Souhegan Watershed Association

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Water Quality Monitoring Program

Water quality monitoring of the Souhegan River was begun in 1991 by the Nashua Regional Planning Commission. As part of their goal to protect and preserve the Souhegan River, the SWA monitors 22 sites along the length of the Souhegan on a biweekly basis from June through September. We also monitor 11 sites on the Merrimack River between Manchester and Tyngsborough. The goal of this monitoring project is to inventory chemical and biological data about the river over a long period of time to see how water quality is changing and to find "hot spots" that need to be improved right away.

One of the tests that we do every two weeks is a test for E-coli bacteria. E-coli bacteria can cause ear infections, eye infections, and diarrhea in people who come in close contact with the water. The state of NH requires that swimming areas have an E-coli count of 88 colonies/100 ml. of water or less.

Besides our normal biweekly river tests, SWA is now testing the river at Watsons Park in Merrimack and posting the results at the kiosk and near the swimming area every week. Look for blue, yellow, or red flags to indicate E. coli levels.

For more information on testing for E-coli and other water-borne patogens look at this site on Sanitary Water Quality created by the US Geological Survey. Note that the New Hampshire standard for safe water for swimming (88 colonies/100 milliliters of water) is more conservative than that established by the US Environmental Protection Agency (126 colonies/100 milliliters of water) for river water in general.

River Quality Monitoring Begins Each Year
in June and ends in September
Volunteers Always Needed

The Souhegan River Watershed Association and the Lower Merrimack River Local Advisory Committee plan water quality monitoring once again this Summer. This program has already proven to be a very effective way to directly benefit the rivers it covers. Volunteer water samplers, drivers, and site alternates are always needed! This year the Souhegan and Merrimack Rivers will be monitored at 32 sites eight times on Tuesday mornings during the summer from June to September.

If you are interested in helping the Water Quality Monitoring Program, contact Being a monitor requires no special skills. The most difficult part is that you have to make it to your site once every two weeks between 5 a.m. and 8 a.m. (on a Tuesday) and then transport your samples to one of several drop off points before 9 a.m.. Sampling takes about 15-20 minutes at the river.

SWA provides all the training and supplies the equipment needed for sampling. You will be assigned one specific site to adopt for the season. All of the monitors communicate with email.

Additional testing opportunities are also available for volunteers interested in doing macroinvertibrate sampling at various sites along both rivers. This involves collecting bugs and identifying them by pollution tolerance. You can check to see what this entails here.

Past Testing Results Available

Since 1991, sponsors of the Souhegan River monitoring have included the Merrimack River Watershed Council with the assistance of the River Watch Network, the U.S. Fish and Wildlife Service, Rivier College, the Merrimack Wastewater Treatment Plant, the Milford Wastewater Treatment Plant, the Nashua Wastewater Treatment Plant, the Greenville Wastewater Treatment Plant, the Manchester Wastewater Treatment Plant, and the NH Department of Environmental Services. Reports on the earlier water quality monitoring seasons may be available in the watershed town libraries. They are titled

  • "Merrimack River Watershed Council, Nashua Monitoring Project, 1991-1995 Summary Report".
  • Souhegan and Merrimack Rivers Water Monitoring Project, 1997 Report, A Cooperative Project of the Souhegan Watershed Association and the Lower Merrimack River Local Advisory Committee, November 30, 1997
  • Souhegan and Merrimack Rivers Water Monitoring Project, 1998 Report.

Reports of past seasons' testing are available elsewhere on this website.

Web pages by Richard Hart.
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