| Citation |
Benoit, N; Paradis, D; Bednarski, J; Russel, H; 2015; Hydrostratigraphic and Groundwater Flow Models of a Complex Unconsolidated Aquifer System, Nanaimo Lowlands, British Columbia, Canada; IAH-CNC Conference 2015; Waterloo; CA; Geological Survey of Canada Open File: 7796; 30p. |
| Abstract/Description or Keywords |
A 3D hydrostratigraphic and groundwater flow models were developed for an unconsolidated aquifer system in the Nanaimo Lowlands, British-Columbia (Canada). A 3D hydrostratigraphic model was developed using existing well logs and published cross-sections as well as new data from roto-sonic coring, borehole geophysics, seismic reflection surveys and surficial geology mapping. The detailed surficial geology consists of 31 different units, which are grouped into 8 major hydrostratigraphic units: 5 aquifers and 3 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 presents 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 in the event of intensive groundwater extraction in this aquifer..... |
