Department of
Environmental Quality

Source Water Assessments in Idaho

What Is a Source Water Assessment?

A source water assessment (SWA) summarizes the likelihood of individual drinking water sources becoming contaminated (usually a short-term "contamination event") and serves as a foundation for public water systems to prepare source water (drinking water) protection plans and implement protection measures. Each source water assessment report: 

• Defines the zone of contribution, which is that portion of the watershed or subsurface area contributing water to the well, spring, or surface water intake (source water area delineation)
• Identifies the significant potential sources of drinking water contamination in those areas (potential contaminant source inventory)
• Determines the likelihood that the water supply will become contaminated (susceptibility analysis)

Source water assessments are the cornerstone for source water protection. Local communities can use the information gathered through the assessment process to create a broader source water protection program to address current problems and prevent future threats to the quality of their drinking water supplies. The information acquired from assessments also assists DEQ in overseeing public water systems.

History of SWAs in Idaho

In 1996, Congress amended the Safe Drinking Water Act to place more emphasis on the protection of surface water and ground water sources used for public drinking water.  Each state with a public drinking water program was required to develop a source water assessment plan for public drinking water sources, conduct assessments on all public water systems, and make the assessments available to the public.

With input from a diverse group of stakeholders and Idaho's Source Water Assessment Advisory Committee, DEQ completed the Idaho Source Water Assessment Plan in October 1999, and it was approved by EPA in November 1999. To date, more than 3,500 public water system sources have been assessed and source water assessment reports completed.

How to View a Source Water Assessment Report

Source water assessment information for Idaho public water systems is accessible using the Source Water Assessment Database. The database provides information on the assessed sources (well, spring, or surface water intake), including a potential contaminant inventory, susceptibility (to contamination) summary, maps (both a static and dynamic map) of the source water delineation, and a summary report. You can search the database by county, public water system number, water system name and/or type of source.

 The Source Water Assessment Database contains the most current source water assessment information for all completed assessments, including new assessments as well as information from historic assessment reports generated prior to 2009 when the database was developed.

 

Enter Source Water Assessment Database

 

The historical reports, developed prior to 2009, are static, stand-alone reports that have not been updated with new contaminant information; however, they may contain additional hydrogeologic information not captured in the current database. Scanned copies of the original reports are available.

 

Historical Reports are temporarily offline. For assistance with Historical Reports, please call one of the contacts listed at the top-right side of this page.