Abstract 1

Methods for Estimating Low-Flow 

Statistics for Massachusetts Streams

By Kernell G. Ries, III, and Paul J. Friesz

Abstract

Methods and computer software are 

described in this report for determining flowduration, low-flow frequency statistics, and August 

median flows. These low-flow statistics can be 

estimated for unregulated streams in Massachusetts using different methods depending on 

whether the location of interest is at a streamgaging station, a low-flow partial-record station, or 

an ungaged site where no data are available. Lowflow statistics for streamgaging stations can be 

estimated using standard U.S. Geological Survey 

methods described in the report.

The MOVE.1 mathematical method and a 

graphical correlation method can be used to 

estimate low-flow statistics for low-flow partialrecord stations. The MOVE.1 method is recommended when the relation between measured 

flows at a partial-record station and daily mean 

flows at a nearby, hydrologically similar streamgaging station is linear, and the graphical method 

is recommended when the relation is curved. 

Equations are presented for computing the 

variance and equivalent years of record for estimates of low-flow statistics for low-flow partialrecord stations when either a single or multiple 

index stations are used to determine the estimates.

The drainage-area ratio method or regression equations can be used to estimate low-flow 

statistics for ungaged sites where no data are 

available. The drainage-area ratio method is 

generally as accurate as or more accurate than 

regression estimates when the drainage-area ratio 

for an ungaged site is between 0.3 and 1.5 times 

the drainage area of the index data-collection site. 

Regression equations were developed to estimate 

the natural, long-term 99-, 98-, 95-, 90-, 85-, 80-, 

75-, 70-, 60-, and 50-percent duration flows; the 

7-day, 2-year and the 7-day, 10-year low flows; 

and the August median flow for ungaged sites in 

Massachusetts. Streamflow statistics and basin 

characteristics for 87 to 133 streamgaging 

stations and low-flow partial-record stations 

were used to develop the equations. The streamgaging stations had from 2 to 81 years of record, 

with a mean record length of 37 years. The 

low-flow partial-record stations had from 8 to 

36 streamflow measurements, with a median of 

14 measurements. 

All basin characteristics were determined 

from digital map data. The basin characteristics 

that were statistically significant in most of the 

final regression equations were drainage area, the 

area of stratified-drift deposits per unit of stream 

length plus 0.1, mean basin slope, and an indicator 

variable that was 0 in the eastern region and 1 in 

the western region of Massachusetts. 

The equations were developed by use of 

weighted-least-squares regression analyses, with 

weights assigned proportional to the years of 

record and inversely proportional to the variances 

of the streamflow statistics for the stations. 

Standard errors of prediction ranged from 70.7 to 

17.5 percent for the equations to predict the 7-day, 

10-year low flow and 50-percent duration flow, 

respectively. The equations are not applicable for 

use in the Southeast Coastal region of the State, or 

where basin characteristics for the selected 

ungaged site are outside the ranges of those for the 

stations used in the regression analyses.
2 Methods for Estimating Low-Flow Statistics for Massachusetts Streams

A World Wide Web application was developed that provides streamflow statistics for datacollection stations from a data base and for 

ungaged sites by measuring the necessary basin 

characteristics for the site and solving the regression equations. Output provided by the Web application for ungaged sites includes a map of the 

drainage-basin boundary determined for the site, 

the measured basin characteristics, the estimated 

streamflow statistics, and 90-percent prediction 

intervals for the estimates.

An equation is provided for combining 

regression and correlation estimates to obtain 

improved estimates of the streamflow statistics 

for low-flow partial-record stations. An equation 

is also provided for combining regression and 

drainage-area ratio estimates to obtain improved 

estimates of the streamflow statistics for ungaged 

sites.

INTRODUCTION

Low-flow statistics indicate the probable 

availability of water in streams during times when 

conflicts between water supply and demand are most 

likely to arise. Because of this, low-flow statistics are 

needed by Federal, State, regional, and local agencies 

for water-use planning, management, and regulatory 

activities. These activities include (1) developing 

environmentally sound river-basin management plans, 

(2) siting and permitting new water withdrawals, 

interbasin transfers, and effluent discharges, 

(3) determining minimum streamflow thresholds for 

maintenance of aquatic biota, and (4) land-use 

planning and regulation. Low-flow statistics are also 

needed by commercial, industrial, and hydroelectric 

facilities to determine availability of water for water 

supply, waste discharge, and power generation.

Low-flow statistics can be calculated from 

streamflow data collected at locations where the U.S. 

Geological Survey (USGS) operates data-collection 

stations, but it is not possible to operate stations at 

every site where the statistics are needed. Because of 

this, methods are needed for estimating low-flow 

statistics for streams for which no data are available.

In 1988, the USGS began the first of three 

studies to develop and evaluate methods for estimating 

low-flow statistics for ungaged Massachusetts streams 

and to provide estimates of the statistics for selected 

locations on ungaged streams. These studies were done 

in cooperation with the Massachusetts Department of 

Environmental Management, Office of Water 

Resources (MOWR) and are referred to as the Basin 

Yield studies. The MOWR uses the streamflow statistics to develop water-resources management plans for 

each of the 27 major river basins in Massachusetts 

(fig. 1) and provides the streamflow statistics to other 

State and local agencies to support their decisionmaking processes.

Five other reports have been published as a result 

of the Basin Yield studies (Ries, 1994a, 1994b, 1997, 

1999, 2000). The first three reports describe studies 

done to develop regression equations for use in 

estimating low-flow statistics for ungaged sites. The 

fourth report describes and provides data for a network 

of 148 low-flow partial-record (LFPR) stations that was 

established in 1988 at the beginning of the first Basin 

Yield study and continued through 1996, during the 

third Basin Yield study. The fifth report describes a 

World Wide Web application that enables users to 

select sites of interest on streams and then to obtain 

estimates of streamflow statistics and basin characteristics for the sites.

Purpose and Scope

This report, the final report of the Basin Yield 

study series, presents methods that can be used to 

estimate low-flow statistics for streams in Massachusetts, and describes the analyses done to develop and 

evaluate the methods. Methods are presented for estimating statistics for locations where various amounts 

of streamflow data are available and for locations 

where no data are available. Previously documented 

and generally accepted methods are presented for 

estimating low-flow statistics for locations where 

streamflow data are available. Analyses done to 

develop and evaluate methods for estimating streamflow statistics for locations where no data are available 

are described. The physical setting of Massachusetts, 

as it relates to the occurrence of low streamflows, is 

also briefly described.

Equations that can be used to estimate the 99-, 

98-, 95-, 90-, 85-, 80-, 75-, 70-, 60-, and 50-percent 

duration flows; the 7-day, 2-year and the 7-day, 10-year 

low flows; and the August median flow are presented 

here. An evaluation of the accuracy of the equations 

and limitations for their use is also provided, along 
Introduction 3

with an example application. The equations provide 

estimates of low-flow statistics for streams with 

natural flow conditions, and supersede those from 

earlier reports.

Previous Studies

Low-flow statistics for most streamgaging 

stations and many LFPR stations in Massachusetts 

were published by the USGS in a series of gazetteers 

published as Water-Resources Investigations Reports, 

in a series of Hydrologic Atlas reports (see U.S. 

Geological Survey, 1987, for a complete listing of both 

series), and in a series of ground-water assessment 

reports published as Water-Resources Investigations 

Reports (Olimpio and DeLima, 1984; Lapham, 1988; 

Myette and Simcox, 1992; DeLima, 1991; Hanson and 

Lapham, 1992; Persky, 1993; Bratton and Parker, 1995; 

Bent, 1995; Friesz, 1996; Klinger, 1996). Statistics 

provided in this report supersede those from the 

previous reports.

Studies that used regression analysis to 

regionalize low-flow frequency statistics in the 

northeastern United States include those for 

Connecticut (Cervione, 1982), central New England 

(Wandle and Randall, 1994), Pennsylvania and New 

York (Ku and others, 1975), Maine (Parker, 1977), 

Massachusetts, New Hampshire, Rhode Island and 

Vermont (Johnson, 1970), southeastern Massachusetts 

(Tasker, 1972), and Massachusetts (Male and Ogawa, 

1982; Vogel and Kroll, 1990; Risley, 1994). Studies 

that regionalized flow-duration statistics include those 

for Connecticut (Thomas, 1966), New Hampshire 

(Dingman, 1978), southeastern Massachusetts (Tasker, 

1972), and Massachusetts (Male and Ogawa, 1982; 

Fennessey and Vogel, 1990; Ries, 1994a, 1994b).

Reports for the first two Basin Yield studies 

(Ries, 1994a, 1994b) provided equations for estimating 

the 99-, 98-, and 95-percent duration streamflows and 

also provided estimates of the streamflow statistics and 

measured basin characteristics for selected ungaged 

streams in eastern Massachusetts river basins. The 

equations were developed for these studies by use of 

regression analyses, which statistically relate the 

streamflow statistics to measured basin characteristics 

for the stations used in the analyses. The studies 

differed in the methods of regression analysis used to 

develop the equations, the number of stations included 

in the analyses (more stations were used in the second 

study), and the locations of ungaged streams for which 

estimated streamflow statistics and basin characteristics were provided. The equations provided in the 

second report superseded those from the first report.

The third Basin Yield report (Ries, 1997) provides an equation for estimating August median 

streamflows. This statistic is used by the U.S. Fish and 

Wildlife Service (1981) and some State agencies as the 

minimum summertime streamflow required for maintenance of habitat for aquatic biota in New England. The 

report also provides estimates of August median 

streamflows for sites on unregulated streams in Massachusetts where the values could be determined from 

available data, and describes how the August median 

streamflow per square mile of drainage area varies 

throughout the State. 

The LFPR network described in the fourth Basin 

Yield report (Ries, 1999a) was established to provide 

additional data for use in the regression analyses and to 

provide a better understanding of the physical 

mechanisms that cause streamflow to vary in time and 

space. The report provides streamflow measurements 

collected systematically at the 148 LFPR stations in the 

network between 1989 and 1996, and also includes any 

historical streamflow measurements available for the 

stations. In addition, the report provides estimated 

streamflow statistics, basin characteristics, location and 

other descriptive information for each of the stations. 

The estimated streamflow statistics include the 99-, 

98-, 97-, 95-, 93-, 90-, 85-, 80-, 75-, 70-, 65-, 60-, 55-, 

and 50-percent duration flows; the 7-day, 2-year and 

the 7-day, 10-year low flows; and the August median 

flow. Basin characteristics measured include drainage 

area; total stream length; mean basin slope; area of 

surficial stratified drift; area of wetlands; area of water 

bodies; and mean, maximum, and minimum basin 

elevation. The basin characteristics were measured for 

the stations from digital maps by use of a Geographic 

Information System (GIS).

The fifth Basin Yield report (Ries and others, 

2000), a fact sheet, describes a World Wide Web 

application that includes (1) a mapping tool that allows 

users to specify locations on streams where low-flow 

statistics are needed, (2) a database that includes 

streamflow statistics, basin characteristics, location, 

and descriptive information for all data-collection 

stations in Massachusetts for which streamflow 

statistics were published previously, and (3) an 

automated GIS procedure that determines the required 

basin characteristics and solves the regression 

equations provided in this report to estimate low-flow 

statistics for the user-selected site. The World Wide 

Web application is further described later in this report.
4 Methods for Estimating Low-Flow Statistics for Massachusetts Streams

CONNECTICUT

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Western Region

Figure 1. Locations of streamgaging stations and low-flow partial-record stations used to develop equations for 

estimating low-flow statistics for ungaged Massachusetts streams and locations of streamgaging stations outside 

Massachusetts used for correlation with low-flow partial-record stations, and boundaries of the 27 major river 

basins and three hydrologic regions in the State.
Introduction 5

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Figure 1. Locations of streamgaging stations and low-flow partial-record stations used to develop equations for 

estimating low-flow statistics for ungaged Massachusetts streams, locations of streamgaging stations outside 

Massachusetts used for correlation with low-flow partial-record stations, and boundaries of the 27 major river 

basins and three hydrologic regions in the State—Continued.
6 Methods for Estimating Low-Flow Statistics for Massachusetts Streams

Physical Setting

Massachusetts encompasses an area of 8,093 mi2 

in the northeastern United States. State environmental 

agencies divide Massachusetts into 27 major river 

basins for planning and regulatory purposes (fig. 1). 

Some of these designated river basins are actually part 

of larger river basins that extend into neighboring 

states. The Millers, Deerfield, Chicopee, and Westfield 

River Basins are part of the Connecticut River Basin. 

The Nashua, Concord, and Shawsheen River Basins are 

part of the Merrimack River Basin. Several designated 

basins in coastal areas of Massachusetts were 

comprised by grouping land areas drained by multiple 

streams that discharge to the same receiving body of 

salt water, such as Boston Harbor and Buzzards Bay.

The climate of Massachusetts is humid. 

Precipitation is distributed fairly evenly throughout the 

State and throughout the year, and averages about 

45 in. annually. Average annual temperatures range 

from 50 ̊F in coastal areas to 45 ̊F in the western 

mountains. Average monthly temperatures range from 

about 30 ̊F in February to about 71 ̊F in July in coastal 

areas, and from about 20 ̊F in January to about 68 ̊F in 

July in the western parts of the State (U.S. Commerce 

Department, National Oceanic and Atmospheric 

Administration, 1989). Average evapotranspiration 

ranges from 19 in. in southeastern Massachusetts to 

22 in. in the western Mountains (Randall, 1996).

Several physical characteristics vary from east to 

west in Massachusetts. Elevations range from sea level 

along the coast in eastern Massachusetts to almost 

3,500 ft in the western mountains. Basin relief and 

mean basin slope, which are highly related, also tend to 

increase from east to west in Massachusetts. The extent 

of lakes, ponds, and wetlands, as a proportion of total 

basin area, generally decreases from east to west in 

Massachusetts. The extent of coarse-grained stratified 

drift, as a proportion of total basin area, also generally 

decreases from east to west.

Except during and for a short time after storms, 

summertime flow in Massachusetts streams comes 

from ground water discharged by aquifers in 

unconsolidated deposits adjacent to the streams. This 

discharge is termed base flow. High-yielding aquifers 

usually are in stratified drift, sand and gravel deposits 

that are located primarily along the valley floors of 

inland river basins and in coastal areas of southeastern 

Massachusetts. The stratified-drift deposits usually are 

surrounded by upland areas underlain by till with 

exposed bedrock outcrops. Till is an unsorted glacial 

deposit that consists of material ranging in size from 

clay to large boulders. Till yields little water to adjacent 

streams in comparison to yields from coarse-grained 

stratified drift. As a result, during summertime, streams 

in till areas tend to have less flow per unit of drainage 

area than streams in areas of coarse-grain stratified 

drift, and some small streams in till areas may go dry 

(Wandle and Randall, 1994).

Ries (1997) defined three hydrologic regions in 

Massachusetts based on differences in August median 

streamflow per square mile of drainage area (fig. 1). 

These regions were the Western, the Eastern, and the 

Southeast Coastal regions. The Western region was 

defined by all major basins that drain to the 

Connecticut River plus those west of the Connecticut 

River Basin (basins 1 through 8 on fig. 1). The Eastern 

region was defined as all basins east of the Western 

region except Cape Cod, the Islands, the southern part 

of the South Coastal Basin, and the eastern part of the 

Buzzards Bay Basin, which define the Southeast 

Coastal region. August median flows per square mile 

were significantly higher, on average, in the Western 

region than in the Eastern region. 

Differences in August median streamflow per 

unit area between the Western and Eastern regions 

appeared to be more a function of climate and 

physiography than surficial geology. Percentages of 

stratified-drift deposits were generally lower in the 

Western region than in the Eastern region, but August 

median streamflows were higher in the Western region 

than in the Eastern region. The higher low flows per 

unit area in the Western region than in the Eastern 

region is likely explained by the combination of lower 

mean annual temperatures, higher mean elevations, 

higher relief, higher precipitation, lower evapotranspiration, and lower areal percentages of wetlands 

and water bodies in western Massachusetts than in 

eastern Massachusetts.

The Southeast Coastal region is underlain 

entirely by stratified-drift deposits, which are mostly 

coarse grained. Surface-water drainage boundaries in 

this region often do not coincide with contributing 

areas of ground water for streams in the area. In 

addition, dam regulations, diversions, or controls by 

cranberry bogs affect most streams in the region. As a 

result, insufficient data were available to define the 

natural flow characteristics of streams in this region.
Estimating Methods for Data-Collection Stations 7

Acknowledgments

The authors would like to thank the MOWR 

for its long-term support of this work. Thanks also 

to Aleda Freeman, Christian Jacqz, and the rest of 

the staff of MassGIS, to John Rader, formerly of 

MassGIS and USGS, and to Peter Steeves of USGS. 

These people worked together to prepare numerous 

digital data layers needed for measuring the basin 

characteristics used in the regression analyses, and to 

develop methods for automating measurements of the 

basin characteristics. The authors would also like to 

express their appreciation to the many other USGS 

employees who assisted with collection and analysis 

of streamflow data, measurements of basin 

characteristics, and preparation of this report. 

ESTIMATING METHODS FOR 

DATA-COLLECTION STATIONS

The USGS operates three types of datacollection stations for which low-flow statistics can 

be estimated. These include (1) streamgaging stations, 

(2) low-flow partial record (or LFPR) stations, and 

(3) miscellaneous-measurement stations. Methods 

used to estimate streamflow statistics at datacollection stations differ depending on the type of 

statistic and on the type of station. Continuous records 

of streamflow are obtained at streamgaging stations. 

