基于MIKE21的密云水库总氮预测研究

Prediction of total nitrogen in Miyun Reservoir based on MIKE21

密云水库是北京市重要的饮用水水源地,近年来密云水库总氮呈现升高趋势,潮河和白河入库总氮总体呈现逐年上升趋势。研究利用MIKE21软件,基于水动力和水质模型耦合,采取不同策略的情景假设,对密云水库总氮进行研究,基于2018年量化不同策略对密云水库总氮的影响程度,提出最优方案。结果表明:1)通过潮白河流域生活源治理,库区总氮年均值降低0.024mg/L,8年后可达到Ⅲ类水质要求,29年后可达到Ⅱ类水质要求。2)通过潮白河流域生活源、农业源治理,库区总氮年均值降低0.059mg/L,3年后可达到Ⅲ类水质要求,12年后可达到Ⅱ类水质要求。3)通过潮白河流域生活源、农业源治理、河道生态建设,库区总氮年均值降低0.118mg/L,2年后可达到Ⅲ类水质要求,6年后可达到Ⅱ类水质要求,为最优方案。4)库滨带使库区总氮年均值升高0.012mg/L,捕鱼使库区总氮年均值降低0.0002mg/L,降雨可使库区总氮年均值升高0.074mg/L。

Miyun Reservoir is an important source of drinking water in Beijing.In recent years,the total nitrogen in Miyun Reservoir showed an increasing trend,while the total nitrogen in Chaohe river and Baihe river showed an increasing trend year by year.Based on the coupling of hydrodynamic model and water quality model,MIKE21 software was used to study the total nitrogen of Miyun Reservoir based on scenario assumptions of different strategies.Based on the quantification of the influence of different strategies on the total nitrogen of Miyun Reservoir in 2018,the optimal plan was proposed.The results showed that:1)Through the treatment of living sources in the Chaobai river basin,the annual average value of total nitrogen in the reservoir will be reduced by 0.024 mg/L,and it can reach the water quality requirements of Class III after 8 years,while reach the water quality requirements of Class II after 29 years.2)Through the treatment of living sources and agricultural sources in the Chaobai river basin,the annual average value of total nitrogen in the reservoir will be reduced by 0.059 mg/L,and it can reach the water quality requirements of Class III after 3 years,while reach the water quality requirements of Class II after 12 years.3)Through the treatment of living sources,agricultural sources and river ecological construction in Chaobai river basin,the annual average value of total nitrogen in the reservoir will be reduced by 0.118 mg/L,and it can reach the water quality requirements of Class III after 2 years,and reach the requirements of Class II water quality after 6 years,which is the optimal solution.4)The reservoir waterfront zone increases the annual mean value of total nitrogen by 0.012 mg/L,and fishing reduces the annual mean value of total nitrogen by 0.0002 mg/L,while rainfall increases the annual mean value of total nitrogen by 0.074 mg/L.