A Physically-Based Approach to Assess the Impact of Climate Change On Canadian Water Resources

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. Alterations of baseflow to rivers due to changing subsurface flow patterns and fluctuations in the depth of the groundwater table and the water levels of lakes are examples of possible consequences of future climate change. Quantification of such impacts as driven by plausible climate-change scenarios is essential for policy makers. To date, there are numerous studies concerning this issue in the literature, but, to our knowledge, many are limited to a relatively small domain, usually up to a watershed or basin scale, and/or they fail to simulate the surface and subsurface flow regimes in a physically-based, fully-integrated manner. In this study, a physically-based model, HydroGeoSphere (HGS), is employed to simulate 2D surface water flow on the land surface together with 3D variably-saturated subsurface flow covering the Canadian landscape. Various implicit/explicit coupling techniques are explored in view of the large computational effort required the handle 3D continental-scale simulations and to accommodate the highly-complex and wide-ranging terrain over the Canadian land mass. The impact of long-term future climate change upon Canadian water resources is explored after calibration against historical meteorological, hydrological and hydrogeological data. The ultimate goal of this study is to fully couple HGS with the Community Climate System Model (CCSM), a highly-respected climate-change model primarily supported by the US National Center for Atmospheric Research (NCAR).