基于MIKE21模型的沙河水库水量水质响应模拟研究

Simulation on water quantity and quality of Shahe Reservoir by MIKE21 model

沙河水库是北运河上游水系重要的汇,同时也是多源污染的重要聚集处,呈现非常规水源补给的缓滞水体特征,作为城市景观水体,对水环境和水生态要求较高,因此,沙河水库的治理对下游的水质改善至关重要.为进一步全面提升沙河水库水环境质量,以昌平区沙河水库为研究区域,采用MIKE21构建库区二维水动力水质模型,对沙河水库水量水质变化情况进行了模拟,并验证了模型参数.在验证模型参数的基础上,分别模拟了水位调控方案与水质改善方案.水位调控方案模拟结果显示,沙河水库管理调控水位在34.0~35.2 m之间时,0~1.5 m水深区间占面积最大,物种最丰富,是最合适的水位调控区间.水质改善方案模拟结果显示,当对溢流污染进行全部截流时,2018年6月1日—10月1日沙河闸考核断面CODCr平均减少28.44 mg·L^-1,NH3⁃N平均减少0.83 mg·L^-1,TP平均减少0.25 mg·L^-1,相比于现状模拟数据,降幅分别达到72.2%、59.3%、67.7%,CODCr已全部达到Ⅳ类考核标准,NH3⁃N仅有1 d超标,TP超标天数降低至7 d.在全部截流的基础上,配合湿地净化措施,2018年6月1日—10月1日沙河闸考核断面CODCr、NH3⁃N已全部达到Ⅳ类考核标准,仅TP有1 d超标,超标日期为8月12日.

Shahe Reservoir is an important sink of the upper canal system of the North Canal,and it is also an important gathering place for multi⁃source pollution.It presents the characteristics of slow water supply from unconventional water sources.As a city landscape water body,it has high requirements on the water environment and water ecology.Reservoir management is critical to the improvement of downstream water quality.In order to further improve the water environment quality of Shahe Reservoir,taking Shahe Reservoir in Changping District as the research area,MIKE 21 FM was used to construct a two-dimensional hydrodynamic water quality model of the reservoir area.The changes of water quality and water quality in Shahe Reservoir were simulated and the model parameters were verified.Based on the model verification parameters,the water level regulation scheme and water quality improvement scheme were simulated separately.The simulation results of the water level control plan show that:when the management and control water level of the Shahe Reservoir is 34.0~35.2 m,the 0~1.5 m water depth interval takes up the largest area,and the species is the most abundant,which is the most suitable water level adjustment interval.The simulation results of the water quality improvement plan show that when all the overflow pollution was intercepted,the average concentration of CODCr in the assessment section of Shahe Gate decreased by 28.44 mg·L^-1,NH3⁃N decreased by 0.83 mg·L^-1,and TP decreased by 0.25 mg·L^-1 from June 1,2018 to October 1,2018,compared with the current simulation data,the reductions have reached 72.2%,59.3%,67.7%.CODCr has all reached the category IV assessment standard while NH3⁃N has exceeded the standard for only 1 day,and the number of days for TP has exceeded 7 Days.On the basis of all river closures,in conjunction with wetland purification measures,from June 1,2018 to October 1,2018,the assessment section of the Shahe Gate CODCr and NH3⁃N have all reached theⅣassessment standard.Only TP has exceeded the standard for one day.The date is August 12.