WATER QUALITY

Streamflow in the Charles River

As the suburban and rural upper Charles River watershed develops at one of the fastest rates in the state, so does the demand for water resources and the impact on streams. Towns increase pumping and search for new groundwater sources, harvesting water originally destined for streams. At the same time, parking lots, newly constructed buildings and other paved areas effectively block off aquifer recharge. This unsustainable behavior results in less water in our streams and rivers which reduces aquatic habitat, decreasing the native fish diversity, and sometimes even destroying fisheries.

In the urbanized areas of the middle and lower watershed, rain and snow fall on land that is predominately impervious (meaning water can't pass through it), picks up pollutants, and flows to the Charles River and its tributaries through storm sewers. While the level of flow in the river may surge immediately after a storm event, creating the appearance of lots of water and plenty of flow, this increased flow is temporary. The flow in the river after the storm is the base flow that sustains the river over time and it is the base flow that declines with more withdrawals and large areas of imperviousness.

The United States Geological Survey (USGS) has been monitoring the Charles River's flow since 1931. There are four USGS flow gages located along the Charles River at the Walker Street Bridge in Medway, below the Cochrane Dam in Dover, upstream of Route 9 in Wellesley, and below the Moody Street Bridge in Waltham. In the summers of 1999 and 2002, the Charles River had some of its lowest flows since the USGS started monitoring.

In addition, flow in the Charles has been monitored by ENSR Consulting and Engineering for the Milford Power Limited Partnership in Milford since October 1995. However, even with these five gages, there are still gaps in flow information for sections of the Charles River as well as tributaries.

In 1995, CRWA began conducting streamflow monitoring on an ad hoc basis. In 2002 we expanded to a more formal, continuous flow monitoring program for nine tributaries in the Upper Charles to assess baseline conditions, characterize flows in dry and wet weather, estimate pollution loadings, and to document the impacts of development. CRWA tributary monitoring will provide a long-term streamflow record that will document the effects of well withdrawals, de-watering via sewer systems, and reduced recharge from impervious areas on the smaller streams in the watershed.

Streamflow monitoring is the first step in identifying the problems and causes of low flows in the Charles River watershed. With the information we have thus far gathered, and knowledge of the large negative impact unsustainable development creates in the water cycle, CRWA is embarking on a number of water-friendly development and redevelopment projects. Our goal in these projects is to help developers and towns design better projects that minimize harm to the river by decreasing impervious surface thus allowing more rainwater to recharge, and promoting water conservation for landscaping and daily tasks. Click here for more information on our "Blue Cities" and development work.

For more information on streamflow in the upper Charles, read the 2004 USGS report entitled Evaluation of Strategies for Balancing Water Use and Streamflow Reductions in the Upper Charles River Basin, Eastern Massachusetts.