基于MIKE11的引排水改善平原河网水环境质量模拟研究

MIKE11-based Simulation Research on Drainage Diversion to Improve the Water Quality of Plain River Networks

调控河道边界出口流量的大小可改变河道内水体流速和流向,从而可有效改善水体水质,改善效果与引排水规模、排水口布局等有关。以宁波市江北镇海平原河网区为例,选取模拟时段2022年10月1日至11月1日,以主要污染物NH3-N为指标,构建MIKE11水质水量耦合模型,考虑出流口泵站出流能力和维持流域最低用水量,通过3个出流口启、闭排列组合,设置出流口流量分别为9、18、24、36 m^(3)/s的28种出流方案,利用构建的水质水量耦合模型模拟分析不同方案下边界出口流量对水体流速及污染物NH3-N的影响,结果表明:①综合水动力水质因素,出流量为18 m^(3)/s时能更好的改善河流水动力条件与水质状况,出流口为24、36 m^(3)/s较大流量时,开放一或两个出流口,河道存在溢流风险,此时需多开启出流口,以保证防洪安全;②模拟后的最优方案可使平均流速达到0.056 m/s,NH3-N平均浓度下降至1.660 mg/L,水质改善率达17.0%,河道水质可从劣Ⅴ类提升至Ⅳ类或Ⅴ类水标准,为河流水动力水质改善提供参考依据。

Controlling the outlet flow rate at the lower boundary of a river can alter the flow rate and direction of the water body,leading to an improvement in the water quality of the river,the improvement effect is related to the scale of diversion and drainage,the layout of the out⁃let,etc.Scientific and rational allocation of water resources is the core of sustainable water resources use.This paper presents a case study of the river network area of Jiangbei Zhenhai Plains,Ningbo,for example,and selects the simulation period from October 1 to November 1,2022,NH3-N as an indicator for the main pollutant,construction of a one dimensional non-constant flow dynamics MIKE11 water quality and water quantity coupling model,taking into account the outflow capacity of the outflow pump station and maintains the minimum water consumption in the basin.The study sets up 28 outflow scenarios with outflow flow rates of 9,18,24 and 36 m^(3)/s through the combination of three outflow opening and closing arrangements.This study aims to simulate the impact of boundary outlet flows on water velocity in various scenarios using a coupled water quality and water quantity model,and analysis of water quality change characteristics.The results show that:①The higher the outlet flow of the basin,the more significant the increase in the flow velocity of the watershed,comprehensive hydrodynam⁃ic and water quality factors,the outflow of 18m^(3)/s can better improve the hydrodynamic conditions and water quality of the river.However,if the flow rate increases to 24 or 36 m^(3)/s and only one or two outlets are opened,the river has the risk of overflow.Therefore,opening more out⁃lets is recommended to ensure flood safety;②the optimal solution after simulation makes the average flow rate of the basin reach 0.056 m/s,the average concentration of NH3-N decreases to 1.660 mg/L,the water quality improvement rate reaches 17.0%,the water quality condition of the river can be improved from poor V to IV or V water standard,the results provide a reference basis for improving the hydrodynamic wa⁃ter quality of the river.