| Title | Assessing rock aquifer vulnerability using downward advective times from a 3D model of surficial geology: a case study from the St. Lawrence Lowlands, Canada |
| |
| Author | Ross, M ; Martel,
R; Lefebvre, R; Parent, M; Savard, M M |
| Source | Aquifer vulnerability and risk; by Rogriguez, R (ed.); Civita, M (ed.); de Maio, M (ed.); Geofísica Internacional vol. 43, no. 4, 2004 p. 591-602 |
| Year | 2004 |
| Alt Series | Geological Survey of Canada, Contribution Series 2003080 |
| Document | serial |
| Lang. | English |
| Media | paper |
| Province | Quebec |
| NTS | 31H/12 |
| Area | St. Lawrence Lowlands; Montreal |
| Lat/Long WENS | -74.0000 -73.5000 45.7500 45.5000 |
| Subjects | hydrogeology; 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 |
| Illustrations | sketch maps; logs; histograms; tables; diagrams; models |
| Program | Canada Economic Development, Funding Program
|
| Program | Conseil Régional de Développement-Laurentides,
Programme de financement |
| Program | Ministère du développement
durable, Environnement et Parcs du Québec, Programme de financement |
| Program | Municipalité régionale de comté d'Argenteuil, Programme
de financement |
| Program | Municipalité régionale de
comté de Deux-Montagnes, Programme de financement |
| Program | Municipalité régionale de comté de
Mirabel, Programme de financement |
| Program | Municipalité régionale de comté
deThérèse-de-Blainville, Programme de financement |
| Program | Fonds québecois de la recherche sur la nature et les
technologies |
| Released | 2004 01 01 |
| Abstract | An 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 ID | 214506 |
|
|