Missouri Public Drinking Water Website

The Source Water Inventory Project (SWIP)

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Frequently Asked Questions

1.  What is source water?
Source water is untreated water from streams, rivers, lakes, or underground aquifers which is used to supply private wells and public drinking water.

The U.S. Environmental Protection Agency defines it as any facility or activity that stores, uses, or produces, as a product or by-product, the contaminants of concern and has a sufficient likelihood of releasing such contaminants to the environment.  The release would be at levels that could contribute significantly to the concentration of these contaminants in the source water of public water supplies.

3.  Where does SOURCE OR drinking water come from?
Most source water is defined as surface or ground water. If you live in a large metropolitan area, the majority of your drinking water probably originates from a surface source such as a lake, stream, river or reservoir. The land area that can have an impact on these water bodies is called a aquifer recharge area, and can be delineated on a map.

If you live in smaller community or have a private well, it is more likely that your water originates from underground and is pumped to the surface through a well. Ground water comes from natural underground layers, often of sand or gravel, that contain water. These formations are called aquifers. The land area that can have an impact on the quality of this underground water is called the watershed.

4.  What are the threats to Source Water?
There are many contaminants that may be present in source water before it is treated.  These include:

  • Microbial contaminants, such as viruses and bacteria, which may come from sewage treatment plants, septic systems, agricultural livestock operations, and wildlife.
  • Inorganic contaminants, such as salts and metals, which can occure naturally or result from urban stormwater runoff, industrial or domestic wastewater discharges, oil and gas production, mining, or farming.
  • Pesticides and herbicides, which may come from a variety of sources such as agriculture, stormwater runoff, and residential uses.
  • Organic chemical contaminants, including synthetic and volatile organic chemicals, which are by-products of industrial processes and petroleum production, and can also come from gas stations, urban stormwater runoff, and septic systems.
  • Radioactive contaminants, which can be naturally occurring or be the result of oil and gas production and mining activities.


6.  Why protect Source Waters?
Protection of drinking water at the source can be successful in providing public health protection and reducing the treatment challenge for public water suppliers. Source water quality can be threatened by many everyday activities and land uses, ranging from industrial wastes to the chemicals applied to suburban lawns.  In some cases, source water protection can eliminate or forestall the need to change or modify treatment processes. Treatment is expensive and source water protection can save consumers significant money.

For more information contact David Erickson

Website funded by Missouri Department of Natural Resources, and administered by the Public Drinking Water Branch
of the Water Protection Program
- 04/23/2008
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University of Missouri - Columbia
(573) 882-7458
130 Mumford Hall,
Columbia, MO 65211