By Laura Nichol
Scientists are making significant progress in their efforts to map Canada’s network of aquifers.
The majority of the world’s fresh water lies underground. Beneath our feet, water flows through tiny spaces between soil materials or within cracks in rocks lying below the soil layer. The water is then held in permeable geological formations, called aquifers. Their composition varies, ranging from fractured rock to thick porous sand.
In Canada, one third of the population depends on groundwater for their drinking water. For the past decade, scientists at Natural Resources Canada (NRCan) have been working with Canadian provinces to map 30 of Canada’s most significant aquifers. They range from bedrock aquifers shared by Quebec and New York to porous aquifers buried in the Canadian Prairies during the last glaciations. Scientists are creating an inventory of their size, location, natural quality and sustainability.
This knowledge will provide the provinces with the scientific evidence to prevent the depletion and contamination of groundwater resources. The national inventory is especially important for effective groundwater management given that aquifers can extend many kilometres and cross municipal, provincial and even international borders.
New Technologies Key to Aquifer Mapping
“Composed of both water and rocks, aquifer mapping is complex, since three-dimensional data is required,” says Alfonso Rivera, the Chief Hydrogeologist for NRCan’s Groundwater Geoscience Program. “To further complicate the process, we are mapping something that we can’t physically see.”
To meet these challenges, scientists have developed a number of new methods, models and technologies.
Some of the most promising developments are those that involve satellite data. “We are now capable of supporting the mapping and assessment of aquifers using remote sensing technologies,” says Alfonso. “For instance, NRCan researchers are working to interpret changes in groundwater storage using gravity measurements from satellite data.”
Scientists are also evaluating evapotranspiration at the national scale by combining remote sensing data such as Leaf Area Indexes with physically-based numerical models. Evapotranspiration is one of the most important components of the water cycle; it is the process whereby water evaporates from the land into the atmosphere. These rates can have significant impacts on groundwater supplies, so they are important for evaluating overall changes in groundwater resources.
Finally, another new technology, used to evaluate the natural groundwater quality, is isotopic fingerprinting. In this procedure, naturally-occurring isotopes are used to characterize the geochemical background values of the groundwater and to evaluate the origin of geochemical anomalies that may have made their way into aquifers.
Setting Standards for Hydrogeological Assessments
With a plethora of complex data, scientists created the Groundwater Information Network, a database to manage and share the data collected on Canada’s major aquifers. “This data management method has been so successful, it is has been adopted in the United States, Australia and Europe,” says Alfonso.
Scientists have already mapped 12 of the aquifers, and seven more are set to be completed by 2014. The eventual goal is to develop a national framework in collaboration with provincial agencies to map Canada’s entire network of aquifers, which number in the thousands.
Explore NRCan’s Groundwater Geoscience Program for data on water wells and aquifers in Canada.
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