变化环境下澜沧江-湄公河流域干旱趋势

Projection of future droughts across the Lancang-Mekong River under a changing environment

为提升变化环境下澜沧江-湄公河(简称澜湄)流经国对干旱的抵御能力,亟需对流域未来干旱趋势进行科学研判。本研究选取了CMIP6的5个GCM模式,使用3种共享社会经济路径-典型浓度路径组合情景下的驱动数据,采用分布式水文模型CREST-Snow,预估了2020—2050年澜湄径流演变和气象、水文干旱发展趋势,量化了澜沧江梯级水库调度对未来径流的调节作用。结果表明:2020—2050年,澜湄流域整体呈湿润趋势,但极端干湿事件发生频率增加,其中2020—2029年干旱频发,2030—2050年更偏湿润,老挝、泰国2020—2050年干旱发生的频率和强度比流域内其他国家更高;澜沧江梯级水库可有效提升下游干季径流量,增幅从上游(99%)至下游(68%)递减,在缓解湄公河干季旱情方面具有重要作用。未来有待进一步加强澜湄水资源合作,优化水库调度方式,促进澜湄流经国水旱灾害防治。

To enhance the resilience of riparian countries associated with the Lancang-Mekong River(LMR)to drought under a changing environment,there is a pressing need to project future droughts across this river basin.Bias corrected projections from five CMIP6-GCMs under three Shared Socioeconomic Pathways(SSPs)were used as forcing data of a distributed hydrologic model(CREST-Snow)to project future streamflow of the LMR,and to examine meteorological and hydrological droughts across the LMR basin during 2020—2050.The regulation effect of cascade reservoirs on the mainstem of the Lancang River on downstream streamflow in the future was also quantified.Results show that although the entire basin will likely experience an overall wetting trend,the frequency of extreme dry and wet events across the LMR basin is likely to increase during 2020—2050.Droughts will more frequently occur during 2020—2029,as opposed to wet events that will be mainly concentrated during 2030—2050.From a spatial perspective,Laos and Thailand are likely to experience more frequent and severe droughts than other riparian countries.Cascade reservoirs on the Lancang River in China can effectively increase dry-season streamflow in downstream areas(decreasing from 99%in the upper stream to 68%in the downstream),playing a positive and important role in mitigating water shortage during dry seasons or droughts.We advocate for enhancing the cooperation through improving regulation of reservoirs across the entire basin,which should benefit water security and mitigation of droughts for all riparian countries of the LMR.