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Drinking water comes from a variety of sources including public water systems, private wells, or bottled water. The United States Environmental Protection Agency (EPA) ensures that public water supplies meet regulations set forth by EPA and is treated to ensure quality water for over 286 million Americans. EPA regulations are not enforced on privately owned wells or any other individual water system, so it is the responsibility of the owners of private wells to ensure that their water is free of contaminants.
The public supply of water in Arizona comes from two sources, surface water and ground water. Well-populated metropolitan areas tend to rely on surface water supplies, whereas small, rural areas tend to rely on ground water for their water needs. Public water systems treat drinking water before it enters the home.
- Surface Water
Surface water is water that collects in a stream, river, lake, or reservoir. According to EPA, 68% of public water system users receive their water from a surface water source, such as a lake. Surface water requires more treatment as there is a higher chance of it being contaminated.
- Ground Water
Ground water is any water located below the ground surface in spaces in the rock. Ground water is used more often as a source by public water suppliers, but supplies water to less people because most areas with large populations receive their water from lakes or rivers. EPA also estimates that approximately 15% of the U.S. population relies on private ground water wells.
For more information regarding the source of water, please refer to CDC's Water Sources page.
Drinking water supplies in the United States are among the safest in the world; however, they can become contaminated, causing waterborne diseases.
Drinking water sources are subject to treatment in order to remove contaminants. Public drinking water systems use various methods of treatment to provide safe drinking water for their communities. Water may be treated differently depending on the quality of the water that enters a treatment plant. Surface water generally requires more treatment and filtration than ground water does.
To learn more about the different treatments for drinking water, see the National Drinking Water Clearinghouse's Fact Sheet Series on Drinking Water Treatments.
To learn more about the treatment of water, please refer to CDC's Water Treatment page.
Regulations are set in place by the EPA to ensure the quality of America's drinking water. The Safe Drinking Water Act (SDWA) gives EPA with the authority to set the standards for drinking water quality and oversee states, localities, and water suppliers who implement those standards. Through the SDWA, all public water systems in the United States need to follow the standards and regulations set by the EPA.
To learn more about regulations in place to protect your drinking water supply, please refer to the CDC's Water Regulation page.