Chaudiere regional aquifer system

Aquifer System

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684f32d9-5d6e-4e06-8d6c-467a544cc6c1
Project
Chaudiere

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Chaudiere regional aquifer system unit description

Update:2014-02-13
The regional aquifer system accounts two types of aquifer: bedrock aquifer and granular aquifer. Chaudiere bedrock has a relatively complex geology, including sedimentary, intrusive, and volcanic rocks. Granular aquifers are found in the alluvial and glaciofluvial deposits which are composed of sand, gravel, silt and till/diamicton. The regional fractured aquifer permeability is controlled mainly by the secondary porosity defined by the density, aperture and degree of interconnected fractures. The low hydraulic conductivity retains the groundwater flow on the top of the fractured rock. Percolating groundwater can occasionally accumulate just above the bedrock strata where it can form a perched water table. It is then conveyed laterally in the direction of the hydraulic gradient or migrates gradually downward. Overlying the regional fractured aquifer is the ubiquitous till unit. When its thickness reaches 5 m, compaction and fine-grained content hinder the vertical hydraulic communication between overlying layers (when present) and bedrock aquifers. Reworked till permits lateral groundwater flow and together with fluvioglacial and alluvial units can be considered as an interface aquifer unit, when directly overlying the fractured aquifers. At lower altitudes, marine and lacustrine clay and silt sediments overlie the glacial deposits. These fine sediments represent a confining unit that limits significant interaction between surface water and groundwater. The major topographic features and surface water network limit groundwater flow in the Appalachian Uplands to mainly local-scale systems from the nearest recharge zone to the closest surface water body. Groundwater there is dominated by recent recharge. The more regional groundwater flow systems can be found down-gradient, in the Appalachian Piedmont. However, due to the low hydraulic conductivities accompanied with the low hydraulic gradients, the regional flow rates seem considerably slower. This is reflected in a longer residence time and contact with aquifer media and the associated increased concentration of chemical constituents in groundwater. Groundwater in the Appalachian Uplands is generally dominated by a fresh Ca-HCO3 water type. The topographic control of the flow regime results in relatively rapid flow and a weakly mineralized water with slightly acidic to neutral pH. In the Appalachian Piedmont, the groundwater is generally more mineralized and represented by hydrogeochemical change of the water type from Ca-HCO3 to Na-HCO3.
Physiography
Hydrogeological regionAppalachians
Hydrogeological context
ReliefThe rock aquifer is bounded by the contact between two distinct physiographic provinces: the south-eastern margin of the Appalachian Piedmont to the North and the Appalachian Uplands to the South. North-northwest of Sainte-Marie, in the direction of the St. Lawrence River, the terrain is horizontal to sub-horizontal with slopes rarely reaching 5%. To the south, the relief is much more rugged and transforms from undulating to mountainous. The topography ranges from sea level at the river mouth, up to 1185 m at the extreme south of the area.
Area6690.00 km2
Lithology
DescriptionThe rock aquifer of Chaudiere has a relatively complex geology that has been simplified into five major units. From north to south, there are the External Humber Zone - North, which consists of shale or slate, sandstone and some conglomerate and limestone. The Internal Humber Zone is composed of pelitic or mafic schist and quartzite. The External Humber Zone - South consists of sandstone and slate. The Dunnage zone is formed of ophiolitic intrusive, volcanic and sedimentary cover rocks. The Gaspé Belt is made of sandstone, siltstone, shale and few beds of conglomerate. Finally, the Intrusive rocks consist of massive migmatite and amphibolite formations. The rock formations are covered by sediments, mainly till and glaciomarine deposits. In smaller scope, there are also alluvial, glaciolacustrine and glaciofluvial deposits. The granular aquifers are found in the alluvial and glaciofluvial deposits which mostly occur in the actual alluvial plains. They are composed of sand, sandy gravel or silt and till or diamicton. The alluvial sediments overlie the aquitard formed by the Champlain Sea sediments. The glaciofluvial sediments overlie the bedrock.
Source
Aquifer
AquifersList of aquifers fractured rock aquifer granular aquifers

Unit properties

Surficial aquifer media
Typical value:porous
Description The granular aquifer is found in alluvial and glaciofluvial sediments.
Source Hydrogeology and Hydrogeochemistry of the Chaudière River Watershed Aquifers, Québec, Canada
Bedrock aquifer media
Typical value:fractured
Description The generally fine-grained texture of the deformed and weakly metamorphosed sedimentary and volcanic rock formations provides very low primary porosity and permeability. The bedrock permeability is controlled mainly by the secondary porosity defined by the density, aperture and degree of interconnected fractures.
Source Hydrogeology and Hydrogeochemistry of the Chaudière River Watershed Aquifers, Québec, Canada
Confinement
Typical value:confined - semi confined - unconfined
Description Granular aquifers are under unconfined conditions. The bedrock aquifer is generally unconfined to semi-confined in the Appalachian Uplands, and semi-confined to confined in the Appalachian Piedmont.
Source Hydrogeology and Hydrogeochemistry of the Chaudière River Watershed Aquifers, Québec, Canada
Surficial sediment thickness
Range: [0 to 132.0309] m
Description The surficial sediments include till, glaciofluvial, alluvial, glaciolacustrine and marine sediments.
Source Hydrogeology and Hydrogeochemistry of the Chaudière River Watershed Aquifers, Québec, Canada
Bedrock hydraulic conductivity
8E-7 m/s
Source Hydrogeology and Hydrogeochemistry of the Chaudière River Watershed Aquifers, Québec, Canada
Regional precipitation
1110 mm/y
Source Hydrogeology and Hydrogeochemistry of the Chaudière River Watershed Aquifers, Québec, Canada
Regional evapotranspiration
447 mm/y
Source Hydrogeology and Hydrogeochemistry of the Chaudière River Watershed Aquifers, Québec, Canada
Regional runoff
478 mm/y
Source Hydrogeology and Hydrogeochemistry of the Chaudière River Watershed Aquifers, Québec, Canada
Regional recharge
Description The infiltration rate is 185 mm/y, however it doesn't represent the recharge, which is 27 mm/y for bedrock aquifer.
Source Hydrogeology and Hydrogeochemistry of the Chaudière River Watershed Aquifers, Québec, Canada
Regional discharge
Description The Appalachian Piedmont is a discharge zone for the regional groundwater flow.
Source Hydrogeology and Hydrogeochemistry of the Chaudière River Watershed Aquifers, Québec, Canada
Aquifer vulnerability
Description The rock aquifer vulnerability is generally low in the north and low to moderate in the south. The granular aquifers have high vulnerabilities.
Source Hydrogeology and Hydrogeochemistry of the Chaudière River Watershed Aquifers, Québec, Canada
Groundwater Quality
Typical value:fresh - hard
Description Groundwater quality is good, but it has problems of pH, manganese, iron and hardness.
Source Hydrogeology and Hydrogeochemistry of the Chaudière River Watershed Aquifers, Québec, Canada