Environmental Consequences of the Sanmenxia Hydropower Station Operation in Lower Yellow River, China

The ecological and environmental impacts of the Sanmenxia Hydropower Station on the lower reach of the Yellow River were examined based on the monitoring data, since the 1970s, of the Sanmenxia Hydropower Station’s normal operation. Different operation modes of the reservoir were considered in addition to the effects of tributaries downstream of Sanmenxia. The environmental consequences were evaluated in terms of the total ion content (TIC), since it is regarded as the most important index reflecting the status of natural water quality in the Yellow River. However, the ecological consequence was assessed according to the severity level of the no-flow events, which has become the major concern of the Yellow River Authorities in recent years. The TIC monitored at the hydrological stations along the lower Yellow River was closely related to the reservoir’s operation mode and the inflow from the tributaries between Sanmenxia and Huayuankou. Also, the variation of the severity level of the no-flow events is primarily controlled by the operation modes. The present study is of fundamental importance to determine the relative optimal operation mode of the hydropower station, so as to harmonize various purposes and constraints such as a decrease of the TIC and the severity level of the no-flow events, an increase in power generation, irrigation, and flood prevention.