Understanding the flows, connectivity, and residence times of water and sediments is critical to quantifying the hydrological and biogeochemical functioning in surface and subsurface systems. Tracers provide a powerful means to investigate transport processes over a wide range of spatial and temporal scales, from rapid event-driven dynamics to long-term groundwater storage and ecosystem memory. This session brings together classical and emerging tracer approaches, including stable and radioactive isotopes, environmental DNA (eDNA), geochemical and artificial tracers, and modelling techniques, to explore how physical, chemical, and biological signals can be jointly used to unravel flow pathways, transit time distributions, and system connectivity.
We welcome contributions that use single or multi-tracer strategies to investigate groundwater residence times, groundwater–surface water interactions, sediment transport, fracture and aquifer connectivity, and responses to hydrological extremes and environmental change. eDNA offers a rapidly developing and complementary tracer of transport and connectivity, providing spatially resolved biological signals that reflect hydrological pathways, sediment dynamics, degradation processes, and biogeochemical controls. Together with established tracers, eDNA opens new opportunities to link physical transport processes with ecological patterns and ecosystem functioning.
The session particularly encourages studies that integrate tracers spanning different temporal and spatial scales, combine field observations with laboratory experiments and numerical modelling, or exploit sediment archives to connect present-day dynamics with longer-term records. Contributions presenting innovative sampling strategies, automated or distributed monitoring systems, novel sensors, and citizen science approaches are also welcome.
By uniting hydrogeochemical, isotopic, modelling, and biological tracer communities, this session aims to foster interdisciplinary exchange and advance our ability to characterise water and sediment pathways across complex hydrological systems. It provides a platform to explore how novel tracer or multi-tracer frameworks can improve understanding of transport processes, system vulnerability, recovery times, and sustainable management of water-dependent ecosystems.