| Titre | Hydrostratigraphic and groundwater flow models of a complex unconsolidated aquifer system, Nanaimo Lowlands, British Columbia, Canada |
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| Auteur | Benoit, N; Paradis, D ; Bednarski, J; Russell, H |
| Source | Conference program and abstracts, IAH-CNC 2015 Waterloo; 2015 p. 170-171 |
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| Année | 2015 |
| Séries alt. | Secteur des sciences de la Terre, Contribution externe 20140418 |
| Éditeur | International Association of Hydrogeologists - Canadian National Chapter |
| Réunion | IAH-CNC Conference 2015; Waterloo, ON; CA; Octobre 27-30, 2015 |
| Document | livre |
| Lang. | anglais |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Province | Colombie-Britannique |
| SNRC | 92F/07; 92F/08; 92F/10 |
| Région | Île de Vancouver |
| Lat/Long OENS | -125.0000 -124.2500 49.6333 49.2500 |
| Sujets | ressources en eau souterraine; aquifères; écoulement de la nappe d'eau souterraine; unités hydrostratigraphiques; modèles; établissement de modèles; diagraphie géophysique; levés géophysiques; levés de
reflexion sismiques; sediments; sables; argiles; graviers; silts; dépôts glaciaires; tills; géologie du substratum rocheux; lithologie; roches sédimentaires; siltstones; grès; sédiments glaciomarins; hydrogéologie; géologie des dépôts
meubles/géomorphologie; géologie régional; stratigraphie; géophysique; Nature et environnement; Sciences et technologie |
| Programme | Géoscience des eaux souterraines , Aquifer Assessment & support to mapping |
| Diffusé | 2015 10 01 |
| Résumé | (disponible en anglais seulement)
To support sustainable groundwater management, tridimensional (3D) hydrostratigraphic and groundwater flow models were developed for an unconsolidated aquifer
system in the Nanaimo Lowlands, British Columbia (Canada). The study area is a coastal strip on eastern Vancouver Island (~580 km2). A 3D hydrostratigraphic model was developed using existing well logs and published cross sections as well as new data
from rotosonic coring, borehole geophysics, seismic reflection surveys and surficial geology mapping. The detailed surficial geology consists of 31 different units that are grouped into 8 major hydrostratigraphic units, of which 5 correspond to
aquifers and 3 to aquitards. These are (from the surface down): Capilano-Salish (sand), Capilano glaciomarine (silty clay), Vashon-Capilano (sand and gravel), Vashon (till), Quadra (sand), Dashwood-Cowichan (compact silt), Mapleguard (sand), and
siltstone to sandstone bedrock. This succession of Late Pleistocene to Holocene sediments is up to 140 m thick and is present over most of the study area, thinning to the southwest with rising topography and bedrock outcrops. Capilano-Salish and
Vashon-Capilano units are shallow aquifers with relatively high vulnerability to surface contamination and low groundwater potential due to their limited thickness. The Quadra sand is the most exploited aquifer unit. It underlies the ubiquitous low
permeability Vashon till and overlies Dashwood-Cowichan aquitard or the bedrock. The Quadra has a thickness of up to 50 m in place and it is predominantly above sea level, which minimizes issues of seawater intrusion. However, only about one-third of
its thickness is saturated likely due to: (1) the covering by the Vashon aquitard that limits groundwater replenishment and (2) its deep incision by modern rivers that substantially drain its flanks. The relatively low permeability sedimentary rock
aquifer is also extensively exploited, but only in areas where the Quadra aquifer is not present. Results of 3D groundwater flow modelling based on the hydrostratigraphic model show that baseflow to major rivers is provided mostly by groundwater
seepage from heavily incised Quadra sand. Different regional groundwater flow patterns are also observed reflecting stratigraphic controls: flow within the Quadra aquifer generally follows surface water drainage basin with discharge to rivers,
whereas flow in underlying Mapleguard and bedrock aquifers is directed towards the Strait of Georgia without significant hydraulic connection with rivers. Hydrogeological insights gained through this study shows that the complexity of this aquifer
system can make groundwater management challenging and that each system component should be carefully understood to ensure sustainable management. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Cet article met l'accent sur le développement de modèles mathématiques de l'hydrostratigraphie et de l'écoulement régional des eaux souterraines
de Nanaimo (Colombie-Britannique). L'aquifère régional Nanaimo représente l'un des principaux aquifères considérés par le Programme de Géosciences pour l'Eau Souterraine du SST. L'article résume les connaissances hydrogéologiques actuelles et permet
une représentation des principaux concepts et paramètres hydrogéologiques pour la zone d'étude. |
| GEOSCAN ID | 295802 |
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