Surface Water Quality

  1. Carlie Miller

    Surface Water Quality Program

Surface Water Quality Monitoring



The Surface Water Quality Monitoring Program protects public health and the environment through baseline monitoring and source identification work.  According to the Washington State Department of Ecology, water quality data are used to characterize waters, identify water quality trends over time, identify emerging problems, determine the effectiveness of pollution control programs, and help direct pollution control efforts to where they are most needed.

The Surface Water Quality Monitoring Program samples conditions in freshwater flowing over land and eventually into marine water.  Waters that are outside the County’s jurisdiction (e.g., within municipal or military areas) are excluded.  These areas include NAS Whidbey properties, the City of Oak Harbor, the Town of Coupeville, and the City of Langley.

Our Sampling Sites

2024 and 2027
All Sites Layout

2024 & 2027 map: This map displays sample sites for the current water year (WY24, October 1 2023 to September 30 2024) and for water year 27 (WY27, October 1 2026 to September 30 2027) rotations. Only the sites displayed with a pink dot (rotational sites) change from year to year. To view this map as a pdf, please click here:  2024 & 2027 Map of Sample Sites 

2024 - 2029 map: This map displays all sampling sites for all rotation years through September 30, 2029. Some variation may occur in future years based on water availability or accessibility to sites. Any changes to these sites will be noted in future surface water quality reports. To view this map as a pdf, please click here: 2024 - 2029 Map of Sampling Sites

Source Identification


The Water Quality Monitoring program builds upon previous sampling efforts.  Public Health staff monitors surface water quality to identify non-point pollutants that have the potential to contaminate the surface and groundwater.  Sources of pollution include failing septic systems, domestic animals, and other natural sources.  Source identification sampling is focused geographically.

Source identification Objectives include locating areas that exceed water quality standards and determining the sources of contamination.


Island County Lakes


For current status of Island County public lakes, go to the WA State Toxic Algae page HERE.

  • Cranberry Lake, Oak Harbor WA
  • Goss Lake, Langley WA
  • Lone Lake, Langley WA
  • Deer Lake, Clinton WA

Lake Closures Policy is based on state guidelines set in June of 2021 which requires local health jurisdictions to post a WARNING when microcystin levels are 8 μg/L or higher, anatoxin-a levels are 1 μg/L or higher, cylindrospermopsin levels are 15 μg/L or higher, and/or saxitoxin levels are 75 μg/L or higher. A lake CLOSURE is required when toxin concentrations are extremely high (> 2,000 μg/L microcystins or > 300 μg/L anatoxin-a) or if pet illnesses/death or human symptoms are reported.

To view the current lake status from any lake in Washington State, visit NWtoxicalgae.org.



Baseline Monitoring


Baseline monitoring is sampling that is repeated within the same watershed at the same locations.  It is more geographically extensive than Source Identification monitoring.

Baseline Monitoring Objectives help determine if water quality standards are met in watersheds that previously have not been sampled or need additional sampling. For each major water quality parameter, determine the range of variation (by geomorphic and land use category) characteristic of Island County surface waters as necessary to help assign possible causes to exceedances and trends.




Surface Water Quality Annual Reports and Presentations.


View our latest annual report and presentation:

Visual Surface Water Quality Report 2021-2022

Surface Water Quality Annual Report WY16 (2021-2022)

Water Quality REPORT 2021

Water Quality Presentation 2020-2021