INTEGRATED MODELLING TO SUPPORT CLIMATE CHANGE STUDIES IN THE GREAT LAKES BASIN

Modelling hydrological processes at the watershed scale is a challenging task due to the complex interconnection between system components. Physically-based integrated models provide a means to examine subsurface and surface flow processes in a fully coupled manner that gives appropriate representation to fluid interaction between these domains. This is especially important if a model is to be used for the examination of watershed behavior under changing conditions, such as future climate change. In the present investigation, HydroGeoSphere has been used to construct an integrated, 3D finite element model for the Upper Parkhill watershed in southwestern, Ontario, Canada. This watershed, which has been identified as vulnerable to the impacts of climate change, is an agricultural, headwaters catchment (~130 km²) dominated by low permeability glacial till. A calibrated numerical model of this watershed was used to simulate watershed response under varied scenarios of external climate stimulus. In an effort to account for the uncertainty in climate modelling, a diversified approach was taken for scenario generation involving conventionally derived projections from general circulation models alongside both synthetic and analogue scenarios. Varied climate data input structures (e.g. daily vs. monthly normal forcing) were also assessed. Changes in groundwater levels, surface discharge and exchange flux between surface and subsurface domains were examined to evaluate potential mid-century climate change impacts. Results from this study provide insight on meteorological forcing practices for climate change studies in the Great Lakes Basin and more generally, for studies using large scale integrated models. Outcomes from this investigation may be used to support sustainable water use and water management practices in the Upper Parkhill watershed and neighboring areas with similar hydrogeologic conditions.