特枯水情对长江中下游悬浮泥沙的影响

基于长江中下游气象资料、历史水沙资料和2006 年10 月现场水沙观测资料, 分析了 典型枯水年大通站的月均径流量和输沙率特征、2006 年特枯水情产生的气候背景以及对长江中下游含沙量和悬沙粒径产生的影响。分析表明, 枯水年长江干流输沙量有显著的减少, 2006 年特枯水情下大通站汛期输沙量仅占多年平均值(1985-2000 年) 的19.8%。在特枯水情 和三峡工程蓄水的背景下, 2006 年10 月长江中下游含沙量平均为0.057 kg/m³, 只占 2003-2005 年10 月平均值的20.6%。2006 年10 月长江中下游悬沙中值粒径平均为4.8 µm, 悬沙中值粒径只占多年平均值的26.3%, 占近期平均值的41.8%。含沙量、悬沙粒度和中游 河床冲淤特性的综合分析表明, 城陵矶-湖口河段水沙垂向交换强, 是三峡兴建以后近期河 道调整频繁的河段。洞庭湖和鄱阳湖对长江干流含沙量的贡献较大, 尤以鄱阳湖的贡献最大, 长江中下游其他支流对长江干流含沙量的贡献较小。汉江和巢湖对长江中下游悬沙粒径的影响相对较大, 而洞庭湖和鄱阳湖则对悬沙粒径的影响相对较小。

The Effect of the Exceptionally Low Water Discharge on Sediment Characteristics of the Middle and Lower Yangtze River

Based on meteorologic data, historical sediment data and current & sediment data collected in October 2006 in the Yangtze River Basin, the analyses of monthly mean water and sediment discharge characteristics, meteorologic characteristics and the effect on suspended sediment concentration and suspended sediment grain diameter under the exceptionally low water discharge were carried out. The results showed that the sediment discharge decreased remarkably in the year of low water discharge, and the sediment discharge of flood season at Datong Hydrographic Gauging Station is only 19.8% of the mean value from 1985 to 2000. The mean suspended sediment concentration in October 2006 was 0.057 kg/m³ in the middle and lower Yangtze River, being only 20.6% of the mean value in October from 2003 to 2005. The mean suspended sediment median diameter in October 2006 was 4.8µm, being only 26.3% of the mean value of historic records and 41.8% of the annual mean value recently. The synthetic analysis of suspended sediment concentration, suspended sediment diameter and scouring/silting characteristics showed that the vertical water and sediment exchange was intense in the reach from Chenglingji to Hukou, where the channel adjustment has taken place frequently in recent years. Under the background of the exceptionally low water discharge and the completion of the Three Gorges Project, the contribution of the suspended sediment concentration from Dongting and Poyang lakes to the main stream was greater than that of any other lakes and tributaries, and the contribution of Poyang Lake was greater than that of Dongting Lake. The influence of the suspended sediment diameter from the Hanjiang River and Chaohu Lake to the main stream was greater than that of any other lakes and tributaries, while the influence of Dongting and Poyang lakes was relatively small.