The Periodic Analysis Of Annual Runoff Time Series In Zhangze Reservoir

Study on the change law of reservoir runoff is an important content ofhydrology and water resources, is the most important base for comprehensivedevelopment and utilization, scientific management and optimal operation, hasan important influence on the development of local society. So, it is veryimportant theoretical and practical sense for mining and identifying change lawof the river runoff, looking for new methods and developing new approaches tostudy it.This paper put Zhangze reservoir as the research object, using theinformation of runoff and rainfall from1956to2008, give a morecomprehensive analysis of the year and inter-annual variation of Zhangzereservoir runoff during the53years, and analyzing the periodic of annual runoffin Zhangze Reservoir using different research methods. The main researchcontents and results are as follows:(1) Analyze the basic data of the runoff in Zhangze reservoir. In this paper,we analyze the time series of the runoff in Zhangze reservoir through analyzingthe year and inter-annual. The analysis shows that: in Zhangze reservoir, the runoff has the consistent change tendency in each decade, the annual runoffmainly concentrated in6-9months, the annual distribution inhomogeneity ofrunoff basically unchanged over the years, the difference of monthly distributionof runoff is not very poor, the concentrated period mainly in the end of July andthe early August; the interannual variability curve of runoff shows a decreasingtend, the annual inflow runoff alternating wet and dry storage, showing arelatively complete runoff change cycle, the data is reasonable andrepresentative, the interannual variability of runoff is more obvious, and therelative mean of annual runoff is good symmetry.(2) A periodic analysis of annual runoff time series in Zhangze Reservoirbased on SSA. The results show that: Pretreating the original time series andthen reconstructing them, get a reconstructing sequence with trend component,and a series of reconstructing sequences with periodic component of2.8,4.4and17.7years; SSA method has a good practicability, provides the foundation forthe further study of hydrology and water resources.(3) A periodic analysis of annual runoff time series in Zhangze Reservoirbased on Wavelet transform and Cross-wavelet transform. The results show that:The first period, the second period, and the third period of annual runoff timeseries in Zhangze Reservoir are30a,4a and12a; The strongest regional thatprecipitation and runoff affecting each other mainly concentrated in a mainperiod about30a, their relationship has a strong significance and overallcharacteristics. (4) A periodic analysis of annual runoff time series in Zhangze Reservoirbased on EEMD method and Hilbert transform. The analysis shows that: inZhangze reservoir, the evolution of the nature annual runoff contains4IMFcomponents and one trend term; from the cycle of Intrinsic Mode Function, thenature annual runoff of Zhangze reservoir may exist several cycles such2.42years,3.83years,7.09years,14.59years.(5) The analysis methods of SSA, Wavelet transform, and EEMD existconsistency in a short periodic analysis of annual runoff time series, so we canexplain that the annual runoff time series have obvious periodic change inZhangze Reservoir; But there are some differences of their long periodicanalysis, this may be due to the limitation of sequence length, to study the longperiodic variation requires a longer runoff data. Summary, we can consider thatthe annual runoff time series have obvious periodic change of2~3a、4a and12~14.6a in Zhangze Reservoir, and we can speculated that the evolution maybe related to the Atmospheric Low-Frequency Oscillation, ENSO, the movementof celestial bodies, the change of sunspots strength and other factors.