近十年鄱阳湖区极端干旱事件频发现象成因初析

近10 a来鄱阳湖区极端干旱事件频发，引起国内外媒体舆论的广泛关注。针对这一情况，运用流域降水、地表蒸散和出湖径流等数据，从流域水量收支平衡的角度，较为系统地分析了导致鄱阳湖区极端干旱事件频发的原因。结果表明，近10 a来鄱阳湖水文干旱起始日期提前，枯水期拉长。虽然干旱持续时间的长短呈现2~3 a的波动，但在总体上呈现逐渐加长的趋势。从流域水分收支的角度来看，近10 a来以水分亏缺为主，流域降水亏缺是基本的致旱因素，流域蒸散量增加则起到一定的增强作用，而出湖径流所起的作用比较复杂，在多数情况下其致旱的影响程度弱于流域降水作用。长江顶托作用强弱变化可以调节流域的水分收支平衡，强化或者减轻湖泊的干旱程度。2003、2004、2007、2008和2009年发生的极端干旱事件主要由流域水分收入项的大幅度减少所造成的，而长江水情变化在多数情况下加剧了流域水分收支的不平衡。这些研究结果明晰了鄱阳湖流域气象干旱与湖泊水文干旱之间的关系以及长江水情变化所扮演的重要角色，为应对未来的干旱变化和制定合理的抗旱防旱对策与措施提供了科学的依据

A PRIMARY INVESTIGATION ON THE FORMATION OF FREQUENTDROUGHTS IN THE POYANG LAKE BASIN IN RECENT DECADE#br#

Located north to the Yangtze River,the Poyang Lake is the largest freshwater lake of China.Extreme droughts have frequently occurred in the lake region in recent decade,and the droughts received increasing international attentions.From a perspective of basin scale water balance,this paper explored the processes and mechanisms of the frequently occurred droughts using long term hydrologic data.The data include precipitation of the Poyang Lake Basin,outflow discharge of the Poyang Lake during 1960-2010,and evapotranspiration of the basin during 2000-2010.Our results demonstrated that the lake drought duration ranged from 1-6 months with a periodic cycle of 2-3 year and the duration tended to prolong with earlier starting dates and postponed ending dates.The frequently occurred lake droughts were resulted from the basin scale water deficits,among which the largest annual deficit was 343.6 mm for 2003,followed by 223.1 mm for 2007.The water deficits were mainly attributed to the deficiency in basin scale precipitation especially in 2003,2007 and 2009,and the increased evapotranspiration during 2000-2010,and the complex variation of outflow discharge within a specific year.At a monthly scale,precipitation anomaly showed a largest variation,followed by outflow discharge and evapotranspiration,demonstrating the dominance of meteorological droughts over hydrological droughts.In most cases,outflow discharge played a role secondary to precipitation in forming lake droughts,varying with the blocking effects of the Yangtze River.The blocking effects may enhance or lessen the lake droughts depending primarily on the water stage at the Hukou,the solely outlet of the lake water outflow to the Yangtze River.The water stage was relative lower than the multi year mean by 0.46 m for 2001,0.94 m for 2004,1.64 m for 2006,1.29 m for 2007 and 1.22m for 2009,indicating the weakened blocking effects of the Yangtze River in the last decade.For an individual water year,substantial reduction of basin scale water income was principally responsible for the extreme lake droughts occurred in 2003,2004,2007,2008 and 2009,and the weakened blocking effects enhanced the water imbalance for the most cases.In general,the study provides an insightful view into the relationship of the meteorological and hydrological droughts,and the role of the Yangtze River in forming the droughts,which are valuable for effective promotion of climate adaptation and water resources management