GEOSCAN Search Results: Fastlink

GEOSCAN Menu


TitleAssessing rock aquifer vulnerability using downward advective times from a 3D model of surficial geology: a case study from the St. Lawrence Lowlands, Canada
AuthorRoss, M; Martel, R; Lefebvre, R; Parent, M; Savard, M M
SourceAquifer vulnerability and risk; by Rogriguez, R (ed.); Civita, M (ed.); de Maio, M (ed.); Geofísica Internacional vol. 43, no. 4, 2004 p. 591-602
Year2004
Alt SeriesGeological Survey of Canada, Contribution Series 2003080
Documentserial
Lang.English
Mediapaper
ProvinceQuebec
NTS31H/12
AreaSt. Lawrence Lowlands; Montreal
Lat/Long WENS-74.0000 -73.5000 45.7500 45.5000
Subjectshydrogeology; surficial geology/geomorphology; groundwater; groundwater flow; groundwater resources; groundwater regimes; aquifers; hydrologic budget; hydrologic environment; modelling; glacial deposits; recharge rates; groundwater discharge; hydrostratigraphic units; Cenozoic; Quaternary
Illustrationssketch maps; logs; histograms; tables; diagrams; models
ProgramCanada Economic Development, Funding Program
ProgramConseil Régional de Développement-Laurentides, Programme de financement
ProgramMinistère du développement durable, Environnement et Parcs du Québec, Programme de financement
ProgramMunicipalité régionale de comté d'Argenteuil, Programme de financement
ProgramMunicipalité régionale de comté de Deux-Montagnes, Programme de financement
ProgramMunicipalité régionale de comté de Mirabel, Programme de financement
ProgramMunicipalité régionale de comté deThérèse-de-Blainville, Programme de financement
ProgramFonds québecois de la recherche sur la nature et les technologies
AbstractAn aquifer vulnerability assessment method which relates vulnerability directly to groundwater Downward Advective Time (DAT) from a 3D geologic model is tested over a 1400 km2 area in the St. Lawrence Lowlands in SW Québec. The goal was to assess the vulnerability of the regional rock aquifer which is overlain by discontinuous and unconsolidated Quaternary units. Hydrogeologic parameters such as groundwater recharge and porosity of each unit overlying the aquifer were integrated to a gOcad 3D stratigraphic grid. This grid was generated from a 3D geologic model made of interlocked surfaces representing the boundaries of Quaternary units and the underlying bedrock topography. Calculations were carried out using a deterministic approach and DAT estimates were obtained for 74% of the model area. Results are tentatively grouped into 6 DAT classes which are interpreted in terms of a relative vulnerability index. The spatial distribution of this index is in good agreement with the hydrogeological settings and available hydrogeochemical data. Results indicate that 40% of the evaluated area falls within the moderately high to very high vulnerability classes. Comparison between this map and a DRASTIC map of the same area reveals some significant discrepancies, particularly in areas of shallow depth to bedrock which are characterized by fast DAT through a thick unsaturated zone. In these areas DRASTIC produces low vulnerability scores while this assessment yields high vulnerability ranking. Overall, this assessment provides a sound basis for regional planning and decision making.
GEOSCAN ID214506