Effect of sediment particle size distribution characteristics on hyporheic exchange under different riverbed topography

Abstract

Hyporheic exchange, the intricate interplay between groundwater and surface water near the riverbed or riverbank, is highly influenced by the natural features of riverbeds and sediment deposition. Of the structural configurations commonly encountered in aquatic environments, straight and meandering channels are of particular interest for hydrological and geomorphological studies. However, little attention has been given to understanding how sediment particle size distribution affects hyporheic exchange in different riverbed morphologies. In this study, we focused on two sections of the lower Beiluo River in northwestern China, representing meandering and straight channels. By analyzing sediment structure and using the hydraulic gradient method to estimate vertical permeability, we were able to assess how riverbed morphology and sediment grain sizes impact water exchange in the hyporheic zone. Our results showed that the meandering channel morphology significantly influenced water flow in the hyporheic zone, particularly in terms of water volume moving downwards. Additionally, sediment grain size distribution played a role in streambed permeability, with different particle sizes like clay, fine sand, and coarse sand having distinct effects on water exchange. Changes in streambed permeability can also affect hyporheic exchange flux, which is further influenced by anthropogenic structures, river topography, and runoff conditions. Furthermore, hyporheic exchange impacts the vertical distribution of clay particles in the hyporheic zone. This research contributes to enhancing river ecosystem health, improving water purification and pollution control strategies, advancing water resource management practices, and establishing a scientific foundation for ecological conservation and sustainable water resource utilization.