FLOW, CONTAMINANT AND THERMAL ENERGY TRANSPORT IN INTEGRATED SURFACE-SUBSURFACE FLOW SYSTEMS: MODEL APPLICATIONS OVER MULTIPLE SPATIAL AND TEMPORAL SCALES

Over the past several years, increasing attention has been directed towards understanding flow, solute and thermal energy transport processes occurring at the interface between surface water and groundwater, and a variety of numerical strategies have been proposed to couple these processes in a holistic, physically-based modelling framework. Management of watersheds and ecosystems requires such numerical models that can simulate surface and subsurface water flow, contaminant migration and heat transport. Moreover, it is now generally accepted within the scientific community that the climate is changing, and that future climate change may have significant impact on water resources in both quantity and quality. In this talk, an overview of the capabilities and recent numerical developments of the HydroGeoSphere (HGS) model are presented together with several applications. HydroGeoSphere is a fully-coupled 3D model designed to simulate water flow and advective-dispersive solute and heat transport on the 2D land surface and in the 3D subsurface under variably-saturated conditions. Full coupling of the surface and subsurface flow regimes is accomplished implicitly by simultaneously solving one system of non-linear discrete equations describing flow and transport in both flow regimes, as well as the water, solute and energy fluxes between continua. The model capabilities and main features are demonstrated with several 3D numerical simulations performed for catchments of various scales. The examples range from the scale of regional watersheds (300 to 7000 km²), to the continental scale that comprises a simulation of the impact of the Wisconsinian glaciation on groundwater flow system evolution (-120 k-year to present) over the entire Canadian land mass. We are also endeavouring to couple HGS with a global climate-change model and to perform a suite of 3D simulations to explore impacts due to plausible climate-change scenarios on Canada’s surface and subsurface water resources.