典型饮用水源地非点源污染的分布式模拟——以滁州市城西水库为例

城西水库（现改名西涧湖）是滁州市唯一地表水源，非点源污染已成为其水质污染的重要原因。基于土地覆被格局，依据非点源污染物质的产生、截留、汇流过程，构建了模拟每个栅格上污染物质向受纳水体的输出贡献量和被各种土地覆被截留量的物理过程模型。以磷素为例，对城西水库流域进行模拟。结果表明： 2000和2010年，流域向城西水库输出总磷量分别达到2 58038和2 46120 kg。库体西北部的市农科所、城郊居委会、水产研究所等地对水质危害最大。多数磷素在向库体的运移过程中被各类土地覆被有效的截留，总量在2000和2010年分别达到5 77449和5 42236 kg，占流域磷素总负荷的691%和68 8%。由于目前土地覆被布局的不尽合理，林地和草地对磷素的截留能力未能充分发挥。建议在流域水文敏感区布设林草缓冲带，将有效减少水库磷素的接纳量

DISTRIBUTED NONPOINT SOURCE POLLUTION MODELLING——A CASE STUDY ON WATER SOURCE AREAS PROTECTION IN THE CHENGXI RESERVOIR，CHUZHOU CITY

The Chenxi Reservoir (now Xijian lake) is a unique surface water resource of Chuzhou city.The nonpoint source pollution is the main reason of its water quality deterioration.Distributed nonpoint source pollution modelling in its watershed can identify the critical source areas.It can be taken as the grounds on making decision for protection of drinking water source and control of source pollution in the Chenxi Reservoir. Based on the pattern of Land use/cover (LULC),a model was established to simulate the quantity of nonpoint source pollution exported to aquatic environment and retained by the different LULC on each cell according to these theories that the generation,retaining,flow accumulation and relative source and sink theory of nonpoint source pollution.This study chose phosphorus as an example and did a simulation in the watershed of the Chenxi Reservoir.The results showed that the region beside the riverway in the middle of watershed and the Xiaosha River feeding the reservoir were the high hydraulic connectivity area.In 2000 and 2010,total phosphorus exported to the reservoir by LULC in watershed was 2 58038 and 2 46120 kg/a,respectively.The Institute of Agricultural Science,Chengjiao Residents Committee,the Institute of Aquaculture as well as Taiping Village in northwestern of watershed were the critical source areas (CSA).Most of the exported phosphorus were effectively retained by the different LULC in the process of flow accumulation.In 2000 and 2010,total phosphorus retained by LULC in watershed was 5 77449 and 5 42236 kg/a,respectively.It occupied 691% and 68.8% of the total phosphorus loads.The abilities of phosphorus retention by forestland and grassland were not brought into full play due to the irrational distribution of existing LULC.Although the ability of phosphorus retention by paddy fields is relative weak,the average phosphorus retained was the highest because the paddy fields were mainly distributed in the hydrological sensitive area (HSA).Total phosphorus retained by the paddy fields in watershed was 3 84724 and 3 54168 kg/a,respectively.It occupied 666% and 653% of the total phosphorus retention. Trees and shrubs should be planted along the shore and on the intersection of runoff.The grassland should have a banding distribution nearby the gentle slope of farmland.Therefore,it can largely improve the ecosystem services efficiency of forestland and grassland by setting vegetation buffer zones.