Variation characteristics of annual runoff and its attribution analysis in Dadu River basin

According to the data of annual precipitation, annual average temperature of climatological stations and annual runoff of Tongjiezi Station in the Dadu River basin from 1951 to 2012, the Mann Kendall rank correlation test was used to identify the trend of annual runoff sequence, the periodic component was tested based on the wavelet analysis method, the sequential clustering method, the cumulative anomaly method and the Pettitt method were used to diagnose the change point, and the effect of climate changes and human activities on the annual runoff of the basin was revealed based on the comparison of the slope change rate of the cumulative amount. The results show that in the past 60 years, during 1951—1968, the annual runoff showed an insignificant decrease trend, the period of 1969—1987 showed an insignificant increase trend, the period of 1988—2012 showed an insignificant decrease trend, and the period of 1951—2012 showed an insignificant decrease trend; there were 7, 11, 17 and 28 years cycle components; in the past 60 years, change points of the annual runoff in the Dadu River basin were in 1968 and 1987; using 1951—1968 as the base period, during 1969—1987, the contribution rate of climate change and human beings activities to the reduction of annual runoff in the Dadu River basin was 36.22% and 63.78% respectively; during 1988—2012, the contribution rate of climate change and human activities to the reduction of annual runoff was 33.68% and 66.32% respectively; and in sum, human activities are the main factor and climate change is the secondary factor.