How submerged aquatic vegetation affects the hydrological connectivity in wetlands: A modeling study of the largest wetland in North China

Wetlands, as one of the most critical natural ecosystems, face increasingly prominent threats of degradation, with the continuous decline of hydrological connectivity being considered a key cause. However, the impact of submerged aquatic vegetation (SAV) on wetland hydrological connectivity has long been overlooked. This study constructs the EFDC hydrodynamic model that takes into account the spatiotemporal changes of SAV and analyzes the evolution of hydrological connectivity in the Baiyangdian Wetland, the largest wetland in North China. The results show that under the growth conditions of SAV, the hydrological connectivity of wetlands exhibits seasonal variation characteristics. The connectivity-domain area, accounting for the effects of SAV density and plant height, decreased on average by 3.5%, 39.2%, and 25.1% across the different growth stages, which are more pronounced in areas with dense vegetation distribution. The water-impeding effect of SAV is the main reason for the decrease in hydrological connectivity, especially during the peak growth period when the impact of SAV on flow velocity exceeds the influence of water depth changes by 14 times. The spatiotemporal differences in SAV distribution density and plant height are the main drivers of the spatiotemporal heterogeneity of hydrological connectivity. In addition, SAV may reduce the flood conveyance capacity of wetlands, leading to increased flood risk. We suggest that remote sensing technology should be combined to determine the spatial distribution of wetland plants, and artificial intervention should be made during the peak growth period to control its growth at key nodes to improve the hydrological connectivity of wetlands. This study enriches the theoretical framework of wetland hydrological connectivity research and provides a scientific basis for wetland SAV management. • Wetlands hydrology varies depending on the growth patterns of submerged aquatic vegetation (SAV). • SAV increases spatiotemporal variation in hydrological connectivity through flow regulation. • SAV obstruction of flow velocity reduces wetland hydrological connectivity. • In outbreak period, SAV greatly affects velocity change rate compared to water depth.