Groundwater: where is it?
In Canada, there is more water underground than there is on the surface. This subterranean water is known as groundwater. It collects in aquifers, formations of rock that yield water when tapped for a well. Groundwater often emerges naturally at the surface, forming a spring or flowing into a river or lake.
Who needs groundwater?
Approximately one in four Canadians (eight million people) rely exclusively on groundwater for their water needs, and about two-thirds of them live in rural areas. In addition to providing us with drinking water, groundwater is also used for livestock, irrigation, aquaculture and mineral and hydrocarbon extraction.
Prince Edward Island is entirely dependent on groundwater collected from sandstone aquifers. Municipalities that rely on groundwater are more vulnerable to water shortages than those drawing their supply from lakes or rivers.
Groundwater is readily contaminated and extremely difficult — and, in some cases, impossible — to clean up. In Canada, groundwater-contamination problems are increasing, due to the growing number of toxic compounds used in industry and agriculture. The number of known contaminated aquifers is expected to rise in coming decades as more contaminated groundwater is discharged into lakes and rivers.
Gasoline storage tanks can leak and contaminate wells. Chemical leakage from landfills or industrial waste-disposal sites can also dirty groundwater. In 1990, for example, chemicals from a tire fire at Hagersville, Ont., threatened to seep into the region's groundwater. Agricultural runoff can also contaminate groundwater, and in rural areas, scientists suspect that many residential wells are contaminated by chemicals from septic systems, used motor oil, road salt, fertilizer, pesticides and livestock waste, according to Natural Resources Canada.
It's important to protect groundwater everywhere, because groundwater can travel hundreds of kilometres underneath the Earth's surface and eventually empty into lakes and rivers. Once contaminated, an aquifer may be spoiled for decades. Statistics Canada reports that mineral-extraction industries discharge 16 percent of their waste water into groundwater, and more than half that waste water is left untreated.
Watersheds related to this theme
Here is a sample of the 325 affected ones: