Catherine A. Chamberlin Glenn A. Hodgkins 20260114 tabular digital data https://doi.org/10.5066/P13VAWJE Catherine A. Chamberlin Glenn A. Hodgkins 2025 publication The U.S. Geological Survey, in cooperation with the Massachusetts Department of Conservation and Recreation, evaluated potential drivers of low streamflows in Massachusetts by use of statistical models with selected low-flow metrics as the dependent variables. Low-flow metrics were computed in six ways: the 2nd and 10th percentile of daily flows during a climate year, these same percentiles normalized by median flows, and the duration of time during each climate year that flow was below two long-term low-flow thresholds. These low flows were described for 107 catchments across Massachusetts (some included drainage area in surrounding states) for all climate years of available streamflow data between 1943 and 2022 that met study criteria. Explanatory variables describing potential drivers of these low streamflows were also calculated for each catchment and climate year so that regressions models could be fit to the data. This data release contains a single table that includes all the calculated low-flow metrics and explanatory variables. This data release was compiled to enable multiple linear regression analysis of low flows and potential drivers of low streamflows at a consistent spatial and temporal resolution. The data combine many different sources (for example U.S. Census Bureau, U.S. Department of Agriculture) and types (for example timeseries data, spatial raster data) of data at different resolutions (for example daily or single time point for temporal resolution, single station measurements or municipality for spatial resolution) into values that are representative of a single catchment for a single climate year. The data are appropriate to use at the scale presented here (catchments and climate years). 19430401 20230331 publication date Complete None planned -73.6749 -70.0383 42.8540 41.5626 ISO 19115 Topic Category inlandWaters USGS Thesaurus hydrology stream discharge streamflow regression analysis droughts precipitation (atmospheric) USGS Metadata Identifier USGS:67d03a7dd34ecfe34cc875a1 None Massachusetts None. Please see 'Distribution Info' for details. None. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. Catherine Chamberlin U.S. Geological Survey Physical Scientist mailing and physical

10 Bearfoot Rd

Northborough MA 01532 508.490.5050 cchamberlin@usgs.gov This dataset was produced as part of a project funded by the Commonwealth of Massachusetts Department of Conservation and Recreation. No formal testing performed. Data were checked for completeness and duplication. Time series and spatial maps of all variables were checked for abnormalities. Data are only provided for catchments that fall at least 50% within the state boundary of Massachusetts. Catchments for stream gages with insufficient streamflow data for analyses in this project are excluded. Two catchments downstream of the Quabbin reservoir are also excluded, as they are outliers in terms of regulation and reservoir storage. U.S. Geological Survey 2023 application/service Accessed September 30, 2024 https://waterdata.usgs.gov/nwis/ https://dx.doi.org/10.5066/F7P55KJN Digital and/or Hardcopy 1943 2023 ground condition NWIS Source of flow data and catchment descriptions U.S. Geological Survey 2024 application/service Accessed on September 30, 2024 https://streamstats.usgs.gov/ss/ Digital and/or Hardcopy 2024 ground condition StreamStats Used for catchment delineation Bent, G. C. Ahearn, E. A. Fair, J. H. Mazo, C.F. Harrington, L.E. 2025 vector digital data https://doi.org/10.5066/P13AI5EP Digital and/or Hardcopy 2025 ground condition LowFlowMA Catchment delineations for gages 01104415, 01104420, and 01104455. Carlson, C.S. 2025 vector digital data https://doi.org/10.5066/P142FWRJ Digital and/or Hardcopy 2025 observed LowFlowSEMA Catchment delineations for gages 