长江中下游水沙通量变化规律

采用水文学、泥沙运动力学与数理统计学相结合的研究方法，对宜昌和大通两个测站近五十年的实测水文、泥沙资料进行分析，以探究长江中下游水沙通量的变化规律。研究表明，水量由中游向下游沿程递增，但各测站的年均增幅不明显；长江中下游泥沙主要来源于长江上游地区的金沙江和嘉陵江。其次是汉江、洞庭湖和鄱阳湖等水系；长江流域来沙主要以悬移质形式下泄，悬沙通量由中游向下游沿程递减，同时各测站悬移质输沙量也逐年呈阶梯性递减趋势；长江中下游水沙通量有明显的季节性变化，洪季通量值明显高于枯季；悬沙颗粒主要由极细砂和粉砂组成，自中游向下游，泥沙颗粒逐渐细化；由于江阴河段附近边界条件的限制，该区域的悬沙粒径明显小于其上下游河段。

Water and Sediment Fluxes in the Middle and Lower Yangtze River

According to the field measurements of runoff and sediment at the Datong,Yichang and Hankou stations, the multi\|method of hydrography,sediment transportation and statistical was applied to study the patterns of variations in the water and sediment fluxes, especially the discharge of water and sediment at the Yichang and Datong stations in recent fifty years. The results showed that the water discharge increased apparently from the middle reach to the lower reach, but no obvious increment at each station,the changing range didn't exceed 4% in the mean annual water discharge at Yichang Station,and only around 0 6% at Datong Station. 98 percent of the sediment in the middle and lower reaches coming from the Jinsha River and Jialing River in the upper reach was composed of the suspended sediment. The suspended sediment flux decreased gradually along the river, while the discharge of suspended sediment declined obviously at each station. In addition, the finest sand and silt made up of the suspended sediment in the middle and lower Yangtze River, and the sediment particles become finer and finer along the river.