Fractured aquifer system of southwestern Quebec

Aquifer System

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Version	Metadata
	1448b4e3-c71c-43e4-97d8-a4d2d6d99037

Project
Mirabel (AFSOQ)

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Fractured aquifer system of southwestern Quebec unit description

Update:2014-01-27

Physiography
The area relief is relatively flat, characterized by the hills in the south. The bedrock aquifer extends on the entire area. It is covered by a thin discontinuous till layer. The subglacial meltwater caused till erosion that formed the outwash cones aquifer. The aquifer can be connected to the underlying bedrock aquifer by till free windows. In the valley, a discontinuous clay unit overlies the till deposit. The clays are absent of the hills, where the bedrock outcrops. Thus, the bedrock aquifer sections that are covered by the clays are confined. Those sections are less vulnerable to surface contamination. The bedrock outcrops designate the sections where the bedrock aquifer is under unconfined water table conditions. Those sections are the important recharge areas. They are more vulnerable to surface contamination. The clay unit is covered by marine/fluvial sediments. Perched aquifers are formed where sedimentary deposits overlie the clay unit. Where the sedimentary deposits overlie a clay discontinuity, they form a superficial aquifer. They are directly in contact with the bedrock aquifer. The superficial aquifers are widespread in the sector. As the bedrock outcrops, the superficial aquifers and perched aquifer are under unconfined conditions and represent recharge areas. In these aquifers, water percolates in the soil and flows through the rock fractures of the bedrock aquifer. The hydraulic conductivity decreasing with depth, groundwater flows easier at shallow. Groundwater quality throughout most of the area is good.
Hydrogeological region	St. Lawrence Platform
Hydrogeological context
Relief	The area is generally flat to gently rolling, and the only areas of relief are the Oka and Saint-Andre hills in the south. Elevations range from 20 m above sea level in the vicinity of the Mille Iles River, to 249 m at the highest point in the Oka Hills.
Area	1498.00 km2
Lithology
Description	In ascending order, the geological units are: 1) sandstone (Covey Hill and Cairnside formations); 2) dolostone and limestone (Theresa, Beauharnois and Carillon formations) and 3) the limestone the Chazy, Black River and Trenton groups. A thin discontinuous layer of till overlies on the bedrock. Over this layer there are clays. On top of the clay layer, there are different sediment deposits such as littoral and fluvial sediments. Those deposits are sporadic.
Source
Aquifer
Aquifers	List of aquifers bedrock aquifer outwash cones aquifer perched/superficial aquifer

Unit properties

Surficial aquifer media


Typical value:	porous
Description	The glaciofluvial and proglacial deposits can form small perched aquifers. The superficial aquifer is highly discontinuous. It is mainly composed of marine, fluvial and eolian sediments.
Source	Canadian Inventory of Groundwater Resources: Integrated regional hydrogeological characterization of the fractured aquifer system of southwestern Quebec

Bedrock aquifer media

Typical value:	fractured
Description	Regionally, the bedrock aquifer has 2 hydrogeological units. From the top to the base: 1- Highly fractured Paleozoic rocks and Quaternary glaciofluvial sediments (the sediments overlie the bedrock) 2- fractured Paleozoic rocks
Source	Canadian Inventory of Groundwater Resources: Integrated regional hydrogeological characterization of the fractured aquifer system of southwestern Quebec

Confinement

Typical value:	confined - semi confined - unconfined
Description	The confining unit is composed of Champlain Sea silt and clay. The unit is discontinous and in locations not thick enough to confine the water table. About 65% of the aquifer is under confined conditions, 31% semi confined and 4% unconfined. The unconfined conditions are mainly found in the hills.
Source	Canadian Inventory of Groundwater Resources: Integrated regional hydrogeological characterization of the fractured aquifer system of southwestern Quebec

Hydrogeological unit thickness
100 m
Description	Regionally, a thickness of 100 m, including glaciofuvial sediments included in the highly fractured rock unit is considered for bedrock aquifer. This portion of the aquifer accounts for most of the flow, however water is present at greater depths.
Source	Canadian Inventory of Groundwater Resources: Integrated regional hydrogeological characterization of the fractured aquifer system of southwestern Quebec

Bedrock hydraulic conductivity

Description	For each hydrogeological unit for the regional bedrock aquifer: 1- Highly fractured Paleozoic rock and Quaternary glaciofluvial sediments: K = 7.81E-4 m/s 2- Fractured Paleozoic rock: Kmin 2.7E-11 m/s; Kmax 7.9E-3 m/s; Kmean 2.7E-5 m/s Hydraulic conductivity decreases with the depth.
Source	Canadian Inventory of Groundwater Resources: Integrated regional hydrogeological characterization of the fractured aquifer system of southwestern Quebec
Methode	Estimation on the basis of in situ permeability tests, Lungeon constant-head injection tests, specific-capacity tests and pumping tests with and without observation wells.

Regional precipitation
1047 mm/y
Description	Evapotranspiration: 40% des precipitations Runoff: 38% des precipitations Superficial and regional aquifer recharge: 22% des precipitations
Source	Quantitative Assessment of Regional Rock Aquifers, South-Western Quebec, Canada

Regional evapotranspiration
418.8 mm/y
Source	Canadian Inventory of Groundwater Resources: Integrated regional hydrogeological characterization of the fractured aquifer system of southwestern Quebec

Regional recharge
45 mm/y
Description	The main recharge areas are Oka and St-Andre hills and the till plain.
Source	Canadian Inventory of Groundwater Resources: Integrated regional hydrogeological characterization of the fractured aquifer system of southwestern Quebec
Methode	Estimated by the Darcy method

Regional discharge

Description	The main discharges are Outaouais River and Mille Iles River.
Source	Canadian Inventory of Groundwater Resources: Integrated regional hydrogeological characterization of the fractured aquifer system of southwestern Quebec

Groundwater usage

Typical value:	agricultural - domestic - industrial
Description	For the regional bedrock aquifer: - rock quarries (9,3M m3/an) - municipal aqueducts (3,4M m3/an) - private wells (2,2M m3/an) - irrigation (1,2M m3/an) - livestock (1,3M m3/an) - golf courses (0,1M m3/an) - bottlers (0,5M m3/an)
Source	Canadian Inventory of Groundwater Resources: Integrated regional hydrogeological characterization of the fractured aquifer system of southwestern Quebec

Aquifer vulnerability

Description	The most vulnerable areas revealed closely overlap the main recharge areas.
Source	Canadian Inventory of Groundwater Resources: Integrated regional hydrogeological characterization of the fractured aquifer system of southwestern Quebec
Methode	DRASTIC

Groundwater Quality

Typical value:	saline - fresh - hard - mixed
Description	The quality of groundwater is variable in the area, but it is relatively uncontamined by human activities. Groundwater quality throughout most of the study area is good.
Source	Canadian Inventory of Groundwater Resources: Integrated regional hydrogeological characterization of the fractured aquifer system of southwestern Quebec