资源环境科技发展态势分析平台

Hydropower is considered green energy and promoted to reduce greenhouse warming. However, hydropower is typically generated using reservoirs and reservoirs are known to emit substantial amounts of the greenhouse gas methane (CH₄) to the atmosphere. In many reservoirs ebullition is the dominant pathway of CH₄ emission. We show that continuous diurnal pumped‐storage operation, which combines water pumping into the reservoir typically during the night and water drawdown during high demand of electricity, is beneficial for reducing CH₄ ebullition associated with hydropower generation. This conclusion is based on ebullition fluxes and water levels measured over three months in Schwarzenbach reservoir located in Germany. The reservoir was managed using three modes of operation: (1) diurnal pumping and turbination, (2) no pumping and no turbination, and (3) diurnal turbination. Cross‐correlation analysis indicates that ebullition fluxes predominantly occur during diurnal water level decrease associated with turbination. Consistently, average ebullition fluxes of CH₄ were negligible during mode (2) and substantial during modes (1) and (3). During mode (3) the average CH₄ ebullition flux was ~197 mg m^‐2d^‐1, ~12 times larger than during mode (1) (16 mg m^‐2d^‐1). Our data indicate that overall CH₄ ebullition is about three times larger during 51 days of operation consisting of 38 days of no turbination followed by 13 days of diurnal turbination than during 51 days of continuous diurnal pumped‐storage operation. This suggests that continuous diurnal pumped‐storage operation leads to reduced CH₄ ebullition from reservoirs and is therefore advantageous compared to modes of operations involving long‐term, large‐amplitude turbination cycles.