Fluvioglacial sands and gravels

Hydrogeological Context




Fluvioglacial sands and gravels unit description

The territory sections, where the glaciofluvial sands and gravels are present count three aquifers: Precambrian bedrock aquifer, sedimentary formations aquifer and glaciofluvial sands and gravels aquifer. The Precambrian bedrock is massive and little fractured, showing an unproductive aquifer. Sedimentary formations are highly fractured and shales are chattered, demonstrating good potential aquifer. These units are covered by discontinuous till layer. At some places, the glaciofluvial sands and gravels aquifer directly overlies the rock aquifers. The glaciofluvial deposits aquifer are located along Sainte-Anne and Jacques-Cartier rivers in the northeast part of Portneuf area. The glaciofluvial sands and gravels have a high permeability, giving a high aquifer potential. However, the extent of glaciofluvial deposits is often limited, thus limiting the amount of usable water. This type of aquifer is exploited for private wells, mostly shallow wells or wellpoint. The water table is under unconfined conditions, thus the aquifer is vulnerable to surface contamination. The groundwater type is calcic chloride.
Hydrogeological regionSt. Lawrence Platform
Hydrogeological context
ReliefGlaciofluvial sands and gravels are found mainly in the north of the region. Deposits are at medium altitudes. They are found in the valleys of the rugged terrain, located north. They have low altitude variation caused by gentle slopes.
Area92.00 km2
DescriptionTwo rock formations are associated with the hydrogeological unit of glaciofluvial sands and gravels: Precambrian bedrock and sedimentary formations. Sections of the Precambrian bedrock considered are mainly composed of granodiorite gneiss. Sedimentary formations, located south include the Trenton Group limestones and shales of the Utica Group. A discontinuous till unit followed by glaciofluvial sands and gravels cover the rock formations.
AquifersList of aquifer surficial glaciofluvial sands and gravels aquifer

Unit properties

Surficial aquifer media
Typical value:porous
Description glaciofluvial sediments composed of sands and gravels, with an important permeability
Bedrock aquifer media
Typical value:fractured
Description The igneous metamorphic rocks and the sedimentary rocks are the hydrogeological units underlying glaciofluvial sands and gravels. The Precambrian rocks don't represent productive aquifer, but the sedimentary formations form productive aquifer.
Typical value:unconfined
Surficial sediment thickness
Description The glaciofluvial sands and gravels thickness varies between 0-2.5 m and 40-45 m.
Methode Universal kriging interpolation of 179 borehole data
Hydrogeological unit thickness
Description The glaciofluvial sands and gravels thickness varies between 0-2.5 m and 40-45 m.
Methode Universal kriging interpolation of 179 borehole data
Well depth
25.9 m Range: [0.33 to 74.1] m
Regional precipitation
1121.5 mm/y Range: [1063.1 to 1168.2] mm/y
Methode Precipitation data are from Environment Canada. The value represents the average of the climate normals (1981-2010) measured on the stations distributed in or near the hydrogeological unit. The stations were selected so the average precipitation is as representative as possible of the whole hydrogeological unit.
Hydrogeological unit potential
Description Despite their high permeability which makes them good potential aquifer, the deposits extent is often restricted, which greatly restrict the amount of usable water.
Groundwater usage
Typical value:domestic
Description Residents who live in this area get their drinking water from shallow wells or wellpoint.
Aquifer vulnerability
6 Range: [0 to 6]
Groundwater Quality
Description water type is calcic chloride