| Baiyangdian Lake plays a significant role in the flood control in catchment, water storage, fish and reed production and maintaining ecological balance, has not only high ecological value, but also high social and economic values. In recent years, Baiyangdian Lake has been facing threatens mainly coming from draught and pollution. Because of the high intensity exploitation of water resources within the upstream basin and the climate drought, it has suffered frequent drying up, deterioration of ecological environment, reduction of area and destruction of biodiversity. Therefore, the changes in Baiyangdian Lake water storage capacity of research and analysis forecasts and to take corresponding measures to control is of great theoretical and practical significance.This paper studies in the following aspects: The hydrological data of precipitation, evaporation, seeping, feeding flow and out flow , water level covering 1956～2000 have been analyzed for Baiyangdian, the relationship between feeding flow to baiyangdian and precipitation in its catchment and the trend of water resources changes have been studied. The Baiyangdian water resources degradation mainly attributed to decrease of upstream runoff. By comparing of precipitation and evaporation the regime of climate drought can be understood. The ability of its anti-drought was declining, and the trend of degradation of quantity appeared. Therefore, in order to maintain the ecological balance of Baiyangdian, relax the dry crisis, artificial water diversion must be needed. (2)In addition to water levels, the other hydrological elements, such as runoff, floods, rain, groundwater and other aspects, was analysed in chaos. In this paper, the chaos characteristics of water level is analysed for the first time. The daily water level of Baiyangdian Lake is the target time series, based on chaos theory, the power Spectrum, the largest Lyapunov exponent, Kolmogorov entropy of the Baiyangdian Lake were calculated. The parameters of delay time and embedding dimension were discussed. Because the relationship between the water level and water volume in Baiyangdian was determinated, water volume has the same chaos characteristics. (3)Based on the chaos analysis of the daily water level of Baiyangdian Lake and forecasts on Chaos Theory, the largest Lyapunov exponent method and the chaos RBF method were used to predict the daily water level of Baiyangdian Lake. To compare two methods, the results show that the chaos RBF method had the smallest error and highest pass rate. (4) Water supplemented program of Baiyangdian Lake have been studied, defined the following basic concepts: ecological drought, the suitable ecological water level, the key day of ecological drought, the ecological characteristics water level, the high frequency water level; then based on statistical methods and surveys, the suitable ecological water levels of the flood season, non-flood season and the anniversary of Baiyangdian were identified. The key day of ecological drought and the ecological characteristics water level were pointed out, according to the different ecological characteristics water levels the supplement program of Baiyangdian Lake was put forward and effect of different supplement program was analysed, provides theoretical support for rational determination of Baiyangdian supplement program.This paper analysed hydrological elements of Baiyangdian Lake systematically, comprehensively and deeply, and the study of water level forecast and supplement program provide evidence for the development of scientific management principles of Baiyangdian, a more rational distribution of Water Resources in Baiyangdian Lake, to relax the ecological crisis , protecting ecological environment of Baiyangdian Lake and the water transfer and supplement program.
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