Low-Flow Statistic Equations and Supplementary Data for Massachusetts

The U.S. Geological Survey (USGS), in cooperation with the Massachusetts Department of Conservation and Recreation, Office of Water Resources, developed regional regression equations for estimating selected low-flow statistics in Massachusetts. This data release contains the datasets used in the regression analyses for the regional low-flow equations for the mainland area of Massachusetts, which excludes the Plymouth-Carver-Kingston-Duxbury aquifer system area of southeastern Massachusetts and Cape Cod. Selected at-site streamflow statistics are provided for the 99-, 98-, 95-, 90-, 85-, 80-, 75-, 70-, 60-, 50-, 40-, 30-, 25-, 20-, 15-, 10-, 5-, 2-, and 1-percent flow durations; monthly 90- and 50-percent flow durations; monthly median of the monthly means; harmonic mean; median of the annual 7-day low-flow; and 7-day, 2-year (7Q2), 7-day, 10-year (7Q10), 30-day, 2-year (30Q2), and 30-day, 10-year low-flow frequencies for 174 USGS streamgages in and near Massachusetts. These streamflow statistics were computed using daily mean streamflow data through water year 2022 for non-frequency statistics and through climate year 2021 for the low-flow frequency statistics. Basin characteristics (hydrography, elevation, physical, land use, soil, surficial geology, and climate) are also provided for 174 streamgages. A geographic information system (GIS) coverage of the streamflow variability index (SVI) was developed as a basin characteristic for southern New England and eastern New York and used in the regional regression analyses. GIS coverages are provided for the regression equation explanatory variables: SVI, SSURGO hydrologic soils type A and B, and Parameter-elevation Regressions on Independent Slopes Model (PRISM) mean annual temperature 1981-2010. The Weighted-Multiple-Linear Regression (WREG) input and output files used to develop the final regional regression equations for Massachusetts are also provided.