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Assessment and Water Quality Monitoring

Source water assessment

Between 1999 and 2005, each public water system in Oregon received a source water assessment report completed by the Oregon Department of Environmental Quality and Oregon Health Authority drinking water programs. The assessment gives the water system and community information on the watershed or recharge area that supplies the well, spring or intake (the “drinking water source area”) and identifies potential risks within the source area. 

Starting in 2016, the agencies are completing Updated Source Water Assessments to provide the water systems and communities more detailed information on the watershed or recharge area that supplies their well, spring or intake. DEQ opened public comment on the content and format of an USWA prototype on May 18, 2016.  This public comment period allowed partner state agencies, stakeholders, and public water providers an opportunity to help make the information more useful and relevant. Comments received were used to improve the document. The prototype was finalized in August 2016.

Updated Source Water Assessments will be provided to all public water systems using surface water and are posted at the link below as they are completed. For groundwater systems, OHA has prioritized new Community and Non-Transient Non-Community water systems and systems that have added a new water source since their original source water assessment was completed. For groundwater system reports, contact Paula Rich, OHA, at 541-726-2587 ext.25.

Public water systems and local communities can use the information in the assessments to voluntarily develop place-based plans and implement drinking water protection strategies

​​​​Source Water As​​sessment and Updated Source Water Assessment results for Oregon Public Water Systems 
Provides links to assessment reports and additional information for individual public water systems in Oregon ​

As part of the Updated Source Water Assessments, DEQ developed a statewide land use/ownership GIS layer to evaluate land cover in drinking water source areas. Statewide surface water maps and land use data are available on the Maps and Data page. Maps for each individual public water system are provided in the Updated Source Water Assessment report.

Source water assessment methods and inventory results, June 2005

Source Water Assessment Inventory Results as of June 2005 for Potential Contaminant Sources identified in Oregon Drinking Water Source Areas for Community and Non-transient Non-community Public Water Systems

Drinking water source monitoring

During the period of 2008 through 2014, Oregon DEQ conducted a series of monitoring tests at the source waters at 35 surface water intakes and 48 groundwater wells. Raw water samples were collected upstream of intakes and at groundwater wells that serve as public water systems in 27 counties across the state. The samples were analyzed at the DEQ Laboratory for over 250 Oregon-specific herbicides, insecticides, pharmaceuticals, VOCs (including cleaners), fire retardants, PAHs, personal care products, and plasticizers. Of all surface water intake sites sampled, 88% had typical wastewater constituents detected and 59% had pesticide detections. In the groundwater sources, 85% had wastewater constituents and 39% of the samples had pesticide detections. With the exception of one chemical (arsenic), the levels of all parameters detected thus far have been very low and have met health standards where available on an individual basis.

Low-level detections of chemicals in drinking water sources are important priorities for prevention because we lack health standards for many individual chemicals and there is no toxicity data for synergistic effects when multiple chemicals are present in finished drinking water. Sampling and analyzing for low levels of a broad range of chemicals in streams provides DEQ and others the ability to prioritize pollutant reduction efforts on activities/land uses that impact those streams.

Drinking Water Source Monitoring project that included collecting groundwater and surface water samples from 34 high-risk drinking water sources as identified through the SWAs. A total of 17 surface water intakes, 16 wells, and 1 spring were tested by DEQ to determine characteristics and detections in the source waters.

Results of the 2008-2010 monitoring

Articles summarizing Phase I 2008-09 monitoring

Additional source water monitoring was conducted between 2012 and 2014 by DEQ and others as part of regional projects. This included sampling for the Cities of Toledo, Lincoln City, Siletz, Irrigon and The Dalles; North Coast Sampling by the Tillamook Estuary Partnership; and USGS sampling of schools.


Water quality data for public water systems in Oregon can be found in a number of places.

Oregon Health Authority’s Drinking Water Data Online is available to access regulatory monitoring data stored in the Safe Drinking Water Information System (SDIWS) database for treated or finished drinking water. 

Additional raw water quality monitoring data in the waterbodies serving public water systems may be available from other sources including DEQ's water quality monitoring data portalUSGS, individual water providers, local partners (i.e. soil and water conservation districts or watershed councils) or local volunteer monitoring.​

2020 Wildfires

The September 2020 wildfires impacted numerous public water systems, with immediate effects to water quality and infrastructure and anticipated long-term changes within watersheds that supply drinking water.


There were 50 public water systems using surface water affected, and 96 public water systems using groundwater have source areas within the wildfire perimeters. Additional information on potential impacts, mitigation measures, and response partners can be found in the following two factsheets:

Longer term impacts to water systems will depend on burn severity, slope gradient, riparian and watershed conditions, and land management practices. DEQ participated on the Erosion Threat Assessment/Reduction Team to evaluate fires that burn on nonfederal land, including private, state, and local jurisdictions. The team assessed post-fire changes on the landscape to identify threats and potential risks to drinking water resources and provide recommendations to protect human life and safety, assets and infrastructure, and important natural and cultural resources. 

Federal agencies completed the Burned Area Emergency Response assessment that identifies short-term mitigation actions for federal lands to stabilize burned areas following wildfire. 

Maps of select river basins with 2020 Wildfire Perimeters and Drinking Water Intakes (including downstream water providers):


Julie HarveyDrinking Water Program Coordinator