01105870, 01105876, 01105880, 011058837, and 011058835951 Welch, S.M. Spaetzel, A.B. Steeves, P.A. 20240724 raster digital data Reston, VA U.S. Geological Survey data release Accessed July 24, 2024 https://doi.org/10.5066/P1I8ZCL2 https://www.sciencebase.gov/catalog/item/6644cff5d34e1955f5a429aa Digital and/or Hardcopy 2024 ground condition SurficialGeology Source provided surficial sand and gravel for southern New England Soil Survey Staff Natural Resources Conservation Service 2024 tabular digital data Washington, DC United States Department of Agriculture Accessed January 18, 2024 https://websoilsurvey.nrcs.usda.gov/ Digital and/or Hardcopy 2024 ground condition SSURGO Soil Surveys of New Hampshire, Vermont, New York, Massachusetts, Connecticut, and Rhode Island downloaded, and hydrologic soil group designations used Jon Dewitz 20210708 raster digital data Sioux Falls, SD U.S. Geological Survey Accessed September 21, 2023 https://doi.org/10.5066/P9KZCM54 https://www.mrlc.gov/data https://www.mrlc.gov/data-services-page Digital and/or Hardcopy 2001 2019 observed NLCD2019 Land cover data for 2001-2019 Jon Dewitz 20230724 raster digital data Sioux Falls, SD U.S. Geological Survey Accessed September 21, 2023 https://doi.org/10.5066/P9JZ7AO3 https://www.mrlc.gov/data https://www.mrlc.gov/data-services-page Digital and/or Hardcopy 2021 observed NLCD2021 Used for 2021 land cover James Falcone 2015 raster digital data USGS Data Series USGS DS948 Reston, VA U.S. Geological Survey Accessed September 21, 2023 https://www.sciencebase.gov/catalog/item/631405bad34e36012efa3040 https://doi.org/10.5066/P9XJKKC3 https://water.usgs.gov/lookup/getspatial?ds948_NWALT Digital and/or Hardcopy 1974 2012 observed NWALT Used for land cover 1974-2012 Manson, S. Schroeder, J. Van Riper, D. Knowles, K. Kugler, T. Roberts, F. Ruggles, S. 2023 tabular digital data Accessed November 14, 2023 https://doi.org/10.18128/D050.V18.0 https://data2.nhgis.org/main Digital and/or Hardcopy 1790 2024 observed NHGIS Nominal timeseries of population by County U.S. Geological Survey 2024 tabular digital data Accessed internally on January 29, 2024 Digital and/or Hardcopy 2000 2020 observed SWUDS Site specific water withdrawal data for 2015 (or 2017) and 2020. U.S. Geological Survey 2024 tabular digital data Accessed online January 19, 2024 https://waterdata.usgs.gov/nwis/wu https://waterdata.usgs.gov/ct/nwis/wu https://waterdata.usgs.gov/ma/nwis/wu https://waterdata.usgs.gov/nh/nwis/wu https://waterdata.usgs.gov/ny/nwis/wu https://waterdata.usgs.gov/ri/nwis/wu https://waterdata.usgs.gov/vt/nwis/wu Digital and/or Hardcopy 1985 2015 observed AWUDS County-level water use estimates 1985-2015 from Connecticut, Massachusetts, New Hampshire, New York, Rhode Island, and Vermont Kenneth A. MacKichan 1951 publication Circular 115 Washington, D.C. U.S. Geological Survey https://doi.org/10.3133/cir115 https://pubs.usgs.gov/publication/cir115 Digital and/or Hardcopy 1950 observed WU1950 State-level water use estimates for 1950 Kenneth A. MacKichan 1957 publication Circular 398 Washington, D.C. U.S. Geological Survey https://doi.org/10.3133/cir398 https://pubs.usgs.gov/publication/cir398 Digital and/or Hardcopy 1955 observed WU1955 State-level water use estimates for 1955 K. A. MacKichan J. C. Kammerer 1961 publication Circular 456 Washington, D.C. U.S. Geological Survey https://pubs.usgs.gov/publication/cir456 https://doi.org/10.3133/cir456 Digital and/or Hardcopy 1960 observed WU1960 State-level water use estimates for 1960 Charles Richard Murray 1968 publication Circular 556 Washington, D.C. U.S. Geological Survey https://doi.org/10.3133/cir556 https://pubs.usgs.gov/publication/cir556 Digital and/or Hardcopy 1965 observed WU1965 State-level water use estimates for 1965 Charles Richard Murray E. Bodette Reeves 1972 publication Circular 676 Reston, VA U.S. Geological Survey https://pubs.usgs.gov/publication/cir676 https://doi.org/10.3133/cir676 Digital and/or