1961—2021年叶尔羌河流域克亚吉尔冰湖溃决洪水变化特征

Variation characteristics of Kyagar Glacial Lake outburst floods in the Yarkand River Basin from 1961 to 2021

叶尔羌河流域冰湖溃决洪水致灾严重,在全球变暖背景下建立完善冰湖溃决洪水数据库,掌握其变化规律是开展冰湖研究和洪水危险性评估、风险管理的基础。基于水文径流数据、科考资料及洪水灾情资料,建立了1961—2021年叶尔羌河流域克亚吉尔冰湖溃决洪水数据库,利用线性趋势、R/S分析、累积距平、Mann-Kendall突变检验、Morlet小波分析等方法分析了冰湖溃决洪水的频次、洪峰流量变化特征,基于多概率分布函数估算了不同重现期情景下的洪峰流量并对其进行了危险性评估。结果表明:叶河流域克亚吉尔冰湖溃决洪水出现频次和洪峰流量在月分布上均呈单峰型,8—9月溃决洪水风险全年最高。1961—2021年克亚吉尔冰湖溃决洪水频次线性变化趋势不明显,呈现高、低交替变化的年代振荡特征,洪峰流量则呈现显著线性减少趋势,其减少速率为15.5 m^(3)·s^(-1)·a^(-1),对于洪水资源化利用而言利大于弊。对于19 a准周期,短期内克亚吉尔冰湖溃决洪水发生频次处于低位,风险较低,并将持续下降到2027年左右,此后进入下一个上升阶段。虽然21世纪初受全球气候变化影响,克亚吉尔冰湖溃决洪水出现短暂的高频期,但这仍不能改变其振荡减少为主的长期变化特征。克亚吉尔冰湖溃决洪水在5 a一遇重现期情景下有一定的致灾风险,10 a及以上不同重现期情景下致灾风险极高。建议后期加强对叶尔羌河克亚吉尔冰湖的动态监测、风险评估以及冰湖溃决突发洪水机理研究,加快水利工程建设力度,趋利避害、提高流域防洪减灾能力。

The glacial lake outburst floods(GLOFs)in the Yarkand River Basin(YRB)may cause severe disas⁃ters.In the context of global warming,establishing a GLOF database and understanding the variation characteris⁃tics of GLOFs are the basis for glacier lake research and the flood risk assessment and management.Based on the hydrological runoff data,scientific expedition data and flood disaster data,a database of Kyagar GLOFs in the YRB from 1961 to 2021 is established.Then,the frequency and peak discharge variations of GLOFs are ana⁃lyzed by using statistical methods such as linear trend analysis,rescaled range analysis,accumulated anomaly analysis,Mann-Kendall test and Morlet wavelet analysis.In addition,the peak discharges under different return period scenarios are estimated by using the Multi-Distribution Fitting Tool software,and the corresponding risk assessment is conducted.The results show that the frequency and peak discharge of Kyagar GLOFs in the YRB both exhibit a unimodal pattern on the monthly timescale.The risk of GLOFs is the highest in August and Sep⁃tember.The frequency of Kyagar GLOFs from 1961 to 2021 does not show an obvious linear trend but exhibits a decadal oscillation.The peak discharge,however,shows a significant linear decreasing trend with a rate of 15.5 m^(3)·s^(-1)·a^(-1),indicating that the benefits outweigh the drawbacks when utilizing floodwater resources.On the quasi-19-year period,the frequency of Kyagar GLOFs is at a low level in conjunction with a relatively low risk in the short term.It will continue to decline until around 2027,after which it will enter the next rising phase.Al⁃though there was a short-lived high-frequency period of Kyagar GLOFs due to global climate change in the early 21st century,this cannot alter the long-term oscillatory decrease trend.The Kyagar GLOFs pose a certain level of disaster risk under the 5-year return period scenario,while the disaster risk is extremely high under the 10-year or above return period scenarios.Therefore,we recommend strengthening the dynamic monitoring and risk assessment of the Kyagar Glacier Lake in the Yarkand River,as well as the research on the mechanisms of GLOFs.Additionally,we need to accelerate the construction of water conservancy projects and enhance the flood control and disaster reduction capabilities.