Impact of floodgates operation on water environment using one-dimensional modelling system in river network of Wuxi city, China

•The impact of floodgates operation on river flow and water quality was evaluated.•Floodgates operation reduced water level and river discharge.•Floodgates operation resulted in growth on the concentration of COD and NH4-N.•Flood control projects are likely to cause water quality deterioration in Taihu Lake.

Floodgates operation is one of the major forms of river regulation in basin development and utilization, and have changed natural structures, processes of running water and associated environments. However, there are few analysis on the impacts of multiple floodgates integration on water environment. In this paper, a one- dimensional modelling system (MIKE 11) was established and applied to evaluate the impact of multiple floodgates integration on river flow regimes and water quality. Compared with the actual operation practice, the without floodgates scenario had been simultaneously assessed. The results showed that floodgate operation reduced water levels and river discharge and had opposite impacts on pollutant concentrations. The concentration of Chemical Oxygen Demand (COD) and Ammonia Nitrogen (NH4-N) significantly increased due to floodgate operation. In addition, the floodgates are likely to threaten the water quality in Taihu Lake. The results provide a scientific basis for successful management of river regulation and serve as a valuable reference for future water environmental impact studies when new river floodgates are proposed.