Hardcopy 1970 observed WU1970 State-level water use estimates for 1970 Charles Richard Murray E. Bodette Reeves 1977 publication Circular 765 Reston, VA U.S. Geological Survey https://pubs.usgs.gov/publication/cir765 https://doi.org/10.3133/cir765 Digital and/or Hardcopy 1975 observed WU1975 State-level water use estimates for 1975 Wayne B. Solley Edith B. Chase William B. Mann IV 1983 publication Circular 1001 https://pubs.usgs.gov/publication/cir1001 https://doi.org/10.3133/cir1001 Digital and/or Hardcopy 1980 observed WU1980 State-level water use estimates for 1980 U.S. Army Corps of Engineers 2023 tabular digital data Accessed December 15, 2023 https://nid.sec.usace.army.mil/ https://nid.sec.usace.army.mil/api/nation/csv Digital and/or Hardcopy 2024 observed NID Locations of dams and storage designated by `NID Storage (Acre-Ft)` Massachusetts Office of Dam Safety 2012 vector digital data Boston, MA Massachusetts Department of Conservation and Recreation Geographic Information System (GIS) Program Accessed August 31, 2023 https://www.mass.gov/info-details/massgis-data-dams https://s3.us-east-1.amazonaws.com/download.massgis.digital.mass.gov/shapefiles/state/dams.zip https://maps.massgis.digital.mass.gov/MassMapper/MassMapper.html Digital and/or Hardcopy 2024 observed MassODS Dam locations used to supplement NID Massachusetts Division of Ecological Restoration (MA DER) Department of Fish and Game 2017 tabular digital data https://www.mass.gov/info-details/ders-restoration-potential-model-tool Digital and/or Hardcopy 2024 observed MassRPM Dam locations used to supplement NID Matthew Walsh 2024 tabular digital data Data provided by Viki Zoltay, Massachusetts DCR, written communication, on April 1, 2024 Digital and/or Hardcopy 1985 2023 observed QuabbinTransfers Water transfers from the Quabbin reservoir to the Wachusett reservoir Menne, M.J. Durre, I. Korzeniewski, B. McNeill, S. Thomas, K. Yin, X. Anthony, S. Ray, R. Vose, R.S. Gleason, B.E. Houston, T.G. 2024 3 tabular digital data Asheville, NC NOAA National Climatic Data Center Accessed online September 25, 2024 http://doi.org/10.7289/V5D21VHZ https://www.ncei.noaa.gov/metadata/geoportal/rest/metadata/item/gov.noaa.ncdc:C00861/html Digital and/or Hardcopy 1943 2023 observed GHCNDaily Precipitation and temperature data Low flow metrics (Q2_cfs, Q10_cfs, Q50_cfs, Q2divQ50_ratio, Q10divQ50_ratio, durQ2_days, durQ10_days): Low flow metrics were calculated for each gage annually using the daily flow timeseries representing the climate year (April 1 - March 31). For Q2_cfs, Q10_cfs, and Q50_cfs, the daily values were ranked, and the 2nd, 10th, and 50th (median) percentiles were selected. To calculate the normalized values of Q2divQ50_ratio and Q10divQ50_ratio, the 2nd and 10th percentiles were divided by the median daily flows. The duration low flow metrics, durQ2_days and durQ10_days, relied on long term low-flow thresholds. For each gage with sufficient data records, daily timeseries from April 1, 1993 through March 31, 2023 were ranked, and the 2nd and 10th percentile flows over the 30 years were calculated. These values were used as cutoffs, and the annual metrics durQ2_days and durQ10_days were calculated as the number of days within a climate year with flow less than or equal to these 30-year 2nd and 10th percentile flows for each basin. NWIS 2024 Catchment Delineations and Diversions (catarea_sqkm, catinMA_frac, cat_method, DivNoted_Boolean, lat_centroid_dd, lon_centroid_dd, lat_gage_dd, lon_gage_dd): Catchment delineations were derived from three different sources. Most catchments were delineated using the StreamStats tool (cat_method = StreamStats). However, 8 catchment delineations were obtained from other sources. Four small catchments (< 8 square kilometers) with high development (>60% developed) were obtained from LowFlowMA (cat_method = ManualDelineation), and four catchments in southeastern Massachusetts were obtained from LowFlowSEMA (cat_method = GroundwaterFlowpathModel). Catchment areas, catchment centroids and overlap with Massachusetts were calculated using spatial analysis in R version 4.5.0. Diversions (outgoing and incoming water transfers were not separated) were indicated according to the site descriptions for each gage. Site descriptions were sourced from Annual Surface Water Record USGS publications. The surface water records from 1961, 1965, 1971, 1973, 1976, 1980, 1987, 1988, 2001, 2006, 2007, 2008, 2009, 2010, 2012, 2013 or reports generated on demand were used, depending on when the gage was actively maintained. Key words that indicated diversions were "diversion(s)", "diverted", "withdrawal(s)", "municipal water supply", "effluent release(s)", "waste-water treatment plant". NWIS StreamStats LowFlowMA LowFlowSEMA 2024 Basin physical properties (SandGravel_frac, HSGBC_frac, HSGD_frac): The fraction of each catchment that was Sand and Gravel (SandGravel_frac) and the fraction that was categorized into either hydrologic soil groups B or C (HSGBC_frac), or into hydrologic soil group D (HSGD_frac), were all calculated with spatial analysis in R. SurficialGeology SSURGO 2024 Land use and land cover (openwaterwetland_frac, developed_frac, ag_frac, LULC_method): Land use and land cover were summarized using data from NWALT, NLCD2019, and NLCD2021. Some standardization was necessary between the products. First, the rasters had to be reclassified. In this project, "water and wetlands" were represented by categories 11 and 12 in NWALT, and by categories 11, 90, and 95 in NLCD. Developed land was represented by categories 21-27 in NWALT, and by categories 21-24 in NLCD. Agriculture was represented by categories 43 and 44 in NWALT, and by 81 and 82 in NLCD. After recategorization, the 2012 NWALT product was compared to the 2011 NLCD product. Any pixels that differed were corrected as follows in all rasters: 1) Any pixel classified as agriculture or "water and wetland" in 2011 NLCD but not in 2012 NWALT was converted to agriculture or "water and wetland", respectively for all NWALT rasters. 2) Any pixel classified as developed in 2012 NWALT but not in 2011 NLCD was converted to developed for all NLCD rasters. The only exceptions were if a pixel were classified as developed in 2012 NWALT but as agriculture or "water and wetland" in 2011 NLCD. In these cases, the original pixel classification was used. Spatial analysis in R was used to summarize land use and land cover pixels by catchment, weighting pixels by their percent overlap with the catchment polygons and calculating the fraction of the number of pixels of each class divided by the total number of pixels in the catchment. For years that were not included in NWALT (LULC_method = Computed-NWALT), NLCD2019 (LULC_method = Computed-NLCD2019), or NLCD2021 (LULC_method = Computed-NLCD2021), values for each catchment were filled using linear interpolation (LULC_method = "Interpolated"), or extrapolation from the nearest value (LULC_method = "Extrapolated"). NWALT NLCD2019 NLCD2021 2024 Population (popdensity_peoplesqkm, population_method): Population counts by county were converted to population counts by catchment using spatial analysis in R version 4.5.0 using the sf package. County values were weighted by the amount of spatial overlap with each catchment, and then these values were summed. Population counts were converted to population density using the area of the basin (popdensity_peoplesqkm). Years in between the decennial population counts (population_method = Calculated) were estimated using linear interpolation (population_method = Interpolated). NHGIS 2024 Dams (normalizedstorage_m, damdensity_persqkm): Three data sources were used for dam locations. The NID was the primary dataset, and it was supplemented by additional dams that were listed in the datasets obtained from Mass ODS and Mass RPM. For each catchment, the number of dams were summed and divided by the area of the catchment