Variations of sediment in upper stream of Yangtze River and its tributary

The observation data show that the sediment yield of Jialing River has decreased since 1980s,while the sediment yield of Jinsha River has increased.The cause of this change is analyzed.It is shown that the influence of engineering works on increment of river sediment of Jinsha River basin is much greater that in Jialing River basin due to the fact that the Jinsha River basin is characterized by deeply dissected plateau-gorge landform and the jailing River basin by gently dissected hill landform.Current decline of sediment yield in the Jialing River is caused by the positive influences of human activities on reduction of sediment,such as revegetation,soil conservation and water conservation works.The increase of sediment yield in Jinsha River is caused by the negative influence of human activities,such as land degradation,engineering works and channeling works.