Hot Spots and Low Flows

NSRWA Summer Sampling Finds Bacterial Hot Spots and Low Flows

The North & South Rivers Watershed Association concluded their 14^th year of River Watch Sampling, a volunteer driven water quality monitoring program at the end of the summer. Trained volunteers take water samples and readings of temperature, salinity, conductivity, and dissolved oxygen at ten sites along the North & South Rivers and the Scituate waste treatment plant. The results of the sampling provide the NSRWA with long-term baseline information on the health of our rivers’ water quality and encourages new groups of volunteers to become citizen scientists. This summer we had sixteen volunteers, ranging from high school students to retirees, help to gather this incredibly valuable information. In this era of budget cuts, for the most part local groups like the NSRWA are the only entity monitoring the health of our rivers!

Bacteria in our rivers

The results this year, not surprisingly, indicated low bacteria most likely due to the lack of rain and thus no storm runoff pollution. The NSRWA continues to see persistently high bacteria counts at the Willow St Bridge site on the South River in Marshfield and at the Washington Street Bridge site in Hanover/Pembroke on the North River. To provide more insight as to the origin of these persistent higher bacterial counts at Willow Street, the NSRWA, in partnership with the Town of Marshfield and the Massachusetts Bays program and with federal grant funding conducted in-depth sampling on the South River over the summer. We hope to have a presentation of those results at a workshop over the winter in Marshfield along with potential solutions for reducing those sources of pollution. In Hanover, the NSRWA has begun talks with the DPW on what the potential sources of contamination at the Washington St. Bridge could be and if there is any potential funding to further investigate it. One theory is that wildlife may be contributing, due to the large wetland system just upstream where the Indian Head and Herring Brook meet to form the headwaters of the North River.

Streams run dry

In addition to our annual water quality sampling, volunteers continued to monitor streamflows in the First and Third Herring Brooks. This summer was a particularly dry one and both brooks experienced many no-flow days. Both of these brooks feed municipal water supplies and both have several dams on them. Dammed parts of the First Herring Brook provide water to Scituate and groundwater wells near the Third Herring Brook provide water to Norwell and Hanover. Conservationists are becoming increasingly concerned that the doubling of water use in the summer and dams that are not managed to allow flow downstream during these low flow periods is resulting in dry streambeds.

The chart below is data collected from this summer on the First Herring Brook in Scituate between the upstream reservoir and the Old Oaken Bucket Pond. As you can see the flow ranges from 0 cubic feet per second (cfs) to over 5 cfs. The extremes in flow are caused by how the reservoir is managed. The town of Scituate holds water in the upper reservoir, thus streamflow goes to zero, then shuttles water from the reservoir to the Old Oaken Bucket pond via the brook to replenish the supply. The NSRWA is working with the town to identify a way to have more natural releases that would allow some water in the stream at all times and accommodate the town’s water needs. Clearly, summertime water conservation would help Scituate to have more flexibility in managing the brook to sustain a minimum level of stream health.

The bacteria sampling program runs through early June through late August. Our streamflow measuring program is year-round. We are enabled to conduct the bacteria sampling because of a generous anonymous donor every year. If you are interested in volunteering please let us know. We are always looking for a fresh group of citizen scientists to lend a hand.