Groundwater is an important source of freshwater for approximately 3 million Ontarians. A number of municipalities in Ontario rely on groundwater as a major source of clean drinking water.
Groundwater is water that seeps into the ground from precipitation and is stored below the surface of the earth in structures called aquifers. An aquifer is a geologic unit (or layer) of permeable material (like sand, gravel or fractured bedrock) that is capable of providing usable quantities of water. The depth at which soil fractures and spaces in rock become fully saturated with water is called the water table.
Groundwater is naturally replenished by surface water from precipitation, streams, and rivers when the water seeping into the ground reaches the water table. Groundwater eventually flows to the surface (discharges) naturally at springs and streams and can form wetlands.
Groundwater can also be extracted through a well drilled into the aquifer. A well is a pipe in the ground that fills with groundwater. This water can be brought to the surface by a pump. Shallow wells may go dry if the water table falls below the bottom of the well. Some wells, called artesian wells, do not need a pump because of natural pressures that force the water up and out of the well. Most of Ontario’s rural residents rely on groundwater, pumped from private wells, to meet their water needs.
Groundwater can be a long-term 'reservoir' of the natural water cycle (with residence times from days to millennia), as opposed to short-term water reservoirs like the atmosphere and fresh surface water (which have residence times from minutes to years).
For more information on groundwater and wells visit the Ministry of Environment
For more information on groundwater visit Environment Canada
