INVESTIGATING THE IMPORTANCE OF STREAMBED PROPERTIES ON HYDROLOGIC AND THERMAL CONDITIONS OF A STREAM USING AN INTEGRATED SURFACE/SUBSURFACE MODEL

The hyporheic zone has been recently identified as being a significant driver of the hydrologic, contaminant and ecological conditions of a stream. While there has been an increase in field-based research directed towards characterizing hydrologic and thermal energy exchange processes that occur at the surface water/groundwater interface within streams, relatively little work has been performed to simulate these exchanges in a fully-integrated surface/subsurface computational framework. A fully-integrated, physically-based modeling framework is needed to elucidate the roles of the various meteorological, hydrological and thermal properties in mediating the hydrology and temperature of streams and surface water bodies. To address this issue, HydroGeoSphere, a fully-integrated surface/subsurface flow and transport model, is used to investigate the importance of several streambed properties on the hydrologic and thermal conditions of a stream. Results from high-resolution 3D numerical simulations are presented to demonstrate the relative importance of the streambed morphology, including hydraulic and thermal conductivity and topography, on the hydrologic and thermal regimes of the entire domain. The simulations also demonstrate the importance of accounting for the hyporheic zone in a fully-integrated surface/subsurface framework. The need to account for streambed morphology, in addition to the hydraulic and thermal properties of the hyporheic zone, highlights the importance of taking a holistic approach when predicting the impacts of, for example, river restoration on aquatic habitats.