Capilano-Salish

Hydrostratigraphic Unit

Project
Nanaimo Lowlands

Datasets

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Capilano-Salish unit description

Update:2016-02-02
The Capilano-Salish unit overlies the Vashon Drift (aquitard); however, locally it can unconformably overlie the Quadra Sand. The Capilano-Salish hydrogeological unit is considered to be an aquifer, however its aquifer potential is low, due to the thin unit thickness (median thickness of 1 m) and its spatial discontinuity. The Capilano-Salish unit is composed of coarse Capilano glaciofluvial outwash gravel and sand and includes the modern deltaic and alluvial deposits of Salish unit that extends to present sea level. The Salish sediments along rivers are mostly recent fluvial deposits that are not considered to be aquifers, but could form important water storage units and could play a crucial role in the interaction between surface and groundwater. Geochemically there is a decrease in concentration from the base of the Capilano Sediments upwards for Ba, Ca, K, Rb and Zn and there is an increase in the concentration for Cu, Fe, Mn, and V (Knight et al., 2015).
Physiography
Hydrogeological regionCordillera
Hydrogeological context
ReliefThe regional topography ranges from sea level at the coast, up to 1819 m (Mount Arrowsmith). The coastal plain terrain is sub-horizontal with slopes lower than 6% except along incised rivers valleys (up to 20%).
Area116.00 km2
Lithology
DescriptionCapilano-Salish sediments are coarse glaciofluvial outwash gravel and sand. The unit includes the modern deltaic and alluvial deposits extending to the present sea level.
Source
Aquifer
Aquifers

Unit properties

Surficial aquifer media
Typical value:porous
Description sand and gravel
Confinement
Typical value:unconfined
Groundwater storage
Description Salish Sediment along rivers could form important water storage units. Specific storage of the unit: 5.2E-3 (1/m)
Hydrogeological unit thickness
2 m
Description mean and median thickness: 1 and 2 m respectively
Surficial unit hydraulic conductivity
Range: [0.00034 to 0.01] m/s
Source Compendium of Re-evaluated Pumping Tests in the Regional District of Nanaimo, British Columbia
Regional precipitation
Range: [ to 5000] mm/y
Description The total precipitation is typically up to 5000mm in the mountains (Mount Arrowsmith).
Source Regional District of Nanaimo Phase One Water Budget Project
Regional recharge
Range: [112 to 396] mm/y
Description For the lowland area, recharge calibrated values range from 112 to 396 mm/yr. Recharge for the hydrostratigraphic unit: 600 mm/yr
Regional discharge
Description The regional analysis of the water budget reveals that 71% of the groundwater is discharging to surface water bodies, whereas the remaining 29% discharges along the coast of the Strait of Georgia.
Hydrogeological unit potential
Typical value:low
Description Because the hydrostratigraphic unit is thin and discontinuous in nature.
Aquifer vulnerability