Runoff temporal characteristics of Luodian River in Yunnan Province
LI Shendong;SONG Zhaoyi;Zhaotong Branch,Yunnan Hydrology and Water Resources Bureau;
Empirical Mode Decomposition( EMD) and Pettit mutation test were used to analyze the runoff variation at Luodian station in Zhaotong City,Yunnan Province from 1961-2014,including the variation cycle,variation tendency,mutation of annual average runoff,annual maximum runoff and minimum runoff. The results show that the annual runoff can be decomposed into three Intrinsic Mode Functions( IMFs) components and one tendency component,the IMFs represent the periods of 3 a,6. 5 a and17 a. The tendency component indicates an increasing tendency from 1961 to 1980,and a decreasing tendency from 1980 to2014. The maximum runoff and minimum runoff can be decomposed into four IMFs components and one tendency component.The IMF represent the small periods of 3 a,6. 5 a,12 ~ 17 a,and a large periods of 27 a and 45 a. The tendency component indicates an obvious decreasing tendency after 1980. The results from Pettit mutation test show that the annual average runoff and annul precipitation has a mutation point around 1986,while the annual maximum and minimum runoffs have a mutation point around 1991.