Streamflow statistics generally are determined directly 

from the records for these stations using methods 

described in the section “Low-flow statistics for 

streamgaging stations.”

Low-flow partial-record and miscellaneousmeasurement stations are often established where 

streamflow information is needed, but either (1) it is 

not physically or economically feasible to continuously 

monitor streamflows at the location, or (2) the amount 

or accuracy of the streamflow information needed does 

not require continuous monitoring at the location. At 

LFPR stations, a series of streamflow measurements 

are made during independent low-flow periods when 

all or nearly all streamflow is from ground-water 

discharge. Usually about 10 low-flow measurements 

are obtained systematically over a period of years. Ries 

(1999) summarized a network of LFPR stations 

operated in Massachusetts during 1989 through 1996 

as part of the three Basin Yield projects. Data for many 

of the network stations are used in the analyses 

described here.

Miscellaneous-measurement stations usually are 

established to obtain streamflow data for hydrologic 

studies of limited regional extent and short duration. 

The number and streamflow range of measurements 

made at these stations varies depending on the 

objectives of the study. High-flow as well as low-flow 

measurements commonly are made at miscellaneousmeasurement stations. Low-flow statistics can be 

estimated for miscellaneous-measurement stations 

when the number and range of low-flow measurements 

collected at the stations approximates the requirements 

for measurements at a LFPR station.

Many stations in Massachusetts have been 

operated at different times as both LFPR stations and 

miscellaneous-measurement stations. Methods used in 

this study to estimate low-flow statistics for LFPR 

stations and miscellaneous-measurement stations were 

the same and are described in the section “Low-flow 

statistics for low-flow partial-record stations.” Because 

the data and analysis methods were the same, both 

station types are referred to as LFPR stations for the 

remainder of this report.

Low-Flow Statistics for 

Streamgaging Stations

Daily mean flows for all complete climatic 

years of record are used to determine flow-duration 

and low-flow frequency statistics for streamgaging 

stations. A climatic year begins on April 1 of the year 

noted and ends on March 31 of the following year. 

Daily mean flows for all complete Augusts for the 

period of record are used to determine August median 

flows. Daily mean flows for USGS streamgaging 

stations in Massachusetts can be obtained by 

downloading them from the World Wide Web address: 

http://waterdata.usgs.gov/nwis-w/MA/, or by 

contacting the Massachusetts–Rhode Island District 

information officer at the address provided on the 

back of the title page of this report.

The USGS has established standard methods 

for estimating flow-duration (Searcy, 1959) and 

low-flow frequency statistics (Riggs, 1972) for 

streamgaging stations. The computer software 

programs IOWDM, ANNIE, and SWSTAT can be used 
8 Methods for Estimating Low-Flow Statistics for Massachusetts Streams

to format input data, manage and display data, and 

complete the statistical analyses, respectively, required 

to determine flow-duration and low-flow frequency 

statistics for streamgaging stations (Lumb and others, 

1990; Flynn and others, 1995). These programs can be 

downloaded from the World Wide Web address: 

http://water.usgs.gov/software/surface_water.html. 

Flow-Duration Statistics

A flow-duration curve is a graphical 

representation of the percentage of time streamflows 

for a given time step (usually daily) are equaled or 

exceeded over a specified period (usually the 

complete period of record) at a stream site. Flowduration curves usually are constructed by first ranking 

all of the daily mean discharges for the period of record 

at a gaging station from largest to smallest, next 

computing the probability for each value of being 

equaled or exceeded, then plotting the discharges 

against their associated exceedance probabilities 

(Loaiciga, 1989, p. 82). The daily mean discharges 

are not fit to an assumed distribution. Flow-duration 

analysis can be done by use of the USGS software 

described above or by use of most commercially 

available statistical software.

Flow-duration statistics are points along a flowduration curve. For example, the 99-percent duration 

streamflow is equaled or exceeded 99 percent of the 

time, whereas the 50-percent duration streamflow is 

equaled or exceeded 50 percent of the time. Strictly 

interpreted, flow-duration statistics reflect only the 

period for which they are calculated; however, when 

the period of record used to compute the statistics is 

sufficiently long, the statistics often are used as an 

indicator of probable future conditions (Searcy, 1959).

Vogel and Fennessey (1994) presented an 

alternative method for determining flow-duration 

statistics that indicate future conditions. This method 

requires determining flow-duration statistics for each 

individual year of record at a gaging station, then using 

the median of the annual values to represent the longterm flow-duration statistics. Median annual flowduration statistics determined by use of this alternative 

method tend to be higher than those calculated from the 

entire period of record by use of the traditional 

approach. The advantages of using the alternative 

method over the traditional approach are that 

confidence intervals can easily be attached to the 

statistics and probabilities of recurrence (recurrence 

intervals) of individual annual values can be analyzed. 

A disadvantage of the approach is that generally at 

least 10 years of record are needed to determine the 

statistics with reasonable confidence.

Low-Flow Frequency Statistics

Low-flow frequency statistics are determined for 

streamgaging stations from series of annual minimum 

mean flows for a given number of days. The statistics 

can be computed for any combination of days of 

minimum mean flow and years of recurrence. For 

example, the 7-day, 10-year low flow is determined 

from the annual series of minimum 7-day mean flows 

at a station. The mean flow for each consecutive 7-day 

period is computed from the daily records, and the 

lowest mean value for each year represents that year in 

the annual series. The 7-day minimum mean flows are 

usually fit to a log-Pearson Type III distribution to 

determine the recurrence interval for an individual 

7-day minimum mean flow (Riggs, 1972), although 

other researchers sometimes have used other 

distributions (Vogel and Kroll, 1989). The value that 

recurs, on average, once in 10 years is the 7-day, 

10-year low flow. The 7-day, 10-year low flow is used 

by the U.S. Environmental Protection Agency and by 

many state and local agencies to regulate waste-water 

discharges into surface waters. 

The USGS has, to a large extent, automated the 

process of determining low-flow frequency statistics 

for streamgaging stations. The computer program 

SWSTAT (Lumb and others, 1990, p. 141) determines 

the annual series of minimum mean flows, ranks them, 

fits them to a log-Pearson type III distribution, and 

plots the resulting line of fit through the annual values. 

How well the data fit the distribution, and the ultimate 

low-flow frequency values to be used, are left to the 

judgment of the individual hydrologist. Usually at least 

10 years of record are needed to determine the statistics 

with reasonable confidence. The annual series should 

be checked for trends, and corrected if necessary, 

before the log-Pearson analysis is done. The output 

from the analysis should be checked for outliers, and 

corrected if necessary, before the frequency curve is 

finalized.
Estimating Methods for Data-Collection Stations 9

August Median Flows

August median flows at streamgaging stations 

can be determined by two methods. The U.S. Fish and 

Wildlife Service (USFWS) (1981) recommends 

calculating August median streamflows as the median 

value of the annual series of August monthly mean 

streamflows for the period of record at a gaging station. 

The USFWS uses the August median flow calculated in 

this manner as the minimum streamflow required for 

summertime maintenance of habitat for biota in New 

England streams.

Charles Ritzi and Associates (1987) suggested 

calculating August median flows as the median of the 

daily mean flows for all complete Augusts during the 

period of record at a streamgaging station. Kulik 

(1990) and Ries (1997) also used this method for 

calculating August median flows. This method 

typically results in values of August median flows that 

are somewhat lower than those determined by use of 

the method suggested by the USFWS. The monthly 

mean values used by the USFWS to calculate August 

median flows tend to be skewed by infrequent storm 

events that cause the monthly means to be larger than 

the medians, thus “the median is a more useful statistic 

than the mean for describing the central tendency” of 

the daily data (Kulik, 1990).

Streamflow Statistics for 

Streamgaging Stations with Short Records

Streamflow statistics are often needed for 

streamgaging stations with short records that may not 

reflect long-term conditions, and thus may not be 

useful as indicators of future conditions. Streamflow 

record extension or augmentation can be used to adjust 

the records for these stations to reflect a longer period. 

This is usually done by developing a relation between 

the daily mean streamflows or the streamflow statistics 

at the short-term station and the daily mean 

streamflows or the streamflow statistics for the same 

period at a nearby and hydrologically similar gaging 

station with a long record.

Vogel and Kroll (1991) demonstrated the value 

of augmenting streamflow records to obtain improved 

estimates of low- and peak-flow frequency statistics 

for streamgaging stations. They also described methods 

that can be used for augmenting records to estimate 

these statistics. Searcy (1959, p.12–14) and Ries 

(1994a, p. 21–22) described methods that can be used 

to extend the records for short-term streamgaging 

stations to estimate flow-duration statistics that reflect 

long-term conditions for the stations. These methods 

are similar to those described below for estimating 

low-flow statistics for LFPR stations.

Low-Flow Statistics for 

Low-Flow Partial-Record Stations

Streamflow statistics for LFPR stations are 

estimated by relating the low streamflow measurements 

made at the stations to daily mean discharges on the 

same days at nearby, hydrologically similar 

streamgaging stations. Lines or curves of correlation 

are developed between the same-day discharges at 

the LFPR stations and the selected streamgaging 

stations, and then the streamflow statistics for the 

gaging stations are entered into the relations to 

determine the corresponding streamflow statistics for 

the LFPR stations. A mathematical correlation method 

described by Hirsch (1982) is used when the relations 

are linear. A graphical correlation method described 

by Riggs (1972) and Searcy (1959) is used when 

the relations are nonlinear. These methods were 

recommended for use by the USGS Office of Surface 

Water in Technical Memorandum No. 86.02, LowFlow Frequency Estimation at Partial-Record Sites, 

issued December 16, 1985. Both methods assume that 

the relation between the discharges at the LFPR station 

and the streamgaging station remains constant with 

time, thus the relation between the same-day flows can 

be used to estimate streamflow statistics that represent 

long-term conditions.

Medium- to high-range streamflow measurements made at some LFPR stations can be useful for 

estimating flow statistics near the median flow. 

Commonly, however, measurements made in these 

ranges need to be excluded from the analyses because 

the measurements were made at times when flow was 

rapidly changing, thus the measurements correlate 

poorly with same-day mean flows at gaging stations.

Mathematical Method

A mathematical record-extension method known 

as the Maintenance Of Variance Extension, Type 1 

(MOVE.1) method (Hirsch, 1982) can be used to 

estimate streamflow statistics for LFPR stations when 

the relation between the logarithms of the same-day 
10 Methods for Estimating Low-Flow Statistics for Massachusetts Streams

GREEN RIVER NEAR WILLIAMSTOWN, MASS. DISCHARGE, IN CUBIC FEET PER SECOND

0.1

1

1 10

10

100

SAME-DAY DISCHARGES

MOVE.1 RELATION 

CORRELATION COEFFICIENT = 0.974

HEMLOCK BROOK AT WILLIAMSTOWN, MASS.

DISCHARGE, IN CUBIC FEET PER SECOND

discharges at the LFPR station and a nearby gaging 

station is linear. The method is applied by first 

calculating logarithms-base 10 of the same-day flows 

for the LFPR and gaging stations and graphing the 

values to ascertain the linearity of the relation. The 

correlation coefficient is also computed as an indicator 

of linearity. If the relation appears linear, the MOVE.1 

method is used; if not, a graphical method is used, as 

explained below.

When the graph of the data appears linear, the 

means (Y and X) and standard deviations (sy and sx) of 

the logarithms-base 10 of the same-day flows for the 

LFPR and gaging stations and the logarithms-base 10 

of the streamflow statistics (Xi) for the gaging station 

are calculated. Estimates of the streamflow statistics 

( ) for the LFPR station are obtained by inserting the 

calculated values into the MOVE.1 equation:

, (1)

and then retransforming the estimates by 

exponentiating the values ( ) to convert the 

estimates into their original units of measurement.

The MOVE.1 relation between an LFPR station, 

Hemlock Brook near Williamstown, Mass., and a 

streamgaging station, Green River at Williamstown, 

Mass., is shown as an example in figure 2. The line 

through the data points was determined by inserting the 

same-day flows for the gaging station into the MOVE.1 

equation as the Xi values to obtain estimated same-day 

flows for the LFPR station, then connecting the points 

to illustrate how the MOVE.1 estimates fit the original 

data.

Yˆ i

Yi

ˆ Y

sy

sx

= + ----( ) Xi – X

10Yˆ i

Figure 2. Example MOVE.1 relation between a low-flow partial-record station, Hemlock Brook near 

Williamstown, Mass., and a streamgaging station, Green River at Williamstown, Mass.
Estimating Methods for Data-Collection Stations 11

100

100

10

10

1

1

0.1

0.10

GREEN RIVER NEAR WILLIAMSTOWN, MASS. DISCHARGE, IN CUBIC FEET PER SECOND

SAME-DAY DISCHARGES

GRAPHICAL RELATION 

HOPPING BROOK NEAR WEST MEDWAY, MASS.

DISCHARGE, IN CUBIC FEET PER SECOND

Graphical Method

The graphical method (Searcy, 1959; Riggs, 

1972) is used when curvature is apparent in the plot of 

logarithms-base 10 of the same-day flows. The method 

is applied by first plotting the original (non-log) values 

of the same-day flows on log-log paper and drawing a 

smooth curve through the plotted points that appears to 

best fit the data. Next, the calculated streamflow 

statistics for the gaging station are entered into the 

curve of relation and corresponding values for the 

LFPR station are read from the graph. Log-log plots 

sometimes have extreme curvature in the very low 

end of the relation. Because of this, it is sometimes 

necessary to replot the data on arithmetic paper to 

adequately define the relation in this range and to avoid 

long downward extrapolations that would otherwise be 

necessary with log-log plots.

The graphical relation between an LFPR station, 

Hopping Brook near West Medway, Mass., and a 

streamgaging station, West River near Uxbridge, 

Mass., is shown as an example in figure 3. The curve 

was fit through the data visually to minimize overall 

differences between the observed and fit values.

Combining Estimates Determined

from Multiple Index Sites

Selection of individual gaging stations for 

relation to a LFPR station is based on distance between 

the stations and similarity of basin characteristics 

between the stations. In Massachusetts, the measured 

streamflows at a LFPR station usually will correlate 

well with more than one gaging station. When this 

happens, MOVE.1 or graphical relations between a 

given LFPR station and each of several gaging stations 

can be developed to estimate the streamflow statistics 

for the LFPR station. This process results in multiple 

estimates of the streamflow statistics for a single LFPR 

station, when only a single best estimate is desired.

Tasker (1975) stated that when independent 

multiple estimates of streamflow statistics are available 

for a single station, the best estimate can be obtained 

by weighting each individual estimate by its variance 

and averaging the weighted estimates. This final 

weighted estimate is best because its variance is less 

than or equal to the variances of each of the 

individual estimates.

Figure 3. Example graphical relation between a low-flow partial-record station, Hopping Brook near West 

Medway, Mass., and a streamgaging station, West River near Uxbridge, Mass.
12 Methods for Estimating Low-Flow Statistics for Massachusetts Streams

Calculated variances for each individual 

estimate of the streamflow statistics for each LFPR 

station were needed to obtain the final best estimates 

for the stations. Variances were calculated by use of 

the equation

, (2)

where:

VS,U is the sample variance of the streamflow

statistic at the LFPR station, in log units;

VS,G is the sample variance of the streamflow

statistic at the gaging station, in log units;

VR is the variance about the MOVE.1 or graphical

line of relation;

M is the number of base-flow measurements;

SES,G is the standard error of the streamflow statistic

at the gaging station, which equals the square

root of VS,G;

b is computed as r(sB,U/sB,G), where r is the

correlation coefficient between the low

streamflow measurements made at the LFPR

station and the same-day mean discharges at

the gaging station (the value of r can be set to

1 when MOVE.1 is used to obtain the

estimate), and sB,U is the standard deviation

of the logarithms-base 10 of the low

streamflow measurements made at the LFPR

station;

sB,G is the standard deviation of the logarithms-base

10 of the mean discharges at the gaging

station on the same days the low-flow

measurements were made at the ungaged

site; and

z is the number of standard deviation units

between the mean of the logarithms-base 10

of the same-day mean discharges at the

gaging station and the logarithm-base 10 of

the streamflow statistic at the gaging station.

Equation 2 is modified from an equation 

developed by Hardison and Moss (1972) to determine 

the variance of estimates of 7-day, T-year low flows 

obtained from an ordinary-least-squares (OLS) 

regression of the logarithms-base 10 of base-flow 

measurements at a LFPR station to the logarithms-base 

10 of same-day mean discharges at a nearby, 

hydrologically similar gaging station. Modifications 

to the Hardison and Moss equation were needed to 

generalize its use for other streamflow statistics and to 

allow for the MOVE.1 or graphical methods of line 

fitting to be used rather than the ordinary-least-squares 

method of line fitting. Assumptions for use of equation 

2 are generalized from Hardison and Moss (1972):

1. The true relation between the logarithms of the 

base-flow measurements at the LFPR station 

and the same-day mean streamflows at the 

gaging station is the same as the true relation 

between the logarithms of the data from which 

the low streamflow statistics are calculated. In 

the case of the 7-day low-flow statistics, the 

data are calculated from an annual series of 

minimum 7-day mean flows. In the case of the 

flow-duration and August median statistics, the 

data are calculated from the daily mean flows.