to determine the dam density (damdensity_persqkm). Calculating total storage required identifying dam complexes, so as not to include duplicate reservoirs in the analysis. Dam complexes were identified and the point locations grouped into one entry using the NID identification numbers, the dam names, the dam owner and operators, and the size of storage listed for each dam. Then, the total storage of all entries within a catchment were summed. For dams from the NID dataset, the NID storage was used. For dams from Mass ODS, dams were assigned a volume of 15 acre feet. Dams from Mass RPM were assigned volumes of 0 acre feet. Dam storage (in m^3) were normalized to catchment area (normalizedstorage_m). NID MassODS MassRPM 2024 Water withdrawals (normalizedwithdrawals_mmpday, WaterWithdrawals_method): Water withdrawal point locations were obtained from the USGS SWUDS database. Locations of public supply, irrigation, and industrial water withdrawals were pulled for 2015 (public supply) and 2017 (irrigation and industrial; assigned to 2015). Point values with withdrawals greater than 1 million gallons per year and with high variability in withdrawal year-to-year were removed as outliers. These point data were then adjusted so that the sums of withdrawals by county and water use type were equal to the summary values reported in the 2015 USGS water use compilation. Historical withdrawals for each of the point locations were estimated using the base values from 2015, and by multiplying them by a historical change coefficients. Historical change coefficients were calculated from the USGS 5-year water use compilation circulars between 1950 and 2015, and represented the percent change in withdrawals by water use type and county between each year and 2015. For each catchment and climate year, water withdrawal estimates from all points within the catchment were summed together. County-level estimates of domestic self-supply water withdrawals from the 5-year compilations were aggregated to catchment by weighted averaging, weighted by the spatial overlap of each catchment and county. Water withdrawals for all types of water use were summed to a total water withdrawal for each catchment. One final adjustment was made to the withdrawal estimates, which was to account for water transfers between the Quabbin and Wachusett reservoir. Transfer volumes for each year were added to withdrawals in catchments that included the Quabbin reservoir and subtracted from withdrawals in catchments that included the Wachusett reservoir. These water withdrawal estimates were then normalized by the catchment area (normalizedwaterwithdrawals_mmpday). For years in between those represented in SWUDS, AWUDS, or the compilations (WaterWithdrawals_method = Calculated), values for each catchment were either linearly interpolated between years (WaterWithdrawals_method = Interpolated) or extrapolated to the nearest data point (WaterWithdrawals_method = Extrapolated). SWUDS AWUDS WU1950 WU1955 WU1960 WU1965 WU1970 WU1975 WU1980 QuabbinTransfers 2024 Meteorology (X6monthperiodendingApr_avg_tavg_C, X2monthperiodendingJun_avg_tavg_C, X2monthperiodendingAug_avg_tavg_C, X2monthperiodendingOct_avg_tavg_C, X6monthperiodendingApr_P_PET_ratio, X2monthperiodendingJun_P_PET_ratio, X2monthperiodendingAug_P_PET_ratio, X2monthperiodendingOct_P_PET_ratio, X6monthperiodendingApr_total_prcp_mm, X2monthperiodendingJun_total_prcp_mm, X2monthperiodendingAug_total_prcp_mm, X2monthperiodendingOct_total_prcp_mm): Daily timeseries of average daily temperature and daily precipitation were aggregated to the basins using weighted averaging. All sites within 60 kilometers of the centroid of each basin were included, and values were weighted proportionally to the distance between the GHCN station and the basin centroid. For each day, potential evapotranspiration was calculated using the Hamon method as a function of latitude, date, and average temperature. For each climate year, daily temperatures were averaged (X[...]