The Greater Mekong Subregion is a transnational area bound together by the Mekong River basin and its immense hydropower resources, historically seen as the backbone of regional economic development. The basin is now punctuated by several dams, successful in attracting both international investors and fierce criticisms for their environmental and societal impacts. Surprisingly, no attention has been paid so far to the actual performance of these infrastructures: is hydropower supply robust with respect to the hydroclimatic variability characterizing Southeast Asia? When water availability is altered, what are the implications for power production costs and CO₂ emissions? To answer these questions, we focus on the Laotian–Thai grid—the first international power‐trade infrastructure developed in the region—and use a power system model driven by a spatially distributed hydrological‐water management model. Simulation results over a 30‐year period show that production costs and carbon footprint are significantly affected by droughts, which reduce hydropower availability and increase reliance on thermoelectric resources. Regional droughts across the Mekong basin are of particular concern, as they reduce the export of cheap hydropower from Laos to Thailand. To put the analysis into a broader climate‐water‐energy context, we show that the El Niño Southern Oscillation modulates not only the summer monsoon, but also the power system behavior, shaping the relationship between hydroclimatological conditions, power production costs, and CO₂ emissions. Overall, our results and models provide a knowledge basis for informing robust management strategies at the water‐energy scale and designing more sustainable power plans in the Greater Mekong Subregion.

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大湄公河的气候-水-能源联系：ENSO引发的区域干旱如何影响电力供应和二氧化碳排放

大湄公河次区域是一个由湄公河流域及其庞大的水电资源所束缚的跨国地区，历史上一直被视为区域经济发展的支柱。流域现在被数个水坝打断，成功地吸引了国际投资者和对它们的环境和社会影响的激烈批评。令人惊讶的是，到目前为止，尚未对这些基础设施的实际性能给予任何关注：就东南亚表征的水文气候可变性而言，水电供应是否稳定？当水的供应量发生变化时，对电力生产成本和CO ₂的影响是什么？排放？为了回答这些问题，我们将重点放在老挝-泰国电网（该地区开发的第一个国际电力贸易基础设施）上，并使用由空间分布的水文-水管理模型驱动的电力系统模型。30年的模拟结果表明，干旱严重影响了生产成本和碳足迹，从而减少了水力发电的利用并增加了对热电资源的依赖。湄公河流域的区域干旱特别令人担忧，因为它们减少了老挝向泰国的廉价水电出口。为了将分析纳入更广泛的气候-水-能源环境，我们表明厄尔尼诺南方涛动不仅调节夏季风，而且调节电力系统的行为，从而塑造水文气候条件之间的关系，₂排放。总体而言，我们的结果和模型为在水能规模上制定强有力的管理策略以及在大湄公河次区域设计更可持续的电力计划提供了知识基础。