2. The relation between the logarithms of the data 

from which the low-flow statistics are 

calculated is the same as the relation between 

the flow statistics for the stations.

3. The time-sampling errors in the streamflow 

statistics that are used to enter the regression 

equation are independent of the variation in the 

base-flow measurements used to define the 

equation.

4. The logarithms of the measured streamflows at 

the LFPR station and the same-day mean 

streamflows at the gaging station follow a 

bivariate normal distribution.

5. The M measurements made at the LFPR station 

are statistically independent estimates of the 

base-flow relation.

Hardison and Moss noted that the first four 

assumptions appeared to be reasonable under the 

conditions in which application of the original equation 

2 was intended. These assumptions are reasonable for 

the modified equation 2 as well. Hardison and Moss 

also noted that assumption 5 could be satisfied by 

applying criteria for using only those measurements 

that can be reasonably assumed independent to define 

the relation. The criterion usually applied is that the 

base-flow measurements used in the relation should be 

separated by significant storm events (Stedinger and 

Thomas, 1985). Collection of low streamflow 

measurements at LFPR stations in Massachusetts has 

generally followed that criterion.

VS, U

VR

M

------ 1 1

M – 3 ------------- z

2

M

M – 3 ------------- SES G,

sB G,

--------------     2 M

M – 3 -------------     = +++

b

2

+ VS G,
Estimating Methods for Data-Collection Stations 13

When estimates are obtained for LFPR stations 

from relations with more than one streamflow-gaging 

station, the individual estimates, , (where i = 1, 

..., n, and n is the number of individual estimates of 

statistic S for LFPR station U) can be weighted by the 

reciprocals of their variances, determined from 

equation 2, to obtain minimum-variance estimates, 

, for each of the statistics from the equation

. (3)

Weighted variances, , can be determined for the 

weighted estimates from the equation

. (4)

Standard errors, , in percent, for the weighted 

estimates can be obtained from the equation (Stedinger 

and Thomas, 1985, p. 18)

. (5)

Equation 2 does not account for errors inherent in the 

discharge measurements made at the LFPR station or 

in the mean daily discharges determined for the gaging 

stations. In addition, the estimates obtained for an 

LFPR station by use of the MOVE.1 or graphical 

method with multiple gaging stations are not truly 

independent because of cross correlation of the 

streamflow records at the gaging stations. As a result, 

the final estimates obtained using equations 2 and 3 

may not truly be the best possible, and the true 

variances and standard errors are somewhat larger than 

those obtained using equations 4 and 5.

The equivalent years of record also can be 

computed for estimates of streamflow statistics for the 

LFPR stations. The equivalent years of record is the 

length of time that a streamgaging station would need 

to be operated at the location of the LFPR station to 

obtain an estimate of the streamflow statistic with equal 

accuracy. The equivalent years of record for LFPR 

stations is computed from an equation developed by 

combining equations 7, 8, and 9 in Hardison and Moss 

(1972) and solving for the number of years of record. 

The resulting equation is:

, (6)

where all variables are as previously defined, and:

NU is the equivalent years of record at the partialrecord station;

NG is the years of record at the streamflow-gaging

station used in the relation;

IS,G is the standard deviation of the logarithms-base

10 of the observed flows (annual series for

frequency statistics or daily flows for

duration statistics) at the streamflow-gaging

station

k is from equation 9 of Hardison and Moss

(1972),

; and (7)

K is from equation 3 of Hardison and Moss

(1972),

; (8)

RS is a correction factor that depends on the

streamflow statistic being estimated, and is

determined by combining the equation that

appears in table 1 of Hardison and Moss

(1972),

, (9)

with the equation

(10)

from Hardison (1969, p. D212) to obtain

. (11)

Subscripts have been changed from their original 

appearance in equations 6 to 11 to generalize from 

T-year statistics to other streamflow statistics. In 

equations 10 and 11 above, kS is the number of 

QS Ui ,

QS Uw ,

QS Uw ,

QS U, iVS U, i ( ) ⁄

i = 1

n

∑

1 VS Ui , ( ) ⁄

i = 1

n

∑ = -----------------------------------------

VS Uw ,

VS Uw , 1 1 VS Ui , ( ) ⁄

i = 1

n

= ⁄ ∑

SES Uw ,

SES Uw , 100 5.3018Vw = exp 1 ( ) –

NU RS

2

IS G,

2 k2 sB U,

sB G,

----------     2

    =

VR

M

------ 1 z

2

+

K-------------     b

2

RS

2

IS G,

2

NG

+ ---------------------      

⁄

k r2 M – 4

M – 2 -------------     1 r

2 = + ( ) –

K 1 z

2 = ( ) +

1 1

M – 3 ------------- z

2

M

M – 3 ------------- S G, SE

B

s ,G

--------------

      2

M

M – 3 -------------     ⁄ +++

RS SES G, ( ) N IS G, = ⁄

SES G, IS G,

1 kS

2

+ ⁄ 2

N = ---------------------

RS

2 1 kS2 = + ⁄ 2
14 Methods for Estimating Low-Flow Statistics for Massachusetts Streams

standard deviation units between the streamflow 

statistic and the mean of the data from which it is 

calculated. From assumption 4 above, the annual series 

of 7-day low flows and the daily mean streamflows 

from which the flow-duration statistics and the August 

median streamflows are calculated are distributed lognormally, and thus kS can be obtained from a table of 

standard normal deviates as appears in most statistical 

textbooks. Values for the 99-, 98-, 95-, 90-, 85-, 80-, 

75-, 70-, 60-, and 50-percent duration streamflows, the 

August median streamflow, and the 7-day, 10- and 

2-year streamflows are 2.3263, 2.0537, 1.6449, 1.2816, 

1.0364, 0.8416, 0.6745, 0.5244, 0.2533, 0.0, 0.0, 

1.2816, and 0.0, respectively (Iman and Conover, 1983, 

p. 434–435). When estimates for LFPR stations are 

obtained from relations with more than one 

streamgaging station, the individual calculations of 

equivalent years of record can be weighted by the 

reciprocals of the variances of the estimated streamflow 

statistics, determined from equation 2, then the 

individual weighted equivalent years of record can be 

averaged to obtain the final weighted equivalent years 

of record for the LFPR station by substituting the 

equivalent years of record estimates for the discharge 

estimates in equation 3 above.

ESTIMATING METHODS FOR 

UNGAGED STREAM SITES

Estimates of streamflow statistics often are 

needed for sites on streams where no data are available. 

The two methods used most commonly to estimate 

statistics for ungaged sites are the drainage-area ratio 

method and regression equations. The drainage-area 

ratio method is most appropriate for use when the 

ungaged site is near a streamgaging station on the same 

stream (nested). Regression equations can be used to 

obtain estimates for most ungaged sites. Additional 

details on application of these methods is provided 

below.

Drainage-Area Ratio Method

The drainage-area ratio method assumes that the 

streamflow at an ungaged site is the same per unit area 

as that at a nearby, hydrologically similar streamgaging 

station used as an index. Drainage areas for the 

ungaged site and the index station are determined from 

topographic maps. Streamflow statistics are computed 

for the index station, then the statistics (numerical 

values) are divided by the drainage area to determine 

streamflows per unit area at the index station. These 

values are multiplied by the drainage area at the 

ungaged site to obtain estimated statistics for the site. 

This method is most commonly applied when the index 

gaging station is on the same stream as the ungaged site 

because the accuracy of the method depends on the 

proximity of the two, on similarities in drainage area 

and on other physical and climatic characteristics of 

their drainage basins. 

Several researchers have provided guidelines as 

to how large the difference in drainage areas can be 

before use of regression equations is preferred over use 

of the drainage-area ratio method. Guidelines have 

been provided for estimating peak-flow statistics, and 

usually the recommendation has been that the drainage 

area for the ungaged site should be within 0.5 and 1.5 

times the drainage area of the index station (Choquette, 

1988, p. 41; Koltun and Roberts, 1990, p. 6; Lumia, 

1991, p. 34; Bisese, 1995, p. 13). One report (Koltun 

and Schwartz, 1986, p.32) recommended a range of 

0.85 to 1.15 times the drainage area of the index station 

for estimating low flows at ungaged sites in Ohio. None 

of these researchers provided any scientific basis for 

use of these guidelines. R.E. Thompson, Jr. (U.S. 

Geological Survey, written commun., 1999), however, 

recently completed a study that provides evidence 

supporting use of ratios between 0.33 and 3.0 for 

streams in Pennsylvania.

Because of uncertainty in an appropriate range 

for use of the drainage-area ratio method for streams in 

Massachusetts, an experiment was designed to 

determine the ratio range in which the method is likely 

to provide better estimates of low streamflow statistics 

than use of regression equations. Five river basins with 

one or more continuous gaging stations in each basin 

were chosen for the experiment to represent the varied 

topography, geology, and precipitation of 

Massachusetts. Two basins, the Green and the West 

Branch Westfield, are in the mountainous western part 

of the State; two basins, the Quaboag and the 

Squannacook, are in the foothills of the central part of 

the State; and one basin, the Wading, is in the flat, 

low-lying landscape typical of eastern Massachusetts.

A total of 25 LFPR stations were established 

upstream and downstream from 8 streamgaging 

stations in the 5 basins. Most of the LFPR stations have 
Estimating Methods for Ungaged Stream Sites 15

smaller drainage areas than those for the streamgaging 

stations because historically most streamgaging 

stations in Massachusetts have been established near 

the downstream ends of rivers. Locations and drainage 

boundaries for the streamgaging stations and LFPR 

stations are shown for each basin in figures 4A to 4E. 

Station descriptions for the stations are in table 1.

Seven to ten discharge measurements were made 

at each of the LFPR stations during 1994 and 1995. 

The measurements were published in the Mass. annual 

data reports for those years (Gadoury and others, 1995; 

Socolow and others, 1996, 1997). The measurements, 

along with historical measurements available at three 

stations, were used to estimate streamflows at the 99-, 

98-, and 95-percent durations and August median flows 

for the stations using the methods described above for 

LFPR stations. Estimates of the flow-duration statistics 

were also derived for the stations using the drainagearea ratio method and the regression equations 

developed by Ries (1994b, 1997). The regression 

equations presented later in this report were not used 

because they were not yet available at the time of the 

analysis.

Two gaging stations were available in some 

basins for the analysis (table 1). To increase the sample 

size for the analysis of the drainage-area ratio method, 

drainage-area ratio estimates and regression-equation 

estimates were determined for the streamgaging 

stations in addition to the estimates determined from 

the records for the stations. The drainage-area ratio 

estimates were determined for each streamgaging 

station by applying the flow per unit area for one 

streamgaging station to the drainage area for the other 

streamgaging station. The longest common period of 

record available for the streamgaging stations in each 

basin was used to compute the streamflow statistics for 

the analysis to avoid differences in the statistics due to 

differences in record length.

The Wading River Basin, unlike the other four 

basins used in the experiment, has water withdrawals 

and regulated streamflows in parts of the basin (see 

table 1, remarks). It was chosen for use in the 

experiment because the unregulated part of the basin is 

the largest unregulated area in southeastern 

Massachusetts. Discharges, drainage areas, and other 

basin characteristics used to solve the regression 

equations were adjusted for stations downstream from 

the diversions and regulation to correct for these 

activities. Of the seven stations (including one active 

and one discontinued streamgaging station) at which 

streamflow measurements were made in the Wading 

River Basin, only three of the stations (01108490, 

01108600, and 01108700) were used to compare 

results of the different estimation methods. Discharges 

and basin characteristics from stations 01108440 and 

01108470 were subtracted from station 01108490, and 

station 01108500 was subtracted from 01108700 to 

determine discharges and basin characteristics 

representative of the naturally flowing areas above 

those stations. The adjusted discharges and basin 

characteristics were used to estimate unregulated 

streamflow statistics for the stations. Station 01108600 

was not affected by regulation or diversions.

The drainage area for the Wading River below 

the West Mansfield streamgaging station (station 

01108500) and above the Norton streamgaging station 

(station 01109000) is not affected by regulation or 

diversions, whereas the drainage area above the West 

Mansfield station is affected by regulation and 

diversions. Streamflow statistics for the West Mansfield 

station were subtracted from those for the Norton 

station to obtain the streamflow statistics for the 

naturally flowing part of the drainage area above the 

Norton station.

The four streamflow statistics (99-, 98-, and 

95-percent duration and August median streamflows) 

estimated by the three different methods (correlation, 

drainage-area ratio, and regression equation) for each 

of the LFPR and streamgaging stations used in the 

analysis are presented in table 7 (back of the report). 

The estimates derived by correlation, shown in the 

column labeled “Correlation method estimate or 

computed,” were considered the best estimates 

available for the LFPR stations for the analysis, 

and they were compared to the estimates derived by 

the other methods. The correlation estimates were 

considered the best estimates because they were 

derived from actual streamflow data for the stations, 

whereas the drainage-area ratio and regression 

estimates were derived indirectly based on an 

assumed or statistical relation between the basin 

characteristics for the LFPR stations and streamgaging stations. Statistics shown for streamgaging 

stations in the column labeled “Correlation method 

estimate or computed” were computed from dailyflow records.
16 Streamflow Statistics and Basin Characteristics for Low-Flow Stations in Massachusetts

STREAMFLOW GAGING

STATION AND NUMBER

LOW-FLOW PARTIALRECORD STATION

AND NUMBER

EXPLANATION

BASIN BOUNDARY

01096000

01095930

01096000

01096035

01095928 01095930

01095990

01095977

A. SQUANNACOOK 

RIVER BASIN

42o45'

42o

35'

71o

50' 71o40'

0 2.5 5 MILES

0 2.5 5 KILOMETERS

0 50 MILES

0 50 KILOMETERS

73o

00'

42o

30'

42o

00'

41o

30'

72o

00'

71o

00'

70o

00'

Figure 4. Locations and drainage boundaries of low-flow partial-record stations and gaging stations in the (A) Squannacook, 

(B) Wading, (C) Quaboag, (D) Green, and (E) West Branch Westfield River Basins, Massachusetts.
Estimating Methods for Ungaged Stream Sites 17

0 50 MILES

0 50 KILOMETERS

73o

00'

42o

30'

42o

00'

41o

30'

72o

00'

71o

00'

70o

00'

71o20'

42o

05'

41o

55'

71o

10'

SHADED AREAS ARE AFFECTED 

BY REGULATION, DIVERSIONS, OR BOTH

B. WADING 

RIVER BASIN

01108440

01108470

01108490

01108500

01108600

01108700

01109000

0 1.0 2 MILES

0 1.0 2 KILOMETERS

EXPLANATION

BASIN BOUNDARY

STREAMFLOW GAGING

STATION AND NUMBER

LOW-FLOW PARTIALRECORD STATION

AND NUMBER

01109000

01108600

Figure 4. Locations and drainage boundaries of low-flow partial-record stations and gaging stations in the (A) Squannacook, 

(B) Wading, (C) Quaboag, (D) Green, and (E) West Branch Westfield River Basins, Massachusetts—Continued.
18 Streamflow Statistics and Basin Characteristics for Low-Flow Stations in Massachusetts

73o

00'

42o

30'

42o

00'

41o

30'

72o

00'

71o

00'

70o

00'

0 50 MILES

0 50 KILOMETERS

C. QUABOAG

RIVER BASIN

72o20'

5 10 MILES

5

0

0 10 KILOMETERS 42o

00

42o20'

72o20' 72o00'

STREAMFLOW GAGING

STATION AND NUMBER

LOW-FLOW PARTIALRECORD STATION

AND NUMBER

EXPLANATION

BASIN BOUNDARY

01175905

01176000

01175660

01175670

01175695

01175905

01176000

01176350

01176435

Figure 4. Locations and drainage boundaries of low-flow partial-record stations and gaging stations in the (A) Squannacook, 

(B) Wading, (C) Quaboag, (D) Green, and (E) West Branch Westfield River Basins, Massachusetts—Continued.
Estimating Methods for Ungaged Stream Sites 19

STREAMFLOW GAGING

STATION AND NUMBER

LOW-FLOW PARTIALRECORD STATION

AND NUMBER

EXPLANATION

BASIN BOUNDARY

01170100

01170030

0 1.0 2 MILES

0 1.0 2 KILOMETERS

01170020

01170025 01170030

01170055

01170100

01170121

01170141

VERMONT

MASSACHUSETTS

D. GREEN 

RIVER BASIN

72o50'

42o50'

42o40'

72o

40'

0 50 MILES

0 50 KILOMETERS

73o

00'

42o

30'

42o

00'

41o

30'

72o

00'

71o

00'

70o

00'

Figure 4. Locations and drainage boundaries of low-flow partial-record stations and gaging stations in the 

(A) Squannacook, (B) Wading, (C) Quaboag, (D) Green, and (E) West Branch Westfield River Basins, Massachusetts—

Continued. 
20 Streamflow Statistics and Basin Characteristics for Low-Flow Stations in Massachusetts

STREAMFLOW GAGING

STATION AND NUMBER

LOW-FLOW PARTIALRECORD STATION

AND NUMBER

EXPLANATION

BASIN BOUNDARY

01180660

01180800

01180660

01180750

01180780

01180800

01180821

01181000

73o10' 72o

55'

42o

25'

42o

15'

E. WESTFIELD 

RIVER BASIN

0 2.5 5 MILES

0 2.5 5 KILOMETERS

0 50 MILES

0 50 KILOMETERS

73o

00'

42o

30'

42o

00'

41o

30'

72o

00'

71o

00'

70o

00'

Figure 4. Locations and drainage boundaries of low-flow partial-record stations and gaging stations in the (A) Squannacook, 

(B) Wading, (C) Quaboag, (D) Green, and (E) West Branch Westfield River Basins, Massachusetts—Continued. 
Estimating Methods for Ungaged Stream Sites 21

Table 1. Descriptions of low-flow partial-record and streamgaging stations used to analyze the applicability of the drainage-area ratio method for estimating 

streamflow statistics for ungaged Massachusetts streams—Continued

USGS

station

No.

