This page describes historical and ongoing programs to monitor the stream level and water temperature of Nagog Brook, and provides links to data and observations.

Nagog Brook is a small stream in the northwest corner of Acton. As shown on the map, the brook originates at the Nagog Pond dam and flows southeastward through the Quail Ridge development and golf course. It then merges with two other tributaries and feeds into Nashoba Brook just south of the intersection of Routes 27 and 2A.

Map shows location of the (1) currently active and (2) historical stream monitoring stations on Nagog Brook

Why Do Stream Level and Water Temperature Matter?

Nagog Brook has been designated as a cold water fish resource by the Massachusetts Department of Environmental Protection. Cold water streams can support sensitive species, such as brown trout and brook trout. Concern has been raised that development in the Nagog Brook watershed could harm the cold water fish resource, by diminishing the volume of water in the stream and/or by raising its temperature.

This concern first surfaced when the Quail Ridge golf course was being developed. Like most golf courses, Quail Ridge uses lots of water for irrigation. As a condition of being allowed to withdraw irrigation water, the facility was required to monitor the temperature and stream flow of Nagog Brook. These data were collected in 2006 and 2007. 

Concern arose again in connection with the Town of Concord’s plan to greatly expand the capacity of its water treatment plant on Nagog Pond. This plan has proven controversial for multiple reasons, including the possibility of harm to the ecosystems of Nagog Pond and Nagog Brook, as extensively covered in prior posts on this website. So as to know whether Nagog Brook was impacted by increased withdrawals from Nagog Pond, the Green Acton Water Committee began collecting water temperature and stream flow data in the summer of 2017. Sue Flint, then the staff scientist for the Organization for the Assabet, Sudbury and Concord Rivers (OARS), helped us design the sampling program, select the site, and install the equipment.

How the Green Acton Data Are Collected

Green Acton collects stream flow data by reading the stream depth on a device that looks like a large ruler, called a staff gage.* A Green Acton volunteer visits the site once a week and visually reads the gage to the nearest 1/100th of a foot. Gage level, date, time, and notes of any observations of interest are reported to the River Instream Flow Stewards (RIFLS), a program of the Massachusetts Division of Ecological Restoration. RIFLS collects stream gage data from volunteer groups all over the Commonwealth, and provides the infrastructure for safely storing and displaying the data. You can view various displays of the Nagog gage data on the RIFLS site here. 

In the summer, when flow is low, the volunteers supplement the quantitative readings with qualitative observations of flow state, chosen from among the following indicators developed by the CrowdWater Project:

  • dry streambed: no visible water and the streambed is dry
  • wet streambed: no visible water, but the streambed is wet (for at least 2 cm below the surface)
  • isolated pools: separated pools of water that are not visibly flowing are present on the streambed
  • standing water: water but no visible flow
  • trickling water: very small flow, but clearly visible flowing water
  • flowing water: a continuous pathway of water that is flowing 

 

Photo of the Nagog Brook stream gage

Green Acton collects temperature data with a small, self-recording temperature sensor called a Tidbit. This device sits submerged in the water, tie-wrapped to the base of the stage gage. It takes a temperature reading every 15 minutes, with an accuracy of plus or minus 0.2 degrees Celsius. The date, time, and temperature are recorded on a memory chip inside the device. Every six months or so, the volunteers retrieve the instrument and download the data. In between downloads, the volunteer checks to make sure the instrument is working properly by watching for a flashing signal light. 

Photo of Tidbit temperature sensor after three years in Nagog Brook

Nagog Brook is Green Acton’s first foray into systematic, quantitative environmental data collection. We are not alone in this regard: projects all over the world, described as “citizen science” or “community science” projects are leveraging the power of volunteers and inexpensive sensors to monitor environmental quality and gather evidence in support of environmental protection.

Data and Observations from Nagog Brook Stream Monitoring

Acknowledgments and Notes

This work would not have been possible without Green Acton’s adult volunteers Carolyn Kiely and Bob Sekuler, and Acton Boxborough Regional High School volunteers Vid Suresh and Song Leav. 

Photo credits: Kim Kastens

* The spelling “gage,” rather than “gauge,” for stream monitoring comes from the U.S. Geological Survey.