Study on Causes of High Turbidity in Water Intake in Strong Tidal Estuaries

The water intake at the estuary of a strong tidal river is affected by high turbidity, leading to sedimentation issues in the receiving river channels. The Zhejiang East Water Diversion Project, with an investment exceeding 10 billion RMB, is a strategic water resource allocation project, with the Xiaoshan Hub as its leading component, drawing an annual average of 890 million cubic meters of water. The water source is the Qiantang River, which has a high sediment content. Analysis of underwater topography changes indicates that since the project's operation in 2014, water diversion has caused siltation in the receiving river network, affecting flood discharge and navigation. Hydrological data from the outer river shows a significant correlation between the sediment concentration at the intake and the tidal range, with a correlation coefficient greater than 0.9. The sediment concentration significantly increases during flood tides. The high turbidity of the raw water at the intake is not caused by substantial erosion of the Puyang River channel but is due to the strong tidal currents at the Qiantang River estuary, which mobilize and resuspend the fine sediment from the riverbed, resulting in high sediment concentration in the diverted water.