Research on sluice–pump operation for enhancing hydrodynamic conditions and water quality improvement mechanisms in polder areas

ABSTRACT This study aims to optimize the hydrodynamic conditions and water quality of river networks enclosed by polders in South China, structures that enhance flood control but often impair hydrodynamics and degrade water quality. Focusing on the Luotang River polder area in Zhejiang, this study employed hydrodynamic modeling to simulate four operational cases over 2 years. Changes in water level, discharge, and flow velocity were analyzed and integrated with a water quality model to assess key pollutants. The results demonstrate that coordinated operations can significantly enhance flood prevention, hydrodynamics, and water quality. Compared with pre-polder conditions, flood control drainage and sluice station operations effectively reduced maximum water levels by 0.59 and 0.62 m, respectively. Ecological water diversion substantially increased flow velocities and enhanced the river network's assimilative capacity, with approximately 60% of rivers showing improvement. During the wet season, priority should be given to flood control drainage or sluice station operation. In the dry season, ecological water diversion effectively maintains ecological water levels while simultaneously enhancing the system's assimilative capacity.