感潮河段生态下泻流量的确定--以大樟溪为例

Research on minimum ecological flow for tidal reach named Dazhang River

为完成闽江“一闸三线”调水工程中大樟溪生态下泄流量的保障设计工作,得出科学有效的河流生态需水调控方式及做好流域水生态健康的保护工作。区别于传统生态下泄流量计算方法,如RCROSS、Montana法等根据断面控制处的流域水文情势,人为规定特定数理统计水平下的水文特征值作为生态流量值,并没有区分河流本身属性及水生态系统在不同河段、时间的区分度的问题。通过水动力模型,计算不同保证率流量边界下重点水生态河段的水位、流量、流速、断面等变化对水生生物、沿岸植被的影响变化,分析不同生态流量对感潮河段水生态的影响。计算结果表明:感潮河段的主要水文、水力条件变化大都取决于下边界潮位的影响;流速、流量、水位在洄游通道重点河段变化不大,对花鳗鲡影响较小;下边界闽江潮位的变化主导了大樟溪莒口闸坝址以下河段的水位及流速变化过程。莒口闸建设对大樟溪水生态影响而言,并非决定性因素,此工程并不会造成较大环境影响。

In order to complete the design task of guaranteeing Dazhang River ecological flow in the Minjiang River“one gate and three lines”water diversion project and help protect the watershed ecological health,scientific and effective river ecological water demand control methods are proposed.The traditional way to calculate ecological flow is through the analysis of hydrological situation at certain cross section based on RCROSS,Montana methods.To manually define a characteristic value according to the mathematical statistics as the design basis of the whole river basin without distinguishing the difference of river property and aqua system at different river reaches and time periods.This project uses hydrodynamic models to calculate the changes in water level,discharge,velocity and cross section changes impact on the aquatic organisms as well as flora and fauna along the riverbank,so as to analyse the overall effects of different ecological flows on the water ecology of tide-sensitive reaches.The result shows that the main hydrological and hydraulic conditions in the tide-sensitive section are mostly affected by downstream tidal level boundary.Flow velocity,discharge and water level do not vary much in the key section of migratory channel,thus have a little influence on the Marbled eel.The minjiang river downstream tidal level changes are the main causes of the water level and velocity changes.The construction of Jukou Sluice is not a decisive factor in terms of its impact on the water ecology of Dazhangxi,and the project will not cause significant environmental impact.