_avg_tavg_C), and precipitation (X[...]_total_prcp_mm) and potential evapotranspiration were summed over the following four time periods: November - April (climate year defined according to the climate year April 30; X6monthperiodendingApr_[...]), May-June (X2monthperiodendingJun_[...]), July-August (X2monthperiodendingAug_[...]), and September-October (X2monthperiodendingOct_[...]). Total precipitation and total potential evapotranspiration for each time period were converted to a ratio (X[...]_P_PET_ratio). Hamon method: Hamon, W.R. 1961. "Estimating Potential Evapotranspiration." Journal of Hydraulics Division 87 (3). https://doi.org/10.1061/JYCEAJ.0000599 GHCNDaily 2024 0.0001 0.0001 Decimal degrees North American Datum of 1983 (NAD 83) Geodetic Reference System 1980 6378137.000000 298.257222 FlowMetrics_ExplanatoryVariables.csv Comma separated value (CSV) file containing low-flow metrics and explanatory variables used in Chamberlin and Hodgkins 2025. Producer Defined GageID US Geological Survey monitoring location site identification number U.S. Geological Survey U.S. Geological Survey site identification number U.S. Geological Survey ClimateYear Climate Year defined as April 1 - March 31. Climate years correspond to the calendar year in which they begin. Producer Defined 1943 2022 Year 1 Q2_cfs The 2nd percentile daily flow for a USGS gage during the climate year. 2% of daily flows are equal to or lower than this value. Producer Defined 0.000 735.640 cubic feet per second These data reflect model values. The original flow data were accurate to 2 significant figures. Q10_cfs The 10th percentile daily flow for a USGS gage during the climate year. 10% of daily flows are equal to or lower than this value. Producer Defined 0.000 992.200 cubic feet per second These data reflect model values. The original flow data were accurate to 2 significant figures. Q50_cfs The 50th percentile daily flow for a USGS gage during the climate year. 50% of daily flows are equal to or lower than this value. Producer Defined 0.000 2500.000 cubic feet per second These data reflect model values. The original flow data were accurate to 2 significant figures. Q2divQ50_ratio The 2nd percentile daily flow divided by the median daily flow for a USGS gage during the climate year. Producer Defined NA Median daily flow was equal to 0 cubic feet per second Producer defined 0.000 0.823 Unitless These data reflect model values. The original flow data were accurate to 2 significant figures. Q10divQ50_ratio The 10th percentile daily flow divided by the median daily flow for a USGS gage during the climate year. Producer Defined NA Median daily flow was equal to 0 cubic feet per second Producer defined 0.000 0.873 Unitless These data reflect model values. The original flow data were accurate to 2 significant figures. durQ2_days The number of days with flow below a 30-year 2nd percentile. Producer Defined NA Insufficient data record to calculate a 30-year 2nd percentile. Producer defined 0 162 Days durQ10_days The number of days with flow below a 30-year 10th percentile. Producer Defined NA Insufficient data record to calculate a 30-year 10th percentile. Producer defined 0 221 Days SandGravel_frac Fraction of catchment underlain by sand and gravel. Producer Defined 0.000 1.000 HSGBC_frac Fraction of catchment with hydrologic soil groups B or C. Producer Defined 0.006 0.936 HSGD_frac Fraction of catchment with hydrologic soil group D. Producer Defined 0.000 0.681 openwaterwetland_frac Fraction of catchment with open water or wetland land use/land cover. Producer Defined 0.000 0.429 developed_frac Fraction of catchment with developed land use/land cover. Producer Defined 0.002 0.880 ag_frac Fraction of catchment with agricultural land use/land cover. Producer Defined 0.000 0.151 LULC_method The method used to generate the values of `openwaterwetland_frac`, `developed_frac`, and `ag_frac`. Producer Defined