Evaluating the tradeoff between hydropower benefit and ecological interest under climate change: How will the water-energy-ecosystem nexus evolve in the upper Mekong basin?

Hydropower plant operation alters natural streamflow regimes, which leads to tradeoff between hydropower benefits and the needs of downstream river ecosystems. This study proposes a novel approach for evaluating how hydropower-ecology tradeoff will evolve under future climate change based on Pareto optimal fronts, and demonstrated its efficacy using a case study of the cascade hydropower plants and downstream river ecosystems of the upper Mekong basin (UMB), a representative transboundary river basin. Future climate projections from multiple global climate models (GCMs) are used. Results show that, although GCMs project a future overall increase in streamflow, the hydropower-ecology conflict will likely be exacerbated by increased streamflow variability. Nearly one third of the GCMs indicate the alleviated conflict between hydropower and ecosystems, one third show little apparent change, and the final third show aggravated conflicts. According to the pessimistic GCMs, maintaining ecological impact at historical levels in the future could result in a hydropower deficit for which thermal power would need to compensate, generating additional 1.33 MMT CO2e in greenhouse gas emissions per year. These results reveal the potential challenges facing hydropower and ecological development in the UMB in the future, and emphasize the importance of developing adaptive mitigation techniques under climate change.