极端干旱事件中洞庭湖水面变化过程及成因

干旱是洞庭湖区长期以来面临的严重自然灾害之一,给周边人们的生产生活造成了极大的影响.针对2006和2011年洞庭湖区发生的极端干旱事件,借助遥感影像大范围、时空连续的优势,结合湖区水文气象等观测资料,从时空两方面阐释了洞庭湖在典型干旱年份水域分布及变化过程,进一步从温度、降水、径流以及蓄水量等方面对比分析不同干旱事件发生、发展过程的一致性和差异性.研究结果表明:2006年干旱大致从7月开始,至12月结束.水面淹没范围由湖心向周边扩展,到7月达到最大值,8月提前进入枯水期,减小范围主要集中在东洞庭湖外围和南洞庭湖的北边.2006年干旱属于由入湖径流减少主导的水文干旱事件;2011年的干旱则从4月开始,至11月结束,在9月以后干旱继续加重.水面淹没范围在6月急剧增大且一直到8月都维持在较高的水平,涨水期水面由中心向四周淹没,退水期水面变化范围与涨水期相反.2011年干旱是由流域降水减少引起的水文和气象干旱事件.研究结果揭示了洞庭湖区干旱成因的多样性和复杂性,对于制定科学合理的干旱灾害防范措施,减缓区域的生态环境问题等具有一定的指导和借鉴意义.

Sharp change of lake levels during the two extreme droughts and its hydroclimatic processes in Lake Dongting, China

Lake Dongting has been subjected to drought which threatens grain production and people''s lives. For investigation of extreme droughts in 2006 and 2011, water surface changes and its tempo-spatial variation characteristics were identified with data of remote sensing images. The similarities and differences for the two drought events were analyzed from respects of changes in temperature, precipitation, runoff and storage capacity, by using the hydrological and meteorological data. The main results are as follows. The first drought lasted from July to December in 2006. The water area expanded from the lake center to all-around low lands. The peaks occurred at July and receded at August in 2006, where the reduced area focused on periphery of east Lake Dongting and north of south Lake Dongting. Drought was mainly caused by discharge reduction in 2006. While in 2011, drought lasted from April to November, and was aggravated in September. The inundated area increased sharply in June and retained a high level until August. During water rose period, water submerges from the center to the surrounding areas, while in water withdrawal period, change direction of water area reverse of water rose period. Drought was caused by combined effects of hydrological and meteorological factors in 2011. The results revealed that there were diversity and complexity of drought causes in Lake Dongting, which can provide useful guidance and advice for making scientific measures to abate drought disaster.