The Hydrogeological Regions Map depicts first order regions of Canada that have distinct groundwater systems. The country is assigned to nine regions as determined by frozen ground, geology, and physiography. Frozen ground has a dominant affect in the continuous permafrost region and the southern limit of this region cuts across both physiographic and geological features. Geology controls surface expression of the landscape and subsurface water-bearing characteristics, and the bedrock contacts that delineate geological terrains and basins represent the major region boundaries. Physiographic features are influenced by geology and coincide closely with geological boundaries but also divide geological units where elevation dominates, primarily along the eastern limit of the Cordillera. Physiographic features provide hydraulic gradients for regional and local flow and combine with climatic and run-off characteristics to dictate the regional moisture surplus or deficit that affects recharge to and discharge from groundwater systems. Moisture index isolines based on the Thornthwaite classification overlay the regions to provide a sense of moisture deficiency or surplus.
The Oak Ridges Moraine in southern Ontario is a ca. 160 km long east-west trending ridge of sand and gravel situated north of Lake Ontario. Study of the Oak Ridges Moraine in the Humber River watershed was undertaken to assess its role in the groundwater system of the buried Laurentian Valley. The Oak Ridges Moraine is interpreted to have been deposited in three stages. Stage I records rapid deposition from hyperconcentrated flows where tunnel channels discharged into a subglacial lake in the Lake Ontario basin. Low-energy basin sedimentation of Stage II was in a subglacial and ice-contact setting of a highly crevassed ice sheet. Stage III sedimentation is characterized by rapid facies changes associated with esker, subaqueous fan, and basinal sedimentation. Detailed sediment analysis challenges the concept that the Oak Ridges Moraine was deposited principally from seasonal meltwater discharges, climatic modulated ice-marginal fluctuations, or in an interlobate position. Instead it is interpreted to have formed in response to late-glacial ice sheet events associated with subglacial meltwater ponding, episodic and catastrophic subglacial meltwater discharge, and subsequent seasonal meltwater discharge. The moraine probably formed as the glacial-hydraulic system re-equilibrated to the presence of a thinned, grounded ice shelf and a subglacial lake in the Lake Ontario basin.
A hydrostratigraphic framework has been developed for southern Ontario consisting of 15 hydrostratigraphic units and 3 regional hydrochemical regimes. Using this framework, the 54 layer 3-D lithostratigraphic model has been converted into a 15 layer 3-D hydrostratigraphic model. Layers are expressed as either aquifer or aquitard based principally on hydrogeologic characteristics, in particular the permeability and the occurrence/absence of groundwater when intersected by a water well or petroleum well. Hydrostratigraphic aquifer units are sub-divided into up to three distinct hydrochemical regimes: brines (deep), brackish-saline sulphur water (intermediate), and fresh (shallow). The hydrostratigraphic unit assignment provides a standard nomenclature and definition for regional flow modelling of potable water and deeper fluids. Included in the model are: 1) 3-D hydrostratigraphic units, 2) 3-D hydrochemical fluid zones within aquifers, 3) 3-D representations of oil and natural gas reservoirs which form an integral part of the intermediate to deep groundwater regimes, 4) 3-D fluid level surfaces for deep Cambrian brines, for brines and fresh to sulphurous groundwater in the Guelph Aquifer, and the fresh to sulphurous groundwater of the Bass Islands Aquifer and Lucas-Dundee Aquifer, 5) inferred shallow karst, 6) base of fresh water, 7) Lockport Group TDS, and 8) the 3-D lithostratigraphy. The 3-D hydrostratigraphic model is derived from the lithostratigraphic layers of the published 3-D geological model. It is constructed using Leapfrog Works at 400 m grid scale and is distributed in a proprietary format with free viewer software as well as industry standard formats.
A basin analysis approach is used to help understand a complex aquifer system in the Oak Ridges Moraine and Greater Toronto areas, southern Ontario, Canada. The aquifer complex consists of a sequence of discontinuous strata that have a prominent regional unconformity. To help visualize this architecture, a stratigraphic database has been developed and used to construct a 3-D stratigraphic model, through selective integration of disparate data. To accurately interpret borehole logs, geological context was supplied by using expert knowledge constrained with a conceptual stratigraphic framework. Utilizing a digital stratigraphic training framework derived from manually coded, high-quality data, an expert system automatically interpreted and coded a large number of low-quality water well records. The expert system was designed to emulate the manual borehole interpretation process by applying knowledge-based geological rules, within the constraints of the digital training framework. Issues of poorly constrained interpolation due to sparse data are addressed by the integration of additional spatial rules defined by thematic map coverages within the expert system. As quantitative hydrogeological modelling moves to more regional scales, geological knowledge input becomes increasingly more valuable. The availability of seamless geological mapping improves 3-D modelling and helps to limit the effect of deficiencies in data coverage and data quality, often encountered in regional hydrogeological studies.
Buried-valley aquifers occur across the Canadian Prairies with a lack of surface expression and complicated network geometries. As part of an effort to map and characterize the Hatfield buried-valley aquifer, the Geological Survey of Canada commissioned a helicopter time-domain electromagnetic survey consisting of 2617 line-km of data over 940 km2 near Esterhazy and Rocanville in southeastern Saskatchewan. Survey results are presented as apparent-conductivity maps and as 3D conductivity-depth models. The Hatfield and Rocanville buried valleys are clearly imaged along with several other erosional and depositional features, some of which have been previously identified at the local scale and are currently utilized as groundwater resources, but for which the extent has not been fully mapped. Other features identified in the survey represent potentially new groundwater resources and can be used to help unravel the details of valley formation, groundwater flow, and aquifer recharge.
