The water quality monitoring results for July are available on the website. Click the Monitoring Tab at the top of the TRWA home page and click on either the sample bottles picture or the link further down the page under Documents to find the result on the website.
In July as shown on the Bridgewater USGS River Flow Gage, the day before we sampled the river it was at a relatively low flow of only 87.3 cubic feet per second (cfs). The night before we sampled there was a brief intense rainstorm that ended just before we went out to sample. This storm increased river flow to 151 cfs when we sampled. Brief intense rainfall during summer droughts runs off quickly and doesn’t soak into the ground sufficiently to replenish groundwater and river base flow so after the storm river flow drops relatively quickly. The day after we sampled, river flow was down to 103 cfs. We saw a few other brief intense rainstorms in July but each time the river flow dropped quickly. Currently 7/21/25 despite a brief storm last night river flow is only 100 cfs.
The weather pattern we are seeing is very close to that predicted by global warming models for our area. These models predict late winter early spring heavy rain and potential flooding followed by hot dry summers punctuated by brief intense rainstorms which can cause short term local flooding and wind damage. These brief summer rainstorms don’t replenish river flows which drop quickly after the storms and deliver stormwater runoff pollution to rivers and streams. Extreme weather is the calling card of global warming but fortunately New England isn’t seeing the extreme heat, floods and hail reported in other parts of the country recently. As discussed below, rainstorm timing and river flow are important elements to interpreting TRWA monitoring results.
The results for July as a consequence of lower river flow and stormwater pollution loading are not as good as last month. We saw higher nitrate levels below the Brockton and the Bridgewater wastewater treatment plants (WWTPs) but fortunately by the time the river reached just below the Taunton WWTP the river was close to its water quality target for Mount Hope Bay protection. Phosphorus levels were high in a couple of places likely caused by urban stormwater runoff and the fact that Bridgewater has not completed its phosphorus removal upgrade scheduled for completion by 5/01/2027. The biggest problem was bacteria levels with all monitoring stations exceeding the enterococci water quality criterion of 35 colony forming units (CFU) by large amounts. This is a result of lack of stormwater treatment by green infrastructure such as infiltration basins, infiltration trenches (rain gardens, tree filters, etc.) in the watershed. Stormwater infiltration even if there is only physical space for an undersized unit that captures and treats the first flush is effective for bacteria and phosphorus control if widely practiced.
Because of TRWA documented water quality standards violations caused by stormwater throughout the Taunton River watershed TRWA believes EPA should use its “residual designation authority” to regulate large non-regulated commercial stormwater sources in our watershed. The Clean Water Act (CWA) recognizes that other stormwater sources may need to be regulated on a case-by-case or category-by-category basis based on additional information or localized conditions. The authority to regulate other sources based on the localized adverse impact of stormwater on water quality through NPDES permits is commonly referred to as the “Residual Designation” authority.
Our next sampling day is Tuesday, August 12th. We will be watching to see if river flow continues to decrease. If there is a brief rainstorm just prior to our sampling, whether it delivers enough stormwater pollution to cause water quality standards violations.