长江上中下游河道水沙特征和水沙关系简

利用1950—2010年间宜昌、汉口和大通站的有关资料，对比分析长江流域上中下游河段的径流量和输沙量特性及其在时间上和空间上的变化规律.1950—2010年宜昌站多年平均径流量为4.32×10¹¹ m³，汉口站为7.07×10¹¹ m³，大通站为8.96×10¹¹ m³，上游来水量与中下游来水量各占一半左右.年际间年径流量存在波动变化，但未出现明显的趋势性增减变化.而三峡水库建成后径流量存在年内削峰补枯现象；1950—2010年宜昌站多年平均输沙量为4.34×10⁸ t，汉口站为3.59×10⁸ t，大通站为3.90×10⁸ t，泥沙主要来源于上游流域.而年际间年输沙量从20世纪80年代开始出现下降，尤其2003年三峡水库建成后输沙量出现锐减，宜昌站年平均输沙量降为0.54×10⁸ t，汉口站为1.17×10⁸ t，大通站为1.52×10⁸ t，汛期输沙量减少更明显，而且不同粒径组的悬沙输沙量出现不一致的下降，这与中下游河床和岸滩沉积物再浮悬泥沙及湖泊补给的泥沙组成有关.对悬沙不同粒径组的输沙量与径流量之间建立散点关系图，表明D≥0.1 mm泥沙粒径组的线性关系较好，而全沙粒径组尤其是细颗粒组相关性较差，符合河流动力学的相关理论.本研究成果对认识近年来人类活动干扰下的长江流域水沙变化有着重要的现实意义.

Characteristics of sediment load and runoff in the upper,middle and lower reaches of the Yangtze River and their relationship

The related data from Yichang, Hankou and Datong gauging stations were collected from 1950—2010 to analyze the characteristics of temporal and spatial variations of the runoff and suspended sediment load in different reaches of the Yangtze River. Multi-year average of runoff (1951—2010) were 4.32×10¹¹ m³, 7.07×10¹¹ m³ and 8.96×10¹¹ m³ at Yichang, Hankou and Datong gauging station, respectively. The runoff from the upper reaches of the Yangtze River was as much as that from the middle and lower reaches. Multi-year average runoff was fluctuant with no significant trend, but the difference of runoff between flood season and drought season was minimized by the construction of the Three Gorges Dam. On the other hand, multi-year average of suspended sediment load at Yichang Hankou and Datong gauging station were 4.34×10⁸ t, 3.59×10⁸ t and 3.90×10⁸ t, respectively, indicating that the main sources of suspend sediment was the upper reaches of Yangtze River. With the decline of suspended sediment load since 1980s, especially in the flood seasons, the suspended sediment load at Yichang, Hankou and Datong gauging station decreased respectively by 0.54×10⁸ t, 1.17×10⁸ t and 1.52×10⁸ t. Because of the resuspension of sediment in riverbed and river shoal and the sediment supply from the lakes along the Yangtze River, the decreases in the suspended sediment load of different grain size levels were unequal. A good linear relation was found between the suspended sediment load with grain size larger than 0.1 mm and runoff while the linear relation was weaken with the finer of grain size. This was in line with the relative theories of river dynamics. The dispersion grew up from the upper reaches to the lower reaches. This study is very helpful to understand the recent changes in the relationship between the runoff and suspended sediment load under human interventions.