U.S. Geological Survey Mill River at Northampton, Massachusetts streamgage (01171500) on October 11, 2022 looking downstream. The low-flow was about 12 cubic feet per second (cfs) for a 56.2-square-mile drainage area.
Regional Regression Equations for Estimating Selected Low-flow Statistics at Ungaged Stream Sites in Massachusetts
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By New England Water Science Center
November 7, 2022
The U.S. Geological Survey, in cooperation with the Massachusetts Department of Recreation and Conservation, Office of Water Resources, completed a study in 2025 to update the regional regression equations for estimating selected low-flow statistics at ungaged sites in Massachusetts.
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Low-flow statistics are crucial for water-resources planning, management and permitting because they inform water-resources decisions. Decision-makers must ensure that there is adequate streamflow to meet various objectives, such as water supply, agriculture, water-quality standards, recreation and aquatic habitat protection.
Regional regression equations for estimating selected low-flow statistics in Massachusetts were last published by Ries and Friesz (2000) based on data through 1995 and were available on the web-based application USGS StreamStats. Additionally, there are no regional regression equations for southeastern and Cape Cod, Massachusetts. Updated low-flow equations would benefit from additional streamflow data and improvements in geographic information system (GIS) data and in streamflow statistical analysis methods.
This low-flow study updated regional regression equations for estimating low-flow statistics in Massachusetts using data through 2022. The low-flow equations were developed for the following statistics:
- 50- to 99-percent flow duration
- monthly 50- and 90-percent flow duration for June to September
- median of the monthly mean for February, June, and August
- 7Q2, 7Q10, 30Q2, and 30Q10
- harmonic mean and median of the annual 7-day low flow
- 50- to 99-percent flow duration for southeastern Massachusetts and Cape Cod
The study began in July 2019 and ended in September 2025 with the publication of a USGS Scientific Investigations Report and three associated USGS data releases. The low-flow equations for estimating these statistics at ungagged sites in Massachusetts are currently (2025) available on the web-based application USGS StreamStats.
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Sources/Usage: Public Domain. View Media Details
Mill River at Northampton, Massachusetts
U.S. Geological Survey Mill River at Northampton, Massachusetts streamgage (01171500) on October 11, 2022 looking downstream. The low-flow was about 12 cubic feet per second (cfs) for a 56.2-square-mile drainage area.
Green River near Colrain, Massachusetts
A downstream view of the Green River near Colrain, Massachusetts close to the USGS streamgage (01170100). The low-flow was about 7.7 cubic feet per second (cfs) for a 41.4-square-mile drainage area.
A downstream view of the Green River near Colrain, Massachusetts close to the USGS streamgage (01170100). The low-flow was about 7.7 cubic feet per second (cfs) for a 41.4-square-mile drainage area.
The U.S. Geological Survey, in cooperation with the Massachusetts Department of Recreation and Conservation, Office of Water Resources, completed a study in 2025 to update the regional regression equations for estimating selected low-flow statistics at ungaged sites in Massachusetts.
Media
Sources/Usage: Public Domain. View Media Details
Low-flow statistics are crucial for water-resources planning, management and permitting because they inform water-resources decisions. Decision-makers must ensure that there is adequate streamflow to meet various objectives, such as water supply, agriculture, water-quality standards, recreation and aquatic habitat protection.
Regional regression equations for estimating selected low-flow statistics in Massachusetts were last published by Ries and Friesz (2000) based on data through 1995 and were available on the web-based application USGS StreamStats. Additionally, there are no regional regression equations for southeastern and Cape Cod, Massachusetts. Updated low-flow equations would benefit from additional streamflow data and improvements in geographic information system (GIS) data and in streamflow statistical analysis methods.
This low-flow study updated regional regression equations for estimating low-flow statistics in Massachusetts using data through 2022. The low-flow equations were developed for the following statistics:
- 50- to 99-percent flow duration
- monthly 50- and 90-percent flow duration for June to September
- median of the monthly mean for February, June, and August
- 7Q2, 7Q10, 30Q2, and 30Q10
- harmonic mean and median of the annual 7-day low flow
- 50- to 99-percent flow duration for southeastern Massachusetts and Cape Cod
The study began in July 2019 and ended in September 2025 with the publication of a USGS Scientific Investigations Report and three associated USGS data releases. The low-flow equations for estimating these statistics at ungagged sites in Massachusetts are currently (2025) available on the web-based application USGS StreamStats.
Media
Sources/Usage: Public Domain. View Media Details
Mill River at Northampton, Massachusetts
U.S. Geological Survey Mill River at Northampton, Massachusetts streamgage (01171500) on October 11, 2022 looking downstream. The low-flow was about 12 cubic feet per second (cfs) for a 56.2-square-mile drainage area.
U.S. Geological Survey Mill River at Northampton, Massachusetts streamgage (01171500) on October 11, 2022 looking downstream. The low-flow was about 12 cubic feet per second (cfs) for a 56.2-square-mile drainage area.
Green River near Colrain, Massachusetts
A downstream view of the Green River near Colrain, Massachusetts close to the USGS streamgage (01170100). The low-flow was about 7.7 cubic feet per second (cfs) for a 41.4-square-mile drainage area.
A downstream view of the Green River near Colrain, Massachusetts close to the USGS streamgage (01170100). The low-flow was about 7.7 cubic feet per second (cfs) for a 41.4-square-mile drainage area.