THREE-DIMENSIONAL GROUNDWATER MAPPING IN STRATIGRAPHICALLY COMPLEX GLACIAL DEPOSITS: CURRENT PROJECTS IN ONTARIO, CANADA

The protection and preservation of Ontario's groundwater resources has become a priority in recent years. At the present time, approximately 3 million Ontario residents use groundwater as their primary domestic supply. Additional strain is put on the groundwater resource by the commercial and industrial sectors. Since many of the populated areas of Ontario are blanketed by Quaternary glacial sediments, the protection of groundwater resources through land-use planning requires a good understanding of the three-dimensional stratigraphy of surficial sediments. These sediments form recharge and discharge zones, local and regional aquitards and aquifers. Regional three-dimensional models will allow new aquifers to be located and existing aquifers to be better defined. Of equal importance, the delineation of aquitards will allow the modelling of potential pathways for aquifer contamination and safe zones where aquifers are protected.

The Ontario Geological Survey (OGS) has recently undertaken three-dimensional mapping projects encompassing the Waterloo Moraine, located in Kitchener-Waterloo, Ontario and more recently the Oro Moraine located north of Barrie, Ontario. These projects areas are large, encompassing 1400 km2 and 1200 km2 respectively, and are stratigraphically complex.

To assist in 3-D modelling of the overburden the OGS has tested several subsurface mapping software packages linked to Microsoft Access. Currently DatamineTM, a package originally developed for the mining industry, is being used for the three-dimensional stratigraphic modelling. Data inputs to the models include; new high-resolution drilling and associated downhole geophysics, new seismic surveys, pre-existing drilling logs, water well records, published and new surficial mapping and the interpretation of natural and man-made exposures. Complex stratigraphy and software limitations have had to be overcome in our efforts to develop realistic models.

Possible project deliverables include; GIS databases, stacked two-dimensional maps, aquifer and aquitard surface maps, aquifer isopach maps, and source water protection mapping. The resulting models will provide important tools in future groundwater resource management in the province of Ontario.