东江流域汛期旱涝急转的时空演变特征

Spatio-temporal variations of drought-flood abrupt alternation during main flood season in East River Basin

基于东江流域32个雨量站1956-2009年的月降雨量资料,通过定义长周期降雨旱涝急转指数LDFAI(Long-cycle Drought-Flood Abrupt Alternation Index)和短周期的降雨旱涝急转指数SDFAI(Short-cycle Drought-Flood Abrupt Alternation Index),分析了东江流域汛期长周期和短周期降雨旱涝急转现象的趋势变化和时空分布特征,结果表明:①高LDFAI和高SDFAI对应着降雨的旱转涝,低LDFAI和低SDFAI对应着降雨的涝转旱,SDFAI在反映旱转涝优于LDFAI。②长周期降雨旱涝急转主要以全涝为主,短周期降雨旱涝急转发生频率最高的是全旱,其次是旱转涝和涝转旱,4-5月的全涝发生的频率高于其他短周期的频率。③前汛期-后汛期、6-7月东江中上游地区和5-6月东江流域全部区域涝转旱的趋势减小,并且旱转涝的趋势增加,东江下游和东江三角洲地区有涝转旱的趋势;4-5月、7-8月和8-9月中上游地区有旱转涝的趋势,东江下游和东江珠三角地区有涝转旱的趋势,而且越往上游地区,旱涝急转趋势变化越明显,此研究结果对于东江流域水资源管理具有重要指导意义。

Based on the monthly precipitation data from 32 rainfaU gauging stations covering 1956 - 2009 in the East River Basin. The immediate flood - drought shift, e.g. shift from drought to flood and vice versa, was analyzed for flooding season using long - cycle drought - flood abrupt alternation index （ LDFAI in short） and short - cycle drought - flood abrupt alternation index （ SDFAI for short）. The major results are： （~）the high LDFAI and SDFAI can well describe the drought - to - flood shifts; while the low LDFAI and SDFAI can well describe the flood - to - drought shifts. SDFAI has better performance when compared to LDFAI with respect to description of flood - drought shifts; （~）LDFAI shows the highest probability of floods and SDFAI the highest probability of droughts. Moreover, the higher probability of floods can be detected during April to May when compared to other time intervals; ~）flood - to - drought shifts are decreasing in the middle and upper East River Basin from prior - flood season to posterior - flood season, from June to July. While drought - to - flood shifts are increasing in the middle and upper East River basin, while flood - to - drought shifts are increasing in the lower East River basin during periods of April to May, July to August and August to September. Moreover, the drought - flood shifts are subject to higher frequency in the upper East River basin when compared to those in the middle and the lower East River ba- sin, which may imply much for the basin - scale water resources management across the East River basin in the changing environment.