Runoff and Sediment Dynamics and Driving Factors in Jiangqiao Hydrological Station of Nunkiang River

Linear regression method,wavelet analysis and sequential Mann—Kendall test analysis were applied to characterize runoff and sediment time series collected at Jiangqiao hydrological station of Nunkiang River from 1955—2006.The results show that during 1955—1966,a period with little human activities,sediment yields remained relatively stable and no correlation between sediment and rainfall was found significant.In contrast,strong sediment fluctuations and a close correlation between sediment and rainfall were identified in 1967—2006,mainly owing to reinforced human disturbances.Linear regression method was adopted quantify the effects of rainfall and human activity on runoff and sediment.Comparing with base period,total runoff volume of the research area reduced by 7.90×109 m3 per year,within which 3.770×109 m3,4.130×109 m3 were affected by human activity and rainfall,respectively.During 1967—2006,the sediment reduced at a rate of 3.329×105 t per year given the decreased rainfall;however,human activity resulted in a sediment increase of 3.899×105 t per year.In summary,human disturbance,rather than rainfall variations,was the driving factor for the decline of runoff and the increment of sediment in the research area during the study period.