Groundwater is the water that is found under the ground surface, in the spaces between rocks, soils and overburden (pore space). The upper limit of the saturated zone is defined by the water table , while the lower limit of groundwater is less well-defined. The lower limit is often determined by an absence of pore space and the presence of a hot environment, usually occurring at great depths. The zone of interest for groundwater is between the ground surface and the depth below which no usable water for human consumption can be encountered. "Usability" can be limited both by the extent of the aquifer (too deep to be economically feasible), or by poor water quality which makes the water unfit for human consumption. Typically, when concentration of total dissolved solids (TDS) exceeds 4,000 mg/L the water is considered to be brackish, or too saline, although it may still have industrial applications. Alberta Environment considers 4,000 mg/L a freshwater limit for applying groundwater protection criteria.

Alberta Environment has produced a document titled "Focus on Groundwater". It is intended to provide the average Albertan with a basic overview of groundwater in Alberta. Topics include: aquifers, groundwater as part of the water cycle, groundwater uses, groundwater quality and quantity, issues related to groundwater, and ideas on actions you can take to protect groundwater. Click on the link below to view the document.

Focus on Groundwater

The greatest depths of usable water in Alberta are mainly in the High Plains close to the Foothills, and deep in buried pre-glacial gravel and sand-filled bedrock channels. The quantity of such water in storage is estimated to be less than 40,000 km³, or roughly enough to cover the province 60 metres deep. However, of this amount only a tiny fraction is extractable by conventional means - like pumping through wells. The "usable" portion, if spread over the province, would be a sheet only about six millimetres thick. Fortunately, the small amount of recoverable groundwater storage in the upper zones can be replenished from surface precipitation, infiltration, and natural groundwater recharge. If carefully managed and pumped at sustainable rates, groundwater can be an important and reliable renewable resource.

View a map of where groundwater wells are distributed in Alberta below

To obtain information on individual groundwater wells and associated groundwater data, go to the Groundwater Information Center.

Groundwater is an important part of the hydrologic cycle, particularly where water is able to infiltrate into soils and rock on the land surface. However, most of the rainfall and snowmelt during the year doesn't reach the water table. Most precipitation either evaporates from the soil surface, is taken up by plants during the growing season and returned to the atmosphere through transpiration, or becomes direct surface runoff. The portion of annual precipitation that becomes groundwater, and then eventually returns to the surface to become part of the baseflow of streams represents on average six percent of total precipitation. However, it can range from anywhere between zero and 30 percent, depending on the topographic relief and permeability of the soil. Coarse, gravelly soils and shallow fractured bedrock have the highest potential infiltration rates.

Infiltration potential is high in parts of the Rocky Mountains and Foothills where deep-fractured rock and limestones and gravel terraces are exposed. In the wetlands and muskeg areas of the northern regions, infiltration tends to be more than average in upland areas and less than average in low-lying areas. In the east and southeast, known as Palliser Triangle, little or no precipitation reaches the groundwater table because most of it evaporates.

The water table, in general, tends to be relatively close to the surface and follows the ground surface. The water table is incorporated into the overall groundwater system. Under gravity, it flows along pressure gradients within the small interconnected pore spaces that occur in rocks and soils. Groundwater prefers to flow through coarse-grained porous and permeable sediments such as gravel and sandstone, or through connected networks of cracks and fractures that occur in bedrock formations. However, some still can occur in less porous and less permeable materials. Glacial clay till and shale are examples of materials where groundwater flows very slowly and in relatively small quantities.

Groundwater flow can flow along the water table like a sheet or it can push the existing water ahead of itself as if confined in a tube. In reality, the types of flow are highly complex and can be any variation between these configurations, and is often accompanied with dispersion, merging and mixing. Travel times are at highly variable flow rates, ranging from less than a millimetre per year in materials with high clay content to well over 100 metres per hour in shallow gravel beds that are in contact with streams and rivers. In flat areas of the plains there may be little or no horizontal groundwater flow because there is only a very small gravity-driven pressure difference due to the flat terrain.

With minor exceptions, such as the tectonic buckling that resulted in the Peace River Arch, and the Sweetgrass Arch within the Milk River sandstone, the general direction of deeper, more saline aquifer groundwater flow is easterly, away from the Rocky Mountains and Foothills.

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Mine seepage from abandoned coal mine near Mountain Park

Groundwater can return to the surface as visible seepage, as small springs emerging at the base of escarpments, or a large springs where fractured porous rock of an extensive aquifer outcrops along a valley wall above or at stream level. Usually, groundwater feeds directly into streams as baseflow under the water line, thus emerging essentially unnoticed most of the time. Lakes are commonly connected to groundwater, although the contribution of groundwater to lake volume is usually relatively minor because movement of water through the surface hydrologic system is much more rapid than what occurs for groundwater. Much of this part of the hydrologic cycle segment involves shallow and relatively active groundwater flow systems.

The deeper and often extensive groundwater flow systems tend to be connected to deep lakes. For example, the waters in the pre-glacial channel gravels at Cold Lake. Another example is the Paskapoo sandstones at Sylvan Lake. These formations also support streamflow of the Red Deer River headwaters. Very deep aquifers, occurring beneath the deepest part of a lake, can also discharge water back into the lake through upwards leakage. However, this water still moves very slowly and can only contribute a small component to the water balance of large surface water bodies.