在分布式水文模型ESSI基础上，以日为时间尺度，以DEM栅格单元为基本模拟单元，构建了区域尺度的长时期连续模拟的分布式非点源有毒污染物模型ESSI-2.该模型具有产流、汇流、产沙、汇沙、有毒污染物分解、输移及汇聚等完整的模拟功能.模型中根据降雨特征和下垫面特征之间的动态对比关系动态选取产流方式；同时采用RUSLE模型计算泥沙剥蚀量，并根据产沙量与径流泥沙输移能力的对比计算泥沙输出量.该模型充分描述了农药的降解、吸附、下渗、输移、汇聚等过程，可以对农药的输移过程和时空分布进行模拟分析.最后，以临沂流域为研究区，对模型进行了案例分析.计算结果表明，该模型适用于临沂流域，能够分析其土壤侵蚀及农药输移过程.%Based on the distributed hydrologic model ESSI,a distributed non-point pesticide pollution mod⁃el, ESSI-2, has been developed by adding sediment component and pesticide-leaching component. ESSI-2 model takes each regular grid of the DEM dataset as a simulating unit and daily period as time step. ES⁃SI-2 model is able to describe the processes of rainfall-runoff, soil erosion, sediment as well as pesti⁃cide-leaching,and it can be used to estimate the long-term water resources. Dynamic runoff mechanism is used in the model,taking into account the runoff as a dynamic process that depends on weather and sub⁃surface conditions. RUSLE model is used to calculate the soil detachment and sediment yield depending on the soil detachment and sediment transport capacity. ESSI-2 model describes the processes of degradation of pesticides, pesticide absorption, pesticide infiltration, as well as pesticide-leaching, so that it can be used to simulate pesticide-leaching and research on temporal and spatial distribution of pesticide. We ap⁃plied our model to Linyi watershed for simulation and validation. The results show that the model is applica⁃ble in Linyi watershed and can be used to research soil erosion and pesticide-leaching.
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