PROCESS BASED STRATIGRAPHIC MODELLING FOR GROUNDWATER STUDIES: CASE STUDIES FROM SOUTHERN CANADA (Invited Presentation)

Three-dimensional geological modelling for regional water supply studies and more site specific contaminate transport studies are commonly hindered by datasets with relatively low resolution and poor spatial continuity. Studies commonly follow similar workflows from assessment of archival data (water well records) to data collection (core, geophysics) and eventually numeric modeling within a geological framework. Considerable differences exist, however, between the style and sophistication of the geological framework used to constrain integration and correlation of disparate datasets. Process based geological models provide a framework within which the heterogeneity and connectivity of aquifers can be assessed and modeled. Furthermore, such models provide a predictive framework for improved data collection and hypothesis testing. Case studies from glaciated terrain of southern Canada demonstrate the value of process based geological models for data integration and 3-D geological model development. These case studies are framed within a literature review of geological model applications in groundwater studies.

An event stratigraphic approach, analogous to sequence stratigraphy, underpinned by glacial process models has been employed in the study of buried valleys, moraines, and eskers (e.g. Oak Ridges Moraine, prairie provinces) to define regional correlatable surfaces. This approach offers distinct advantages over lithostratigraphic approaches for the integration of disparate data (sediment descriptions, seismic data, airborne electromagnetic data), which otherwise lack commonalities for correlation. Furthermore it supports the spatial correlation of genetically related sedimentary facies within a single model unit. Modelling of spatial heterogeneity can then be completed through development of genetic depositional models on the basis of sedimentary facies models. For the Oak Ridges Moraine, subaqueous fan models were developed for tunnel channel and moraine deposits. Such models provide the necessary constraints on flow parallel and transverse length relationships, and permit improved assignments of sedimentary facies to hydrofacies.