湘江捞刀河流域氨氮和总磷水环境容量计算

Calculation of water environmental capacity of ammonia-nitrogen and total phosphorus in Laodao River Basin of the Xiang River

水环境容量的定量计算是实现水环境精细管理的前提,但相关参数在无充分资料的中小流域较难获得,其变化的难以确定给水环境容量求解带来较多不确定性。网格分布式水文模型和一维河网水质模型计算可以求解部分参数,提升水环境容量计算精度。选取长株潭城市群代表性区域——湘江一级支流捞刀河流域为研究对象,通过建立网格分布式水文模型和一维河网水质模型,结合水环境容量计算公式求解流域内不同控制单元水环境容量和剩余环境容量。结果表明:网格分布式水文模型可以较好地模拟流量,为水环境容量求解提供关键水文参数;金井河口和白沙河口所在控制单元的氨氮入河量超过水环境容量,其他控制单元的氨氮入河量在水环境容量范围内;流域上下游控制单元总磷的剩余环境容量接近0,而中游几个控制单元的剩余环境容量为负,有污染物应削减量。该研究可为无充分资料地区环境容量求解提供参考。

The quantitative calculation of water environmental capacity is a prerequisite for the fine management of water environment.However,the parameters and their changes are hard to ascertain,especially in middle and small-scale catchments with insufficient datasets,which bring uncertainties to the calculation of water environmental capacity.The distributed hydrologic model and the one-dimensional(1-D)river network model can solve some parameters,thus improving the calculation accuracy of water environmental capacity.A representative catchment in the Chang-Zhu-Tan area,the Laodao River catchment,which is one of the first-level tributaries of the Xiang River Basin,was chosen.The distributed hydrologic model and the 1-D river network model were constructed,and then the water environmental capacity and remaining environmental capacity of different control units were solved,combined with the calculation formula of water environment capacity.The results showed that the distributed hydrologic model performed well in simulating streamflow,which provided vital hydrologic parameters necessary for calculating water environmental capacity.Second,the discharges of ammonia nitrogen exceeded water environmental capacity at control units of outlets of Jinjing and Baisha sections,while the other control units had pollutant discharges lower than their water environmental capacity.In the upper and lower reaches of the Laodao River Basin,the remaining environmental capacity of total phosphorus at the control units approximated 0,while in the middle reaches of the river,the remaining environmental capacity of several control units was negative,and some pollutants should be reduced.The study provided a reference method for calculating water environmental capacity in areas with a lack of data.