长江近口段水动力特征对来水变异的响应

三峡水库的调蓄作用使长江中下游的径流动力发生异变,并诱使长江近口段的潮汐动力发生变化。本文基于长江近口段近20 a的流量和潮位资料,运用水文学、统计学和调和分析的方法研究长江近口段的水动力特征对三峡水库调蓄作用产生的来水变异的响应。研究结果表明:三峡水库的调蓄作用使长江近口段的径流动力发生变化,泄水期1—3月多年月平均流量增幅达20%以上;蓄水期9—11月多年月平均流量减少,10月的多年平均流量减少8 488 m³/s。长江近口段径流动力的变化使潮汐动力发生相应调整,大通-江阴段保证率为10%～70%的高、低潮位显著下降,而保证率为80%～100%的高、低潮位则小幅上升。泄水期1—3月平均潮差和M₂分潮振幅减小,近口段的潮汐动力减弱;蓄水期9—11月平均潮差和M₂分潮振幅增加,尤其是10月份潮差增加最为显著,近口段潮汐作用显著增强。

Response of hydrodynamics in tidal reach of the Yangtze River to variation in runoff

The operation of Three Gorges Reservoir causes the variation of runoff in the middle and lower reaches of the Yangtze River, inevitably resulting in the changes in tidal dynamics. Based on the data of river discharge and tidal level in recent 20 years, the response of hydrodynamics in tidal reach of the Yangtze River to variation in runoff was investigated by statistical analysis and tidal harmonic analysis. The results show that the operation of Three Gorges Reservoir causes the significant change in interannual distribution of runoff, with river discharge increase by more than 20% percent in discharging period and decease during storage period. Besides, in river reach between Datong and Jiangyin, the tidal level with guarantee ratio of 10%~70% is significantly decreased, but the tidal level with guarantee ratio of 80%~100% is slightly increased. Furthermore, the tidal range and amplitude of M₂ tidal constitute is decreased during discharging period, indicating a decrease in tidal dynamics, while the tidal range and amplitude of M₂ tidal constitute is increased during storage period, indicating a increase in tidal dynamics.