基于MIKE 21模型的洋河水库水质模拟

Simulated water quality test and examination of Yanghe Reservoir(Hebei)based on the MIKE 21 model

近年来,由洋河水库富营养化引起的供水安全问题日益突出。为应对洋河水库富营养化问题,基于迁移扩散及对流扩散理论,利用MIKE 21二维水动力模型对其水质进行了模拟。考虑污染物随水流入库及出库过程,分析了在水动力作用下TN、TP、NH3-N随时间迁移扩散的质量浓度变化及分布情况。结果表明：模拟初期污染物以扩散为主,高浓度区域主要集中在入流处,在入流高峰期污染物向整个库区扩散,垂直水库中心线以西出现高质量浓度水域;入流与出流稳定期污染物以降解为主,水库中心水域污染物质量浓度较高。最终模拟得到库区TN质量浓度约为4.5 mg/L,TP质量浓度为0.06-0.075 mg/L,NH3-N质量浓度为0.20-0.25 mg/L;9月水库实测TN、TP、NH3-N质量浓度分别为5.0 mg/L、0.008 mg/L、0.20 mg/L,与模拟结果基本一致。研究表明,8月中旬到9月中旬,洋河水库污染物浓度较高水域极易暴发富营养化,此结论可为洋河水库水质评价、供水安全及污染物治理提供参考。

In order to ensure the water quality of those reservoirs which provide drinking water for the local residents,the present paper has analyzed the actual time-taking and reasons of eutrophication based on the theory of relocation-diffusion and the convection-diffusion. It is just starting from the above needs that this paper has chosen Yanghe Reservoir of Hebei as the case study sample. And,as a matter of fact,we have adopted a 2-D hydrodynamic model of MIKE 21 to simulate the water quality of the aforementioned water area. When taking into account the inflow and outflow process of the pollutants,this paper has gained the concentration variation and distribution of TN,TP and NH3-N under the hydrodynamic conditions. In the initial phase of simulation,the results prove that the pollutants tend mainly to disperse to the surrounding areas of the reservoir,with the high content pollutants concentrated in the inflow area. What is more,at the peak of the inflow moment,the pollutants tend to spread over the whole reservoir,of which the pollutants tend to be more thickly concentrated in the western part to the center line than in other areas. Since the inflow and the outflow are staying stable,the reservoir depends on the self-purification to decompose the pollutants,with the high content concentration rates scattering in the central area of the reservoir. And,finally,the model we have proposed shows that the TN concentration rate turns to be about4. 5 mg/L,whereas the TP concentration turns to be about 0. 06-0. 075 mg/L while the NH3-N concentration— about 0. 20-0. 25 mg/L in the said area. In Sept.,2012,the measured registration shows that the concentration rates of TN,TP and NH3-N turn out to be respectively 5. 0 mg/L, 0. 008 mg/L and 0. 20 mg/L. Therefore,the simulation results prove basically the same as the data observed. In other words,the model that has been established in this paper proves to be reliable. Between the mid-August and mid-September,the eutrophication would be easier to come about with high concentration pollutants in the Reservoir.Thus,the conclusion we have gained can be expected to provide reliable evidence for water quality assessment,and so can the safety water supply and pollutant treatment in the reservoir.