Latitude

° ′ ′′

Longitude

° ′ ′′ Station name Period of record Drain- age

area

Total 

stream 

length

Stratified

drift

area

Mean 

basin 

elevation

Minimum 

basin 

elevation

Region Remarks

Squannacook River Basin (subbasin of Nashua River Basin)

01095928 42 40 24 71 46 39 Trapfall Brook near Ashby -- 5.89 14.6 0.66 858 480 001095930 42 40 27 71 46 14 Willard Brook near West Townsend -- 12.34 31.8 2.12 878 442 001095977 42 40 41 71 43 29 Squannacook River near West 

Townsend

-- 44.3 87.3 8.19 725 295 0

01095990 42 39 08 71 40 22 Squannacook River at Townsend 

Harbor

-- 57.6 119 13.8 649 262 0

01096000 42 38 03 71 39 30 Squannacook River near West Groton 1950–

present

64.4 130 17.1 618 247 0 Occasional regulation by mill 

upstream.

01096035 42 36 07 71 37 43 Squannacook River below State 

Route 225 at West Groton

-- 69.9 139 19.6 595 224 0 Occasional regulation by mill 

upstream.

Wading River Basin (subbasin of Taunton River Basin)

01108440 42 02 18 71 16 32 Wading River at West Street, near 

South Foxboro

-- 4.83 12.4 1.96 270 180 0 Regulation by lakes and ponds. 

Diversions from basin for municipal supplies.

01108470 42 01 39 71 17 57 Hawthorne Brook at Shepardville -- 5.32 8.49 2.48 268 192 0 Regulation by lakes and ponds. 

Diversions from basin for municipal supplies.

01108490 42 01 07 71 16 02 Wading River at West Street, near 

Mansfield

-- 18.7 40.3 10.3 251 148 0 Natural flows for this station 

obtained by subtracting flows from 01108440 and 01108470.

01108500 42 00 00 71 15 38 Wading River at West Mansfield 1954–86 19.6 42.6 11.2 247 146 0 Regulation by lakes and ponds. 

Diversions to and from basin for municipal supplies.

01108600 41 59 11 71 14 27 Hodges Brook at West Mansfield -- 3.83 8.37 2.49 175 128 0

01108700 41 57 06 71 13 27 Wading River at Chartley -- 29.2 62.9 16.8 214 95 0 Natural flows for this station 

obtained by subtracting flow from 01108500.

01109000 41 56 51 71 10 38 Wading River near Norton 1926–

present

43.4 85.4 25.7 180 68 0 Natural flows for this station 

obtained by subtracting flow from 01108500.

Table 1. Descriptions of low-flow partial-record and streamgaging stations used to analyze the applicability of the drainage-area ratio method for estimating 

streamflow statistics for ungaged Massachusetts streams

[USGS station No.: Station numbers for streamgaging stations are in bold; all others are low-flow partial-record stations. Station name: All stations are in Massachusetts except as otherwise indicated. 

Areas are in square miles; lengths are in miles; elevations are in feet. Period of record: The word “present” refers to the year of publication for this report (2000). Region: 0 is eastern; 1 is western. No., 

number; USGS, U.S. Geological Survey; -- , no continuous data]
22 Methods for Estimating Low-Flow Statistics for Massachusetts Streams Green River Basin (subbasin of Deerfield River Basin) 01170020 42 48 51 72 44 53 Green River at Harrisville, Vt. -- 5.18 9.60 0.30 1,790 1,450 1 01170025 42 47 43 72 39 52 Green River at West Guilford, Vt. -- 16.9 34.4 0.66 1,610 899 1 01170030 42 47 54 72 39 33 Hinesburg Brook at West Guilford, Vt. -- 5.79 10.8 0.11 1,520 899 1 01170055 42 44 27 72 40 27 Green River above Roaring Brook near Green River, Vt. -- 31.8 61.6 1.23 1,470 597 1 01170100 42 42 12 72 40 16 Green River near Colrain 1968– present 41.3 83.8 1.48 1,360 499 1 01170121 42 40 43 72 39 10 Green River 0.4 miles below Stafford Brook near Colrain -- 47.8 99.3 1.80 1,290 397 1 01170141 42 39 12 72 37 32 Green River below Workman Brook near Greenfield -- 51.9 110 2.11 1,240 298 1 Quaboag River Basin (subbasin of Chicopee River Basin) 01175660 42 17 30 72 00 04 Sevenmile River at State Route 31, near Spencer -- 6.07 11.5 0.53 904 686 1

01175670 42 15 54 72 00 19 Sevenmile River near Spencer 1961–

present

8.69 16.7 1.11 871 636 1

01175695 42 13 26 72 02 42 Sevenmile River at Podunk Street at 

East Brookfield

-- 40.6 80.8 4.55 891 607 1

01175905 42 12 45 72 12 14 Quaboag River near Warren -- 138 298 29.9 815 594 1 Flood-retarding reservoirs 

upstream.

01176000 42 10 56 72 15 51 Quaboag River at West Brimfield 1913–

present

149 319 31.7 809 397 1 Flood-retarding reservoirs 

upstream.

01176350 42 08 37 72 18 50 Quaboag River near Palmer -- 180 374 41.4 796 393 1 Flood-retarding reservoirs 

upstream.

01176435 42 10 43 72 21 53 Quaboag River at Three Rivers -- 212 415 50.5 777 341 1 Flood-retarding reservoirs 

upstream.

Table 1. Descriptions of low-flow partial-record and streamgaging stations used to analyze the applicability of the drainage-area ratio method for estimating 

streamflow statistics for ungaged Massachusetts streams

—Continued

USGS

station

No.

Latitude

° ′ ′′

Longitude

° ′ ′′ Station name Period of record Drain- age

area

Total 

stream 

length

Stratified

drift

area

Mean 

basin 

elevation

Minimum 

basin 

elevation

Region Remarks
Estimating Methods for Ungaged Stream Sites 23

West Branch Westfield River Basin (subbasin of Westfield River Basin)

01180660 42 20 00 73 05 02 West Branch Westfield River at 

Becket

-- 12.8 21.9 0.27 1,670 1,230 1

01180750 42 16 47 72 58 52 West Branch Westfield River at 

Chester

-- 53.8 83.0 1.19 1,530 597 1

01180780 42 16 26 73 04 09 Hamilton Brook at Becket Center -- 1.15 1.47 .0 1,730 1,570 101180800 42 15 49 73 02 48 Walker Brook near Becket Center 1963–76 2.95 6.99 .12 1,560 1,300 1

01180821 42 16 40 72 58 49 Walker Brook at State Route 20 at 

Chester

-- 72.5 117 2.58 1,510 596 1

01181000 42 14 14 72 53 46 West Branch Westfield River at 

Huntington

1936–

present

94.0 161 3.91 1,420 397 1

Table 1. Descriptions of low-flow partial-record and streamgaging stations used to analyze the applicability of the drainage-area ratio method for estimating 

streamflow statistics for ungaged Massachusetts streams—Continued

USGS

station

No.

Latitude

° ′ ′′

Longitude

° ′ ′′ Station name Period of record Drain- age

area

Total 

stream 

length

Stratified

drift

area

Mean 

basin 

elevation

Minimum 

basin 

elevation

Region Remarks
24 Methods for Estimating Low-Flow Statistics for Massachusetts Streams

0.01 0.02 0.05 0.1 0.2 0.5 1 2 5 10 20 50 100

4

0

1

2

3

LOWESS CURVE THROUGH DRAINAGE-AREA RATIO ESTIMATES

LOWESS CURVE THROUGH REGRESSION ESTIMATES

DRAINAGE-AREA RATIO ESTIMATES

REGRESSION ESTIMATES

POINT OMITTED FROM PLOT AT RATIO = 0.0915,

REGRESSION DIFFERENCE = 6.41, DRAINAGEAREA RATIO DIFFERENCE = 11.05

RATIO OF LOW-FLOW PARTIAL-RECORD STATION DRAINAGE 

AREA TO GAGING STATION DRAINAGE AREA

ABSOLUTE PERCENT DIFFERENCE, DIVIDED BY 100

Absolute percent differences between the 

drainage-area ratio estimates and regression estimates, 

and the data-based estimates (correlation estimates for 

LFPR stations and calculated statistics for gaging 

stations) were determined for each of the streamflow 

statistics for each station. These absolute percent 

differences for the four statistics were averaged for 

each station to obtain the average percent difference for 

the estimation method at the station (table 7). The 

average absolute percent differences from the databased estimates for the drainage-area ratio method and 

the regression equations are plotted against the 

drainage-area ratio for the station (the drainage area for 

the LFPR station divided by the drainage area for the 

index gaging station) in figure 5. Smoothed curves are 

plotted through each set of data to indicate the range of 

ratios in which the drainage-area ratio method provides 

generally better results than the regression equations. 

The smoothed curves were obtained by use of a 

LOWESS (LOcally-WEighted Scatter plot Smoother) 

algorithm (Minitab, Inc., 1998b, pp. 15–20 to 15–25, 

Cleveland, 1979).

The LOWESS curves indicate that differences 

between the data-based estimates and the drainage-area 

ratio method estimates are generally smaller than the 

differences between data-based estimates and the 

regression equation estimates when the ratio of the 

drainage area for the LFPR station is within about 0.3 

and 1.5 times the drainage area of the index gaging 

station. This range of drainage area ratios was used to 

separate the data into four groups based on estimation 

method and whether the drainage-area ratio for the 

location was within the noted range. The groups were 

(1) drainage-area ratio estimates for stations with 

drainage-area ratios less than 0.3 and greater than 1.5, 

(2) drainage-area ratio estimates for stations with 

drainage-area ratios between 0.3 and 1.5, (3) regression 

estimates for stations with drainage-area ratios less 

than 0.3 and greater than 1.5, and (4) regression 

estimates for stations with drainage-area ratios between 

0.3 and 1.5. Medians and standard deviations of the 

absolute percent differences are presented for each 

group in table 2, along with the medians and standard 

deviations for all of the estimates, for all drainage-area 

ratio estimates, and for all regression-equation 

estimates.

Figure 5. Relation of drainage-area ratio to average absolute percent difference in streamflow 

statistics between data-based estimates and estimates derived from the drainage-area ratio method 

(solid curve), and from the regression equations (dashed curve).
Estimating Methods for Ungaged Stream Sites 25

Table 2 shows that the median absolute percent 

difference for the drainage-area ratio method is about 8 

percent lower than that for the regression equations 

when all the data are considered; however, the standard 

deviation for the drainage-area ratio method is much 

larger than that for the regression equations. When 

drainage-area ratios for the stations are between 0.3 

and 1.5, the median difference for the drainage-area 

ratio method is about 30 percent less and the standard 

deviation is about 11 percent less than the 

corresponding values for the regression equations. 

When drainage-area ratios for the stations are less than 

0.3 or greater than 1.5, the median difference for the 

drainage-area ratio method is about 25 percent greater 

and the standard deviation is about 100 percent greater 

than the corresponding values for the regression 

equations.

Statistical tests were done on the grouped data to 

test for significant differences in the variances and 

medians of the groups. Differences in variance were 

tested by use of Levene’s test for homogeneity of 

variances (Minitab, Inc., 1998b, p. 3–48 to 3–51). 

Levene’s test was used because the data were not 

normally distributed, and this test is applicable for any 

continuous distribution. Although there are substantial 

differences in variance among the groups, none of the 

groups could be considered significantly different from 

the others based on the test. Differences in medians 

were tested by use of the Mann-Whitney rank-sum test 

(Minitab, Inc., 1998b, p. 5–11 to 5–13). This test 

showed that the median difference for the drainagearea ratio estimates is significantly larger (p=0.052) 

than the median difference for the regression equation 

estimates when the drainage-area ratio is less than 0.3 

or greater than 1.5. The test also showed that the 

median difference of the drainage-area ratio estimates 

is significantly less than (p=0.003) the median 

difference of the regression equation estimates when 

the drainage-area ratio is between 0.3 and 1.5. 

On the basis of the above analysis, it should be 

expected that the drainage-area ratio method will 

provide estimates of streamflow statistics that are, on 

average, as good as or better than estimates obtained 

using the regression equations tested when the 

drainage-area ratio is between about 0.3 and 1.5. It 

should be noted, however, that this finding is based on 

a comparison of differences between two types of 

estimates (drainage-area ratio estimates and regression 

equation estimates) and a third type of estimate 

(correlation estimates) for the LFPR stations used in 

the analysis. It was not possible to test the estimation 

methods against only observed statistics for 

streamgaging stations, as would be preferred, because 

there were too few streamgaging stations available for 

the analysis that were located on the same, unregulated 

streams. The finding was also based on a comparison of 

drainage-area ratio estimates with estimates from 

regression equations that are now superseded by the 

equations provided later in this report. Results would 

likely differ somewhat if the new equations were used; 

however, time and funding were not available to update 

the analysis.

The upper limit of the drainage-area ratio range 

in which the drainage-area ratio estimation method is 

recommended for use over use of regression equations 

is poorly defined because there are only two data points 

(at 4.33 and 4.67) between ratios of 1.42 and 15.9. 

Absolute percent differences were larger for the 

drainage-area ratio estimates than for the regression 

estimates at the drainage-area ratios of 4.33 and 4.67, 

but the upper limit of the recommended range of 

drainage-area ratios could be anywhere between 1.42 

and 4.33. In addition, users of the drainage-area ratio 

method also should consider that potential errors of 

estimates for individual sites cannot be quantified. If a 

standard error of estimate or confidence intervals are 

needed, then it may be useful to use the regression 

equations to obtain the estimates.

Table 2. Medians and standard deviations of absolute percent 

differences between streamflow statistics estimated using 

available data and by using the drainage-area ratio method 

and regression equations

[<, actual value is less than value shown; >, actual value is greater than value 

shown]

Group

Drainagearea

ratio range

Number

in group

Median

absolute

percent

difference

Standard

deviation

All estimates All 72 40.3 151.6

Drainagearea ratio 

method

All 36 34.9 186.0

< 0.3 and > 1.5 20 65.7 240.8

0.3 to 1.5 16 15.5 37.7

Regression 

equations

All 36 43.2 108.9

< 0.3 and > 1.5 20 40.3 140.4

0.3 to 1.5 16 45.5 48.6
26 Methods for Estimating Low-Flow Statistics for Massachusetts Streams

Regression Equations

Multiple linear-regression analysis (regression 

analysis) has been used by the USGS and other 

researchers throughout the United States and elsewhere 

to develop equations for estimating streamflow statistics for ungaged sites. In regression analysis, a streamflow statistic (the dependent variable) for a group of 

data-collection stations is statistically related to one or 

more physical or climatic characteristics of the drainage areas for the stations (the independent variables). 

This results in an equation that can be used to estimate 

the statistic for sites where no streamflow data are 

available. Equations can be developed by use of several 

different regression analysis algorithms. The various 

algorithms use different methods for minimizing differences between the values of the dependent variable for 

the stations used in the analysis (the observed values) 

and the corresponding values provided by the resulting 

regression equation (the estimated or fitted values). 

Choice of one algorithm over another depends on the 

characteristics of the data used in the analysis and on 

the underlying assumptions for use of the algorithm.

Equations obtained by use of regression analysis 

take the general form

, (12)

where Yi is the estimate of the dependent variable for 

site i, X1 to Xn are the n independent variables, b0 to bn

are the n + 1 regression model coefficients, and εi is the 

residual error (difference between the observed and 

estimated value of the dependent variable) for site i. 

Assumptions for use of regression analysis are 

(1) equation 12 adequately describes the relation 

between the dependent and the independent variables, 

(2) the mean of the εi is zero, (3) the variance of the εi

is constant and independent of the values of Xn, (4) the 

εi are normally distributed, and (5) the εi are 

independent of each other (Iman and Conover, 1983, 

p. 367). Regression analysis results must be evaluated 

to assure that these assumptions are met.

Streamflow and basin characteristics used 

in hydrologic regression usually are log-normally 

distributed; therefore, transformation of the variables 

to logarithms is usually necessary to satisfy regression 

assumption 2. Transformation results in a model of 

the form

. (13)

The algebraically equivalent form when logarithmsbase 10 are used in the transformations and the 

equation is retransformed to original units is:

. (14)

The Generalized-Least-Squares (GLS) 

regression algorithm (Tasker, 1989) was developed 

for use in regression analysis of peak- and low-flow 

frequency statistics, such as the 100-year peak flow 

and the 7-day, 10-year low flow, because streamflow 

data are correlated spatially and in time. Thus, 

assumption 5 for use of regression is not strictly 

satisfied in hydrologic regressions when the most 

commonly used form of regression analysis, OrdinaryLeast-Squares (OLS), is used. Tasker and Stedinger 

(1989) demonstrated that GLS analysis is theoretically 

most appropriate and generally provides the best 

results when used for hydrologic regressions. GLS 

allows the weight given to each station used in the 

analysis to be adjusted to compensate for spatial 

correlation and differences in record length among the 

stations. Because GLS was developed specifically for 

use with flow-frequency statistics, however, it requires 

substantial extra effort to use it for regression with 

flow-duration statistics (Ries, 1994b)

 Vogel and Kroll (1990) used GLS to develop 

a regression equation to predict 7-day, 10-year low 

flows for Massachusetts streams; however, they found 

that the equation parameters (b0 to bn) were nearly 

identical when either OLS or GLS was used to develop 

the equation even though OLS does not correct for 

differences in record length or cross-correlation among 

the stations used in the analysis. In addition, Vogel and 

Kroll (1990) found that prediction errors obtained 

when GLS was used were only marginally smaller than 

those obtained when OLS was used.

Weighted-Least-Squares regression analysis 

(WLS) was used to develop the equations presented in 

this report for estimating the 99-, 98-, 95-, 90-, 85-, 

80-, 75-, 70-, 60-, and 50-percent duration flows; the 

7-day, 10- and 2- year low flows; and the August 

median flow. WLS can compensate for differences in 

record length, but it does not correct for crosscorrelation among the stations used in the analysis. 

Stedinger and Tasker (1985) concluded that gains in 

Yi b0 b1X1 b2X2 ... bnXn ε = + + ++ + i

logYi b0 b1 X1 log b2 X2 = +++ log ...

bnlogXn ε + + i

Yi 10b0 X1

b1 ( ) X2b2 ( )... Xnbn ( )10ε = i
Estimating Methods for Ungaged Stream Sites 27

model precision when GLS is used instead of WLS 

increase with decreasing standard error of estimate and 

increasing cross correlation. WLS and GLS models 

with large standard errors and low cross correlations 

were nearly identical. Because Vogel and Kroll (1990) 

found cross correlation of data they used in their 

analysis was only 0.35, equations for predicting lowflow statistics for Massachusetts streams using WLS 

should have model precision that is nearly the same as 

equations developed using GLS. Additionally, the WLS 

algorithm can easily be used to adjust the weights for 

stations used in the analysis to compensate for nonconstant variance of the regression residuals when this 

is necessary to avoid a violation of regression 

assumption 3.

When several independent variables are being 

considered for use in a regression analysis, usually a 

variable-selection algorithm is necessary to aid in 

determining which combination of the independent 

variables provides the best estimates of the dependent 

variable. Neter and others (1985, p. 421–429) describe 

an all-possible-regressions algorithm that examines all 

possible combinations of the independent variables and 

ranks them according to some criterion. This algorithm 

was used for the Basin Yield studies to select subsets of 

the independent variables for inclusion in the final 

regression equations, with minimization of Mallow’s 

Cp used as the selection criterion (Neter and others, 

1985, p. 426–428). These subsets were further 

analyzed using WLS regression analysis to select a 

final model for each analyzed streamflow statistic. The 

final models were selected on the basis of the following 

statistical parameters: (1) Mallow’s Cp statistic; 

(2) , the percentage of the variation in the 

dependent variable explained by the independent 

variables, adjusted for the number of stations and the 

number of independent variables used in the regression 

analysis; (3) the mean square error (MSE), the sample 

model error variance of the estimates for the stations 

included in the analysis; and (4) the PRESS statistic, an 

estimate of the prediction error sum of squares 

(Montgomery and Peck, 1982, p. 255). Diagnostic 

checks were done to test for model adequacy and 

violations of assumptions for regression analysis. The 

independent variables selected for the final models had 

to be statistically significant at the 95-percent 

confidence level, and the signs and magnitudes of the 

coefficients had to be hydrologically reasonable.

Equation 13 provides unbiased estimates of the 

mean response of the dependent variable, meaning that 

the expected value of εi is zero. However, equation 13 

yields estimates of the logarithm-base 10 of the 

dependent variable when what is desired is estimates in 

their original units of measure. Equation 14 is a 

retransformation of equation 13 that produces 

estimates in the desired units, but it predicts the median 

rather than the mean response of the dependent 

variable, and thus it is biased. In the case of streamflow 

data, the median tends to be lower than the mean.

Several investigators have discussed the 

problems of bias in retransformed logarithmic 

equations and proposed various bias-correction factors 

(BCF) as solutions (Bradu and Mundlak, 1970; Duan, 

1983; Ferguson, 1986; Koch and Smillie, 1986; Cohn 

and others, 1989; Gilroy and others, 1990). Duan’s 

“smearing estimate” was used as the BCF in previous 

Basin Yield studies (Ries, 1994a, 1994b, 1997) by 

replacing the error term of equation 14 with the mean 

error of the retransformed residuals. This BCF is 

advantageous in that it does not require normally 

distributed regression residuals and is simple to 

calculate.

Cohn and others (1989) show that if the residuals 

are normally distributed a BCF developed by Bradu 

and Mundlak (1970) is optimal, in that it provides 

Minimum Variance Unbiased Estimates (MVUE) of 

the dependent variable. Gilroy and others (1990) 

demonstrate that the MVUE estimator and Duan’s 

smearing estimator are about equally effective at 

eliminating retransformation bias, however the MVUE 

estimator has the advantage of being unbiased 

regardless of the number of stations used in the 

analysis. Equations for computing the MVUE 

estimator are provided in Cohn and others (1989) and 

in Gilroy and others (1990). Because of their 

complexity, they are not reproduced here. Cohn and 

others (1989) also provided a FORTRAN program for 

computing the MVUE BCF. This program was used to 

determine MVUE factors for the regression equations 

provided later in this report. Smearing estimate BCFs 

were also determined for the regression equations. 

Estimated streamflow statistics for the stations used in 

the regression analyses were determined from 

equations using both types of BCFs, and the means of 

the estimates were compared against the means of the 

observed data. The means of the MVUE estimates were 

Radj

2
28 Methods for Estimating Low-Flow Statistics for Massachusetts Streams

generally closer to the means of the observed data than 

the means of the smearing estimates, thus the MVUE 

estimates were used in the final equations.

Data Base Development

Streamflow statistics and basin characteristics 

were included in the regression analyses for 37 gaging 

stations and 107 LFPR stations. Streamflows at all of 

the stations included in the analyses were essentially 

unregulated during low streamflow periods. Thirty-four 

streamgaging stations were in Massachusetts and three 

were in bordering states (two in Rhode Island and one 

in Connecticut) but had more than two-thirds of their 

drainage areas in Massachusetts. Available records 

through climatic year 1995 were used to compute the 

streamflow statistics for the gaging stations. Record 

lengths range from 2 to 83 years, with a median of 27 

years (table 3). Streamflow statistics were also 

computed for 14 other streamgaging stations that were 

not used in the analyses but were used to estimate 

streamflow statistics for the LFPRs. Names and 

descriptions of the streamgaging stations are in table 3. 

Locations of the streamgaging stations and the LFPR 

stations are shown in figure 1.

All 107 LFPR stations used in the analyses were 

in Massachusetts. Names and descriptions of the LFPR 

stations are in table 8 (at back of report). The LFPRs 

had from 8 to 36 streamflow measurements available 

for relation to streamgaging-station discharge records, 

with a median of 14 measurements. One-quarter of the 

LFPR stations had 10 or fewer measurements, and onequarter had 18 or more measurements. Calculated 

streamflow statistics in cubic feet per second for the 

streamgaging stations and estimated streamflow 

statistics for the LFPR stations used in the analyses, 

along with variances in base-10 logarithms, standard 

errors in percent, and years of record for streamgaging 

stations or equivalent years of record for LFPR stations 

are provided in table 9 (at back of report). These 

statistics were calculated or estimated using the 

methods described earlier in this report.

Basin characteristics measured for use in the 

analyses were selected on the basis of their theoretical 

relation to differences in flow magnitudes of streams, 

results of previous studies in similar hydrologic 

environments, and on the ability to measure them. The 

characteristics measured were drainage area, in square 

miles; areas of stratified drift, wetlands, and water 

bodies, in square miles; total length of streams, in 

miles; maximum, minimum, and mean basin elevation, 

in feet; maximum, minimum, and mean elevation in 

stratified drift, in feet; and mean basin slope, in 

percent. The measured basin characteristics for the 

stations used in the regression analyses are provided 

in table 10 (at back of the report).

All basin characteristics were measured from 

digital-map data using an automated GIS procedure 

developed for the Basin Yield studies. The automated 

procedure was created using the AML programming 

language of the ARC/INFO GIS software 

(Environmental Systems Research Institute, Inc., 

1990). The automated procedure determines the 

drainage-basin boundary for any selected site on a 

Massachusetts stream and creates a digital data layer of 

the basin boundary. The procedure determines the 

drainage-basin boundary for the site, then overlays the 

boundary on the other digital data layers to determine 

the other basin characteristics for the site. The digital 

data layers used by the procedure include (1) drainage 

subbasins at 1:24,000 scale, (2) hydrography at 

1:25,000 scale, (3) surficial geology at 1:125,000 scale, 

and (4) Digital Elevation Models (DEMs) at 1:25,000 

scale and 1:250,000 scale. These data layers are 

documented by and are available from MassGIS 

(http://www.state.ma.us/mgis) as separate products. 

They have also been packaged into a watershed library 

(http://www.state.ma.us/mgis/ix_wat.htm), which also 

contains several derivative data layers needed for using 

the automated procedure.

The drainage subbasins data layer includes 

drainage-basin boundaries for about 2300 locations in 

Massachusetts and areas in other states that contribute 

streamflow to Massachusetts. Subbasin boundaries for 

most USGS data-collection stations are included in the 

data layer. The subbasin boundaries were delineated by 

the USGS and digitized by MassGIS, and average 

about 4 mi2 in extent.

The hydrography data comprise three layers, 

one each for streams, water bodies, and wetlands. 

These data were scanned from Mylar separates of the 

three types of blue-line features from 1:25,000-scale 

USGS topographic quadrangle maps. The streams 

were enhanced by adding centerlines through the 

water bodies, wetlands, and streams represented on 

the maps by double lines. This enhancement allows 

accurate measurements of total stream length to be 

obtained, and also creates a stream network that 

enables flow routing.
Estimating Methods for Ungaged Stream Sites 29

Table 3. Descriptions of streamgaging stations used in the regression analysis and for correlation with low-flow partial record 

stations, or both—Continued

Station

No.

Latitude

° ′ ′′

Longitude

° ′ ′′ Station name Period of record Remarks

Streamgaging stations used in the regression analysis and for correlation with low-flow partial-record stations

01096000 42 38 03 71 39 30 Squannacook River near West Groton, 

Mass.

1950–present Occasional regulation by mill upstream 

01096910 42 27 04 71 13 43 Boulder Brook at East Bolton, Mass. 1972–82 --

01097300 42 30 39 71 24 25 Nashoba Brook near Acton, Mass. 1964–present --

01100700 42 48 41 71 01 59 East Meadow Brook near Haverhill, 

Mass.

1963–73 --

01101000 42 45 10 70 56 46 Parker River at Byfield, Mass. 1946–present Occasional regulation by mill and ponds 

01105600 42 11 25 70 56 43 Old Swamp River near South 

Weymouth, Mass.

1966–present --

01106000 41 33 30 71 07 47 Adamsville Brook at Adamsville, R.I. 1941–77 --

01107000 42 03 41 71 03 59 Dorchester Brook near Brockton, Mass. 1963–73 --

01109200 41 52 46 71 15 18 West Branch Palmer River near 

Rehoboth, Mass.

1962–73 --

01111200 42 06 17 71 36 28 West River at West Hill Dam near 

Uxbridge, Mass.

1962–89 Flood-control dam upstream 

01111300 41 58 52 71 41 11 Nipmuc River near Harrisville, R.I. 1964–90, 

1994–present

--

01162500 42 40 57 72 06 56 Priest Brook near Winchendon, Mass. 1919–present No daily record during August 1936

01165500 42 36 10 72 21 36 Moss Brook at Wendell Depot, Mass. 1917–81

01166105 42 35 39 72 21 41 Whetstone Brook at Wendell Depot, 

Mass.

1986–90 --

01169000 42 38 18 72 43 32 North River at Shattuckville, Mass. 1940–present Occasional small diurnal fluctuation 

01169900 42 32 31 72 41 39 South River near Conway, Mass. 1967–present Small diurnal fluctuation since 1982 

01170100 42 42 12 72 40 16 Green River near Colrain, Mass. 1968–present --

01171500 42 19 05 72 39 21 Mill River at Northampton, Mass. 1939–present --

01171800 42 18 09 72 41 16 Bassett Brook near Northampton, Mass. 1963–73 --

01173260 42 23 52 72 08 51 Moose Brook near Barre, Mass. 1963–73 --

01174000 42 28 42 72 20 05 Hop Brook near New Salem, Mass. 1948–81 --

01174050 42 28 49 72 13 27 East Branch Fever River near Petersham, 

Mass.

1984–85 --

01174565 42 27 18 72 22 56 West Branch Swift River at Shutesbury, 

Mass.

1984–85 --

01174900 42 20 08 72 22 12 Cadwell Creek near Belchertown, Mass. 1962–present --

01175670 42 15 54 72 00 19 Sevenmile River near Spencer, Mass. 1961–present Occasional regulation by ponds 

upstream 

01176000 42 10 56 72 15 51 Quaboag River at West Brimfield, Mass. 1913–present Flood-retarding reservoirs upstream 

01180000 42 17 27 72 52 15 Sykes Brook at Knightville, Mass. 1946–72 --

01180500 42 15 31 72 52 23 Middle Branch Westfield River at Goss 

Heights, Mass.

1910–89 Data for August 1965–66 not used due 

to construction of flood-control 

reservoir upstream

Table 3. Descriptions of streamgaging stations used in the regression analysis and for correlation with low-flow partial record 

stations, or both

[Period of record: Periods of record shown are based on climatic years, which begin on April 1 of the year noted. The word “present” refers to the year of 

publication for this report (2000). No., number]
30 Streamflow Statistics and Basin Characteristics for Low-Flow Stations in Massachusetts

Streamgaging stations used in the regression analysis and for correlation with low-flow partial-record stations—Continued

01180800 42 15 49 73 02 48 Walker Brook near Becket Center, Mass. 1963–76 --

01181000 42 14 14 72 53 46 West Branch Westfield River at 

Huntington, Mass.

1936–present --

01187400 42 02 03 72 55 49 Valley Brook near West Hartland, Conn. 1941–71 --

01197015 42 31 12 73 13 48 Town Brook at Bridge Street, 

Lanesborough, Mass.

1981–82 --

01197300 42 20 59 73 17 56 Marsh Brook at Lenox, Mass. 1963–73 --

01198000 42 11 31 73 23 28 Green River near Great Barrington, 

Mass.

1952–70, 1994, 

1995

--

01331400 42 35 20 73 06 48 Dry Brook near Adams, Mass. 1963–73 --

01332000 42 42 08 73 05 37 North Branch Hoosic River at North 

Adams, Mass.

1932–89 Infrequent small diurnal fluctuation 

01333000 42 42 32 73 11 50 Green River at Williamstown, Mass. 1950–present Infrequent small diurnal fluctuation 

Streamgaging stations used for correlation with low-flow partial-record stations, but not used in the regression analysis

01073000 43 08 55 70 57 56 Oyster River near Durham, N.H. 1935–present --

01105730 42 06 02 70 49 23 Indian Head River at Hanover, Mass. 1967–present Some regulation by mills and ponds

01105870 41 59 27 70 44 03 Jones River at Kingston, Mass. 1967–present Regulation by pond and cranberry bogs. 

Ground- and surface-water drainage 

boundaries do not coincide

011058837 41 35 32 70 30 30 Quashnet River at Waquoit Village, 

Mass.

1989–present Some regulation by cranberry bog. 

Ground- and surface-water drainage 

boundaries do not coincide

01109000 41 56 51 71 10 38 Wading River near Norton, Mass. 1926–present Regulation by lakes and ponds. 

Diversions to and from basin for 

municipal supplies

01109403 41 49 51 71 21 06 Ten Mile River at East Providence, R.I. 1987–present Regulations and diversions from 

reservior

01118000 41 29 53 71 43 01 Wood River at Hope Valley, R.I. 1942–present Seasonal regulation by pond since 1968. 

Regulation at low flow until 1952

01121000 41 50 37 72 10 10 Mount Hope River near Warrenville, 

Conn.

1941–present Occasional regulation by ponds

01184490 41 54 50 72 33 00 Broad Brook at Broad Brook, Conn. 1962–present Regulation by reservoir and mill

01187300 42 02 14 72 56 22 Hubbard River near West Hartland, 

Conn.

1939–55,

1957–present

--

01188000 41 47 10 72 57 55 Burlington Brook near Burlington, 

Conn.

1932–present --

01197000 42 28 10 73 11 49 East Branch Housatonic River at 

Coltsville, Mass.

