Low water flow in Nashoba Brook triggers outdoor water use restrictions

September 21, 2024

Effective September 11, the Acton Water District (AWD) has announced more stringent restrictions on water use. The new restrictions were triggered when streamflow in Nashoba Brook dropped below 0.57 cubic feet per second (cfs), an indicator of dry conditions in our region. Each AWD customer is now limited to one day per week for non-essential outdoor water use.

The streamflow of Nashoba Brook is measured by the U.S. Geological Survey in the Nashoba Brook conservation land near Wheeler Lane, using an automated gage that takes a measurement every 15 minutes. The data are made available to the public online in near real time. As shown in the graph below, the water level in the stream has been dropping continuously since August 20, and dipped below the 0.57cfs threshold on September 9.

A graph of the water flow at Nashoba Brook from August 20 to September 19, 2024. The graph shows that the water level has been steadily and precipitously dropping since late august.
The wiggly purple line represents the stream flow of Nashoba Brook. The horizontal grey lines are the median flow for each date based on 60 years of data. The vertical line marks the date, September 9, when the streamflow first dropped down to 0.57 cfs. Graphic: Graph from USGS Water for the Nation.


As of September 17, the flow in Nashoba Brook had slowed to a bare trickle, only 0.17 cfs. Compare this month’s trickle in the video below with the 353 cfs, reported by the Acton Exchange at this same site during the floods of last December.

Nashoba Brook looking upstream towards the pedestrian bridge near Wheeler Lane. Video credit:  Sept. 17, 2024, Kim Kastens.


The “low-flow trigger” of 0.57 cfs is a condition of the AWD’s permit to withdraw water under the Massachusetts Water Management Act, which was renewed with more stringent conditions in December 2023. Water restrictions will have to remain in effect until the Nashoba Brook flow exceeds 0.57 cfs for seven consecutive days.


As detailed on the AWD website, “nonessential outdoor water uses that are subject to mandatory restrictions include lawn irrigation via above ground sprinklers and automated irrigation systems, pool filling, vehicle washing (except in a commercial car wash) and washing of exterior surfaces (i.e. power washing). These activities are restricted to one day per week before 7a.m. and after 7p.m. Hand watering of lawns, gardens, and ornamental plantings is not subject to mandatory restrictions.” The watering schedule is as follows:

  • Tuesday: North Acton – North of Brook Street including Great Road from Brook Street to Littleton line
  • Wednesday: Acton Center/East Acton – North of Route 2 to South of Brook Street (562 Main Street follows this schedule) including Pope Road and Great Road to Concord line
  • Thursday: West Acton – South of Route 2 and West of Main Street (even side of Main Street follows this schedule)
  • Friday: South Acton – South of Route 2 and East of Main Street (odd side of Main Street follows this schedule)


In other AWD news, District Manager Matt Mostoller announced at the AWD Commissioners meeting of September 9 that ground has been broken on the PFAS treatment system at the Central Acton Water Treatment Plant. The system is expected to become operational in 2025. It will be the second of three planned PFAS treatment systems, following the successful completion of the North Acton PFAS system, which has been delivering water with non-detectable levels of PFAS since June of this year.

A sandy construction site. In this image, it looks like a sand pit (with no equipment).
Site work at the Central Acton Water Treatment Plant site, in preparation for installing the PFAS treatment system. Photo: Matt Mostoller


Kim Kastens is a volunteer writer, editor, and board member for the Acton Exchange. She also chairs Green Acton’s Water Committee.

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