by T Marie Allman

Created on: September 20, 2010   Last Updated: September 21, 2010

Our planet is covered by vast amounts of water, only one percent of which is useable by humans.  The quality of the water available for our use is therefore very important and can be affected by many different factors.  Oceans, streams, lakes and aquifers are all susceptible to the quality of the sources that feed them.  Water quality is an environmental issue that affects us all.  It is important for us to understand how our way of life affects levels of harmful constituents in our water, for the health and safety of all animal life on Earth.

Most of the water we drink comes from natural underground storage systems called aquifers.  Aquifers are porous beds of rock where water has collected over millions of years.  Aquifers are replenished by water seeping down from the surface.  When the water moving into an aquifer contains harmful chemicals, those chemicals can end up in our drinking water. 

Some of the worst perpetrators of aquifer pollution are farms and croplands.  The use of manure and other fertilizers and the use of pesticides on the fields almost certainly ensure contamination of any water source below.  When rain or irrigated water percolates through the soil and down to the aquifer, it carries some of the chemicals that were used on the crops.

Another source of contaminants is leaking underground storage tanks, or LUSTs.  There are thousands of old gasoline tanks in the ground, many of which have corroded and are now leaking.  The fuel from the tanks is transported by water moving underground to aquifers and to streams and lakes.  When an aquifer is at a higher elevation than a body of water at the surface, water from the aquifer can be a source for that lake or stream.  Any contaminants within the aquifer are transferred to the surface water.

Contamination enters water through methods other than percolation.  Runoff is a serious problem in many areas, particularly where surface pollution is common.  Many lakes and streams have constantly high levels of contaminants from fertilizers, pesticides, gasoline spills and other pollutants.  Anything that is thrown into street gutters can eventually make its way into a water source, whether that source is an aquifer, lake or stream.

Some sources of contamination have nothing to do with manufactured chemicals.  Natural contamination can occur in aquifers from high concentrations of harmful metals or radioactive compounds. 

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