1936–present Flow regulated by powerplants and 

reservoir. Diversion for municipal 

supply

01198500 42 01 26 73 20 32 Blackberry Brook at Canaan, Conn. 1950–71 --

01199050 41 56 32 73 23 29 Salmon Creek at Lime Rock, Conn. 1962–present --

Table 3. Descriptions of streamgaging stations used in the regression analysis and for correlation with low-flow partial record 

stations, or both—Continued

Station

No.

Latitude

° ′ ′′

Longitude

° ′ ′′ Station name Period of record Remarks
Estimating Methods for Ungaged Stream Sites 31

The surficial geology data layer includes seven 

categories: (1) sand and gravel deposits, (2) till or 

bedrock outcrops, (3) sandy till over sand, (4) end 

moraines, (5) large sand deposits, where distinguished 

from sand and gravel deposits, (6) fine-grained 

deposits, and (7) floodplain alluvium. The automated 

procedure determines the total area in each category 

within the drainage-basin area. Each category was 

tested separately as a basin characteristic and in 

combination with other categories in preliminary 

regression analyses.

The 1:25,000-scale DEM data were used to 

define or aid in defining drainage-basin boundaries for 

locations on streams where basin characteristics and 

streamflow statistics were needed. The DEM data used 

for the boundary delineations were processed so that 

the stream network derived from the DEMs would conform exactly with the data layer of streams derived 

from the USGS topographic maps. This was necessary 

to assure correct automatic delineation of drainage 

boundaries. When a user of the automated procedure 

selects a location on a stream for which no boundary 

exists in the subbasin boundary data layer, the modified 

DEMs are used to determine the boundary for the location up to the points at which the new boundary intersects existing boundaries in the subbasin boundary data 

layer. The previously defined boundaries are then used 

to define the remainder of the boundary and the drainage area for the new location. This process minimizes 

reliance on the DEMs for determining drainage boundaries for selected locations, however drainage boundaries for some small basins are determined entirely 

from the modified DEMs. The original (un-processed) 

1:25,000-scale DEMs were used to determine minimum, mean, and maximum elevations in the drainage 

basin and also in the stratified-drift areas in the basin. 

The 1:250,000-scale DEMs were used to compute 

mean basin slopes, in percent.

Some of the measured basin characteristics were 

combined to determine additional characteristics for 

use in the analyses. These characteristics included 

(1) relief, in feet, computed by subtracting the minimum from the maximum basin elevation; (2) relief in 

stratified-drift areas, in feet, computed by subtracting 

the minimum from the maximum elevation in the stratified-drift areas within the basin; (3) GWHEAD, in 

feet, a surrogate used in previous Basin Yield studies 

for the effective head in the stratified drift, computed 

by subtracting the minimum from the mean basin elevation; (4) drainage density, in miles per square mile, 

computed by dividing the total stream length by the 

basin area; (5) percentage of water bodies, computed 

by dividing the area of water bodies by the basin area, 

and multiplying the result by 100; (6) percentage of 

wetlands, computed by dividing the area of wetlands 

by the basin area, and multiplying the result by 100; 

(7) percentage of storage, computed by adding the 

areas of wetlands and water bodies, dividing by the 

basin area, and multiplying the result by 100; (8) total 

percentage of stratified drift, computed by dividing the 

total area of surficial geology categories 1, 5, 6, and 7 

by the basin area, and multiplying the result by 100; 

(9) total drift per unit stream length, in square miles per 

mile, computed by dividing the total area of surficial 

geology categories 1, 5, 6, and 7 by the total stream 

length; (10) percent coarse-grained drift, computed by 

dividing the area of surficial geology categories 1, 5, 

and 7 by the basin area, and multiplying the result by 

100; and (11) coarse-grained drift per unit stream 

length, in square miles per mile, computed by dividing 

the area of surficial geology categories 1, 5, and 7 by 

the total stream length.

Several of the stations that were used in the 

regression analyses were also used in the drainagearea-ratio analysis described previously. In some cases, 

the streamflow statistics shown for these stations in 

table 7 differ from those shown in table 10, and the 

basin characteristics shown in table 9 differ from those 

shown in table 1. The streamflow statistics differ 

because the regression analyses were done two years 

after the drainage-area-ratio analysis was done, and 

during that time period the methods for determining 

streamflow statistics for the LFPR sites was improved, 

and in some cases additional streamflow measurements 

were made at the sites. The basin characteristics differ 

because the data layers, GIS methods, and regression 

equations used for the drainage-area ratio analysis were 

those described by Ries (1994b, 1997), and they differ 

from the data layers, GIS methods, and equations 

described in this report. Values shown in tables 9 and 

10 supersede those shown in tables 1 and 7.

Development of the Equations

Regression equations for predicting the 99-, 98-, 

95-, 90-, 85-, 80-, 75-, 70-, 60-, and 50-percent 

duration flows; the 7-day, 10- and 2- year low flows; 

and the August median flow were developed using 

WLS regression, as described above. The equations are 

presented in table 4, along with the number of stations 

used in the analysis and several measures of model 

adequacy.
32 Methods for Estimating Low-Flow Statistics for Massachusetts Streams

The measures of model adequacy include (1) the 

coefficient of determination, otherwise known as the 

adjusted R-squared ( ); (2) the average standard 

error of estimate, SEr, in percent; (3) the average 

standard error of prediction, SEp, in percent; and 

(4) the median absolute deviation (MAD), in percent. 

The is a measure of the proportion of the variation 

in the dependent variable that is explained by the 

independent variables, adjusted for the number of 

stations and the number of independent variables used 

in the analysis. The SEr is a measure of the average 

precision with which the regression equations estimate 

the streamflow statistics for stations used in the 

analyses, whereas the SEp indicates the average 

precision with which the equations can be used to 

estimate streamflow statistics for ungaged sites with 

basin characteristics similar to those for the stations 

used in the regression analyses. About 68 percent of 

streamflows estimated by using regression equations 

will have errors within the noted average standard 

errors. Half of the regression-equation estimates for 

stations used in the analyses had absolute errors, in 

percent, that were greater than the MAD, and half of 

them were less than the MAD.

The number of stations used in the analyses 

ranged from 87 (34 streamgaging stations and 53 LFPR 

stations) for the equation for the 50-percent duration to 

133 (34 streamgaging stations and 99 LFPR stations) 

for the equations for the 85- percent duration. The 

number of stations differed because limits were placed 

on the standard errors of estimate allowed for the LFPR 

stations used in the analysis, and because some stations 

were removed from the analyses because they were 

outliers. Limits of standard errors of estimate set for 

inclusion of LFPR stations in the analyses were 30 

percent for the 99-percent duration flow and the 7-day, 

10-year low flow; 25 percent for the 98-percent 

duration flow; 20 percent for the 95-percent duration 

flow and the 7-day, 2-year low flow; and 15 percent for 

all other statistics. The limits were set higher for the 

lower flows because, for the same error in flow in cubic 

feet per second, the percentage error increases as the 

actual flow decreases. Streamflow statistics were 

omitted from table 9 for stations not used in the 

regression analyses.

Weighting Procedure

According to Montgomery and Peck (1982, 

p. 99), when observations of the dependent variable in 

a regression analysis have different accuracies, the 

individual observations should be assigned weights that 

are inversely proportional to their variances. Because 

of this, weights for the stations used in the regression 

Radj

2

Radj

2

Table 4. Summary of regression equations developed for estimating low-flow statistics for Massachusetts streams

[Statistic: Pxx is the xx-percent duration flow, Q7,y is the 7-day, y-year low flow, Aug50 is the August median flow, all in cubic feet per second. 

Equation: DA is drainage area (square miles); SL is mean basin slope (percent); DR/ST is area of stratified drift per unit of total stream length (square miles 

per mile); REG is region, 0 for eastern, 1 for western. Radj

2 : Coefficient of determination (percent). SEr and SEp: Average standard errors of estimate and prediction, respectively (percent). MAD: Median absolute deviation (percent)]

Statistic Equation

Number

 of

stations

Radj

2 SEr SEp MAD

P50 0.955(DA)

1.020 87 98.1 17.3 17.6 13.4

P60 0.763(DA)

1.050(DR/ST + 0.1)0.123 97 97.6 19.2 19.8 15.5

P70 0.607(DA)

1.070(DR/ST + 0.1)0.357100.121(REG) 115 96.7 22.7 23.5 17.8

P75 0.509(DA)

1.080(DR/ST + 0.1)0.432100.158(REG) 123 95.9 25.0 25.8 20.6

P80 0.507(DA)

1.060(SL)0.191(DR/ST + 0.1)0.693100.145(REG) 129 95.2 27.3 28.4 18.8

P85 0.365(DA)

1.080(SL)0.255(DR/ST + 0.1)0.746100.159(REG) 133 95.0 30.8 31.9 21.0

P90 0.329(DA)

1.080(SL)0.396(DR/ST + 0.1)0.985100.160(REG) 132 94.0 35.2 36.6 26.8

P95 0.171(DA)

1.120(SL)0.457(DR/ST + 0.1)0.999100.190(REG) 126 92.1 43.7 45.6 31.0

P98 0.116(DA)

1.130(SL)0.412(DR/ST + 0.1)1.030100.247(REG) 124 87.8 57.9 60.3 35.1

P99 0.082(DA)

1.160(SL)0.427(DR/ST + 0.1)1.050100.255(REG) 119 86.7 62.4 65.1 37.3

Q7,2 0.173(DA)

1.130(SL)0.272(DR/ST + 0.1)0.858100.199(REG) 119 88.5 47.3 49.5 28.0

Q7,10 0.080(DA)

1.170(SL)0.514(DR/ST + 0.1)1.180100.260(REG) 114 84.4 67.7 70.8 36.7

Aug50 0.418(DA)

1.080(SL)0.175(DR/ST + 0.1)0.745100.192(REG) 131 95.1 31.5 33.2 23.1
Estimating Methods for Ungaged Stream Sites 33

analyses were initially assigned as the reciprocal of the 

variances of the streamflow statistics, shown for each 

statistic for each station in table 9. However, weighted 

residuals from initial regression analyses using these 

weights were not normally distributed, as stations with 

very large or small variances relative to the others 

tended to be outliers. Plots of the weighted residuals 

showed that the LFPR stations mostly formed a large, 

dense cluster, whereas the gaging stations were more 

scattered. This clustering of LFPR stations was more 

pronounced for the lower (in flow) flow-duration 

statistics than for the higher flow-duration statistics; 

this was caused by the fact that variances for the flowduration statistics for the LFPR stations were mostly 

substantially higher than those for the streamgaging 

stations. Variances for the streamgaging stations and 

the LFPR stations were similar for the 7-day, 2- and 

10-year low-flow frequency statistics, but very high or 

low variances for individual stations still caused those 

stations to be outliers, thus causing non-normal 

residuals. Because of this, another weighting scheme 

was needed that was theoretically reasonable, would 

reduce the number of weight-induced outliers, and 

would not cause the weighted residuals for the LFPR 

and streamgaging stations to form separate clusters.

 Record length often has been used in hydrologic 

regression analyses as an easily calculated surrogate to 

weight the stations according to differences in the 

accuracy of their streamflow statistics. Record length is 

used to adjust the weights for the stations in the GLS 

regression algorithm (Tasker, 1989). Record length can 

be used for the weights because the variance of a 

streamflow statistic at a streamgaging station is highly 

inversely related to the record length for the station. 

When LFPR stations are used along with streamgaging 

stations in a regression analysis, however, appropriate 

weighting of the LFPR stations becomes a problem.

Equivalent years of record, computed using 

equation 6, could be used to weight the LFPR stations 

used in the regression analyses, but equivalent years of 

record is not highly related to the variance of a statistic 

for a LFPR station. For example, based on a linear 

regression, the reciprocal of the variance of the 

75-percent duration flow explains about 80 percent of 

the variation in the years of record for the streamgaging 

stations used in this study, but it explains only about 

17 percent of the variation in the equivalent years of 

record for the LFPR stations. The other parameters in 

equation 6 explain most of the remaining variation in 

equivalent years of record for the LFPR stations. As a 

result, the variances of a statistic for two LFPR stations 

can be the same, but their equivalent years of record 

can be very different.

Equation 6 tends to produce estimates of 

equivalent years of record that are higher, on average, 

than the actual years of record for a streamgaging 

station with the same variance as that of the LFPR 

station. Because of this, if years of record (actual and 

equivalent) were to be used alone as the weights in the 

regression analysis, the LFPR stations would have 

larger influence in the analysis than the streamgaging 

stations in relation to the accuracies of the statistics for 

the stations.

Several potential weighting schemes were tested. 

The weights used in the regression analyses for the 

flow-duration statistics and the August median were 

computed using the equation

(15)

where W is the weight, N is either the actual years of 

record for streamgaging stations or the equivalent years 

of record computed using equation 6 for LFPR 

stations, and Vc is the variance of the streamflow 

statistic for the station computed from regression 

equations that relate the variance to the magnitude of 

the streamflow statistics. A separate regression 

equation was computed for each statistic. Dividing N

and Vc by their means removes differences in the scales 

of the variables, yet maintains their spread. Use of 

variances computed from regression equations in place 

of the actual calculated variances resulted in (1) similar 

variances for a given magnitude of streamflow for both 

the streamgaging stations and the LFPR stations, (2) a 

single population of weighted statistics rather than 

separate populations for streamgaging stations and 

LFPR stations, (3) elimination of outliers created by 

some stations having much larger or smaller variances 

than the others, and (4) correction for non-constant 

variance of the regression residuals resulting from 

greater spread of the data for stations with small flows 

than for stations with large flows. 

The weights used in the regression analyses for 

the 7-day, 2- and 10-year low flows were computed by 

use of the equation

. (16)

W N ⁄ mean( ) N

Vc mean Vc ⁄ ( ) = ----------------------------------

W 1 Vc mean Vc = ⁄ ( ) ⁄ ( )
34 Streamflow Statistics and Basin Characteristics for Low-Flow Stations in Massachusetts

These weights proved to be adequate for 

developing the equations for the 7-day, 2- 

and 10-year low flows because the 

variances of the flow statistics for the 

LFPR stations and the streamgaging 

stations used in the analyses were similar, 

and clustering of the weighted LFPR 

stations did not occur.

Prediction Intervals

Prediction intervals at the 90-percent 

confidence level can be calculated for 

estimates obtained from the regression 

equations. Prediction intervals indicate the 

uncertainty inherent in use of the 

equations. Assurance is 90 percent that the 

true value of the streamflow statistic for an 

ungaged site will be within the prediction 

interval.

Tasker and Driver (1988) have 

shown that a 100(1-α) prediction interval 

for the true value of a streamflow statistic 

obtained for an ungaged site by use of 

weighted regression equations corrected 

for bias can be computed by

, (17)

where Q is the streamflow statistic for the 

site, BCF is the bias correction factor for 

the equation, and T is computed as:

. (18)

In equation 18, t(α/2,n-p) is the critical value 

from the students t-distribution at alphalevel α (α = 0.10 for 90-percent prediction 

intervals); n-p is the degrees of freedom 

with n stations used in the regression 

analysis and p parameters in the equation 

(the number of basin characteristics plus 

one); and Si is computed from equation 19 

below. Critical values from the students tdistribution are contained in many 

introductory statistics textbooks.

1

T

--- Q

BCF -----------     Q T Q

BCF -----------     < <

T 10 t

( ) α ⁄ 2, n p – Si [ ]

=

The value of Si is computed using the equation

(19)

where γ2 is the model error variance; xi is a row vector of the 

logarithms of the basin characteristics for site i, augmented by a 1 

as the first element; U is the covariance matrix for the regression 

coefficients; and xi′ is the transpose of xi (Ludwig and Tasker, 

1993). The values of BCF, t(α/2,n-p), γ2, and U needed to determine 

prediction intervals for estimates obtained from the equations in 

table 4 are presented in table 5.

Example Computations

The procedure necessary to obtain the estimates is explained 

by an example computation of the 95-percent duration low flow for 

the selected site on the Hawes Brook at Norwood, Mass. (LFPR 

station number 01104980). First, the necessary basin characteristics 

for the site are measured from the various GIS data layers. Values 

for drainage area, mean basin slope, area of stratified drift, total 

length of streams, and region are 8.64 mi2, 2.27 percent, 2.20 mi2, 

15.5 mi, and zero (eastern region = 0), respectively. DRT/TST is 

computed by dividing the stratified-drift area by the total stream 

length, and adding a constant of 0.1, to obtain a value of 0.242 mi. 

Substituting these values into the equation to predict the 95-percent 

duration low flow (table 4) yields

Q95 = 0.171(8.64)1.120(2.27)0.457(0.142+0.1)0.999100.190(0)

= 0.675 ft3/s.

To determine a 90-percent prediction interval for this estimate, the 

xi vector is

xi = {1, log10(8.64), log10(2.27), log10(0.242), 0},

the model error variance from table 3 is γ2 = 0.03302, and the 

covariance matrix, U, for the 95-percent duration low flow is

The standard error of prediction computed from equation 19 

is Si = [0.03302 + 0.0255]0.5 = 0.2419, and T computed from 

equation 18 is T = 101.654(0.2419) = 2.512. The 90-percent prediction 

interval is estimated from equation 17 as

, or, 

.

