Our scientists collect water samples from more than 85 long-term river and stream stations. The freshwater monitoring team collects 24-hour data for dissolved oxygen, temperature, pH, and conductivity in many rivers and streams statewide. We also collect monthly data on bacteria, pH, phosphorus, and more. This data displays long-term trends in stream health and contributes to watershed studies and water quality improvement plans.
To learn more about how our Freshwater Monitoring team collects and processes samples, see the Standard Operating Procedures and Quality Assurance Monitoring Plans below.
Monitoring plans and 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
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 the measures taken to ensure that our results are accurate and consistent.
Parameters and analytes measured
Routinely measured indicators of water quality are listed in the table, below. "SM + number" refers to a number from Standard Methods for the Examination of Water and Wastewater . "EPA + number" refers to Clean Water Act Analytical Methods from the Environmental Protection Agency. Links for these methods lead to PDF documents on EPA's website. Additional constituents are sometimes measured to meet special needs.
Analyte table
| Indicator |
Method |
| fecal coliform bacteria |
SM 9222D |
| ammonia |
SM 4500 NH3H |
| conductivity |
SM 2510B |
| streamflow |
See 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 |
| phosphorus, soluble reactive |
SM 4500 PG |
| phosphorus, total |
SM 4500 PH* |
| suspended solids |
SM 2540 D |
| temperature |
via thermistor |
| turbidity |
SM 2130 |
*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
| parameter |
code in data |
description |
method |
Storet code |
unit |
detect limit |
| Conductivity |
COND |
Measured with Beckman meter which could not be field calibrated. Formerly EIM method SM 2510-B. |
SM2510F |
P95 |
umhos/cm |
0 |
| Fecal Coliform Bacteria |
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 05/01 |
SM4500PG |
P671 |
mg/L |
0 |
| Oxygen |
OXYGEN |
Winkler with biodate correction for thiosulfate. (after Feb 89) |
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 MEL 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 |