Hydrogeological regions of Canada

Hydrogeological Regions provide a framework to introduce the regional hydrogeology of Canada and to connect apparently disparate studies into a broader framework. The hydrological regions are first order areas used to capture and summarize data that will help develop more detailed profiles of each region. Comparison of findings within and between regions will allow scalable extension to sub-regional and watershed scale mapping.

Canada has been classified into nine principal hydrogeological regions. Each region is described briefly based on the following five hydrogeological characteristics (Heath, 1984):

system components and geometry;

water-bearing openings;

rock matrix composition;

storage and transmission;

recharge/ discharge.

The hydrogeological classification emphasizes major geological provinces and rock formations. Fundamental water-bearing openings and rock matrix properties help determine the quantity (storage), flux (transmission), and composition of formation waters. These same properties and any overlying sediment cover affect recharge/ discharge rates for regional formations. While regional attributes are general, a simple aquifer mapping scheme can further describe the nature and character of aquifers in each region. For example, general groundwater settings across the country could be described as has been done by USGS principal aquifers [1]. Thus the regional framework can potentially link from national scales to watershed scales by identifying typical aquifer types based on readily available geological maps that use water-bearing character as a common attribute.

The nine hydrogeological regions include:

Cordillera

Mountains with thin sediment over fractured sedimentary, igneous and metamorphic rocks of Precambrian to Cenozoic age. Intermontane valleys are underlain by glacial and alluvial deposits of Pleistocene age.

Plains (Western Sedimentary Basin)

Region-wide basin of sub-horizontal Paleozoic to Cenozoic sedimentary rocks are overlain by thick glacial deposits filling buried valleys. Incised post-glacial valleys provide local relief. Shallow gas, coal, and brines may occur.

Canadian Shield

Undulating region of thin glacial sediment overlying complex deformed, fractured PreCambrian igneous, metamorphic and sedimentary rocks. Region contains several terrains: sedimentary basins, structural belts, and glacial-lacustrine basins.

Hudson Bay (Moose River) Basin

Sedimentary basin of Paleozoic to Mesozoic sub horizontal carbonate and clastic sediment covered by surficial deposits, with low relief and poor drainage.

Southern Ontario

Eastern Great Lakes region is underlain by gently-dipping Paleozoic, carbonate, clastic and gypsum-salt strata overlain by glacial sediments up to 200 m thick with tunnel valleys. Karst, bedrock valleys, shallow gas and brines are also important components.

St. Lawrence Lowlands

Lowlands underlain by shallow-dipping Paleozoic sedimentary rocks and thick glacial sediment in glacial-marine basins. Appalachian and Precambrian uplands discharge water to valleys. Shallow gas and saltwater intrusion are possible.

Appalachia

Upland to mountainous region with thin surficial sediment on folded Paleozoic sedimentary and igneous rocks. Range of rock types yields a wide range of water compositions. Valleys contain important alluvial aquifers.

Maritimes Basin

Lowlands with flat-lying, Carboniferous clastic , salt, and gypsum rocks contain shallow coal deposits. Surface glacial sediment is thin and discontinuous. Salt water intrusion is possible.

Permafrost

Arctic islands and most areas north of 60o contain frozen ground affects on groundwater flow. Diverse topography and geology define sub-regions of sedimentary basins and crystalline rocks. Glacial sediment is thin, discontinuous; local peat accumulations are significant.