Si γ

2

xiUxi [ ] + '

0.5 =

U

0.154371 0.038763 – 0.024844 0.178711 0.016523

–0.038763 0.045306 0.026013 – –0.010435 –0.009947

0.024844 0.026013 – 0.215936 0.141923 0.060291 –

0.178711 0.010435 – 0.141923 0.386539 0.015753

0.016523 0.009947 – –0.060291 0.015753 0.071684

=

1

2.512 ------------- 0.6751.017 -------------     Q95

0.675

1.017 -------------     < < 2.512

0.264 Q95 < < 1.67
Estimating Methods for Ungaged Stream Sites 35

Table 5. Values needed to determine 90-percent prediction intervals for estimates obtained from the equations—Continued

Dependent 

variable BCF t γ2 U

P50 1.003 1.662 0.00556 0.0854720 -0.0560165

-0.0560165 0.0424162

P60 1.003 1.660 0.00684 0.207555 -0.037260 0.210624

-0.037260 0.041084 0.019092

 0.210624 0.019092 0.326740

P70 1.005 1.657 0.00944 0.163451 -0.038750 0.179908 0.029080

-0.038750 0.042838 0.005409 -0.014309

 0.179908 0.005409 0.321624 0.064405

 0.029080 -0.014309 0.064405 0.054811

P75 1.006 1.656 0.01141 0.149847 -0.041152 0.157830 0.026810

-0.041152 0.043708 0.002937 -0.013412

 0.157830 0.002937 0.284083 0.059967

 0.026810 -0.013412 0.059967 0.051001

P80 1.007 1.655 0.01360 0.118875 -0.038593 0.009972 0.124035 0.019158

-0.038593 0.046913 -0.024336 -0.006071 -0.006589

 0.009972 -0.024336 0.183858 0.099280 -0.057213

 0.124035 -0.006071 0.099280 0.284838 0.020611

 0.019158 -0.006589 -0.057213 0.020611 0.067052

P85 1.009 1.654 0.01706 0.136687 -0.034752 0.018759 0.159536 0.018791

-0.034752 0.039592 -0.015993 -0.005497 -0.011277

 0.018759 -0.015993 0.192606 0.135772 -0.053629

 0.159536 -0.005497 0.135772 0.366356 0.016069

 0.018791 -0.011277 -0.053629 0.016069 0.065965

P90 1.011 1.654 0.02202 0.114435 -0.032504 0.004651 0.120264 0.019455

-0.032504 0.039590 -0.013401 -0.001500 -0.012562

 0.004651 -0.013401 0.183669 0.112504 -0.053751

 0.120264 -0.001500 0.112504 0.300342 0.018315

 0.019455 -0.012562 -0.053751 0.018315 0.068902

P95 1.017 1.654 0.03302 0.154371 -0.038763 0.024844 0.178711 0.016523

-0.038763 0.045306 -0.026013 -0.010435 -0.009947

 0.024844 -0.026013 0.215936 0.141923 -0.060291

 0.178711 -0.010435 0.141923 0.386539 0.015753

 0.016523 -0.009947 -0.060291 0.015753 0.071684

P98 1.028 1.655 0.05447 0.146494 -0.039856 0.024356 0.169566 0.019479

-0.039856 0.047367 -0.027332 -0.010335 -0.009705

 0.024356 -0.027332 0.220827 0.140684 -0.063551

 0.169566 -0.010335 0.140684 0.374380 0.017814

 0.019479 -0.009705 -0.063551 0.017814 0.073700

P99 1.031 1.656 0.06196 0.155123 -0.041195 0.027513 0.180199 0.019040

-0.041195 0.050395 -0.033160 -0.011029 -0.008574

 0.027513 -0.033160 0.251192 0.159684 -0.067073

 0.180199 -0.011029 0.159684 0.402732 0.016396

 0.019040 -0.008574 -0.067073 0.016396 0.074477

Table 5. Values needed to determine 90-percent prediction intervals for estimates obtained from the equations

[Dependent variable: Pxx is the xx-percent duration flow; Q7,y is the 7-day, y-year low flow; Aug50 is the August median flow. BCF: The bias correction factor 

used in equation 17. t: The critical value from the Students t distribution used in equation 6. γ2: The regression model error variance used in equation 19. 

U: The covariance matrix used in equation 19]
36 Methods for Estimating Low-Flow Statistics for Massachusetts Streams

Thus, the most probable estimate of the 95-percent 

duration low flow for station 01104980 is 0.675 ft3/s, 

and there is a 90-percent probability that the true value 

of Q95 is between 0.264 and 1.67 ft3/s.

Limitations for Use of the Equations

Regression equations can be used to estimate 

streamflow statistics for ungaged sites with natural flow 

conditions in most of Massachusetts. If the equations 

are used to estimate streamflow statistics for sites 

where human influences on streamflows are present, 

such as water-supply withdrawals and dam regulations, 

the user should adjust the estimates for the human 

influences. 

Applicability of the equations is limited by the 

range of data used to develop the equations and by the 

accuracy of the estimates. Ranges of applicability for 

each equation are shown in table 6. The measures of 

model adequacy listed in table 4, and the prediction 

intervals calculated using equations 17 to 19, indicate 

potential errors that can be expected when basin 

characteristics for the selected sites are within the 

ranges of those for the sites used in the regression 

analyses.

The equations generally are not applicable in 

almost all of the South Coastal Shore subbasin of the 

South Coastal Basin, the eastern part of the Buzzards 

Bay Basin, Cape Cod, and the islands of Martha’s 

Vineyard and Nantucket. These areas, which are almost 

entirely underlain by coarse-grained stratified-drift 

deposits, are not adequately represented by sites in the 

regression analyses. Streams in these areas 

commonly have ground-water drainage divides that 

are not coincident with topographic drainage divides. 

Estimates obtained by use of the regression 

equations for selected sites in these areas could 

have substantial errors.

World Wide Web Application for 

Use of the Equations

The automated procedure for measuring basin 

characteristics, described in the Data Base 

Development section, was modified for use in a World 

Wide Web (Web) application that serves streamflow 

statistics for user-selected stream sites. The Web 

application (http://ma.water.usgs.gov/streamstats) was 

Table 6. Ranges of basin characteristics used to develop the 

regression equations

[mi, mile; mi2, square mile; --, not applicable]

Basin characteristic

Name

in

equations

Minimum Mean Maximum

Drainage area (mi2) ................... DA 1.61 14.9 149

Total basin stream length (mi)... -- 1.79 27.9 319

Mean basin slope (percent) ....... SL .32 5.28 24.6

Area of stratified drift per 

unit stream length (mi2/mi) ...

DR/ST .00 .144 1.29

Region ....................................... REG 0 -- 1

Table 5. Values needed to determine 90-percent prediction intervals for estimates obtained from the equations—Continued

Dependent 

variable BCF t γ2 U

Q7,2 1.019 1.657 0.03810 0.158738 -0.046861 0.027795 0.181537 0.018992

-0.046861 0.058491 -0.031551 -0.005478 -0.006372

 0.027795 -0.031551 0.223389 0.145159 -0.065982

 0.181537 -0.005478 0.145159 0.407552 0.016782

 0.018992 -0.006372 -0.065982 0.016782 0.072663

Q7,10 1.036 1.658 0.07122 0.165118 -0.044475 0.027261 0.193316 0.022249

-0.044475 0.054996 -0.029584 -0.004231 -0.008217

 0.027261 -0.029584 0.248129 0.168050 -0.069078

 0.193316 -0.004231 0.168050 0.452158 0.019891

 0.022249 -0.008217 -0.069078 0.019891 0.077525

Aug50 1.009 1.656 0.01785 0.148786 -0.037505 0.015571 0.169781 0.024324

-0.037505 0.039103 -0.017540 -0.011161 -0.011969

 0.015571 -0.017540 0.192826 0.127179 -0.053990

 0.169781 -0.011161 0.127179 0.364703 0.024260

 0.024324 -0.011969 -0.053990 0.024260 0.069070
Combining Estimates Determined by Different Methods 37

developed jointly by the USGS and MassGIS and it 

incorporates a data base of previously published 

streamflow statistics as well as the automated 

procedure for measuring basin characteristics and 

obtaining regression equation estimates of streamflow 

statistics for ungaged sites. The previously developed 

automated procedure was translated from an AML 

script to an Avenue script (Environmental Systems 

Research Institute, Inc., 1996a) to enable it to function 

in the Web application, and a subroutine was added to 

solve the regression equations and calculate the 

prediction intervals presented in this report.

A user interface was developed for the 

application by Syncline, Inc., of Cambridge, Mass., 

under contract to the USGS. The user interface is a Java 

applet that delivers interactive maps to users using the 

ArcView Internet Map Server (Environmental Systems 

Research Institute, Inc., 1996–97) software 

extension to ArcView (Environmental Systems 

Research Institute, Inc., 1996b). Users locate sites on 

streams for which they want streamflow statistics by 

using the interface to add various digital map data and 

to move around and zoom in to the area of interest. 

Users can obtain streamflow statistics for a datacollection station by selecting its location marker on 

the map. The data base provides any previously 

determined streamflow statistics for the selected site, 

including peak-flow statistics not discussed in this 

report. Users can also obtain estimated streamflow 

statistics for any location along a stream (within the 

areas of applicability) by running the automated 

procedure. Further documentation for the Web 

application is provided in a fact sheet (Ries and others, 

2000), and in help pages and other links within the 

application.

COMBINING ESTIMATES DETERMINED 

BY DIFFERENT METHODS

Improved estimates of streamflow statistics for 

LFPR stations can be obtained by combining the 

weighted correlation-based estimates determined from 

equation 3 with those obtained from the regression 

equations. The estimates are weighted by the 

reciprocals of their standard errors and averaged by 

using the equation

, (20)

where the terms are as previously defined, except 

 is the regression equation estimate of 

streamflow statistic S for the LFPR station and SEr is 

the standard error of the regression equation estimate 

determined for the station from (a) equation 19, (b) the 

regression equation standard error of estimate from 

table 4 if the station was used in the regression 

analysis, or (c) the regression equation standard error 

of prediction from table 4 if the station was not used in 

the regression analysis. The standard error of estimate 

determined from equation 19 will provide the most 

precise weighted estimate, but it is difficult to calculate. 

Use of the standard errors from table 4 should be 

adequate for most needs.

When an ungaged site is on the same stream as a 

streamgaging or LFPR station and the drainage area for 

the ungaged site is between 0.3 and 1.5 times the 

drainage area of the streamgaging or LFPR station, 

improved estimates of the streamflow statistics for the 

ungaged site can be obtained using a weighting 

procedure to combine the estimates from regression 

equations with the streamflow statistics determined for 

the data-collection station. The procedure is modified 

from that of Pope and Tasker (1999, p. 16) and 

Choquette (1988, p. 42). The estimates are combined 

by first computing the correction factor,

, (21)

where CD is the correction factor for D, the datacollection station (streamgaging or LFPR station), 

 is the streamflow statistic S determined from 

available data for the data-collection station, and 

 is the streamflow statistic determined from the 

regression equation. Next, a correction factor, CU, is 

determined for the ungaged site. If the drainage area 

for the ungaged site (DAU) is less than 1.5 times larger 

than the drainage area for the data-collection station 

(DAD), use the equation

, (22)

where is the absolute value of the difference 

between DAU and DAD. If DAU is smaller than and 

within 0.3 times DAD, use the equation

Q . (23) S Uw' ,

QS Uw , SEw ( ) ⁄ ( ) QS Ur , SEr + ( ) ⁄ ( )

1 SEw ( ) ⁄ ( ) 1 SEr + ( ) ⁄ ( ) = ----------------------------------------------------------------------------------

QS Ur ,

CD QS Dw , QS Dr , = ⁄

QS D, w

QS Dr ,

CU CD

DA CD ∆ ( ) – 1

0.5DAD

= – ---------------------------------

∆DA

CU CD

DA CD ∆ ( ) – 1

0.7DAD

= – ---------------------------------
38 Methods for Estimating Low-Flow Statistics for Massachusetts Streams

The effect of the correction factor is that more weight 

is given to the streamflow statistic for the datacollection station the closer the ungaged site is to it. If 

DAU is greater than 1.5 times or less than 0.3 times 

DAD, no correction is necessary.

SUMMARY

This report is the sixth and final report of the 

Basin Yield series of reports prepared in cooperation 

with the Massachusetts Department of Environmental 

Management. The report provides methods for 

estimating low-flow statistics for Massachusetts 

streams. Different methods are provided depending on 

whether the location of interest is a streamgaging 

station, a low-flow partial-record station, or an ungaged 

site where no data are available. Standard USGS 

methods and computer software are described for 

determining flow-duration and low-flow frequency 

statistics for streamgaging stations. Two methods are 

described for determining August median flows for 

streamgaging stations. References are provided to 

reports that describe methods for extending or 

augmenting records for streamgaging stations with 

short records to reflect long-term conditions.

Mathematical and graphical correlation methods 

are presented for estimating low-flow statistics for lowflow partial-record stations. The MOVE.1 

mathematical method is recommended for use when 

the relation between measured flows at the low-flow 

partial-record (LFPR) station and daily mean flows at a 

nearby, hydrologically similar streamgaging station is 

linear. A widely used graphical method is 

recommended when this relation is curved. The report 

contains equations for computing the variance and 

equivalent years of record for estimates of low-flow 

statistics determined using the two methods. Estimates 

of low-flow statistics for LFPR stations can be 

improved by combining estimates determined from 

multiple index stations. The report contains equations 

for calculating combined estimates and the variances, 

standard errors, and equivalent years of record of these 

estimates.

Two methods are presented for estimating lowflow statistics for ungaged sites where no data are 

available -- the drainage-area ratio method and use of 

regression equations. The drainage-area ratio method is 

applied by dividing the streamflow statistics for a 

nearby, hydrologically similar index streamgaging 

station by the drainage area for the station, then 

multiplying these values by the drainage area of the 

ungaged site of interest to obtain estimates of the 

streamflow statistics for the site. A comparison of 

streamflow statistics estimated using the drainage-area 

ratio method and regression equations to those 

determined from available data for 25 LFPR and 8 

streamgaging stations in 5 Massachusetts river basins 

indicated that drainage-area ratio estimates generally 

are as accurate or more accurate than regression 

estimates when the drainage-area ratio for an ungaged 

site is between 0.3 and 1.5 times the drainage area of 

the index data-collection site. Regression equations can 

be used to obtain estimates for most ungaged sites.

Regression equations were developed to estimate 

the natural, long-term 99-, 98-, 95-, 90-, 85-, 80-, 75-, 

70-, 60-, and 50-percent duration flows; the 7-day, 

2-year and the 7-day, 10-year low flows; and the 

August median flow for ungaged sites in 

Massachusetts. As many as 37 streamgaging stations 

and 107 LFPR stations were included in the analyses. 

Streamflow statistics and basin characteristics for these 

stations were presented in the report. The number of 

stations used to develop the individual equations 

ranged from 87 for the 50-percent duration flow to 133 

for the 98-percent duration flow. The gaging stations 

had from 2 to 81 years of record, with a mean record 

length of 37 years. The LFPRs had from 8 to 36 

streamflow measurements, with a median of 14 

measurements. 

All physical characteristics of the basins for the 

stations used in the regression analyses were 

determined from digital data bases using GIS computer 

software. Drainage area, the area of stratified-drift 

deposits per unit of stream length plus 0.1, mean basin 

slope, and an indicator variable that was 0 in the 

eastern region and 1 in the western region of 

Massachusetts were used in 9 of the 13 final regression 

equations. Mean basin slope was not used in the 

equations for the 50- through 75-percent duration 

flows. The indicator variable for region was not used in 

the equations for the 50- and 60-percent duration flows. 

Only drainage area was used in the equation for the 

50-percent duration flow. All basin characteristics that 

appeared in the equations were positively correlated to 

the streamflow statistics used as the dependent 

variables.

The equations were developed by use of 

weighted-least-squares regression analyses. Weights in 

the analyses were assigned proportional to the actual 
References Cited 39

(for streamgaging stations) or equivalent (for LFPR 

stations) years of record and inversely proportional to 

the variances of the streamflow statistics for the 

stations. Standard errors of prediction ranged from 70.8 

to 17.6 percent for the equations to predict the 7-day, 

10-year low flow and 50-percent duration flow, 

respectively. The proportion of the variation in the 

dependent variables that is explained by the 

independent variables ( ) ranged from 84.4 to 98.1 

percent for the 7-day, 10-year low flow and 50-percent 

duration flow, respectively. The equations are not 

applicable in the Southeast Coastal region of the State, 

or where basin characteristics for the selected ungaged 

site are outside the ranges of those for the stations used 

in the regression analyses. If the equations are used to 

estimate streamflow statistics for sites where human 

influences on streamflows are present, such as watersupply withdrawals and dam regulations, the user 

should adjust the estimates for the human influences.

A World Wide Web application is described that 

enables users to obtain streamflow statistics for most 

stream locations in Massachusetts. The Web 

application provides streamflow statistics for datacollection stations from a data base and for ungaged 

sites by measuring the necessary basin characteristics 

for a selected site and solving the regression equations. 

Output provided by the Web application for ungaged 

sites includes a map of the drainage-basin boundary 

determined for the site, the measured basin 

characteristics, the streamflow statistics estimated 

from the equations in this report, and 90-percent 

prediction intervals for the estimates.

