Water quality monitoring methods for rivers & streams

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.

Monitoring plan and operating procedures

Quality Assurance Monitoring Plan: Statewide River and Stream Ambient Water Quality Monitoring is the latest long-term monitoring plan.
Standard Operating Procedure (SOP) — Ambient Freshwater Water Quality Monitoring contains our published Standard Operating Procedures.

Types of monitoring stations

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

Scientist stands on low bridge and lowers sampling bottle down by rope. — Collecting a water sample from a bridge.

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

Table shows methods and analytes
Indicator	Method
bacteria, fecal coliform	SM 9222D
ammonia	SM 4500 NH3H
conductivity	SM 2510B
streamflow	Streamflow methods
metals	EPA 200.8 and 245.7
nitrate plus nitrite	SM 4500 NO3I
nitrogen, total	SM 4500 NB
oxygen	SM 4500 OC
pH	EPA 150.2 (pdf)
phosphorus, soluble reactive	SM 4500 PG
phosphorus, total	SM 4500 PH*
suspended solids	SM 2540 D
temperature	thermistor
turbidity	SM 2130
bacteria, E. coli	SM 9222D

Scientist on bridge walkway prepares sampling bottles for use. — Several samples can be collected at once.

*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

Parameters
Parameter	Code in data	Description	Method	STORET code	Unit	Detection limit
Conductivity	COND	Measured with Beckman meter which could not be field calibrated. Formerly EIM method SM 2510-B.	SM 2510F	P95	umhos/cm	0
Bacteria, fecal coliform	FC		SM16-909C	P31616	#/100ml	1
Streamflow	FLOW	Ecology rating	RATINGF	P60	CFS	0
Ammonia – Nitrogen	NH3_N	Collected in acid-washed passenger, acid-preserved, shipped on ice. EIM Method was EPA350.1 prior to 05/01	SM4500NH3H	P610	mg/L	0.01
Nitrate – Nitrogen	NO3_N	Method originally assumed to be EPA352.1; changed to SM in 2004.	SM4500NO3I	P620	mg/L	0.01
Phosphorus, Sol Reactive	OP_DIS	Collected in acid-washed passenger, acid-preserved, shipped on ice. EIM Method was EPA365.3M prior to May 2001	SM4500PG	P671	mg/L	0
Oxygen	OXYGEN	Winkler with biodate correction for thiosulfate (after Feb. 1989).	EPA 360.2	P300	mg/L	0
pH	PH	Liquid probe (mostly low ionic strength probe), calib. 3x daily.	PHMETERF	P400	pH	1
Barometric pressure	PRESS	Both analog and digital	BAROF	P25	mm/Hg	0
Suspended solids, TSS	SUSSOL	—	SM2540D	P530	mg/L	1
Temperature	TEMP	thermistor in river	TEMPTHERMF	P10	deg C	0
Phosphorus, total	TP_P	Collected in acid-washed passenger, acid-preserved, shipped on ice. Sometimes from Manchester Lab as SM4500PI, sometimes as EPA 365.1.	EPA365.1	P665	mg/L	0.01
Total Persulfate Nitrogen	TPN	Collected in acid-washed passenger, acid-preserved, shipped on ice. Manchester/reg10 VAX call this P100021. (Former method: "valderama")	SM4500NB	P600	mg/L	0.01
Total Persulfate Nitrogen, Dissolved	TPN_DIS	Collected in acid-washed passenger, field-filtered, acid-preserved, shipped on ice.	SM4500NB	—	mg/L	0.01
Turbidity	TURB	—	SM2130	P82079	NTU	1

Dashes (—) indicate no data available.

Contact information

Markus Von Prause
Ambient Water Quality Monitoring Lead
mark.vonprause@ecy.wa.gov
360-407-6681

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