Extrapolated Values taken from 1975 NWALT product for years prior to Climate Year 1974, or values taken from 2021 NLCD product for Climate Year 2022. Producer defined Computed-NWALT Values computed from an NWALT raster representative of that climate year. Producer defined Interpolated Values are a linear interpolation between the closest computed years. Producer defined Computed-NLCD2019 Values computed from an NLCD raster representative of that climate year. NLCD rasters are from the 2019 release. Producer defined Computed-NLCD2021 Values computed from an NLCD raster representative of that climate year. NLCD rasters are from the 2021 release. Producer defined popdensity_peoplesqkm Estimated population density of the catchment. Producer Defined 20.27 892.66 People per square kilometer population_method Method for generating the value in `popdensity_peoplesqkm`. Producer Defined Interpolated Value is a linear interpolation between the nearest calculated values. Producer defined Calculated Value is calculated using decennial U.S. Census data representative of the climate year. Producer defined normalizedwithdrawals_mmpday Estimates of water withdrawals normalized by catchment area. Negative values indicate an estimated net input of water from interbasin transfers. Producer Defined -0.12 2.81 millimeters per day WaterWithdrawals_method Method used to produce the value of `normalizedwithdrawals_mmpday`. Producer Defined Interpolated Value generated from linear interpolation between the nearest calculated values. Producer defined Calculated Value calculated using data from 5-year USGS water use circulars. Producer defined Extrapolated Value taken from 1950 for years prior to 1950 or taken from 2020 for 2021 and 2022. Producer defined DivNoted_Boolean Boolean indicator of whether diversions were mentioned in the NWIS site description Producer Defined 0 No mention of water diversion in the site description. Producer defined 1 Water diversion mentioned in the site description. Producer defined normalizedstorage_m Storage of water held behind dams from the National Inventory of Dams, normalized by the catchment area. Producer Defined 0.00 0.82 meters damdensity_persqkm Number of dams, normalized by catchment area Producer Defined 0.00 0.51 dams per square kilometer of catchment X6monthperiodendingApr_avg_tavg_C Average temperature November 1 through April 30. Climate year corresponds to the climate year of April 30. Producer Defined -3.60 5.70 Degrees Celsius X2monthperiodendingJun_avg_tavg_C Average temperature May 1 through June 30. Producer Defined 13.00 18.82 Degrees Celsius X2monthperiodendingAug_avg_tavg_C Average Temperature July 1 through August 30 Producer Defined 18.18 24.37 Degrees Celsius X2monthperiodendingOct_avg_tavg_C Average temperature September 1 through October 31 Producer Defined 10.08 17.37 Degrees Celsius X6monthperiodendingApr_P_PET_ratio Ratio of total precipitation to total calculated potential evapotranspiration for November 1 through April 30. Climate year corresponds to the climate year on April 30. Producer Defined 2.331 7.859 Unitless X2monthperiodendingJun_P_PET_ratio Ratio of total precipitation to total calculated potential evapotranspiration for May 1 through June 30. Producer Defined 0.263 3.337 Unitless X2monthperiodendingAug_P_PET_ratio Ratio of total precipitation to total calculated potential evapotranspiration for July 1 through August 30. Producer Defined 0.198 2.204 Unitless X2monthperiodendingOct_P_PET_ratio Ratio of total precipitation to total calculated potential evapotranspiration for September 1 through October 31 Producer Defined 0.465 5.083 Unitless X6monthperiodendingApr_total_prcp_mm Total precipitation calculated for November 1 through April 30. Climate year corresponds to the climate year on April 30. Producer Defined 321.8 965.8 millimeters X2monthperiodendingJun_total_prcp_mm Total precipitation calculated for May 1 through June 30. Producer Defined 51.7 653.8 