firstly, hydrologic process of every Hydrologic Response Unit (HRU) and hydrologic effect of pond system should be studied by setting up hydrologic model. Secondly, by modelling sediment and phosphorus migration and their precipitating in ponds, the loss law of sediment and phosphorus in watershed will become clear. At the same time, effect of pond cutting NPS load will be clear. According to the survey of the farmers and historical data, the spatial distribution of agricultural irrigation water requirement can be determined. Based on the above research, the storage capacity and placement of ponds are optimized by non-dominated sorting genetic algorithm II. The capacity and space configuration scheme of the ponds resulted from optimizing can reduce NPS load and guarantee irrigation water requirement. The research results will provide a scientific basis for ponds system planning and construction in TGAR and regions like TGAR. At the same time, the research will provide the reference for controlling non-point source pollution by placing the pond system.

针对三峡库区的面源污染严重、现有的水塘系统不能有效削减面源污染的现实，以库区开县宋家沟小流域(20 km2)为实体，在流域范围内通过合理配置水塘的库容和位置，达到削减流域面源污染的目的。首先，通过建立水塘水文过程模型，明确流域汇水区水文过程及水塘系统的水文效应，然后通过建立泥沙和磷素的流失迁移模型和池塘中的沉淀模型，明确泥沙和磷素的流失规律与水塘系统的面源污染削减效应，再根据农户调查和历史资料确定流域内农业灌溉需水的空间分布，在此基础上，运用非支配排序遗传算法对水塘进行库容优化和位置布局，确定基于面源污染有效消减及灌溉有效保证下可实施的水塘库容与空间配置方案，为实现水塘系统最佳减污、增效，解决三峡库区及有相同地形条件的山地丘陵地区的水塘规划和建设提供科学依据；为治理面源污染的水塘系统的空间布局研究提供参考。

针对三峡库区的面源污染严重、现有的水塘系统不能有效削减面源污染的现实，以库区开州区箐林溪小流域(20 km2)为研究区，在流域范围内通过合理配置水塘的库容和位置，达到削减流域面源污染的目的。首先，基于遥感影像提取了流域的池塘信息，整个流域池塘的分布密度是32口/平方公里，流域中池塘总的汇水区的面积占了整个流域面积的56.5%；通过池塘的淤积实际取样分析，反演的流域的泥沙流失强度为6.14 t ha-1 y-1 到107 t ha-1 y-1，基于WaTEM/SEDEM模拟了池塘对整个流域泥沙流失的影响，整个流域的池塘可以拦截泥沙1029.6×104 t y-1。利用SWAT模型模拟了流域的水文和面源污染（NO3-N和TP）流失过程，池塘可削减洪峰流量26%，当水库和池塘同时存在时，可以削减洪峰流量57%，在没有池塘分布下2012-2017年流域产水量是548mm，当有池塘存时，整个流域的产水量更小，2012-2017年均值是425mm；池塘的存在可以使NO3-N减少21%，TP的流失强度减少了34%，可以看出池塘和水库对P的拦截效应要比对N的拦截效应更强。将优化算法和流域模型模拟耦合起来，运用非支配排序遗传算法对水塘进行库容优化和位置布局，确定基于面源污染有效消减及灌溉有效保证下可实施的水塘库容与空间配置方案，为实现水塘系统最佳减污、增效，解决三峡库区及有相同地形条件的山地丘陵地区的水塘规划和建设提供科学依据；为治理面源污染的水塘系统的空间布局研究提供参考。