Aaron PackmanNorthwestern University, Civil and Environmental Engineering
Historically, surface waters and groundwaters have been considered to represent distinct systems with little hydrologic connectivity. However, coupling between hydrodynamic and geomorphic processes causes surface and subsurface waters to be highly connected over a wide range of scales. A wide range of processes cause exchange of water and suspended matter between rivers and underlying sediments. Recent observations have demonstrated that fine particles and suspended microorganisms show complex dynamics in rivers, including continuous deposition and resuspension in streambed sediments. This provides substantial opportunity for interaction of stream-borne material with underlying sediments, and this interaction is expected to alter the hydrogeological properties of fluvial deposits, increase the opportunity for metabolism of terrestrial particulate organic matter in rivers, and mediate the migration, persistence, and growth of microorganisms. In this presentation, I will briefly review current understanding of surface-groundwater exchange processes, develop a conceptual model for deposition and resuspension of fine particles and microorganisms in rivers, and present a stochastic modeling framework for these processes. I will close by discussing the limits of current understanding and prospects for future development of more general models for coupled hydrologic, geomorphic, and microbial processes in watersheds.
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