millimeters X2monthperiodendingAug_total_prcp_mm Total precipitation calculated for July 1 through August 30. Producer Defined 52.9 558.0 millimeters X2monthperiodendingOct_total_prcp_mm Total precipitation calculated for September 1 through October 31 Producer Defined 57.3 540.5 millimeters catarea_sqkm Calculated catchment area. Producer Defined 1.08 2570.79 Square kilometers catinMA_frac Fraction of the catchment that falls within Massachusetts. Producer Defined 0.502 1.000 lat_centroid_dd Latitude of the calculated centroid of the catchment according to North American Datum 1983. Producer Defined 41.6438 42.7371 Decimal Degrees lon_centroid_dd Longitude of the calculated centroid of the catchment according to North American Datum 1983. Producer Defined -73.4414 -70.0758 Decimal Degrees lat_gage_dd Latitude of the gage station of the catchment according to North American Datum 1983. U.S. Geological Survey 41.5854 42.7529 Decimal Degrees lon_gage_dd Longitude of the gage station of the catchment according to North American Datum 1983. U.S. Geological Survey -73.4898 -70.1070 Decimal Degrees cat_method Method used to delineate the catchment area. Producer Defined StreamStats Catchment delineated using StreamStats tool. StreamStats ManualDelineation Catchment delineation taken from LowFlowMA and was produced manually. Producer defined GroundwaterFlowpathModel Catchment delineation taken from LowFlowSEMA and was produced using flow path modeling. Producer defined Interannualvariability_Boolean Boolean indicator that this data point is included in the interannual variability analysis in Chamberlin and Hodgkins 2025. Producer Defined 0 Data point is excluded from this analysis. Producer defined 1 Data point is included in this analysis. Producer defined SpatialTemporal_Boolean Boolean indicator that this data point is included in the spatial temporal variability analysis in Chamberlin and Hodgkins 2025. Producer Defined 1 Data point is included in this analysis. Producer defined Trend40_Boolean Boolean indicator that this data point is included in the 40-year trend analysis in Chamberlin and Hodgkins 2025. Producer Defined 0 Data point is excluded from this analysis. Producer defined 1 Data point is included in this analysis. Producer defined Trend80_Boolean Boolean indicator that this data point is included in the 80-year trend analysis in Chamberlin and Hodgkins 2025. Producer Defined 0 Data point is excluded from this analysis. Producer defined 1 Data point is included in this analysis. Producer defined SpatialAnalysis_Boolean Boolean indicator that this data point is included in a spatial analysis of a specific drought year in Chamberlin and Hodgkins 2025. Producer Defined 0 Data point is excluded from this analysis. Producer defined 1 Data point is included in this analysis. Producer defined IncludesDurationMetrics_Boolean Boolean indicator that this data point is included analyses of `durQ2_days` and `durQ10_days` in Chamberlin and Hodgkins 2025. Producer Defined 0. Data point is excluded from this analysis Producer defined 1. Data point is included in this analysis Producer defined This data release contains a single table of all the calculated low-flow metrics and explanatory variables ("FlowMetrics_ExplanatoryVariables.csv"). Chamberlin, C.A., and Hodgkins, G.A., 2025, Low-flow metrics and explanatory variable data for 107 basins in Massachusetts, 1943-2022: U.S. Geological Survey data release, https://doi.org/10.5066/P13VAWJE U.S. Geological Survey - ScienceBase mailing address

Denver Federal Center

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Mail Stop 302

Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Digital Data https://doi.org/10.5066/P13VAWJE None 20260114 Catherine A. Chamberlin U.S. Geological Survey Physical Scientist mailing and physical

10 Bearfoot Rd

Northborough MA 01532 United States 508-490-5050 cchamberlin@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998