Glaciofluvial sand and gravel aquifer (esker)

Aquifer

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Glaciofluvial sand and gravel aquifer (esker) unit description

Update:2014-03-27
Eskers trend across the Ottawa valley from north to south and have been mapped at the surface and inferred at depth within the Champlain basin part of the valley by Gorrell (1991). Extensive sedimentological work has been completed on the subaqueous fan portions of the eskers (see refs in Cummings and Russell, 2007). Detailed investigations of the Vars-Winchester and Crysler-Finch eskers have been completed to support Source Water Protection Studies (Cummings and Russell, 2007). The Vars-Winchester esker is an elongate, 40-km long, partially-buried ridge of sand and gravel extends north-south across the study area. It consists of two key elements, a gravely central-ridge and a sandy-fan carapace. The gravely central-ridge of the Vars-Winchester (VW) esker is 2 to 20 metres high (average 15 m). Since the VW esker is mostly buried, its lateral and longitudinal continuity is uncertain. Conceptually, the esker is assumed to be continuous; however, potential gaps have been identified. Since the esker underlies Champlain Sea mud unit, the aquifer is confined except where the esker outcrops at surface. The esker aquifer is recharged from precipitation that falls directly on the exposed esker and possibly from streams that intercept the esker. The gravelly core of the VW esker has a higher permeability than its surroundings, offering a preferential pathway for groundwater flow. Hence flow within the system may occur preferentially along the length of the esker where the regional gradient allows. The longitudinal groundwater flow within the esker may not be unidirectional. Groundwater flow within the esker, converge towards the Castor River and diverge at the local topographic high of Maple Ridge in the south. Based on bedrock topography, another groundwater divide seems to occur in the north near Vars. Groundwater discharges into streams. Esker aquifers are prolific and have production rates of up to 31 L/s. The eskers are excavated by a number of sand, gravel and aggregate companies.
Physiography
Hydrogeological regionSt. Lawrence Platform
Hydrogeological context
ReliefThe region is a low-relief landscape with hills commonly controlled by bedrock and drumlins. Topography ranges from approximately 35 to 120 meters above sea level.
Area1188.00 km2
Lithology
Description******************************TO MODIFY******************************************** The Vars-Winchester esker area consists of four main geological units. In ascending order, these units are: bedrock, till, glaciofluvial sand and gravel in esker and Champlain Sea mud and sand. The latter may be overlain by alluvial sediments and organic deposits. The esker designates an elongate, 40-km long, partially-buried ridge of sand and gravel extends north-south across the study area. Vars-Winchester esker consists of two key elements, a gravely central-ridge and a sandy-fan carapace. The gravely central-ridge of the Vars-Winchester esker is 2 to 20 metres high (average 15 m).
Source
Aquifer
AquifersList of aquifers Vars-Winchester esker aquifer Crysler-Finch esker aquifer

Unit properties

Surficial aquifer media
Typical value:porous
Description Vars-Winchester esker consists of two key elements, a gravely central-ridge (highly permeable) and a sandy-fan carapace (moderately permeable).
Source The Vars-Winchester esker aquifer, South Nation River watershed, Ontario: CANQUA Fieldtrip, June 6, 2007
Methode Literature; field
Confinement
Typical value:confined
Description The aquifer is confined by Champlain Sea mud, except where the esker outcrops at surface.
Source Hydrostratigraphic model of the South Nation watershed region, south-eastern Ontario
Methode Literature
Surficial sediment thickness
24 m
Description Above the esker, the sediment thickness is up to 24 m of mud.
Source Sequence stratigraphy of a glaciated basin fill, with a focus on esker sedimentation
Methode Literature
Hydrogeological unit thickness
10 m Range: [0 to 25] m
Source Sequence stratigraphy of a glaciated basin fill, with a focus on esker sedimentation
Surficial unit hydraulic conductivity
Range: [1e-06 to 0.001] m/s
Source Sequence stratigraphy of a glaciated basin fill, with a focus on esker sedimentation
Regional precipitation
Range: [800 to 1000] mm/y
Description ************************************ERASE THE VALUES?**********************************************
Source Vars-Winchester esker characterization study: Conceptual and numerical hydrogeological model of the Vars-Winchester esker system, South Nation River basin, Eastern Ontario
Regional evapotranspiration
Range: [500 to 600] mm/y
Description ************************************ERASE THE VALUES?**********************************************
Source Vars-Winchester esker characterization study: Conceptual and numerical hydrogeological model of the Vars-Winchester esker system, South Nation River basin, Eastern Ontario
Regional runoff
Range: [200 to 400] mm/y
Description ************************************ERASE THE VALUES?**********************************************
Source Vars-Winchester esker characterization study: Conceptual and numerical hydrogeological model of the Vars-Winchester esker system, South Nation River basin, Eastern Ontario
Regional recharge
Description For the Vars-Winchester esker, 75% of the feature is buried beneath Champlain Sea mud. The esker aquifer is recharged from precipitation that falls directly on the exposed esker and possibly from streams that intercept the esker.
Source The Vars-Winchester esker aquifer, South Nation River watershed, Ontario: CANQUA Fieldtrip, June 6, 2007
Methode A mass balance calculation suggests that recharge directly from precipitation is inadequate and additional recharge pathways are required.
Regional discharge
Description The esker aquifers discharge into streams.
Source The Vars-Winchester esker aquifer, South Nation River watershed, Ontario: CANQUA Fieldtrip, June 6, 2007
Hydrogeological unit yield
Description Esker aquifers have production rates of up to 500 gallons per minute (31 L/s).
Source The Vars-Winchester esker aquifer, South Nation River watershed, Ontario: CANQUA Fieldtrip, June 6, 2007
Hydrogeological unit potential
Typical value:high
Source Geophysical characterization of buried esker aquifers in Eastern Ontario
Groundwater usage
Typical value:agricultural - domestic
Description Esker aquifers are a reservoir for drinkable water supplying 7 municipalities, representing around 17000 persons, more than 80% of people relying on municipal groundwater supplies in the area. The eskers are also exploited by a number of sand, gravel and aggregate companies.
Source The Vars-Winchester esker aquifer, South Nation River watershed, Ontario: CANQUA Fieldtrip, June 6, 2007
Groundwater Quality
Typical value:fresh
Description Esker water is fresh, similar to that of precipitation.
Source Vars-Winchester esker characterization study: Conceptual and numerical hydrogeological model of the Vars-Winchester esker system, South Nation River basin, Eastern Ontario