Pine Tree Brook showed low flow on June 15th. Photo by Sean McCanty.

On the morning of June 9th, forty-eight brave volunteers ventured through the rainy morning to their sampling sites.  Every volunteer plays an important role in collecting data and helping to inform our understanding of the water quality of the Neponset River Watershed. Here’s to four more months of successful water monitoring this season!

The month of June was significantly drier than average, with a total rainfall of 2.81 inches, which is only about 60% of the average 4.63 inches of rainfall for June, worsening the already significant drought in the region. The temperature in June was slightly warmer than average, with an average of 66.7℉ compared to the average temperature of 66.5℉ in June from 1891-2020.

Unfortunately, due to backlogs and staffing issues at the Massachusetts Water Resources Authority (MWRA), as of 8/10/22, we are still waiting for our June E. coli and nutrient data.

For any questions about the June CWMN results, please email NepRWA Environmental Fellow, Eleanor Yeomans, at yeomans@neponset.org

Dissolved Oxygen

The two main sources of dissolved oxygen in our streams are aquatic plants that release oxygen as well as fast-moving waters that cause air to be mixed into the water; additionally, warmer water is able to hold less dissolved oxygen than colder water.  Due to the slightly warmer temperatures combined with the low rainfall, the dissolved oxygen levels in June were, on average, lower than they were in May.

Dissolved oxygen is important for aquatic life because many underwater critters access the oxygen they need to respire, or breathe, through dissolved oxygen in the water. Certain animals, including trout, require more dissolved oxygen than others, their dissolved oxygen requirement is represented by the cold water standard in the graph below. Other species are more tolerant of low dissolved oxygen levels, and their needs are reflected by the warm water standard.

Low dissolved oxygen levels are linked to drought conditions and sustained high temperatures and can lead to a reduction in the population sizes of the numerous aquatic species that are reliant on oxygen in the water.

The relatively high levels of dissolved oxygen in June indicate that the majority of waterways in the Neponset River Watershed offer a healthy habitat for plants and animals, however, a large proportion of the sites that were sampled had lower than optimal dissolved oxygen levels.  This indicates that the hot and dry summer weather has begun to adversely impact dissolved oxygen levels in the Neponset River Watershed.

Seventy-five percent of the sites at which dissolved oxygen measurements were taken reached the recommended number of milligrams of oxygen per liter for cold-water fish. A total of 10 of our measured sites had lower than recommended dissolved oxygen levels, with 5 falling below warm water standards as well.

The dissolved oxygen results are summarized in the graph below: