Châteauguay system aquifer

Aquifer System

Version Metadata
5501473e-14b1-464b-8649-957c6acfb57e
Project
Chateauguay

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Châteauguay system aquifer unit description

Update:2013-06-18
Chateauguay sector counts two aquifer types: fractured rock aquifer and superficial aquifer. The fractured rock aquifer is present throughout the sector. It is composed of different geological units. From the base, there is a sandstone unit (Covey Hill and Cairnside Formations), followed by interbedded sandstone and dolomite (Theresa Formation), surmounted by a dolomite unit (Beauharnois Formation). This aquifer is almost completely covered by a layer of till. Till has the effect of confining the fractured rock aquifer, reducing the vulnerability of the groundwater. Other Quaternary deposits of small scope are present. These deposits designate shallow aquifers when they are coarse, have a high hydraulic conductivity and are directly on bedrock. These deposits include alluvial, wind, coastal and glaciofluvial sediments, e.g. Mercier esker. The two aquifers (superficial and fractured rock) are connected only where glacial and marine sediments are absent. At regional level, the water percolates into recharge areas at Mont Covey and semi- confined at the foot of this mountain. Water percolates through cracks and vertical fractures and flows northward, horizontally along the beds of sedimentary rocks. Resurgences are located where there's a contact between the riverbeds and sedimentary rocks. The main resurgence is the Chateauguay River, but groundwater also flows into wetlands, other streams and St. Lawrence River. Groundwater is used for municipal, agricultural, quarrying, and domestic and others purposes. Except the contamination problems at the site of the esker Mercier, groundwater quality is good but has a salinity problem.
Physiography
Hydrogeological regionSt. Lawrence Platform
Hydrogeological context
ReliefThe ground elevation varies from 22 m on the banks of the St. Lawrence River to 1160 m at the summit of Mt Lyon. Covey Hill reaches 340 m. At the basement of Covey hill, a plain tilts gently towards the St. Lawrence River. To the south, the terrain is changing from corrugated to mountain.
Area3395.00 km2
Lithology
DescriptionFrom bottom to top, the geological units pass sandstone (Covey Hill Formations and Cairnside) to interbedded sandstone and marine dolomite (Theresa Formation). Sandstone decreases gradually giving way to a succession of laminated dolomite (Beauharnois Formation). A layer of tilt covers almost the entire territory. Other Quaternary deposits of restricted scope are present.
Source
Aquifer
AquifersList of aquifers: fractured sedimentary rock aquifer Mercier esker aquifer Fine marine and glacial sediments are below Mercier esker, but there are windows, allowing for direct hydraulic exchange between the underlying bedrock.

Unit properties

Surficial aquifer media
Typical value:porous
Description Superficial aquifers accounts quaternary coarse deposits that are directly on the roc. Those sediments have a high hydraulic conductivity. Those superficial aquifer media are alluvial, eolian, coastal and fluvioglacial sediments (e.g. Mercier esker).
Bedrock aquifer media
Typical value:fractured
Description Water percolates through vertical fractures and then flows in the interbedded voids.
Confinement
Typical value:confined - semi confined - unconfined
Description At Covey Hill, the groundwater is unconfined. At the base of the hill, till deposits causes semi-confined aquifer conditions. In the sectors where the elevation is lower than 60 m, the aquifer is confined by the clay and silt deposits.
Surficial sediment thickness
8 m Range: [0 to 55] m
Hydrogeological unit thickness
Description Mean thickness of the hydrogeological units Covey Hill: 200-500 m Cairnside: 100 m Formation of Theresa and Beauharnois: 150 m Laval Formation: 100 m
Source Numerical Simulation of Groundwater Flow in the Chateauguay River Aquifers
Well depth
34.1 m Range: [0.6 to 573] m
Bedrock hydraulic conductivity
0.009376 m/s Range: [0.000564 to 0.123687] m/s
Regional precipitation
953 mm/y Range: [630 to 1485] mm/y
Description The precipitations varie in the territory. From December to March, they fall as snow.
Regional evapotranspiration
491 mm/y Range: [301 to 631] mm/y
Regional runoff
192 mm/y Range: [84 to 640] mm/y
Regional recharge
99 mm/y Range: [0 to 404] mm/y
Regional discharge
Description Chateauguay River is the principal discharge. A volume of approximatively 234M m3/yr discharges to surface waters through streams and wetlands and to the St Lawrence River.
Source Numerical Simulation of Groundwater Flow in the Chateauguay River Aquifers
Groundwater usage
Typical value:porous - fractured
Description Municipal (aqueducts): 11.83M m3/yr (38%) Agricultural: 8.18M m3/yr (26%) Quarries: 4.66M m3/yr (15%) Domestic (private wells): 3.51M m3/yr(11%) Water treatment at the former Mercier Lagoons: 1.56M m3/yr (5%) Food processing: 0.55M m3/yr (2%) Bottlers: 0.56M m3/yr (2%) Tourism and recreative: 0.18M m3/yr (1%) This represents more than 30M m3/ yr of groundwater.
Source Regional Sustainability of the Chateauguay River Aquifers.
Aquifer vulnerability
101.33 Range: [50 to 190]
Groundwater Quality
Typical value:saline - fresh - hard - mixed
Description The CA-HCO3 water type is dominant in all hydrogeological units. Saline water is associated with Champlain Sea. The principal chemical processes are: mixing of fresh water and saline water; possibly halite dissolution, dolomite and gypsum dissolution; Fe-Mn and F-Sr dissolution bearing minerals. Mercier Lagoons are contamined with hydrocarbon.
Source Groundwater Quality, Geochemical Processes and Groundwater Evolution in the Chateauguay River Watershed, Quebec, Canada