三峡工程对长江下游感潮河段极值水位的影响

Impacts of the Three Gorges Project on the evolution of the extreme water level in the lower tidal reach of the Yangtze River

以往河流极值水位的研究往往选取年最大和最小水位开展分析,但这容易忽略了小概率因素带来的随机性的影响。为了更合理揭示长江感潮河段极值水位的演变趋势,并分析三峡工程对其影响,文章通过概率密度函数法及NS_TIDE调和分析,分析了长江下游感潮河段极值水位的演变规律。结果表明:三峡工程的流量调节对长江下游高水位有着显著的影响,高水位的变化在三峡工程建成前后由上升变为下降趋势,但三峡工程对于低水位的影响较小;而在三峡工程流量调控的影响下,分潮振幅变化趋势与概率密度函数法得到的水位变化趋势相反,即对极值水位影响也相反,表明长江口感潮河段由于三峡工程流量调节后,导致潮汐振幅的改变对极值水位的影响较小,极值水位的变化直接对流量条件的响应更为显著。

The annual maximum and minimum water levels were always analyzed on the extreme riverwater level in previous studies.While the random impacts caused by low probability factors were easily ignored.To make the evolution trend of the extreme water level in the lower tidal reach of the Yangtze River and its response to the Three Gorges Project be reveal,the evolution law of the extreme water level in the lower reach of the Yangtze River were analyzed using the probability density function(PDF)method and NS_TIDE harmonic analysis.The results demonstrate that the impact on the high water levelof flow regulation of the Three Gorges Project is significant,but minor on the low water level.The trend of the high water level changes from rising to falling after the completion of the Three Gorges Project.The changing trend of the amplitudes of the tidal constituents is opposite to that of the water level obtained by the PDF method,indicating that the extreme water level is more significantly influenced by the direct effect of flow regulation,while the impact of change of tidal amplitude is minor on the extreme water level in the tidal reach of the Yangtze river.