Source Water Assessments of Public Water Systems - EH: Minnesota Department of Health

Source Water Assessments
of Public Water Systems

What is a Source Water Assessment?

A Source Water Assessment is a document - produced by the Minnesota Department of Health (MDH), provided to the public water system, and made available to the public - which summarizes a variety of information regarding the water sources used by a public water system. Specifically, the assessment includes the following:

  • A description of the drinking water source(s) used by the water system (i.e. your well or wells) and the area that contributes water to the source(s). This will include a map showing the location of your water source(s).
  • A determination of the "susceptibility" of your drinking water source to contamination. Susceptibility describes how likely it is that a water source may become contaminated. For wells, susceptibility is based on well construction, the type of aquifer that supplies the well(s) and previous water sampling results.
  • Drinking water contaminants of concern to anyone using the water source. For wells, this will be based on any detection of regulated contaminants during previous water sampling.

Along with the text portion of the assessment, a map will be generated showing the Inner Wellhead Management Zone for the well(s) or a Drinking Water Supply Management Area (DWSMA), if one has been approved. Note that only systems that have formally entered the wellhead protection planning process will have an approved DWSMA. For more information about Source Water Assessments and to download or view an example of a Source Water Assessment, see:

Water Sources

To find and view source water assessments, click on the button below. Or, keep reading to find out more about source water assessments.

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Why Source Water Assessments Were Created and Updated

Under the 1996 amendments to the federal Safe Drinking Water Act, MDH was required to produce Source Water Assessments for all Minnesota public water systems by May 30, 2003 - and make these assessments available to the public. The idea behind assessments is the creation of a document that can provide a concise summary of available information regarding a water system's source(s). This information is then provided to both the public water system owner/operator and the public at large.

How Source Water Assessments Were Created And Updated

Source water assessments were created by MDH using existing data such as water sampling results, water system surveys, and well records. For systems using surface water, the assessment was created in consultation with representatives from the public water system.

Assessments are updated as soon as new information (such as well construction data) is added to the databases used to generate the assessments. The assessments shown on the website are then updated to reflect these changes.

How Source Water Assessments Are Being Used

Some of the ways source water assessments are being used include:

  • By the public - to understand where their drinking water comes from.
  • By contamination cleanup programs - to set priorities and determine the level of cleanup needed.
  • By permitting programs - to assess if a proposed land use has the potential to adversely affect a public water supply.
  • By MDH - when bringing water suppliers into the wellhead protection program.

A Source Water Assessment is Not a Wellhead Protection Plan

A "source water assessment" and a "wellhead protection plan" are two different documents, with separate and distinct purposes. However, the source water assessment can aid a water system in its wellhead protection planning process and provides an update of the system's progress in source water protection. Note that the source water assessment is produced by MDH, while the wellhead protection plan is developed by the water system and its wellhead protection planning team.

For More Information

For more information about source water assessments in Minnesota, contact the Source Water Protection Planner for your County: For national information:
Updated Wednesday, February 08, 2017 at 10:37AM