St. Hermas

Hydrogeological Context

Message Warning
This dataset is not reviewed: more information will be made available following the review

Project
Mirabel (AFSOQ)

Datasets

Download

St. Hermas unit description

Update:2014-01-20
The sector of St-Hermas contains a valley and the slope of St-Andre hills, located southward. This sector has two main interconnected aquifers: bedrock aquifer that extends on the entire sector and the outwash cones aquifer which is discontinuous in the valley. The bedrock aquifer mainly contains sandstones. The outwash cones aquifer contains glaciofluvial and proglacial sediments. It overlies the bedrock aquifer. These aquifers are covered by a discontinuous till unit and an important Champlain Sea clay unit, causing confined conditions in the valley. These conditions generate low vulnerability of the water resource. Fluvial, marine and other sediments that overlie the clay unit form small unconfined perched aquifer. The sediments are directly in contact with the bedrock where the clay unit is absent. It forms recharge areas, which are more vulnerable. Percolated water flows through fractures in the rock. The hydraulic conductivity decreases with depth, showing that water flows easier at shallow. The groundwater quality is the best of the region, despite few salinity problems in the valley center.
Physiography
Hydrogeological regionSt. Lawrence Platform
Hydrogeological context
ReliefThe sector is marked by the presence of a valley in the center, surrounded by ancient fluvial terraces to the north and south. Ground elevation in the valley varies between 13 and 34 m. Ancient fluvial terraces are staggered into three parts due to a lowering of base level. The elevation of the terraces levels are 44-54 m; 54-64 m and 64-73.2 m. The edges of the terraces are abrupt.
Area88.00 km2
Lithology
DescriptionIn the valley, the geological units are made up of sandstones (Covey Hill and Cairnside formations). The rock is covered with a discontinuous till unit and a Champlain Sea clay unit that covers the valley. South of the valley, there is a discontinuous unit of glaciofluvial (ancient fluvial terraces). The clay are absent of some parts of the sedimentary unit.
Source
Aquifer
AquifersList of aquifers: fractured rock aquifer perched/superficial aquifer outwash cones aquifer The glaciofluvial aquifer is discontinuous.

Unit properties

Surficial aquifer media
Typical value:porous
Description The fluvial and coastal sediments form discontinuous aquifers, which are perched if they aren't in direct contact with the bedrock aquifer.
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 Regarding the first unit, the highly fractured Paleozoic rocks are absent of the St-Hermas sector.
Source Canadian Inventory of Groundwater Resources: Integrated regional hydrogeological characterization of the fractured aquifer system of southwestern Quebec
Confinement
Typical value:confined - semi confined
Description The valley is almost filled with Quaternary sediments, primarily Champlain Sea clays. Some fluvial and marine deposits aren't covered by the clay unit. There is also an important till unit.
Source Canadian Inventory of Groundwater Resources: Integrated regional hydrogeological characterization of the fractured aquifer system of southwestern Quebec
Groundwater storage
Surficial sediment thickness
23.51 m Range: [0 to 80] m
Description The surficial sediments includes a clay and a till units that reaches a thickness near of 25 m.
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
Well depth
30.5 m Range: [1.15 to 91.6] m
Groundwater depth
2.945 m Range: [-0.2 to 7.12] m
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
Description exceeding 1000 mm/y
Regional recharge
96 mm/y Range: [0 to 276] mm/y
Description The recharge mainly occurs where the clay unit is discontinous.
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)
Aquifer vulnerability
107.68 Range: [83.5 to 166]
Groundwater Quality
Typical value:saline - fresh - hard - mixed
Description The dominant water type is Na-Ca-Mg-HCO3. Groundwater has the highest relative quality in the region. Manganese concentration is elevated in wells. Local salinity problems were observed in this sector.
Source Canadian Inventory of Groundwater Resources: Integrated regional hydrogeological characterization of the fractured aquifer system of southwestern Quebec
Methode Water sampling and analysis