Abstract: Dams affect hydrologic cycle and water environment through intercepting river water. Therefore, “impounded rivers” or river reservoirs often affect river basin environments. That has become a worldwide problem, especially the effect on N₂O emissions. This study investigates cascade reservoirs in the Wujiang River, and analyzes therelated parameters and N₂O concentrations. It has been shown that the cascade development doeshave impacts on water parameters, nitrogen loadings and N₂O emission. Saturation of N₂O averaged 347% in the entiresurface water represents a N2O source with respect to atmosphere,
under influences of age of reservoirs, nutrient status and organic matters. N₂O is emitted more in spring and summer than in winter and autumn. The key factors of influence are T, pH and DO. Organic matters and nutrient status are important in old reservoirs such as the Wujiangdu reservoir. Nitrification is a dominate process for N₂O emission in surface water. But for water in discharge, denitrification is a dominate process. The annual average N₂O fluxes were 0.33 μmol·m⁻²·h⁻¹ for river water, 0.64 μmol·m⁻²·h⁻¹ for discharge water, and 0.43 μmol·m⁻²·h⁻¹ for surface water in dams. Compared to other surface water
in the world, emission of N₂O acts as moderate emission fluxes in the Wujiang River. High concentration in discharge water should be emphasized since it contributes huge amount of N₂O emission during hydroelectric production.

Key words: cascade reservoir development, emission flux, nitrous oxide (N₂O), source-sink effect