Eco-hydrological Processes Oriented Synergetic Operation of Multi-Reservoir in the Middle Stream of the Yellow River

Hydrological processes are playing a significant role in maintaining the riverine ecosystem. With the development of social economy, disturbance of human activities on the riverine ecosystem has increased. The connectivity of rivers is being destroyed by the construction of numerous dams, water withdraw, and other water resources development activities, which obstructs the transmission of substance, energy and information, influencing the ecological service function of rivers. The Yellow River has limited water and plenty of sand. The water use keeps increasing in the upstream while lots of sand flows into the middle stream during the flood season, resulting in decreasing runoff and severe sedimentation in the downstream. The analysis of ecological factors and hydrological characteristics in different periods reveals that the flow regime in downstream of Yellow River has been changed by the operation of the Sanmenxia Reservoir and the Xiaolangdi Reservoir in the middle stream, generating stress on the riverine ecosystem. To mitigate the negative impact on the riverine ecosystem in the downstream from the reservoir operation in the midstream of the Yellow River, indicative species and their habitat conditions are sifted and recognized on the basis of major ecological problems of this river. Then the minimum environmental flow, proper environmental flow, flood, high flow pulse process and other key eco-hydrological processes of river are analyzed and computed. Setting the sediment transport, habitat restoration and fish protection as targets, the eco-hydrological processes oriented simulation model of multi-reservoir operation is built with multi-spatial nesting and multi-processes coupling methods. Taking the typical representative years as example, the synergetic operation plan of multi-reservoir is proposed to balance ecology and economy. The results show that the flow regime of the downstream is optimized through the synergetic operation of multi-reservoir in middle stream. The model developed in this study can improve the flow regime condition in the downstream by satisfying the water demand process of the riverine ecosystem. Furthermore, the flood protection, water supply, sediment transport, and other demands can be guaranteed at the same time. This paper provides the decision support for the improvement of the river carrying capacity and the restoration of riverine ecosystem.