Multiple Time-scale Characteristics of Flow Variations in the Middle Huolin River and Corresponding Effects Analysis
霍林河中游径流量序列的多时间尺度特征及其效应分析

Huolin River is one of the most important water supply sources for the Xianghai,Kerqin,and Chaganhu wetlands in the west Songnen Plain.A multiple time-scale analysis was used to analyze an annual flow series of 46 years of the Baiyunhushuo hydrologic station,which is located at the middle reaches of Huolin River.Our main objective was to discuss the periodic characteristics of the flow series,and examine the temporal patterns of the Huolin River recharging into floodplain wetlands in its lower reaches,and its corresponding effects exerted on downstream floodplain wetlands environmental evolutions.Wavelet analysis showed that the annual flow of Baiyunhushuo hydrologic station varied mainly in three time scales.The intensity of periodical signals of different time scales was strongly partially distributed in its time-frequency domain.More than 30 years interdecadal variation played a leading role in the temporal pattern,and showed a scale increasing tendency.At this scale,the flow of Baiyunhushuo hydrologic station in the Huolin river presented an alternative fluctuation of rain,draught and rain.Accordingly,the landscape of floodplain wetlands in downstream area presented a periodic feature,it is especially prominent before the 1990s.Compared with intense human activities,the periodic flow patterns of middle and small scales with relative low energy,have unobvious effects on wetlands environmental evolvement,it is especially distinctive after the 1990s.It should be noted that the dual actions of flow evolution of natural factors and human disturbances exerted influences of different degrees on flow signals in different periods.A further discussion should be made regarding the influencing factors,including precipitations,evaporations and human disturbances,for figuring out the reason and role of floodplain wetland landscape evolutions,thereby bringing forward scientific and feasible measures for the protection and restoration of wetland ecosystems.Rationally allocating and managing water resources,reducing river regulation and abstraction actions would be in favor of the protection of the existing wetlands ecosystem and the restoration of degeneration ones in the basin.