Based on the measured runoff and sediment data of Cuntan hydrologic station that at upper situating Yangtze River's main stream

this study analyzed the temporal trends of runoff and sediment transport as well as the variations of their relationships during 1953-2018 by statistical methods including linear regression

Mann-Kendall test

and sediment rating curve. Double mass curve was further used to analyze the driving factors of water and sediment variation. The results showed that the average annual water and sediment discharge of Cuntan station was 342.5 billion m

3

and 361 million tons

respectively. The average monthly water and sediment discharge was 29.48 billion m

3

and 30.13 million

tons

respectively

which mainly distributed in June to October

accounting for more than 70% and 95% of the total annual runoff and sediment

respectively. The trend analysis indicated that the variation trends of annual precipitation and runoff were not obvious

however

annual sediment discharge showed a significantly decreasing trend. The monthly runoff increased significantly from January to April and the changes in other months were not significant

while the monthly sediment discharge showed a significantly decreasing trend in each month. In this study

the relationships between water and sediment could be fitted by power functios

and the fitting parameters were affected by the time scale. Statistical test detected that there was no significant difference between the measured value suspended sediment load and the estimated values by sediment rating curve. Double mass curve analysis found that human activities

such as water conservancy construction and soil and water conservation

were the main factors driving the sediment reduction in Cuntan station

accounting for 69%~93% in different decades

among which human activities had contributed more than 90% since 2000.