基于PCRaster的流域非点源氮磷负荷估算

Estimation of nitrogen and phosphorus loads in the Xitiaoxi catchment using PCRaster software

以太湖流域上游的西笤溪流域为研究区,应用动态环境模拟语言PCRaster构建月水文和氮磷营养物质输出模型,分析流域内氮磷输出的时空分布特征。以输出系数法为基础,将分布式水文模型与非点源负荷模型相结合,应用地理信息技术构建基于栅格的非点源污染模拟模型,根据1988～2007年的水文、水质实测数据对模型进行率定和验证,定量分析西笤溪流域非点源污染负荷量与氮磷输出的空间分布。研究结果显示:基于单元网格的月水文模型在该流域具有较好的应用效果,率定和验证期的Nash系数和线性相关系数R2均超过了0.80。应用模型估算西笤溪流域非点源污染2002～2005年总氮年输出量为1670～2035t/a,2002～2007年总磷输出量为102～164t/a。氮磷负荷的空间分布表明以稻麦或水稻/油菜轮作的农田是非点源污染的最主要来源。

A monthly eco-hydrological model is developed to simulate the process of nutrient loading on the Xitiaoxi catchment of southeastern China.The environmental modeling language PCRaster is used in the model development.The eco-hydrological model combines a monthly water balance model with the export coefficient model（MECM） for estimating total nitrogen（TN） and total phosphorus（TP） loads.The spatial-temporal distribution of nutrients loads on the catchment is analyzed.The result shows that the monthly streamflows at both Hengtangcun and Fanjiancun stations are well simulated by the eco-hydrological model as revealed by high values of Nash-Sutcliffe coefficients（R2 0.8）.The simulated TN loads vary from 1670 to 2035 t/a during 2002-2005,which are within the reasonable ranges.For the period 1999-2007,the TP load simulation is from 102 to 164 t/a,which are consistent with the observed values of Hengtangcun station.The spatial distribution of simulated nutrients loads indicates that the dominant sources of pollutions are from rice/wheat or rice/rapeseed lands.The results demonstrate the applicability of MECM in identifying sources of pollutions for water resources and fertilization managements on large-sized catchments.