三峡水库蓄水后长江中游水沙时空变化的定量评估

Quantifying the spatio-temporal variation of flow and sediment in the middle Yangtze River after the impoundment of the Three Gorges

定量评价三峡蓄水后长江中游流域水文情势的时空变化,为长江中游生态保护和区域水资源管理提供科学依据。采用变化范围法分析了长江干流5个水文站的流量、含沙量日均数据,定量评估了三峡工程蓄水后,长江中游水沙变化度最大的江段和水文指标类别,及其对应的生态影响。研究结果表明三峡蓄水后,下游河道含沙量的变化度远大于流量,除城陵矶站外,含沙量较蓄水前有了大幅度下降,宜昌站的含沙量下降幅度达到了一个数量级,洞庭湖对长江干流含沙量有明显的调蓄作用。流量的变化度随着与大坝距离的增加而减小,且在7～11月流量下降幅度明显。这些水文节律的变化将影响下游鱼类产卵栖息地以及滞洪区水生生物与周边植被的生长。

In the present work,spatial and temporal changes of hydrological regime in the middle reaches of the Yangtze River after the impoundment of the Three Gorges Project were quantitatively evaluated,which provides a scientific evidence for the ecological protection of the middle reaches of the Yangtze River and regional water resources management. The range of variability approach was used to analyze average daily data for discharge and sediment concentration from five hydrological stations on the stem stream of the Yangtze River. Thus,river sections with the maximum water and sediment variation degree in the middle reach of Yangtze River and hydrological index categories and their corresponding ecological effects after the impounding of Three Gorges Project were quantitatively evaluated. The results showed that the changes of sediment concentration downstream were far greater than that of discharge after the impounding of the Three Gorges Project,which had a large scale decline compared with that of before the impounding except for Chenglingji station. Decrease range of sediment concentrations in Yichang station attained to one order of magnitude. The regulations of Dongting Lake on sediment concentration were obvious. Variation of discharge decreased with the increase of the distance from the dam,with a decrease of flow obvious between July and November.These changes in hydrological regime will affect both the fish-spawning habitat downstream and the growth of the aquatic organisms in the retarding area and the surrounding vegetation.