The Oak Ridges Moraine, a deposit formed during the last glaciation, is a major source of drinking water for southern Ontario. The aim of the co-operative Oak Ridges Moraine project was to discover if the deposit can continue to supply the increasing water needs of the most densely populated area in Canada. Because of concerns raised by the results of the project, there is now a Conservation Act for the Oak Ridges Moraine, which controls land use and water resources. Also, the Water-Well Act in Ontario has been rewritten and well drillers are now required to provide more accurate location and sample information. (NATMAP project)

Figure 1. Regional stratigraphic framework comprises: a) last-glacial timeframe; b) 3-D conceptual geologic model. (Courtesy of David Sharpe) larger image [JPEG, 127.8 kb, 1000 X 713, notice]

Figure 2. Digital elevation model shows ORM as an E-W drainage divide running east of the Niagara Escarpment. (Courtesy of Frank Kenny) larger image [JPEG, 124.2 kb, 800 X 452, notice]

Synopsis

The Oak Ridges Moraine project demonstrated that public sector scientific research could raise the awareness of environmental issues within government and the public. This research project also demonstrated the value of creative collaborative agreements between different levels of government and interested partners.

Rationale

Renewed hydrogeological research at the Geological Survey of Canada (GSC) was initiated in 1993 following a positive survey response from clients. The Oak Ridges Moraine (ORM) study was a multi-agency project to assess regional groundwater science. This approach was endorsed by key government agencies, municipal governments, and consultants in Ontario. The ORM is a prominent glacial landform north of Lake Ontario (Figure 2). The area has one of the most heavily used groundwater resources in Canada. However, expanding use of this resource and decisions relating to landuse planning (e.g. watershed management) in the rapidly developing Toronto area, were hindered by the lack of a 3-D geological context. The ORM study was designed to produce a regional digital database and hydrogeological framework for assessing surface water-groundwater systems across the ~11,000 km2 area.

Approach

The study used a multidisciplinary basin analysis approach to mapping and characterizing the reservoir potential of the region. Basin analysis supports the progression from data compilation and geological conceptualization to model development, and subsequently to quantitative flow system analysis. This is achieved by developing geological models of the glacial sedimentary deposits. A regional conceptual model (Figure 2) was used to guide development of a digital 3-D stratigraphic framework for the region that integrated, detailed mapping, seismic profiles and cored boreholes, with over 75,000 water well records.

Geology

The ORM is a 160 by 20 km landform rising 300 m above Lake Ontario (Figure 1). This elevated ridge of sand and gravel forms a drainage divide between Lake Simcoe and Lake Ontario (Figure 2). The ORM has the thickest glacial deposits in southern Ontario with local thickness up to 200 m. The Quaternary succession is the oldest known in southern Canada dating back 100,000 years. The thick accumulation of sediment contains a large number of high yield aquifers with complicated distribution, geometries and sizes.

Outcomes

The project profoundly changed the approach to water investigations in the ORM region and how they will be carried out in the future. Exciting new science results include improved understanding of late glacial catastrophic subglacial meltwater floods. These floods formed much of the present day landscape. Coarse sediment deposited by these events form the regional high yield aquifers. This work provided much of the regional geological understanding that contributed to land use changes regarding water resources and a Conservation Act for the ORM. Long-term relationships were established with key Ontario agencies that will aid future partnerships.

Participants

Work proceeded with the cooperation and resources of an array of provincial agencies, regional municipalities, universities, and private firms, and funding from GSC's national mapping (NATMAP) and groundwater programs.

More Information

Key refereed papers, field guides, data releases, contacts, and partners are available on the Oak Ridges Moraine project website. The website is a valuable student resource and has been used by a number of student groups.