Community Water Monitoring Network

The Community Water Monitoring Network or “CWMN” is an Environmental Protection Agency-approved, volunteer-based approach to water quality monitoring that has been running at NepRWA for over 20 years.

Since 1995, CWMN has provided critical scientific data that enables us to advocate for the cleanup of pollution.

Forty-one sampling sites throughout the Neponset River Watershed are tested each month by a group of citizen volunteers. From May to October, each site is tested once a month and the water quality data is used to locate and clean up suspected contaminated areas.

For any questions about the CWMN Program, including volunteer opportunities, please contact our Environmental Science Fellow, Eleanor Yeomans at or 781-575-0354 x 302.

What do CWMN Volunteers do?

CWMN volunteers take water samples at sites throughout the Neponset River Watershed, assessing the sites and water for:

  • Depth of the water body
  • Rate of water flow
  • Clarity, color, and odor of the water
  • Temperature of the air & water
  • Current and prior weather
  • Dissolved oxygen levels

The Watershed Association and various laboratories then test the water samples for:

  • pH
  • Presence of E.coli bacteria
  • Total Phosphorus
  • Total Nitrogen
  • Ammonia
  • Chlorophyll

CWMN Volunteers: Click here for resources

Why is water monitoring needed?

We monitor water quality around the Neponset River Watershed in order to catch and reduce both “point source” and “non-point source pollution.” Both types of pollution are responsible for degrading water quality, injuring wildlife, damaging wildlife habitat, degrading recreational resources (e.g., for fishing, swimming, and boating), and damaging human health.

Whereas “point source” pollution originates from a single, identifiable source (i.e., a leaking sewer pipe), “nonpoint source” pollution originates from a variety of sources. For example, in a residential neighborhood, nonpoint source pollution may contain fertilizers, herbicides, pesticides, ice-melt products, pet waste, anti-freeze, motor oil, car exhaust products, and litter, that all flow together over the ground when it rains, yielding contaminated stormwater.

Water quality testing enables us to identify waters with high levels of pollutants and then find and stop that pollution (especially point source pollution) at its source.

Volunteer opportunities

To become a regular CWMN volunteer (or an emergency contact volunteer – a substitute for water monitors who occasionally cannot participate), contact NepRWA Environmental Fellow, Eleanor Yeomans, at

Regular volunteers need to attend a training session and commit to testing an assigned site.  Emergency contact volunteers need to attend training and be ready to help when contacted.

Water Sampling

Volunteers are needed to take water samples at several area locations for the upcoming CWMN season. Water sampling takes place 6 times from May to October. Each volunteer has a specific site or sites where they sample from. Samples are taken between 6:00 AM and 7:30 AM in the morning and then taken to one of our four area Drop-off locations. Sampling typically takes 15-20 minutes from the time the volunteer gets to the site to the time they depart for the Drop-off location. Once at the Drop-off location the volunteer hands off the samples to the Drop-off Coordinator and fills out some simple paperwork.

Dissolved Oxygen Sampling

Volunteers who monitor dissolved oxygen levels are given a route with several sites and driving directions. Prior to the day of sampling, the volunteer will come by the NepRWA offices and pick up a handheld dissolved oxygen meter and some supplies. On the day of sampling, volunteers will go from site to site with the handheld meter and measure oxygen levels at five or six different locations. Each route is designed so that sites are not too far from each other and most can be completed in an hour or two depending on traffic on the day of sampling. Training will be provided on how to properly calibrate use the meter and record the necessary information on the paper field sheets.

Drop-off Coordinator

Coordinators come and pick up supplies at the NepRWA offices a few days prior to the sampling event. On the day of sampling Coordinators typically arrive at the drop-off location around 6:15 AM and leave to deliver samples to our offices in Canton no later than 7:45 AM. Once at the NepRWA office, the samples are unloaded and some paperwork is filled out completing the Coordinators duties. Typically the time commitment associated with this position is 2.5-3 hours on the day of sampling. Lifting of coolers with ice and water samples is required.

Transport to MWRA laboratory on Deer Island

One volunteer is needed to take all of the samples from our offices in Canton to the laboratory on Deer Island. The volunteer arrives at the office at 8:30 AM on the day of sampling and takes possession of the water samples distributed in 4 large coolers. Typically the time commitment associated with this position is 2.5-3 hours on the day of sampling. Once the samples have been dropped off the coolers and paperwork are returned to the NepRWA offices along with any supplies handed off to the driver from the laboratory staff (typically a few boxes of empty sample bottles).

If you would like to know more about the CWMN Program, please contact NepRWA Executive Director, Ian Cooke, at 781-575-0354 x305 or

Map of the 41 CWMN sites