SWAT与MIKE21耦合模型及其在澎溪河流域的应用

SWAT AND MIKE21 COUPLED MODELS AND THEIR APPLICATION IN THE PENGXI WATERSHED

结合SWAT分布式模型研究污染负荷的优势和MIKE21模型对水动力水质先进的模拟技术,构建SWAT与MIKE21耦合模型。根据澎溪河地形、土壤、植被、气象、水文、水质资料,在空间上建立流域SWAT水文单元与MIKE21水动力模型边界的连接,在量值上建立SWAT模型各水文单元污染物负荷输出量与MIKE21模型污染浓度输入量之间的分配关系,研究澎溪河流域输沙量、氮、磷负荷量和水污染。模拟结果表明:2009年3月至2010年3月澎溪河渠马、高阳、黄石、双江大桥4个断面的总氮、总磷浓度和叶绿素a含量的模拟值与实测值具有较好的一致性,澎溪河回水区水质为中营养~中富营养状态,水体氮、磷等营养盐浓度主要受面源污染的影响。SWAT与MIKE21耦合模型可靠性好,适合于流域水污染研究。

This paper combined the SWAT model of advantage on pollution load and MIKE21 model of advantage on water quality simulation to build coupled models.The coupled models overcome the shortcoming of inaccurate simulation of SWAT in river and inadequate hydrologic computing of MIKE21 in watershed.This study established the connection of SWAT HRUs and MIKE21 boundary in space,and the pollutant load distribution relationship between SWAT model and MIKE21 model.The models were applied to study water pollution in the Pengxi watershed,which consist of Donghe,Taoxi,Nanhe,Puli and mainstream sub-watersheds.Based on the data from digital elevation,soil types,vegetation types,meteorology,hydrology,water quality,the Pengxi watershed was divided into twenty five computing sub-watersheds and 225 hydrological response units(HRUs).The SWAT HRUs of five computing sub-watersheds of Pengxi watershed were taken as backwater area,the SWAT HRUs of twenty computing sub-watersheds were considered as the boundary conditions of river terrain grid from MIKE21 model,the SWAT HRUs of two computing sub-watersheds were considered as the point sources of Pengxi river terrain grid from MIKE21 model,and SWAT HRUs of three computing sub-watersheds were considered as the linear sources of Pengxi river terrain grid from MIKE21 model.The simulated results of monthly sediment,phosphorus and nitrogen discharge in 1994-2010 at the Pengxi watershed outlet showed that average annual sediment discharge was 456 million tons;The maximum and minimum annual nitrogen loads were 11 375.58 tons and 3 114.20 tons,respectively.The maximum and minimum annual phosphorus loads were 758.37 tons and207.61 tons respectively.Nitrogen and phosphorus loads were high from July to September,the mean monthly loads of nitrogen and phosphorus in the flood period were 928.67 tons and 173.47 tons,respectively.The nitrogen and phosphorus loads from December to February is low,the mean monthly loads of nitrogen and phosphorus in the dry period were 61.91 tons and 11.56 tons respectively.The simulated results showed that the average concentrations of TP in the sections of Quma,Gaoyang,Huangshi and Shuangjiang bridge were 0.012-0.191mg/L,the average concentrations of TN of four sections were 0.64-3.24mg/L,the average contents of Chla of four sections were 0.19-61.08μg/L.The Pengxi backwater was mesotrophic or meso-eutrophic water type.High concentrations of the TN and the TP were easy to be developed in high water season.The Chla whose concentration was higher than 30ug/L was easy to be developed from March to May.Soil erosion and non-point pollution were important sources of Pengxi backwater eutrophication.The study results showed that the coupled models had high accuracy and reliability,the SWAT and MIKE21 coupled models were suitable for study on watershed pollution.