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TitleThree dimensional hydrostratigraphic model of the Nanoose - Deep Bay area, Nanaimo Lowland, British Columbia
AuthorBenoit, N; Paradis, D; Bednarski, J M; Hamblin, T; Russell, H A J
SourceGeological Survey of Canada, Open File 7796, 2015, 30 pages,
PublisherNatural Resources Canada
Documentopen file
Mediadigital; on-line
File formatreadme
File formatpdf; adf; xml; ovr
ProvinceBritish Columbia
NTS92F/07; 92F/08; 92F/10
AreaNanoose; Deep Bay; Nanaimo Lowlands; Parksville; Qualicum Beach; Bowser; Vancouver Island
Lat/Long WENS-125.0000 -124.2500 49.6167 49.2500
Subjectshydrogeology; surficial geology/geomorphology; aquifers; groundwater regimes; groundwater; groundwater resources; bedrock geology; glacial deposits; hydrostratigraphic units; surface waters
Illustrationslocation maps; cross-sections; stratigraphic columns
ProgramAquifer Assessment & support to mapping, Groundwater Geoscience
Released2015 04 22; 2016 10 25
AbstractTo support improved sustainable groundwater management of the Nanaimo Lowland, British Columbia (BC), a three-dimensional (3D) hydrostratigraphic model was developed for the Nanaimo Lowland aquifer system. The study area is a coastal strip running from Nanoose to Deep Bay on eastern Vancouver Island (~580 km2). The 3D model was developed using existing driller's logs, published cross-sections and new data which include rotosonic coring, borehole geophysics logs, seismic reflection profiles and surficial geology mapping. The detailed surficial geology consists of 31 different units which, for modelling, are grouped into 9 major hydrostratigraphic units (from youngest to oldest): Capilano-Salish (sand aquifer), Capilano glaciomarine (silty clay aquitard), Vashon-Capilano (coarse sand and gravel aquifer), Vashon (till aquitard), Quadra (sand aquifer), Cowichan-Dashwood (compact silt aquitard), Dashwood-Mapleguard (sand aquifer), sedimentary bedrock and metamorphic bedrock (aquifer near surface with potential decreasing with depth). 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 deposits are shallow and contain unconfined aquifers with relatively high vulnerability to surface contamination and low groundwater resource potential due to their limited thicknesses. Quadra Sand is the most exploited aquifer unit. It underlies the ubiquitous and low permeability Vashon till and it overlies Cowichan-Dashwood aquitard or bedrock. Quadra sediment has an average thickness of 19 m and it is generally above sea and river levels. This would minimize the potential of seawater intrusion and direct surface water extraction, respectively, in the event of intensive groundwater extraction in Quadra unit. The Quadra is an important aquifer, however only about one-third of its thickness is saturated likely due to the overlying Vashon till aquitard that limits groundwater replenishment. Dashwood-Mapleguard sand is a lower confined aquifer unit that extends below sea level. It may have hydrogeological properties and resource potential similar to the Quadra sand, but it is present only in areas where the bedrock elevation is low, generally closer to the coastline. It may be more vulnerable to sea water intrusion, and remains poorly understood. The relatively low permeability regional bedrock aquifers of the Nanaimo Group are generally exploited only where the Quadra aquifer is not present. Their hydrogeological potential is poorly understood due to lack of subsurface data. This hydrostratigraphic model will be used to support groundwater flow modelling.
Summary(Plain Language Summary, not published)
This open file describes the development of a regional hydrostratigraphic model in three dimensions (3D) for Nanaimo Lowlands (BC). The model improves the understanding of the relatively complex aquifer system in the region. It was used to build the groundwater flow model, assess the groundwater budget parameters and run different groundwater use scenarios. As such, the hydrostratigraphic model represents the basis for updating the sustainable management of groundwater Nanaimo Lowland (BC). Annexed electronic files of the hydrostratigraphic flow model allow its use for the development of regional management strategies. The research was carried out by the Geological Survey of Canada (Natural Resources Canada) under the Groundwater Geoscience Program, in partnership with the BC Ministry of Environment (MoE); Ministry of Forests, Lands, and Natural Resource Operations (MFLNRO); and the Regional District of Nanaimo (RDN).