Scientific Investigations Report 2007–5291

Characteristics and Classification of Least Altered Streamflows in Massachusetts

U.S. Geological Survey Scientific Investigations Report 2007–5291

By David S. Armstrong, Gene W. Parker, and Todd A. Richards

Prepared in cooperation with the
Massachusetts Department of Conservation and Recreation; the Massachusetts Department of Fish and Game, Riverways Program; and the Division of Fisheries and Wildlife


This report was published in June 2008. The report includes a CD-ROM in a back-cover pocket. On the World Wide Web (WWW) the report is available for viewing and printing as Portable Document Format (PDF) files. The information on the CD-ROM is presented here as hyperlinked Excel (.xls) and Word (.doc) files. Sixty one .xls files in Appendix 5 are accessible by a menu which lists sites sorted numerically in station-number order and alphabetically in station-name order. Each .xls file in Appendix 5 has four tabs: Water Year cfs, Water Year cfsm, Climate Year cfs, and Climate year cfsm. The one .xls file in Appendix 6 has three tabs: lower percentile_rounded, HIT indices_rounded, and upper percentile_rounded.

Front Cover: outside and inside front cover (PDF, 2 pages, 842 KB)
Front Section: title pages, table of contents, conversion table, acronyms (PDF, 8 pages, 102 KB)
Body Section: report body, figures, tables, and references (PDF, 64 pages, 3,880 KB)
Back Section: figures and tables in the back (PDF, 64 pages, 3,880 KB)
Appendix Section REVISED 23-Jul-2008: appendixes 1 through 6 with blued hyperlinks to open .doc, .htm, .pdf, and .xls files (PDF, 21 pages, 235 KB)
Back Cover: inside and outside back cover PDF (2 pages, 312 KB)


Streamflow records from 85 streamflow-gaging stations at which streamflows were considered to be least altered were used to characterize natural streamflows within southern New England. Period-of-record streamflow data were used to determine annual hydrographs of median monthly flows. The shapes and magnitudes of annual hydrographs of median monthly flows, normalized by drainage area, differed among stations in different geographic areas of southern New England. These differences were gradational across southern New England and were attributed to differences in basin and climate characteristics. Period-of-record streamflow data were also used to analyze the statistical properties of daily streamflows at 61 stations across southern New England by using L-moment ratios. An L-moment ratio diagram of L-skewness and L-kurtosis showed a continuous gradation in these properties between stations and indicated differences between base-flow dominated and runoff-dominated rivers.

Streamflow records from a concurrent period (1960–2004) for 61 stations were used in a multivariate statistical analysis to develop a hydrologic classification of rivers in southern New England. Missing records from 46 of these stations were extended by using a Maintenance of Variation Extension technique. The concurrent-period streamflows were used in the Indicators of Hydrologic Alteration and Hydrologic Index Tool programs to determine 224 hydrologic indices for the 61 stations. Principal-components analysis (PCA) was used to reduce the number of hydrologic indices to 20 that provided nonredundant information. The PCA also indicated that the major patterns of variability in the dataset are related to differences in flow variability and low-flow magnitude among the stations.

Hierarchical cluster analysis was used to classify stations into groups with similar hydrologic properties. The cluster analysis classified rivers in southern New England into two broad groups: (1) base-flow dominated rivers, whose statistical properties indicated less flow variability and high magnitudes of low flow, and (2) runoff-dominated rivers, whose statistical properties indicated greater flow variability and lower magnitudes of low flow. A four-cluster classification further classified the runoff-dominated streams into three groups that varied in gradient, elevation, and differences in winter streamflow conditions: high-gradient runoff-dominated rivers, northern runoff-dominated rivers, and southern runoff-dominated rivers. A nine-cluster division indicated that basin size also becomes a distinguishing factor among basins at finer levels of classification. Smaller basins (less than 10 square miles) were classified into different groups than larger basins.

A comparison of station classifications indicated that a classification based on multiple hydrologic indices that represent different aspects of the flow regime did not result in the same classification of stations as a classification based on a single type of statistic such as a monthly median. River basins identified by the cluster analysis as having similar hydrologic properties tended to have similar basin and climate characteristics and to be in close proximity to one another. Stations were not classified in the same cluster on the basis of geographic location alone; as a result, boundaries cannot be drawn between geographic regions with similar streamflow characteristics. Rivers with different basin and climate characteristics were classified in different clusters, even if they were in adjacent basins or upstream and downstream within the same basin.


This database, identified as “USGS Scientific Investigations Report 2007–5291 CD-ROM Appendixes 1, 3, 5, and 6” has been approved for release and publication by the Director of the USGS. Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.

Suggested Citation

Armstrong, D.S., Parker, G.W., and Richards, T.A., 2008, Characteristics and classification of least altered streamflows in Massachusetts: U.S. Geological Survey Scientific Investigations Report 2007–5291, 113 p., plus CD-ROM.

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