Lower deposits aquifer

Aquifer

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

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Lower deposits aquifer unit description

Update:2014-03-17
Lower sediment is formed of poorly exposed, interbedded lake sediment and till. It comprises sand, silt, clay, till, and distinctive organic-rich and fossil-bearing beds. The unit overlies the bedrock and is covered by Newmarket Till, Oak Ridges Moraine sediments and Halton Till. The aquifer is confined by the Newmarket Till aquitard. However, the till is incised and sometimes eroded entirely, resulting in local high-conductivity windows between upper and lower aquifer systems. The unit is characterized by sandy formations with good hydraulic conductivity and aquifer potential. Lower sediment hosts a number of key regional aquifers that have prolific yields; however, the aquifer-aquitard system is poorly known. A part of the groundwater percolating through Oak Ridges Moraine sediments recharges lower sediments aquifers. In the lower sediments, groundwater discharges as springs along deep river valleys where the river has eroded into or beneath the Newmarket Till or it can migrate through the complete sediment column to discharge at Lake Ontario. Lower sediments groundwater is used for municipal water supply and transmits inter-watershed flow. Groundwater quality is good, however the lowest formation of the unit may have water-quality problems related to methane and dissolved organic carbon.
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.
Area8637.75 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. Lower sediment is a grouping of four formations: Don Formation, Scarborough Formation, Sunnybrook Till, and Thorncliffe Formation. Lower sediment, is formed of poorly exposed, interbedded lake sediment and till. It comprises sand, silt and clay, till, and distinctive organic-rich and fossil-bearing beds.
Source
Aquifer
AquifersList of aquifers Lower Sediments aquifers

Unit properties

Surficial aquifer media
Typical value:porous
Description Lower sediment comprises sand, silt and clay, till, and gravel channels; distinctive organic-rich and fossil-bearing beds may occur locally.
Source A 3-dimensional geological model of the Oak Ridges Moraine area, Ontario, Canada
Confinement
Typical value:confined
Description Newmarket Till is the confining unit, but lower sediments can be connected to surface aquifers where buried channels eroded confining Newmarket Till
Source A 3-dimensional geological model of the Oak Ridges Moraine area, Ontario, Canada
Groundwater storage
Description For Thorncliffe Formation (upper part of the unit), the storage coefficient is 0.005 - 0.00001.
Source The need for basin analysis in regional hydrogeological studies: Oak Ridges Moraine, Southern Ontario
Hydrogeological unit thickness
Range: [75 to 160] m
Description Lower sediment becomes thinner where bedrock rises towards Niagara Escarpment west of Humber River.
Source Application of seismic stratigraphy and sedimentology to regional hydrogeological investigations: an example from Oak Ridges Moraine, southern Ontario, Canada
Surficial unit hydraulic conductivity
Description For Thorncliffe Formation (upper sandy silt part of the unit), the hydraulic conductivity is from 2E-3 to 1E-7 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 discharge
Description The main discharges are springs along deep river valleys where the river has eroded into or beneath the Newmarket Till and Lake Ontario.
Source Sediment-aquifer play types in a list of 30 key Canadian aquifers
Hydrogeological unit yield
Description About 10% of wells draw water from lower sediment, with yields of up to 10 l/min for private wells and >100 l/min for municipal wells. Lower sediment hosts a number of key regional aquifers that have prolific yields; however, the aquifer-aquitard system is poorly known.
Source Application of seismic stratigraphy and sedimentology to regional hydrogeological investigations: an example from Oak Ridges Moraine, southern Ontario, Canada
Hydrogeological unit potential
Description Lower sediment hosts a number of key regional aquifers that have prolific yields; however, the aquifer-aquitard system is poorly known.
Source A 3-dimensional geological model of the Oak Ridges Moraine area, Ontario, Canada
Groundwater usage
Typical value:domestic
Description Municipal water supply and sewer discharge transmit inter-watershed flow
Source A 3-dimensional geological model of the Oak Ridges Moraine area, Ontario, Canada
Groundwater Quality
Typical value:fresh
Description Lower formation aquifers with organic beds may have water-quality problems related to methane and dissolved organic carbon.
Source The need for basin analysis in regional hydrogeological studies: Oak Ridges Moraine, Southern Ontario