长江流域宜昌站旱涝急转及极端干旱事件变化规律分析

Analysis on Drought-Flood Abrupt Alternation and Extreme Low Flow Change Rule in the Yichang Station of Yangtze River

摘要: 本文基于长江流域宜昌站1882~2007年径流量资料，通过径流旱涝急转指数和轮次分析法，分析了长江流域宜昌站径流旱涝急转现象和极端枯水情况，研究结果表明：长周期径流旱涝急转在 1950年以前发生次数较多，而1950年以后发生次数相对较少；除下1985年涝转旱额外显著外，从1951~2007年旱涝转化现象相对于1951年之前有平稳的趋势。极端枯水总量总体呈增加趋势，到70年代达到最大，并且主要发生时段为1~4月的非汛期。极端枯水事件总体呈增加趋势，到70年代达到最多。极端枯水总量与发生次数同步性并不突出。利用不同百分位值分析，只有第20百分位值筛选出来的极端枯水事件比较符合宜昌站的实际干旱情况，可以用来描述分析宜昌站的干旱情况。

Abstract:  Based on the runoff data during 1950-2007 at Yichang Station in the Yangtze River Basin, by using long-cycle runoff drought-flood abrupt alternation index (RDFAI) and Round Analysis, this article analyzed the drought-flood abrupt alternation and extreme low flow. The results showed that the time of LRDFAI before 1950 is more frequent than that after 1950, besides that in 1985. Phenomenon of RDFAI of before 1950 had more smooth trends than that after 1951. The extreme low water volume totally showed an increasing trend, and it reached maximum in the 70s, and the time mainly occurred in non-flood season from January to April. Totally, extreme low water events showed an increasing trend, and it reached maximum in the 70s. The amount of extreme low water and the frequency synchronization are not prominent. Using different percentile value analysis, extreme low water events that are chosen by the 20th percentile value show more accordance with the actual drought situation of Yichang station, and it can be used to describe the drought situation of Yichang station.