中文摘要：

本研究分析了1960-2008年鄱阳湖流域的气候和水文变化特征，用水量和能量平衡关系解释和印证了这些特征，并由此揭示了鄱阳湖流域水文变化特征的成因及干旱和洪涝发生的规律。得到以下主要结论：1）正常或偏湿年份鄱阳湖流域6月份容纳水量能力已达到饱和，若6．7月降水量超出正常年份，则流域超饱和，洪涝发生。长江中上游降水量7月份的异常偏多会对鄱阳湖流域的洪涝起触发和强化作用。2）鄱阳湖流域7－10月蒸发量大于降水量，特别是7-8月蒸发量大于降水量的一倍以上，所以若4．6月流域降水量少于平均年同期量的20％以上，则累积效应使秋旱发生。当初冬（11月）降水偏少时，秋旱可持续到来年的初春，形成严重的春旱。长江中上游降水量对鄱阳湖流域的春旱没有直接影响，但7墙月降水量偏少时则对秋旱起重要的强化作用。3）长江对鄱阳湖流域的水文过程和旱涝的发生、发展的影响主要在7-8月的“长江与鄱阳湖耦合作用”时期和9．10月的“弱长江作用”期。

英文摘要：

Observational data from 1960-2008 were analyzed to obtain the mean annual climate and hydrological variations in the Poyang Lake basin, China. These variations were explained by the surface water and energy budgets, and the characteristics of these variations and the budgets were further used to deduce the rhythms of flood and drought developments in the lake basin. Some conclusions can be drawn as follows. （1） The precipitation in the lake basin increases at a large rate from January to June, reaching the annual maximum in late June. Amplifying monthly precipitation, particularly from April to June, coupled with weak surface evaporation and transpiration （ET）, saturates the soils and produces a large amount of surface runoff which raises the lake level. In July, rainfall decreases sharply with clear sky and high ET, which reduces surface runoff and reverses the hydrological processes developed in the first half of the year. These drying processes continue through October, making the basin dry again. （2） When June and July have above average monthly precipitation the lake basin becomes supersaturated, and floods develop. In such conditions, if July rainfall in the middle and upper reaches of the Yangtze River basin is above average, the Yangtze River blocking （or reversed flow） effect can trigger, intensify, and prolong Poyang Lake floods. Thus, Poyang Lake floods generally occur in July and August. （3） Because the lake basin is drying after July with strong ET, if there is below average rainfall in July and the months afterwards, ET would be greater than rainfall, causing drying. Drought could occur in fall. This fall drought can persist through the winter and into the following spring and result in severe spring drought in the lake basin. Thus, the droughts occur in the fall and spring months in the lake basin. （4） The Yangtze River effects on the floods and droughts in the lake basin are most significant during the ＂river-lake coupling period＂ from July to August. Strong effects can