Lake Saint-Martin aquifer system

Aquifer System

Version	Metadata
	052d6f1f-eb7f-421d-97f9-80e9ca900825

Project
Lake Saint-Martin - Manitoba

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Lake Saint-Martin aquifer system unit description

Update:2014-02-28

Physiography
The Lake Saint-Martin aquifer system includes crater fill deposits of the Lake Saint-Martin Impact Structure and the surrounding carbonate formations of the Manitoba Interlake. The Impact Structure exhibits a central uplifted core of Precambrian basement rocks surrounded by a shallow concentric crater basin. The crater-fill sediments consist of impacted-related carbonate breccia, granitic microbreccias and meltrock of the Permian St. Martin Complex overlain by Jurassic red beds, dolomitic mudstones and evaporites. The permeability of the surrounding carbonate aquifer can be quite high due to intense impact-related fracturing and faulting along the crater rim. Considering the high permeabilities in both the carbonate and breccia aquifers, their heads are continuous across the crater rim and they are viewed as a single aquifer system. In the central portion of the impact structure, the red bed aquitard is overlain by a shallow phreatic aquifer hosted by karstic evaporites. Outside the impact structure, The most significant recharge zone is in the northwest uplands and is usually associated with partial or complete bedrock outcrop. Another recharge zone is located between Lakes Manitoba and Pineimuta. Within the impact structure, north and northeast of Gympsumville, is the recharge area for the shallow, unconfined karst-hosted aquifer . From these recharge areas, groundwater flows radially, outward, toward lakes and organic deposits, such as swamps, marshes and bogs. A regional discharge zone for deep aquifers has developed in the concentric area of structural uplift surrounding the crater. Except in upland regions, the bedrock aquifers are confined by tills and glacio-lacustrine clays of varying thickness. In general, the aquifer vulnerability is low, except in the recharge areas where it is higher. Outside the impact structure, Groundwater quality is good, but within the impact structure total dissolved solids, hardness, sodium and fluoride occur naturally at elevated levels.
Hydrogeological region	Western Canada Sedimentary Basin
Hydrogeological context
Relief	The Lake St. Martin area has lower elevations along the lakes (240-2 245 m) and in the north-east part of the region (240-245 m). The higher elevations represent the crater rims (260-270).
Area	1459.00 km2
Lithology
Description	In ascending order, granitic Precambrian rocks outcrop on the eastern rim of the impact structure and in the central uplifted core. The Winnipeg Formation doesn't outcrop and consists mainly of quartzose sandstone interbedded with shale layers. The Red River Formation is composed of dolomites. The Stony Mountain and Stonewall Formations contain calcareous shale and dolomites. The Stonewall formation has low permeability. The Silurian Interlake Group consists mainly of dolomites with a few shaly interbeds. The Ashern Formation overlies the Interlake group in the westernmost part of the study area and is composed of dolomitic shale with a basal rubbly zone. The St. Martin Complex consists of a highly heterogeneous assemblage of rock-types associated with the formation of the impact structure. It is composed of shock-metamorphosed, brecciated, granitic gneiss. The overlying Amaranth Formation represents a sequence of crater-fill sediments and consists of red beds (dolomitic shales, siltstones and sandstones with a few conglomeratic beds and black organic rich layers) overlain by gypsum deposits. Finally, Quaternary deposits cover most of the St. Martin area. These deposits consist mainly of silty, sandy tills containing gravel or boulder inter-beds.
Source
Aquifer
Aquifers	List of aquifer regional bedrock aquifer Shallow phreatic aquifer hosted by karstic evaporites

Unit properties

Bedrock aquifer media


Typical value:	fractured
Description	Because of the high permeabilities in both the carbonate and breccia aquifers, their heads are continuous and they are viewed as a single aquifer system. Within the impact structure, the red beds form a leaky aquitard that is overlain by a shallow phreatic aquifer hosted by karstic evaporites.
Source	Groundwater resources of the Lake Saint-Martin Area, Manitoba

Confinement

Description	Except where there is an unconfined karstic aquifer, the bedrock aquifers are confined by tills and glacio-lacustrine clays of varying thickness.
Source	Groundwater resources of the Lake Saint-Martin Area, Manitoba

Well depth
Range: [13.4 to 113.3] m
Source	Groundwater resources of the Lake Saint-Martin Area, Manitoba

Regional precipitation
481.9 mm/y
Methode	Precipitation data are from Environment Canada. The value represents the average of the climate normals (1981-2010) measured on the stations distributed in or near the hydrogeological unit. The stations were selected so the average precipitation is as representative as possible of the whole hydrogeological unit.

Regional recharge

Description	Upland area (usually associated with partial or complete bedrock outcrop) is the most significant recharge zone is in the northwest of the study area. Another recharge zone is located between Lakes Manitoba and Pineimuta. The north and northeast of Gympsumville is the recharge area for a shallow, unconfined aquifer hosted by karstic evaporates in the northern half of the Lake St. Martin area.
Source	Groundwater resources of the Lake Saint-Martin Area, Manitoba

Regional discharge

Description	A regional discharge zone has formed in a concentric area of uplifted Paleozoic formations surrounding the Lake Saint-Martin impact structure.
Source	Groundwater resources of the Lake Saint-Martin Area, Manitoba

Hydrogeological unit potential

Typical value:	high
Description	Commonly wells have high specific capactity, suggesting a good aquifer potential.
Source	Groundwater resources of the Lake Saint-Martin Area, Manitoba

Groundwater usage

Typical value:	domestic
Description	Potable needs (after treatment if required) and livestock.
Source	Groundwater resources of the Lake Saint-Martin Area, Manitoba

Aquifer vulnerability

Description	In general, the vulnerability is low, except in the recharge areas where it's higher. Locations impacted by nitrates present moderate levels of vulnerability.
Source	Groundwater resources of the Lake Saint-Martin Area, Manitoba

Groundwater Quality

Typical value:	fresh - hard
Description	Total dissolved solids, hardness, sodium and fluoride occur naturally at elevated levels within the impact structure. In some places, nitrate concentrations are also high.
Source	Groundwater resources of the Lake Saint-Martin Area, Manitoba