Hydrogeological terrains and typical settings of southern Ontario

Groundwater is an important component of the hydrologic cycle of southern Ontario, which is significant to water supply and to groundwater discharge to surface water. To improve our understanding of groundwater, we develop a framework of typical terrains or hydrogeological settings that use geologic and topographic controls to describe how water moves through the southern Ontario landscape. Surface sediment and bedrock types, permeability, physiography and topographic gradients yield distinctive regional hydrogeological settings. Hence, we review a small number of hydrogeological settings, which contribute to a simple characterization of regional surface water and groundwater conditions across southern Ontario. Climate, stream and well monitoring data are integrated with local terrain information to assess the hydrological and hydrogeological response of typical settings. In each setting, the movement of water has differences in fluxes and temporal patterns as it flows across the surface and through the subsurface. We describe seven hydrogeological settings: five in sediment (clay, sand, till upland, till complex, and gravel); and two in bedrock. The selected hydrogeological settings characterize ~90% of all terrain at the regional scale based on a simplified geological map of southern Ontario. The identified settings cover large areas, and include several different sediment/ bedrock landscapes of the Paleozoic basin and Shield margin. It is expected that the main hydrogeological characteristics and hydrologic behaviour of these settings are represented in the hydrograph trends for each terrain.