Oak Ridges Moraine sediments aquifer

Aquifer

Version Metadata
78509ec7-38a2-45a6-8ce7-0d499a91f313
Project
Oak Ridges Moraine

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Oak Ridges Moraine sediments aquifer unit description

Update:2014-03-17
In ascending order, the stratigraphic units of the Oak Ridges Moraine (ORM) are: Paleozoic bedrock, Lower deposits, Newmarket Till, Oak Ridges Moraine sediments, and Halton Till. Oak Ridges Moraine sediments overlie a regional unconformity (cut on Newmarket Till) with infill tunnel channels and forms a prominent east-west ridge. Channels infill with coarse glaciofluvial sediments form prolific regional aquifers. ORM sediments consist mostly of silt and fine sand, but also include large gravel seams and minor clay and diamicton. The aquifer is unconfined, except where it underlies Halton Till. Hydraulic conductivity is good and the aquifer potential is one of the highest of the country. ORM sediment forms a major recharge area. Water percolates (200-400mm/ yr) through the moraine ridge and mostly discharges from dozens of headwater stream springs sourced in the ORM. Groundwater that does not discharge from headwater stream springs can move deeper through the ORM into lower aquifers, then discharge as springs along deep river valleys where the river has eroded into or beneath the Newmarket Till. It can also migrate through the complete sediment column to discharge at Lake Ontario. These discharge pathways are controlled by the distribution of permeable channel and subaqueous fan structures, by confining aquitards, and by regional gradients with up to 300 m head differential to Lake Ontario. The ORM sediment aquifer is exploited for domestic uses due to high yields and good water quality.
Physiography
Hydrogeological regionSouthern Ontario Lowlands
Hydrogeological context
ReliefOak Ridges moraine has elevations around 430 m. Elevations are higher on the moraine ridge and decreases slightly on the edges. It forms the height of land east of the Niagara Escarpment.
Area3120.00 km2
Lithology
DescriptionIn ascending order, the stratigraphic units of the Oak Ridges Moraine are: Paleozoic bedrock, Lower deposits, Newmarket Till, Oak Ridges Moraine sediments, and Halton till. Oak Ridges Moraine sediments overlie the regional unconformity (with Newmarket Till), infill tunnel channels and form a prominent east-west ridge. These sediments consist mostly of silt and fine sand, but also include gravel and minor clay and diamicton. Gravel is prominent in tunnel channels and the overall fill succession fines upward.
Source
Aquifer
AquifersList of aquifers Oak Ridges Moraine sediments aquifer

Unit properties

Surficial aquifer media
Typical value:porous
Description The moraine sediments consist mostly of silt and fine sand, but also include large gravel seams and minor clay and diamicton.
Source Geostatistical mapping of leakance in a regional aquitard, Oak Ridges Moraine area, Ontario, Canada
Confinement
Typical value:unconfined
Description The aquifer is generally unconfined, except the section covered by Halton till on the south flank of the moraine complex.
Source A 3-dimensional geological model of the Oak Ridges Moraine area, Ontario, Canada
Hydrogeological unit thickness
Range: [2 to 125] m
Description The maximal thickness (125 m) is found in 4 sediments wedges, mainly in the western part of the moraine. In general, channels incising Newmarket till are filled with sand and gravel up to 50 m thick.
Source A 3-dimensional geological model of the Oak Ridges Moraine area, Ontario, Canada
Groundwater depth
Range: [15 to 40] m
Source Application of seismic stratigraphy and sedimentology to regional hydrogeological investigations: an example from Oak Ridges Moraine, southern Ontario, Canada
Surficial unit hydraulic conductivity
0.00029 m/s Range: [3e-06 to 0.007] m/s
Source Application of seismic stratigraphy and sedimentology to regional hydrogeological investigations: an example from Oak Ridges Moraine, southern Ontario, Canada
Regional precipitation
Range: [710 to 820] mm/y
Source The need for basin analysis in regional hydrogeological studies: Oak Ridges Moraine, Southern Ontario
Regional evapotranspiration
Range: [530 to 560] mm/y
Source The need for basin analysis in regional hydrogeological studies: Oak Ridges Moraine, Southern Ontario
Regional runoff
Range: [200 to 470] mm/y
Source The need for basin analysis in regional hydrogeological studies: Oak Ridges Moraine, Southern Ontario
Regional recharge
Range: [200 to 400] mm/y
Description ORM is the major recharge area. Regional values are highest on sandy Oak Ridges Moraine sediment aquifer.
Source A 3-dimensional geological model of the Oak Ridges Moraine area, Ontario, Canada
Regional discharge
Description The main discharges are sources in the ORM; as stream springs at the foot of ORM, as springs along deep river valleys where the river has eroded into or beneath the Newmarket Till and into Lake Ontario.
Source Sediment-aquifer play types in a list of 30 key Canadian aquifers
Hydrogeological unit potential
Typical value:high
Description The ORM aquifer complex is one of the highest producing, best quality aquifers in Canada
Source A 3-dimensional geological model of the Oak Ridges Moraine area, Ontario, Canada
Groundwater usage
Typical value:domestic
Description The aquifer supplies water to more than 100 000 wells.
Source A 3-dimensional geological model of the Oak Ridges Moraine area, Ontario, Canada