Nitrous oxide emissions from tropical hydroelectric reservoirs

1] We report original data on nitrous oxide (N 2 O) fluxes from two tropical reservoirs, their rivers below the dam, and from natural aquatic ecosystems and rainforest soils in French Guiana and Panama. We also review published N 2 O fluxes from other tropical reservoirs and natural environments. We show that: (1) N 2 O emissions from tropical reservoirs occur mainly at the reservoir surface, fluxes downstream of dams being minor; (2) Because pre-flooding natural N 2 O fluxes are significant, the net N 2 O emissions from reservoirs are less than $50– 70% of gross N 2 O emissions; (3) the contribution of N 2 O to the global warming potential of emissions from reservoirs could be significant for gross emissions, but less than 10% for net emissions, disregarding N 2 O degassing emissions.