Abstract: Drought has been recognized as one of the most wide-spread and costly natural disasters in the Mekong River basin.To investigate the spatiotemporal characteristics of drought can largely facilitate scientific drought management and risk mitigation.Using the global long-term (1901-2016)monthly precipitation data from CRU and the nearly 30-year(1985-2016)observational streamflow record from 4 hydrological gauging stations,this study investigates the characteristics of meteorological drought in the past half century and the trend of hydrological drought in the past 30years in the Mekong River basin,through estimations of multi-scale Standardized Precipitation Index(SPI)and Standardized Streamflow Index(SSI).Results indicate that while with slight upward trend from the whole-basin perspective,the SPI is found with obvious downward trend in the northeastern Thailand,most of Cambodia and Myanmar,suggesting these regions are overall subject to intensified drying during the past half century,especially in the northeastern Thailand.The long sequence analysis indicates that most of the Mekong River basin is found with drought frequency over 25%.In the southern Cambodia and Mekong delta of Vietnam,the frequency of extreme drought is even close to 10%.Further analyses on hydrological drought show that the trend of SSI greatly varies with gauging station location over the past 30-yr(1986-2016).The SSI of upstreamflow station(Chiang Saen)shows obvious decreasing trend,especially after 2010.In contrast,the SSI estimates from NongKhai and Mukdahan are both found with evident upward trend.As for the downstream station(Stung Treng),the trend of SSI seems little change over the past 30 years,but the SSI estimation is mostly less than zero since 2005,suggesting that this region is susceptible to hydrological droughts recently.These above analyses can provide scientific decision support for drought management and drought prevention in the Mekong River basin.

Key words: droughts, Standardized Precipitation Index(SPI), Standardized Streamflow Index(SSI), spatio-temporal variation, Mekong River basin

摘要： 干旱是湄公河流域影响范围最广、造成损失最大的自然灾害之一。开展湄公河流域干旱特性分析研究,有助于全面把握湄公河流域干旱时空变化规律,对于科学应对、防范干旱灾害具有重大的科学意义。本研究中借助全球过去近百年(1901-2016年)长序列月降雨网格化产品和干流4个典型水文站过去近30年(1985-2016年)流量观测序列,结合不同时间尺度标准化降水指数(SPI)和标准化径流指数(SSI)估算,分析了湄公河流域过去近半个多世纪(1950-2016年)的气象干旱特征及近30年的水文干旱变化趋势。结果表明,流域整体的SPI值呈现轻微上升趋势,但泰国东北部、柬埔寨大部及缅甸等地区的SPI呈现显著下降趋势,表明上述地区变干趋势明显,尤其是泰国东北部地区。基于长序列分析发现,流域绝大多数地区的气象干旱发生频率超过25%,其中柬埔寨南部、越南湄公河三角洲等下游地区发生重特大级别干旱的频率接近10%。进一步分析水文干旱特性发现,位于上中下游等不同河段的站点SSI在过去近30年的变化趋势不尽相同。其中,上游清盛站SSI总体上呈下降趋势,特别是2010年之后;位于中游的廊开及穆达汉站SSI上升趋势明显;而下游上丁站的SSI变化不明显,但2005年之后的绝大多数年份SSI为负值,表明该站控制地区在过去近十年受水文干旱影响较为频繁。上述分析及研究结果能够为湄公河流域干旱管理与旱灾防范提供科学决策支撑。 

关键词: 干旱, 标准化降雨指数, 标准化径流指数, 时空特性, 湄公河