Source Water Assessment Program (SWAP) Mapping Tool

Source Water Assessment Program (SWAP)

1996 amendments to the federal Safe Drinking Water Act (SDWA) require states to implement Source Water Assessment Programs (SWAP). Read Washington’s SWAP Report 331-148 (PDF).

There are four major components to the federally mandated SWAP program. We are to ensure we have met the following requirements for each federally regulated public drinking water system. 

  1. Delineate source water protection area(s) (SWPA) for each source (well, spring, surface water intake). 
  2. Inventory each SWPA for potential contaminant sources. 
  3. Conduct a susceptibility assessment for each drinking water source. 
  4. Make the findings of 1-3 readily available to interested parties.

Under WAC 246-290-135, Group A systems are required to develop wellhead protection programs and/or watershed control programs that include SWPA delineation, potential contaminant inventories, and susceptibility assessment for each source. 

Source Water Assessment Program Online Mapping Tool (SWAP Map)

We host the SWAP Map to provide a graphical representation of drinking water source protection areas and potential contaminants. Making this information available helps utilities protect their sources from unintended contamination. Additionally, local governments and other entities use this map to understand potential critical areas when assessing land use approvals or updating local ordinances. 

What Data is Used on SWAP Map

The SWAP Online Mapping Tool uses a combination of data submitted by public water systems and data from Ecology. Data tables for water system layers display information submitted by water systems and housed in our Sentry Internet. We do not display source location publicly to protect crucial infrastructure. The layers on SWAP Online Mapping Tool include:

  • Drinking Water System Points. This layer displays a single data point for each public water system (Group A and B). The data point is manually placed as a spatial reference to the system’s service area or sources. This point does not represent the source location. 
  • Ecology Contaminants. This layer is derived from Department of Ecology and displays facility/site interactions with active or potential impact on the environment. This data includes a variety of programs including water quality, water resources, toxics cleanup and hazardous waste.  
  • Wellhead Protection Areas. This layer displays protection areas for groundwater source systems. This data is submitted by water systems in their wellhead protection plans. If no data is available for a water system, an “assigned” protection area is displayed.
  • Surface Water Protection Areas. This layer displays protection areas for surface water source systems. This data displays areas up to 30 miles upland and upstream of surface water intakes. Generally, this layer is generated by DOH using watershed boundaries and digital elevation models. 
  • Drinking Water Service Areas. This layer displays areas served by public water systems. The boundaries are submitted by water systems in their water system plans. Not all systems have service area boundaries mapped. 
  • County Boundary. This layer displays county boundaries in Washington State. 

How to Use the SWAP Online Mapping Tool

  • Click to open SWAP Online Mapping Tool.
  • When the welcome window opens, review the disclosure, then click the “I agree to the above terms and conditions” box. Then select “OK.” The map is now open. 
  • The top of the map has blue buttons called “widgets.” Hovering over a widget tells you what it does. The main widgets to navigate the map are:
    • Layers. Here you can turn layers on and off. Reorder the layers to your liking. Increase or decrease the transparency for easier viewing. 
    • Search. Here you can search by physical address, water system name, or water system ID. When searching for a water system, several layer options will display system points, source water protection areas, and service areas. Make your selection from the drop down and the map will zoom to your selection.  
    • Filter. Here you can set filters on the various layers to display certain information. For example, if you want to just look at the areas specific to a system, you can use the filter to remove other systems from view. Make sure the layer you wish to filter is turned and the “toggle switch” of the filter is turned on. 
  • For a detailed description of widgets and map navigation, select the “Help” button in the upper right-hand corner. 
  • Reach out to sourcewaterprotection@doh.wa.gov if you need additional assistance.

Updating data and correcting errors on SWAP Online Mapping Tool

For information about collecting and submitting data electronically, follow the guidelines identified in Collecting Water System Data Electronically 331-391 (PDF). 

If you identify water system errors on the SWAP Online Mapping Tool, reach out to sourcewaterprotection@doh.wa.gov with a description of correction needed. 

Corrections to Ecology's contamination data should be sent to Ecology at gis@ecy.wa.gov.

More Resources to Implement SWAP