The impact of human activity on hydrology and sediment is great. On the upper reaches of the Yangtze River great amount of sediment is transported into the mainstream

which increases turbidity of the river and lengthens the turbidness time because of the sharp increa sing of population

the frequent destruction and the deterioration of the ratio of abundance to dryness

but the variation has not been found in checking，so it is thought that the sediment load at Yichang station in 1980's is completely the same as that in 1950's

i

e.，520 million ton

and affir med that the sediment load on upper reaches of the Yangtze River has not been changing for thirty years or more and it would not change essenti ally in the future

In this paper a preliminary study is made to the effect of human activity on the increment of sediment load in the section of Three Gorges

The results obtained is that the annual average sediment load at Y ichang station is 659 million tons and would be 685 millon tons in fnture fifty years.