Rafael M. Almeida, Ayan S. Fleischmann, João P. F. Brêda, Diego S. Cardoso, Hector Angarita, Walter Collischonn, Alexander S. Flecker, Bruce Forsberg, Roosevelt García-Villacorta, Carla Gomes, Phillip M. Hannam, Stephen K. Hamilton, Rodrigo Paiva, N. LeRoy Poff, Suresh Sethi, and Qinru Shi. (Under review)
Abstract The Amazon Basin is a global hotspot for future hydropower development. Yet, the basin-scale effects of a changing climate on future Amazon hydropower have been little explored. Here we use the outputs of a spatially resolved continental-scale hydrologic model forced with 25 global circulation models to project midcentury changes in river discharge and hydropower generation at 351 proposed Amazon dam sites. Basin-wide, we find that mean river discharge and hydropower generation may decrease by 13% and 19%, respectively, under RCP 4.5 (a stabilization scenario for global greenhouse gas emissions), and by 16% and 27% under RCP 8.5 (a no-mitigation scenario). Projected alterations in discharge and hydropower generation vary widely across the basin, with negligible changes in Andean Amazon countries, on the west, opposing sharp decreases in Brazil, on the east. At proposed dams in Brazil, changes in discharge regimes will increase the proportion of time with zero hydropower generation and decrease the frequency that dams operate at full generation capacity. Consequently, the minimum electricity sale price for Brazilian hydropower projects to break even increases on average by ~50% under RCP 4.5 and ~100% under RCP 8.5. These substantial cost increments under future climate conditions could considerably reduce the economic competitiveness of many proposed Amazon dams relative to increasingly cheaper alternative renewables such as wind and solar. Climate-resilient planning will be critical for balancing tradeoffs between hydropower production and many inevitable environmental impacts of large dams in the Amazon.