Groundwater Contamination
Global Geography 12
Groundwater – water that is found in the soil and rock (under ground)
Contaminant – any substance that is not wanted or does not belong
People used to think that contaminants left on or under the ground will stay there. In
fact, groundwater often spreads contaminants from dumps and spills far beyond the site
of the original contamination.
Groundwater contamination is extremely difficult, and sometimes impossible, to clean
up because the water is out of reach – below ground. After removing the source of
contamination, very little can be done.
Groundwater contaminants come from two categories of sources: point sources and
distributed, or non-point sources.
Point sources
 Septic systems
 Leaks or spills of chemicals
 Municipal landfills
 Livestock wastes
 Mill tailings in mining areas
 Sludge disposal areas
 Graveyards
 Runoff of salt and other chemicals from
roads and highways
 Spills related to highway or railway
accidents
Non-point (distributed) sources
 Fertilizers on agricultural land
 Pesticides on agricultural land
and forests
 Contaminants in rain, snow,
and dry atmospheric fallout
1. How and why do people use groundwater?
2. Give at least three reasons why groundwater contamination is a serious problem.
3. What do you think is the difference between a point source and a non-point source
of contamination?
Septic systems are designed so that some of the sewage breaks down in the tank and
some breaks down and gets absorbed by the surrounding subsoil. Contaminants that
may enter groundwater from septic systems include bacteria, viruses, detergents, and
household cleaners.
Contamination can make groundwater unsuitable for use. In many cases,
contamination is only recognized after groundwater users have been exposed to
potential health risks. The cost of cleaning up contaminated water supplies is usually
extremely high.
4. What do you think are the health risks of drinking water contaminated with sewage?
5. Give at least two reasons why septic systems are a common cause of groundwater
contamination.
Once an aquifer (a large underground source of water) is contaminated, it may be
unusable for decades. Contaminants may stay in the water anywhere from two weeks
or 10 000 years.
6. Refer to your pollution vocabulary sheet. What would you call a contaminant that
only lasts two weeks?
7. What would you call a contaminant that lasts thousands of years?
Furthermore, the effects of groundwater contamination do not end with the loss of wellwater supplies. This groundwater passes through the hydrologic (water) cycle, so
sometimes the contaminants come to the surface and end up in lakes and rivers.
8. What problems, other than contaminated drinking water, might occur when lakes
and rivers become contaminated?
Contamination problems are increasing in Canada because of the large and growing
number of toxic compounds used in industry and agriculture. Scientists also predict that
more contaminated aquifers will be discovered, new contaminants will be identified,
and more contaminated groundwater will appear in wetlands, streams and lakes.
9. In what recent resource did we hear about the growing number of toxic chemicals?
In Canada, pollution of surface water by groundwater is probably at least as serious as
the contamination of groundwater supplies. Preventing contamination in the first place
is by far the most practical solution to the problem.
Adapted from:
Environment Canada, “Water Pollution”,
www.ec.gc.ca/water/en/manage/poll/e_poll.htm
Accessed November 21, 2008
1. How and why do people use groundwater?
People get groundwater from wells (and sometimes from springs). It is the main
source of drinking water and tap water in rural areas. Groundwater is also used for
farming (irrigation) and sometimes for industries.
2. Give at least three reasons why groundwater contamination is a serious problem.
Groundwater is serious because:
 A lot of people need clean water
 Contamination can make people sick
 It’s very hard to clean up groundwater contamination
3. What do you think is the difference between a point source and a non-point source
of contamination?
A point source is a single location that causes the pollution. A non-point source is a
large area or more than one location.
4. What do you think are the health risks of drinking water contaminated with sewage?
You can get very sick from poisons or diseases.
5. Give at least two reasons why septic systems are a common cause of groundwater
contamination.
The whole point of a septic system is to get the waste into the soil, so it can easily get
into groundwater from there. The other reason is that there are lots of septic systems
everywhere.
6. Refer to your pollution vocabulary sheet. What would you call a contaminant that
only lasts two weeks?
A non-persistant pollutant
7. What would you call a contaminant that lasts thousands of years?
A persistant pollutant
8. What problems, other than contaminated drinking water, might occur when lakes
and rivers become contaminated?
It could affect the natural environment- the fish, plants and animals of an ecosystem.
It could also affect water for other uses, like swimming.
9. In what recent resource did we hear about the growing number of toxic chemicals?
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