On Evolution Modes of Water Resources in the Yellow River Basin
黄河流域水资源演化模式分析

The knowledge about evolution modes of water resources is important not only for hydrologists but also for water resources managers, especially for the Yellow River, which is suffering from water resources deficit. In this paper, analysis on evolution modes of water resources in the Yellow River Basin was carried out with the EMD-Hilbert Transform method based on precipitation and annual runoff of the past 50 years in the Huayuankou Station. The results have shown that the change of precipitation can be described by four intrinsic mode functions (IMF) and a decreasing tendency function, while the runoff series have been decomposed to 3 IMFs and also a decreasing tendency function. Comparing the evolution modes of annual runoff with that of annual precipitation, we have found that they were not changing in-phase, though there were some correlations between them. In the time scale, the change of runoff appeared to lag behind that of precipitation, which to some extent may due to the adjustment capacity of the underlying surface. In addition, according to periodicity of the IMFs, it can be inferred that the change of water resources in the Yellow River Basin may be due to QBO and ENSO events, which has called for further research work.