Analysis of Annual Runoff Variation Characteristics in Main Rivers of China

The relevant statistical properties including the characteristics of interannual variations and annual distribution of runoff,trends,sudden change,periodicities for main rivers of China,are discussed based on the stochastic analysis.The results show that annual runoff in main rivers of China has large non-uniformity,especially larger in Haihe River Basin,Huaihe River Basin,Songhua River Basin and Liao River Basin;compared with before 1980,in addition to a little increasing non-uniformity in Huaihe River and Songhua River,the non-uniformity in main rivers of China generally decreases;the amount of water resources in South are larger than in North but the change range and intensity of annual runoff in northern rivers are greater than in southern rivers.Compared with before 1980,in addition to a little increasing annual runoff in Wangjiaba station and Haerbin station,the annual runoff in main rivers of China generally decreases in varying degrees.The drought in downstream of Yellow River Basin and Haihe River Basin occurred nearly 60 years,and even much higher than the frequency of abundance of other river basins;Affected by climate change and human activities,in addition to indistinctive increasing trend of annual runoff in Shijiao station,Wangjiaba station and Haerbin station,the annual runoff in most of China main rivers declines in the trend,especially in Haihe River Basin,Liao River Basin and the downstream of the Yellow River Basin;the sudden change points of annual runoff in the Yangtze River Basin and Pearl River Basin mainly occur between the 50's to70's in the 20th century and the beginning of the 21st century while it mainly occur in the 20's,60's and 90's of the 20th century in Songhua River Basin;In Yellow River Basin,Haihe River Basin,Huaihe River Basin and Liao River Basin,the sudden change points of annual runoff mainly occur between the 50's and 80's in the 20th century;there exists different periodicities in annual runoff series for main rivers in China;the main periodicity is generally below 20 years,that is,3~7,8~10,12~20 years cycle.