Variable renewable energy pathways in the Lower Mekong Basin under projected river flow extremes

The Lower Mekong River Basin faces growing challenges in deploying variable renewable energy under intensifying hydroclimatic extremes. To evaluate these impacts, we develop an integrated modeling framework that links an energy expansion model with a synthetic streamflow generator. The results indicate that severe extended periods of low flows (10,000-year events) reduce hydropower output by 24.3 ± 8.7 terawatt-hour (−13.7% ± 4.9%), increasing wind capacity requirements by 10.6 ± 12.5 gigawatts (1.15% ± 1.36%) and raising system-wide costs by 8.7 ± 3.2 billion U.S. dollars. Conversely, extended periods of high flows of similar severity boost hydropower generation by 23.3 ± 9.2 terawatt-hours (+ 13.1% ± 5.2%), decreasing wind capacity needs by 9.3 ± 11.7 gigawatts (1.02% ± 1.27%) and lowering system costs by 7.8 ± 3.0 billion U.S. dollars. Prolonged drought conditions accelerate wind development to sustain decarbonization, while surplus flows from floods may delay investment—introducing long-term uncertainty for energy system resilience. These findings underscore the need for proactive, region-specific strategies to ensure resilient and sustainable energy transitions under intensifying hydroclimatic extremes.