Dongting Lake region is known as the land of fish and rice,and world famous Wetland Nature Reserve.Global warming and the frequent occurrences of extreme weather and climate events are inevitably affecting the water resources of the region.Utilizable precipitation is a kind of water resource that can be utilized in actual use and its changes directly affect the agricultural production,wetland protection and other aspects of the region.Based on the regional mean monthly temperature and precipitation series from 1910 to 2013 constructed by the all 21 meteorological stations in Dongting Lake region,the evaporation was calculated by Takahashi's equation and its reliability was verified,then utilizable precipitation was obtained by the relationship of water balance.After that,the statistical methods were used to analyze the changes of utilizable precipitation series.The results indicated that utilizable precipitation of Dongting Lake region concentrated from Mar.to Jun.,accounting for 60.0％ of the whole year.Annual utilizable precipitation of Dongting Lake region over the past 104 years had no significant linear change trend but had obvious inter-decadal fluctuation with a periodic oscillation of 20～25 a.The changes of utilizable precipitation had seasonal differences,it had ascending trends in winter and summer,but descending in autumn and no significant change in spring.However,the linear trend of precipitation in each season did not pass the significance test and inter-decadal fluctuation was the main characteristics of change.The abrupt change test showed that the annual utilizable precipitation over recent 100 years had a abrupt rising jump and the same phenomenon in winter and summer,and it showed that although the utilizable precipitation in the year and the above seasons was characterized by the inter-decadal variability,there were also sudden increases in a certain period.The results of Morlet wavelet transformation showed that the annual and seasonal utilizable precipitation series had several periodic oscillations of multi time scales over Dongting Lake region and all have experienced 10～13 shifts of wet or dry periods,and each wet or dry period existed inter-annual fluctuations.This article aims to provide an important theoretical basis for future agricultural production,flood prevention and drought resistance in this region,and provide theoretical guidances for the development of climate change strategy.%洞庭湖区是久负盛名的鱼米之乡,同时又是国际著名的重要湿地自然保护区.全球气候变暖、极端天气和气候事件的频繁发生必然对湖区水资源产生不可忽视的影响.可利用降水量是可被实际利用的降水资源,其变化直接影响到湖区的农业生产、湿地保护等方方面面.利用洞庭湖区21个气象站构建的1910-2013年区域平均逐月气温、降水序列,采用陆面蒸发经验模型计算得到逐月蒸发量,并验证其可靠性;再根据水量平衡关系,得到可利用降水量,最后采用数理统计方法分析洞庭湖区可利用降水量的变化特征.结果表明,洞庭湖区可利用降水主要集中在3-6月,占全年的60.0％;1910-2013年湖区年可利用降水量无显著线性变化趋势,以20～25 a周期的年代际波动为主;洞庭湖区可利用降水量变化存在季节差异,近百年来冬季和夏季可利用降水量有所增多,秋季可利用降水量略有减少,春季无明显变化,但各季节可利用降水量的变化趋势均未通过显著性检验,整体仍以年代际波动为主.突变检验结果显示,近百年洞庭湖区年、冬季、夏季可利用降水量均存在1个显著增多的突变点,表明尽管年、冬季、夏季可利用降水量呈现以年代际波动为主的变化特征,但一定时段内仍存在突然增多的现象.小波分析结果显示,近百年来年和四季可利用降水量均存在多时间尺度的周期振荡,均经历了10～13个偏多或偏少期的转换,且在这些偏多或偏少期内可利用降水量仍存在明显的年际波动.文章旨在为今后洞庭湖区的农业生产和防汛抗旱提供理论依据,同时为制定洞庭湖区应对气候变化的战略提供一定的理论指导.
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