Where does drinking water come from?

There are 2 basic sources of drinking water:

1. Groundwater
2. Surface Water

Groundwater

Groundwater is water found beneath the earth’s surface.  Groundwater comes from rain and snow seeping into rocks and soil.  Groundwater is stored in underground areas called aquifers. Aquifers supply wells and springs.  Wells range from about 15 to 2000 feet deep.

Surface Water

Surface water is the water naturally open to atmosphere - such as rivers, lakes, streams, and reservoirs.  Precipitation that does not infiltrate the ground or evaporate into the sky runs off into surface water bodies.  Groundwater can seep into a stream, river or other surface water body, recharging those surface water bodies.

A water system obtains its water from:

1. wells drilled into the ground that pump out groundwater
2. devices called surface water intakes placed on a river, stream or reservoir.

A variety of conditions and activities may affect the quality of a drinking water source. These include:

• geology (rock and soil types)
• depth of a well or location of a water surface intake
• how the land surrounding the source is used (for industry; agriculture or development)
• the use of pesticides and fertilizers
• the presence of contaminated sites, leaking underground storage tanks, and landfills.

The sources of drinking water (both tap water and bottled water) include rivers, lakes, streams, ponds, reservoirs, springs and wells.  As water moves over land, naturally occurring minerals are dissolved and, in addition, substances resulting from the presence of animal or human activity combine with the water.  Drinking water, including bottles water, may reasonably be expected to contain at least small amounts of some contaminants.  Contaminants that may be present in the water include:

• Microbial contaminants, such as viruses and bacteria, come from sewage treatment plants, septic systems, agricultural, livestock operations and wildlife.
• Inorganic contaminants, such as salts and metals, are naturally occurring substances or result from urban storm water runoff, industrial or domestic waste-water discharges, oil and gas production, or farming. Examples include arsenic, asbestos, copper, lead and nitrate.
• Pesticides and herbicides, come from a variety of sources such as agriculture, urban storm water runoff, and residential uses. These are man-made chemicals used to control pests, weeds and fungus.  Examples include herbicides such as atrazine and insecticides, such as chlordane.
• Organic chemical contaminants, including synthetic and volatile organic chemicals, are by-products of industrial processes and petroleum production and may also come from gas stations, urban storm water runoff and septic systems. These are man-made chemicals such as solvents, degreasers and gasoline components. Examples include benzene, methyl tertiary butyl ether (MBTE) and vinyl chloride.
• Radioactive contaminants, radionuclides may be naturally occurring or be the result of oil and gas production and mining activities. Examples include radium and uranium.
• Pathogens, disease causing organisms such as bacteria and viruses. Common sources are animal and human fecal waste.
• Radon, colorless, odorless, cancer causing gas that occurs naturally in the environment.
• Disinfection Byproduct Precursors, a common source is naturally occurring organic matter in surface water.  Disinfection byproducts are formed when disinfectants (usually chlorine) is used to kill pathogens reacts with dissolved organic matter (for example, leaves) present in surface water.