Research progress of the unsteady hyporheic flow exchange process

The study of hyporheic exchange involves the physical mechanism, influencing factors and biochemical effects on the interaction of a surface water-groundwater system, which is a hot research topic in recent years in the disciplines of hydrology, ecology and environmental science. The process of hyporheic exchange includes water movement, solute transport and energy transfer process. The research of hyporheic exchange under the steady-state flow conditions as the controlling factor can no longer meet the requirements of the development of related disciplines. Therefore, the research on the unsteady hyporheic exchange processes and its results have attracted attention in recent years. The current research is mostly based on physical model tests (e. g., indoor flume tests, tracer tests), supplemented by numerical simulations or remote sensing techniques for validation, and then summarizes the laws of hydrodynamic and energy exchange processes during the unsteady hyporheic exchange. Future research will integrate multiple high-precision monitoring tools at multiple spatial and temporal scales to study the influencing factors in hyporheic exchange (e. g., river level fluctuations), develop more accurate coupled surface water-groundwater models, and systematically understand the unsteady hyporheic exchange processes. The findings of the unsteady hyporheic exchange will effectively guide water resources protection and ecological restoration and comprehensive management.