新疆阿克苏河流域洪水演变趋势研究

Evolution trend of flood in the Aksu River basin,Xinjiang

全球气候变暖将加剧水循环,增大洪水风险。阿克苏河流域位于天山南坡,是北半球中纬度典型的高山流域。本流域不仅有暴雨洪水、冰川和积雪融水造成的洪水,而且还有冰川溃决突发洪水。以阿克苏河的两条支流库玛拉克河和托什干河为研究对象,利用块最大值抽样方法(block maximum)和超定量阈值(peak over threshold,POT)抽样方法提取出1958—2011年的洪水事件,其中基于POT方法在两条支流分别提取106次和112次洪水事件,主要集中在6月、7月和8月份。研究表明:阿克苏河的两条支流库玛拉克河和托什干河的年最大洪水强度分别以8.48 m^(3)·s^(-1)和3.40 m^(3)·s^(-1)的速率增加;在洪水发生时间上,以冰川融水补给为主的库玛拉克河,洪水发生时间有提前的趋势,而以降雨和融雪水补给为主的托什干河,洪水发生时间变得更加分散,表现为春季最大洪水提前、秋季最大洪水推后。

Global warming has accelerated water cycling and increased flood risk.The Aksu River basin,locat⁃ed on the southern slope of the Tianshan Mountains,is an important tributary of the Tarim River basin.Floods in the Aksu River basin is not only caused by storm,glacier and snow melt water,but also glacial-lake outburst floods(GLOF).Based on the long-term daily streamflow data of the Kumarak River and the Toshgan River,two headwaters of the Aksu River,this study investigated the changing nature of flood events from 1958 to 2011.In addition to the bulk maximum method,this work also applied the Peak Over Threshold(POT)method to extract flood events and 106 and 112 flood events were identified in the Kumarak River and the Toshgan River,concentrated in June,July and August.The flood intensity of the Kumarak River and the Toshgan Riv⁃er both increased based on the two flood-identification methods.The occurring time of flood of the glaciermelt water dominated Kumarak River has pushed forward,while that of the rainfall and snowmelt recharged Toshgan River has become more dispersed as the spring flood being pushed forward while the autumn flood being postponed.