Abstract: 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.

Key words: the Yangtze River, sediment load, runoff, relationship between the runoff and sediment load, the Three Gorges Dam