三峡工程运行前后长江中游河段水质变化模拟

三峡工程运行后在枯水期增加了下泄流量,提高了长江中下游河段枯水期沿程水位与平均流量,改变了中下游河段污染物排放的水动力扩散特性,进而对河道的水质产生了一定的影响。以三峡工程运行前后武汉河段汉口站水位和流量变化为例,分析其在枯水期、汛期和蓄水期3个典型时段的水文情势变化特征,采用数值模拟方法研究河道排污口附近主要污染物指标(COD和NH3-N)的扩散特性和响应变化规律,并进一步总结分析水位和流量变化对长江中下游沿江城市排污口附近水质特征变化的影响。结果表明:三峡工程运行后,由于流量年内分布趋于均匀化,各个不同时期的污染物扩散范围总体呈现减小趋势。

Simulation of water quality variation in middle reaches of Yangtze River before and after operation of Three Gorges Project

The increased discharge flow after operation of Three Gorges Project increases the water level and average flow during dry season, changes the hydrodynamic diffusion characteristics of pollutant discharge and influences the water quality conditions to some extent in the middle and lower reaches of the Yangtze River. This paper takes the change of water level and flow rate in Wuhan section as an example to analyze the hydrological conditions in dry season, flood season and water storage period before and after Three Gorges Project′s operation and simulates the diffusion characteristics and variation of COD and NH3-N near the sewage outlets. We further analyzes the effects of change of water level and flow rate on the water quality characteristics near the sewage outlets along the middle and lower reaches of the Yangtze River. The results showed that after operation of Three Gorges Project, due to the inter-annual flow process flattening, the range of pollution diffusion in different periods showed a decreasing trend as a whole.