中文摘要：

鄱阳湖区长期遭受洪涝与干旱的侵扰，严重影响着当地的社会生产与活动。为探索减少这一地区洪涝与干旱灾害的有效对策，本研究采用时序距平分析法与基于分形理论的极差分析法相结合的方式，详细分析了鄱阳湖区1959年～2005年近50年来降水的变化过程。结果表明，虽然该地区的降水量在1年长时间尺度上的变化过程主要为分形式的布朗运动，具有长记忆特性，或持续性，但不同站点年降水量序列的分形维度差异很大，彼此相似程度不高。当时间尺度为5年时，Hurst指数在整个区域上的平均值要远比时间尺度为1年时的相应值更接近1．0，而当时间尺度为10年时，鄱阳湖区各站点降水量距平变化的过程呈现高度的一致性，50年来总体以少水期与多水期交替出现的形式变化。特别重要的是，湖区在3月～6月因降水多可能造成洪涝灾害年份的出现具有约10年长的周期。相反，湖区在7月～10月和11月～2月因降水少可能造成旱灾年份的出现尽管并不完全同步，但却均拥有约30年长的周期。持续如此长的少水期使得大量湖区湿地被逐步开耕，因此在鄱阳湖区有效地实施退田还湖补偿政策不仅有利于生态系统的恢复，而且还可极大地减小特大洪水时整个区域遭受灾难性后果的几率与带．围．

英文摘要：

Poyang Lake region has long been exposed to both floods and droughts such that its regional socio-economic development has been severally restricted. To find effective measures to reduce damages caused by floods and droughts, we combine time series anomaly analysis with rescaled range analysis which is based on fractal theory. The method of IDW（Inverse Distance Weighted） is used in this research, which shows that the general distribution of annual mean precipitation in Poyang Lake increases gradually from northwest to southeast. A detailed analysis of the spatio-temporal variation of precipitation over the last 50 years shows that the change in annual precipitation is mainly in fractal Brownian motion, and the process of time-series change in annual precipitation has long-memory or persistent characteristics. However, different stations vary in fractal dimensions significantly, and the degree of similarity at the timescale of 1 year is not very high. When we expand the time-scale upto 5 years, the average value of the Hurst index for the whole area becomes much closer to 1.0 than the time-scale of 1 year does. When time-scale is 10 years, the anomaly changes of precipitation in the whole region are highly consistent, showing a pattern with low and high precipitation alternately occurring over the last 50 years. Of particular importance, the lower-than-average precipitation that causes frequent drought can last around 30 years in both periods of July-October and November-February, in spite that they are not completely synchronized. Comparatively, the higher-than-average precipitation in March-June period lasts only around 10 years. The long duration of persistent lower precipitation exposes a large amount of wetland in the lake area. These exposed wetlands were cultivated because of the growing population pressure and economy interests drive. Such vicious cycle and higher polder embankment caused by larger floods will eventually put the whole area on the verge of social and economic disasters when extreme floo