Cascade reservoir development exerts greenhouse gas emissions through nutrient retention and modification of hydrological regimes

To explore the characteristics and driving mechanisms of greenhouse gas emissions (GHG) from high-altitude cascade reservoirs, the present study selected three reservoirs in the upper Yellow River. During the spring ice-melting period, the static floating chamber method and gas chromatography were used to measure the fluxes and concentrations of CO2 and CH4 at the water-air interface, with simultaneous monitoring of water environmental factors. The results showed that the concentrations and fluxes of GHGs in the reservoir areas were higher than those in natural river reaches. CO2 fluxes (3.13-20.22 mmol·m⁻²·d⁻¹) increased along the flow direction, while CH4 fluxes (0.03-0.48 mmol·m⁻²·d⁻¹) decreased. The impacts of water environmental factors such as dissolved organic carbon on emissions varied among reservoirs. This study clarifies how cascade reservoirs regulate GHG emissions through nutrient retention and hydrological changes, providing a scientific basis for high-altitude reservoir carbon cycle research and low-carbon management.