基于MIKE11的江南平原河网动态水环境容量分析

Dynamic water environment capacity of river network in Jiangnan Plain based on MIKE11 model

传统水环境容量以90%保证率下的设计枯水流量作为计算条件,存在水文计算条件单一、计算结果固定等局限性,不能很好地表征水流方向不定、产汇流过程复杂、污染负荷分散的江南平原河网的水环境容量。以宜兴市官林镇水系为研究对象,基于MIKE11水质模型计算河网控制单元水环境容量,以探究江南平原河网水环境容量的动态特性。结果表明:MIKE11模型法下官林控制单元COD、氨氮和总磷月均水环境容量为-152.80、0.92和-1.69 t;桐梓控制单元COD、氨氮和总磷月均水环境容量为220.23、4.49和1.45 t;皇新控制单元COD、氨氮和总磷月均水环境容量为15.42、0.90和0.14 t,呈现出明显动态特征。代表河道水环境容量与流量流速等水文要素有密切关系,市镇级等水质达标河道水环境容量与流速呈正相关,村级等未达标河道水环境容量与流速呈负相关。本研究可为平原河网水环境保护与管理提供重要参考和新思路。

Water environment capacity calculated using traditional methods has limitations such as single hydrological calculation conditions and fixed calculation results,as the low water flow rate is normally designed at a 90%guarantee rate.Thus,the traditional methods cannot well characterize the water environment capacity of Jiangnan Plain river network which is with unpredictable flow directions,complicated hydrological processes,and dispersed pollutants.Aiming to help reveal the dynamic characteristics of water environment capacity of river network in Jiangnan Plain,this study took the river system of Guanlin Town,Yixing City as an example to calculate the water environmental capacity of the river network control unit based on the MIKE11 water quality model.The results were that an obvious dynamics was observed for the water environment capacity via the MIKE11 model method and the monthly average water environment capacities were-152.80 t for COD,0.92 t for ammonia nitrogen and-1.69 t for total phosphorus in Guanlin control unit,220.23 t for COD,4.49 t for ammonia nitrogen and 1.45 t for total phosphorus in Tongzi control unit;and 15.42 t for COD,0.90 t for ammonia nitrogen and 0.14 t for total phosphorus in Huangxin control unit,respectively.The water environment capacities of the representative rivers were closely related with the flow velocity and other hydrological elements,for example,the urban rivers with a standard water quality exhibited a positive correlation between the water environment capacity and the flow velocity,but the rural rivers with a water quality not up to standards showed a contrary pattern.This study can provide an important reference and new ideas for the water environment protection and management of the plain river network.