Hydrodynamic and water quality impacts of water transfer project on regulating reservoir, a case study of Dongzhang reservoir

Regulating reservoirs play vital roles in water transfer project, of which the hydraulic and water quality status are usually affected by diverted water. To study the environmental impacts of Pingtan and Minjiang Estuary water resources allocation project on regulating reservoir, a two-dimensional hydrodynamic and water quality model of Dongzhang reservoir is established and calibrated. Combined with flow field features, Dongzhang reservoir is divided into six parts. The sensitivities to sudden water pollution events of different parts of Dongzhang Reservoir are analyzed. Dry year is the most unfavorable operation typical year. Wind field is the main driving force on flow field whether the water transfer project operates. The water transfers will change main flow route greatly of Dongzhang reservoir in dry season. Mixed with diverted water from Dazhang stream, the total phosphorus concentration of Dongzhang reservoir will increase in short-term. For reaching the water quality standard of Dongzhang reservoir, a total phosphorus concentration threshold of Dazhang stream is predicted. The study will guide the pollution control work along the water transfer project. Also, it should be helpful in ecological restoration and management of Longjiang basin.

Automated summary

The study establishes a hydrodynamic and water quality model of Dongzhang reservoir and analyzes the sensitivities to sudden water pollution events. It finds that dry years are the most unfavorable operating years, and wind field is the main driving force for flow field. Water transfer projects significantly change the main flow route of the reservoir in dry seasons and result in an increase in total phosphorus concentration in the short term. The study provides guidance for pollution control, ecological restoration, and management.