Our long-term river and stream monitoring team collects long-term data to track trends in stream health and contribute to watershed studies and water quality improvement plans. Our water quality scientists also maintain a network of continuous monitoring stations, in partnership with our streamflow scientists, to collect 24-hour data for dissolved oxygen, temperature, pH, and conductivity in many rivers and streams statewide. Learn how we measure Washington freshwater quality below.
Each of our stream-monitoring stations is a long-term, sentinel, basin, or specific study station.
| Type of station |
Number of stations |
Timing and purpose of monitoring |
| Long-term |
66 |
Measured monthly every year, primarily for trends |
| Sentinel |
8 |
Measured monthly every year, for reference conditions, trends due to climate change, and to support other types of monitoring |
| Basin |
12 |
Monthly for one year to support the Water Quality Assessment and especially to help refine category assignments for the Assessment |
We may monitor additional stations in some years to support special projects.
How we collect samples
We have stream ecologists statewide collecting monthly samples from stations year round. Each scientist covers a region of the state. Contact us to learn more.
Our ecologists use a rope and weighted containers to collect single surface-grab samples from highway bridges or, depending on accessibility, from the stream bank. Temperature is measured in-stream using a long-line thermistor or electronic tracking device. Water samples are measured in the field, or are processed for shipment to the Manchester Environmental Laboratory. In addition, they measure streamflow at long-term and some basin stations.
Learn about data quality
Data quality assurance for rivers & streams describes what we do to ensure that our results are accurate and consistent.
Analytes and parameters measured
Routinely analyzed indicators of water quality are listed in the table below. Additional constituents are sometimes measured to meet special needs.
SM = Standard Methods for the Examination of Water and Wastewater; EPA = Methods for Chemical Analysis of Water and Wastes Links for these methods lead to PDF documents on EPA's website.
Analyte table
*Note on total phosphorus: As of June 2018, EPA program 40 CFR Part 136 requires the minimum detection limit (MDL) for SM4500 PH to be reported as 0.066 parts per billion and the reporting limit (RL) as 0.10 ppb.
Parameter table
SM = Standard Methods for the Examination of Water and Wastewater; EPA = Methods for Chemical Analysis of Water and Wastes
Dashes (—) indicate no data available.