The TRWA water quality sampling results for September 8th are available. Go to our website homepage and click on the Water Quality Monitoring tab at the top of the website homepage and either the picture of the sample bottles or the link under the Documents section to see the latest results as well as the results from past years.
The September river flow as measured at the Bridgewater USGS gauge, which covers about half the watershed and measures the flow coming into the area we sample, was 67 cubic feet per second (cfs) when we sampled on 9/8/26. The last large rainstorm before we sampled was a brief but very intense rainstorm on August 4th which caused localized street flooding and river flow to quickly spike to 776 cfs. On August 11 there was a smaller storm which caused river flow to increase to 122 cfs. But as happens during New England’s climate change induced drought weather pattern stream flow quickly fell after both of these storms to the 50 to 70 cfs range. When we sampled in September, it was after a relatively rain free period with river flow 67 cfs, the lowest of any sampling day this year.
Climate change has given our watershed and New England a drought summer weather pattern consisting of short-duration intense storms with relatively long intervals of warm, dry weather. As we see from the USGS river flow record, our rainfall during drought runs off quickly to the ocean rather than replenishing our river base flow and public and private wells. For this reason TRWA supports better stormwater management through updated state and local standards for new development called the watershed protection standard and EPA residual designation of existing unregulated commercial stormwater sources to bring them under stormwater management. As we see on the national news coverage of flash flooding and disappearing water supplies we need to do a better job managing our stormwater.
The monitoring results showed higher nitrogen levels than our target below the Brockton and Bridgewater wastewater treatment plants (WWTPs) possibly due to the low river flow. By Taunton, however, instream nitrate levels met our target for Mount Hope Bay. Phosphorus levels were elevated in the Town River below the Bridgewater treatment plant because that plant is not required to remove phsophorus until 5/01/2027 and river flow was low. Last month, July, every location sampled violated state water quality criteria for bacteria by a large amount reflecting the pollution input from inadequately managed stormwater from impervious surfaces in the watershed. By contrast this month, September, because of lack of rain and stormwater input over half our samping locations met the bacteria criteria and the magnitude of violations at other locations was much lower.
The drought continues, river flow on September 21st was only 73 cfs despite a significant rainstorm on September 14th. We continue to see the up and down pattern in river flow typical of a watershed in drought. TRWA’s sampling is important to tell us how the river and tributaries are responding to the climate change-induced drought we are seeing each summer and provide important insight concerning what must be done to minimize the impact of drought on our watershed’s water quality and drinking water supplies.