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Groundwater Sources

Excellent quality water can be found underground in aquifers.  The water must be obtained from aquifers that are protected from agricultural, industrial and microbiological contaminants.  The quality should be monitored on a frequent basis to verify continual quality.

An aquifer is the underground formation of rock, sand and gravel that water flows through.  For example, there may be a layer of gravel or broken rock underground.  Water can flow slowly through the spaces between the pieces of gravel or rock as an aquifer.  Water can even flow through porous rock like limestone or sandstone.  The aquifer is not a large, cavernous tunnel underground.

Aquifers exist at many different levels, from those very close to the surface, to the deeper ones several thousands of feet down.  Aquifers get their water from recharge areas, at an elevated point, typically in a mountainous area, where some of the rain and snow seep into the ground.  When enough water has saturated the surface soil layer, the water will begin to move underground as an aquifer.  The water will remain underground until one of two things happens:  it can emerge at the surface or in a body of water as a spring, or it can be accessed and brought to the surface by a well.

Many municipalities use deep wells to access deep, protected aquifers several hundred feet below the surface.  The water brought up from these depths is regularly tested to verify compliance with state and federal drinking water standards.  For our spring waters, a protected spring site is chosen where the water comes to or near the surface.  Because of ease of access to the water, many bottled water companies or smaller municipalities may use springs as a source of water.

Aquifers can provide not only an underground supply of fresh water, but also protection for that water from surface water contaminants.

Some information for thought:

Water Table

The water table is an underground water source closer to the surface than an aquifer and it is rarely protected from surface or soil contamination by impervious or confining geological layers the way an aquifer is.  Like an aquifer, the water is typically found within a layer of sand, gravel or even soil and usually is supported by an impervious layer of rock or clay underneath it.  The water might flow slowly underground or it might be stationary.

Artesian well or artesian spring

When the water in an aquifer is under enough pressure that it is pushed up to the surface through a well or spring, it is artesian.  This artesian condition happens when the source or recharge area for the aquifer is at a point higher than the well or spring opening.  As an example, if the recharge area for an aquifer is up in the mountains, and in a valley below, a well provides access to the aquifer, the water might be under enough pressure to be pushed up to the surface and out of the well.

Deep Well

Typically, deep well water is obtained from an aquifer beneath a confining layer of rock or clay.  There is not sufficient pressure in the aquifer to force the water to the surface of a drilled well, so it is pumped to the surface.

Confining layer

A confining layer is typically a layer of rock or clay that is on top of or underneath an aquifer and keeps the water flow within a specific layer.  A confining layer will prevent the water from seeping deeper underground or rising to a higher level where it might mix with other aquifers or the water table.

Impervious layer

Rock and clay that form underground geological layers are called impervious layers.  Impervious means impassable or impenetrable.  The impervious layers are important for our aquifers because they are present above the aquifers and provide a good protective barrier against contaminants in soil or water closer to the surface.  These contaminants will not be able to penetrate the impervious layers to compromise our water quality.

Where does water originally come from?

Earth has a unique hydrologic cycle that involves nearly all of the available water on the planet.  Water in the clouds falls on the earth in the form of rain and snow.   Much of the water will remain on the surface, eventually evaporating and rising back up into the atmosphere from soil, lakes, oceans, etc.  From the atmosphere and clouds, the rain and snow begin the whole process over again.  Theoretically, the earth's available water has been involved in this evaporation and precipitation cycle for millions of years.

How does groundwater become contaminated?

Chemicals spilled on the surface, poured into wells or leaking from underground storage tanks can contaminate nearby groundwater.  Additionally, there are natural sources of contamination, such as radon and arsenic that might effect underground water quality.  It is best to use only deep, protected aquifers that are not subject to contamination from the sources listed above.

How to monitor ground water quality

Monitor the quality of the water from deep, protected aquifers regularly.  Testing includes simple, continuous checks such as flow rate, clarity, mineral level and pH.  Weekly tests check for bacteria and quarterly or annual testing checks for minerals, metals, microorganisms (including cryptosporidium), organic compounds like pesticides and herbicides, radioactivity, chlorine and chlorination by-products, etc.

Treatments for contaminated water

As discussed in other sections of this site, there are treatments available for a variety of contaminants.  Ion-exchange, reverse osmosis, chlorination, ozonation, activated carbon filtration, ultraviolet light irradiation, are a few of the many tools available to treat water for its' intended purpose.  However, for drinking water purposes, it is best to obtain a water source free of contaminants.