Finally, the report presents an equation that 

can be used to combine regression and correlation 

estimates to obtain improved estimates of the 

streamflow statistics for LFPR stations. The report 

also presents equations that can be used to combine 

regression and drainage-area ratio estimates to obtain 

improved estimates of the streamflow statistics for 

ungaged sites. These equations are applicable when 

the drainage area of the ungaged site is between 0.3 

and 1.5 times the drainage area of a streamgaging or 

LFPR station.

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U.S. Fish and Wildlife Service, 1981, Interim regional policy 

for New England stream flow recommendations: 

Region I, Concord, NH: U.S. Fish and Wildlife Service, 

3 p.
42 Methods for Estimating Low-Flow Statistics for Massachusetts Streams

Vogel, R.M., and Fennessey, N.M, 1994, Flow-duration 

curves. I: New interpretation and confidence intervals: 

Journal of Water Resources Planning and Management, 

v. 120, no. 4, p. 485–504.

Vogel, R.M., and Kroll, C.N., 1989, Low-flow frequency 

analysis using probability-plot correlation coefficients: 

Journal of Water Resources Planning and Management, 

v. 115, no. 3, p.338–357.

_____1990, Generalized low-flow frequency relationships 

for ungaged sites in Massachusetts: Water Resources 

Bulletin, v. 26, no. 2, p. 241–253.

_____1991, The value of streamflow record augmentation 

procedures in low-flow and flood-flow frequency 

analysis: Journal of Hydrology, v. 125, pp. 259–276

Wandle, S.W., Jr., and Randall, A.D., 1994, Effects of 

surficial geology, lakes and swamps, and annual water 

availability on low flows of streams in central New 

England, and their use in low-flow estimation: U.S. 

Geological Survey Water-Resources Investigations 

Report 93-4092, 57 p.
TABLES 7–10

Table 7 45

Table 7. Low-flow statistics estimated using available data, the drainage-area ratio method, and regression equations; and absolute percent differences between 

the data-based estimates and estimates from the drainage-area ratio method and regression equations for stations used to analyze to applicability of the drainagearea ratio method for estimating low-flow statistics for ungaged Massachusetts streams—Continued

Station

No.

Index

streamgaging

station

No.

Drainagearea

ratio

Low-flow 

statistic

Data-based 

estimate 

(ft3/s)

Drainage-area ratio 

method Regression equations

Remarks

Estimate 

(ft3/s)

Absolute 

percent 

difference

Estimate 

(ft3/s)

Absolute 

percent 

difference

Squannacook River Basin (subbasin of Nashua River Basin)

01095928 01096000 0.092 99 0.026 0.60 2,223 0.38 1,369

98 .046 .72 1,472 .44 85295 .15 1.04 612 .62 327

August .86 1.83 114 1.00 16.5

Average .27 1.05 1,105 .61 641

01095930 01096000 .192 99 .60 1.26 110 1.08 80.5

98 .76 1.51 99.7 1.27 67.595 1.22 2.18 78.7 1.70 39.1

August 2.53 3.83 51.4 2.52 0.4

Average 1.28 2.19 85.0 1.64 46.9

01095977 01096000 .688 99 2.58 4.54 76.0 4.38 69.9

98 3.22 5.44 68.9 5.36 66.695 5.08 7.84 54.3 7.02 38.1

August 10.2 13.8 35.3 11.0 7.5

Average 5.27 7.90 58.6 6.93 45.5

01095990 01096000 .895 99 5.05 5.90 16.8 5.89 16.6

98 6.10 7.07 15.9 7.33 20.295 8.97 10.2 13.7 9.56 6.6

August 16.2 17.9 10.5 15.3 5.9

Average 9.08 10.3 14.2 9.50 12.3

Table 7. Low-flow statistics estimated using available data, the drainage-area ratio method, and regression equations; and absolute percent differences between the 

data-based estimates and estimates from the drainage-area ratio method and regression equations for stations used to analyze to applicability of the drainage-area ratio method for estimating low-flow statistics for ungaged Massachusetts streams

[Station No.: Station numbers for streamgaging stations are in bold in the station number column. Low-flow statistic: Low-flow statistics are the 99-, 98-, and 95-percent duration and the August median 

flows, in cubic feet per second (ft3/s); average is the average of the four streamflow statistics. Data-based estimates: Data-based estimates were calculated for streamgaging stations from the daily mean 

flows for the period of record and estimated for low-flow partial-record stations by correlating measured flows to same-day mean flows at the index streamgaging station.]
46 Methods for Estimating Low-Flow Statistics for Massachusetts Streams Squannacook River Basin (subbasin of Nashua River Basin)—Continued 01096000 -- 1.000 99 6.60 -- -- 7.03 6.5 98 7.90 -- -- 8.86 12.2 95 11.4 -- -- 11.4 0.1 August 20.0 -- -- 17.9 10.4 Average 11.5 -- -- 11.3 7.3 01096035 01096000 1.085 99 6.74 7.16 6.2 7.99 18.5 98 8.19 8.58 4.8 10.1 23.8 95 12.2 12.4 1.6 12.9 6.1 August 22.5 21.7 3.6 20.1 10.7 Average 12.4 12.5 4.0 12.8 14.8 Wading River Basin (subbasin of Taunton River Basin)

01108490 01109000 0.359 99 1.13 0.75 33.3 0.26 76.6 Drainage-area ratio computed as unregulated area for 

01108490 (8.55 mi2) divided by unregulated area for 

01109000 (23.8 mi2).

98 1.19 .83 30.6 .34 71.795 1.41 1.15 18.4 .59 58.0

August 1.94 2.16 11.3 1.69 12.7

Average 1.42 1.22 23.4 .72 54.7

01108600 01109000 .161 99 .36 .34 6.37 .15 58.4

98 .38 .37 2.12 .19 48.795 .44 .52 15.7 .32 27.6

August .61 .97 58.6 .76 24.1

Average .45 .55 20.7 .36 39.7

Table 7. Low-flow statistics estimated using available data, the drainage-area ratio method, and regression equations; and absolute percent differences between 

the data-based estimates and estimates from the drainage-area ratio method and regression equations for stations used to analyze to applicability of the drainagearea ratio method for estimating low-flow statistics for ungaged Massachusetts streams

—Continued

Station

No.

Index

streamgaging

station

No.

Drainagearea

ratio

Low-flow 

statistic

Data-based 

estimate 

(ft3/s)

Drainage-area ratio 

method Regression equations

Remarks

Estimate 

(ft3/s)

Absolute 

percent 

difference

Estimate 

(ft3/s)

Absolute 

percent 

difference
Table 7 47

Wading River Basin (subbasin of Taunton River Basin)—Continued

01108700 01109000 0.403 99 1.10 0.85 23.0 0.38 65.6 Drainage-area ratio computed as unregulated area for 

01108700 (9.60 mi2) divided by unregulated area for 

01109000 (23.8 mi2).

98 1.17 .93 20.7 .48 59.395 1.47 1.29 12.2 .79 46.1

August 2.25 2.42 7.6 2.1 10.5

Average 1.50 1.37 15.9 .91 45.4

01109000 -- 1.000 99 2.10 -- -- 1.10 47.7 Statistics computed for the period corresponding to the 

period of record for station 01108500, 1954–86. 98 2.30 -- -- 1.40 39.0

95 3.20 -- -- 2.26 29.4

August 6.00 -- -- 5.75 4.2

Average 3.40 -- -- 2.63 30.1

Green River Basin (subbasin of Deerfield River Basin)

01170020 01170100 0.125 99 0.52 0.80 53.9 0.26 49.3

98 .62 .94 52.4 .30 51.295 .77 1.15 50.1 .45 41.3

August 1.38 2.01 45.7 1.08 21.9

Average .82 1.23 50.5 .52 40.9

01170025 01170100 .408 99 2.90 2.61 10.0 1.40 51.9

98 3.34 3.06 8.4 1.59 52.595 4.02 3.75 6.7 2.12 47.2

August 6.62 6.53 1.4 4.28 35.3

Average 4.22 3.99 6.6 2.35 46.7

Table 7. Low-flow statistics estimated using available data, the drainage-area ratio method, and regression equations; and absolute percent differences between the data-based estimates and estimates from the drainage-area ratio method and regression equations for stations used to analyze to applicability of the drainagearea ratio method for estimating low-flow statistics for ungaged Massachusetts streams—Continued

Station

No.

Index

streamgaging

station

No.

Drainagearea

ratio

Low-flow 

statistic

Data-based 

estimate 

(ft3/s)

Drainage-area ratio 

method Regression equations

Remarks

Estimate 

(ft3/s)

Absolute 

percent 

difference

Estimate 

(ft3/s)

Absolute 

percent 

difference
48 Methods for Estimating Low-Flow Statistics for Massachusetts Streams Green River Basin (subbasin of Deerfield River Basin)—Continued 01170030 01170100 0.140 99 0.87 0.90 2.6 0.40 54.1 98 1.00 1.05 5.0 .45 55.2 95 1.20 1.29 7.5 .62 48.3 August 1.93 2.24 16.1 1.25 35.3 Average 1.25 1.37 7.8 .68 48.2 01170055 01170100 .771 99 4.60 4.93 7.2 3.09 32.8 98 5.34 5.78 8.2 3.58 33.0 95 6.48 7.09 9.4 4.61 28.9 August 10.9 12.3 12.8 8.95 17.9 Average 6.83 7.52 9.4 5.06 28.1 01170100 -- 1.000 99 6.40 -- -- 3.81 40.5

98 7.50 -- -- 4.42 41.195 9.20 -- -- 5.75 37.5

August 16.0 -- -- 11.6 27.3

Average 9.78 -- -- 6.40 36.6

01170121 01170100 1.156 99 7.05 7.40 5.0 4.52 35.9

98 8.20 8.67 5.7 5.27 35.795 9.97 10.6 6.3 6.81 31.7

August 16.9 18.5 9.5 13.8 18.6

Average 10.5 11.3 6.6 7.59 30.5

Table 7. Low-flow statistics estimated using available data, the drainage-area ratio method, and regression equations; and absolute percent differences between 

the data-based estimates and estimates from the drainage-area ratio method and regression equations for stations used to analyze to applicability of the drainagearea ratio method for estimating low-flow statistics for ungaged Massachusetts streams

—Continued

Station

No.

Index

streamgaging

station

No.

Drainagearea

ratio

Low-flow 

statistic

Data-based 

estimate 

(ft3/s)

Drainage-area ratio 

method Regression equations

Remarks

Estimate 

(ft3/s)

Absolute 

percent 

difference

Estimate 

(ft3/s)

Absolute 

percent 

difference
Table 7 49

Green River Basin (subbasin of Deerfield River Basin)—Continued

01170141 01170100 1.256 99 7.32 8.04 9.8 5.20 29.0

98 8.6 9.42 9.5 6.09 29.295 10.6 11.6 9.4 7.76 26.7

August 18.6 20.1 8.1 15.3 17.6

Average 1.3 12.3 9.2 8.59 25.6

Quaboag River Basin (subbasin of Chicopee River Basin)

01175660 01175670 0.698 99 0.12 0.20 72.0 0.23 94.9 Correlation estimates shown are the weighted averages of 

those based on both gaging stations in the basin. 98 .16 .25 55.9 .27 65.

95 .34 .43 25.7 .43 25.7

August 1.46 1.26 13.7 1.22 16.4

Average .52 .54 41.8 .54 50.6

01175660 01176000 .041 99 .12 .65 451 .23 94.9

98 .16 .81 405 .27 65.295 .34 1.22 260 .43 25.7

August 1.46 2.60 78.1 1.22 16.4

Average .52 1.32 298 .54 50.6

01175670 01176000 .058 99 .29 .93 221 .43 47.2

98 .36 1.16 222 .50 37.895 .61 1.74 185 .76 23.9

August 1.80 3.72 107 2.01 11.7

Average .76 1.89 184 .92 30.2

Table 7. Low-flow statistics estimated using available data, the drainage-area ratio method, and regression equations; and absolute percent differences between 

the data-based estimates and estimates from the drainage-area ratio method and regression equations for stations used to analyze to applicability of the drainagearea ratio method for estimating low-flow statistics for ungaged Massachusetts streams—Continued

Station

No.

Index

streamgaging

station

No.

Drainagearea

ratio

Low-flow 

statistic

Data-based 

estimate 

(ft3/s)

Drainage-area ratio 

method Regression equations

Remarks

Estimate 

(ft3/s)

Absolute 

percent 

difference

Estimate 

(ft3/s)

Absolute 

percent 

difference
50 Methods for Estimating Low-Flow Statistics for Massachusetts Streams Quaboag River Basin (subbasin of Chicopee River Basin)—Continued 01175695 01175670 4.669 99 2.26 1.35 40.3 1.98 12.5 Correlation estimates shown are the weighted averages of those based on both gaging stations in the basin. 98 2.88 1.68 41.7 2.32 19.4 95 4.68 2.85 39.1 3.53 24.6 August 11.9 8.40 29.4 10.5 11.8 Average 5.43 3.57 37.6 4.58 17.1 01175695 01176000 .272 99 2.26 4.35 92.5 1.98 12.5 98 2.88 5.43 88.5 2.32 19.4 95 4.68 8.15 74.1 3.53 24.6 August 11.9 17.4 46.2 10.5 11.8 Average 5.43 8.83 75.3 4.58 17.1 01175905 0175670 15.92 99 18.1 4.62 74.5 7.01 61.3 Correlation estimates shown are the weighted averages of 

those based on both gaging stations in the basin. 98 21.5 5.73 73.3 8.69 59.6

95 30.6 9.71 68.3 13.2 56.9

August 62.5 28.6 54.2 43.6 30.2

Average 33.2 12.2 67.6 18.1 52.0

01175905 01176000 .926 99 18.1 14.8 18.2 7.01 61.3

98 21.5 18.5 14.0 8.69 59.695 30.6 27.8 9.2 13.2 56.9

August 62.5 59.3 5.1 43.6 30.2

Average 33.2 30.1 11.6 18.1 52.0

Table 7. Low-flow statistics estimated using available data, the drainage-area ratio method, and regression equations; and absolute percent differences between 

the data-based estimates and estimates from the drainage-area ratio method and regression equations for stations used to analyze to applicability of the drainagearea ratio method for estimating low-flow statistics for ungaged Massachusetts streams

—Continued

Station

No.

Index

streamgaging

station

No.

Drainagearea

ratio

Low-flow 

statistic

Data-based 

estimate 

(ft3/s)

Drainage-area ratio 

method Regression equations

Remarks

Estimate 

(ft3/s)

Absolute 

percent 

difference

Estimate 

(ft3/s)

Absolute 

percent 

difference
Table 7 51

01176000 01175670 17.19 99 16.0 4.98 68.9 13.5 15.6 Statistics computed for the period corresponding to the 

period of record available at the time of analysis for station 01175670, 1961–1996.

98 20.0 6.19 69.1 17.0 14.795 30.0 10.5 65.0 22.7 24.4

August 64.0 30.9 51.7 55.4 13.4

Average 32.5 13.1 63.7 27.2 17.0

Quaboag River Basin (subbasin of Chicopee River Basin)—Continued

01176350 01175670 20.72 99 27.3 6.01 78.0 17.0 37.8 Correlation estimates shown are the weighted averages of 

those based on both gaging stations in the basin.

Some basin characteristics for this station are larger than 

those for any station used in the regression analyses to determine the equations.

98 32.1 7.46 76.8 21.7 32.495 44.3 12.6 71.6 28.6 35.3

August 84.7 37.3 56.0 70.0 17.4

Average 47.1 15.8 70.6 34.3 30.7

01176350 01176000 1.206 99 27.3 19.3 29.3 17.0 37.8

98 32.1 24.1 24.9 21.7 32.495 44.3 36.2 18.3 28.6 35.3

August 84.7 77.2 8.9 70.0 17.4

Average 47.1 39.2 20.3 34.3 30.7

01176435 01175670 24.41 99 33.4 7.08 78.8 23.0 31.0 Correlation estimates shown are the weighted averages of 

those based on both gaging stations in the basin.

Some basin characteristics for this station are larger than 

those for any station used in the regression analyses to determine the equations.

98 39.2 8.79 77.6 29.8 23.995 54.6 14.9 72.7 38.2 30.1

August 105 43.9 58.2 88.3 15.9

Average 58.0 18.7 71.8 44.8 25.2

01176435 01176000 1.42 99 33.4 22.7 32.0 23.0 31.0

98 39.2 28.4 27.6 29.8 23.995 54.6 42.6 22.0 38.2 30.1

August 105 90.9 13.4 88.3 15.9

Average 58.0 46.2 23.7 44.8 25.2

Table 7. Low-flow statistics estimated using available data, the drainage-area ratio method, and regression equations; and absolute percent differences between 

the data-based estimates and estimates from the drainage-area ratio method and regression equations for stations used to analyze to applicability of the drainagearea ratio method for estimating low-flow statistics for ungaged Massachusetts streams—Continued

Station

No.

Index

streamgaging

station

No.

Drainagearea

ratio

Low-flow 

statistic

Data-based 

estimate 

(ft3/s)

Drainage-area ratio 

method Regression equations

Remarks

Estimate 

(ft3/s)

Absolute 

percent 

difference

Estimate 

(ft3/s)

Absolute 

percent 

difference
52 Methods for Estimating Low-Flow Statistics for Massachusetts Streams West Branch Westfield River Basin (subbasin of Westfield River Basin) 01180600 01180800 4.325 99 0.51 1.12 120 0.627 23.2 Correlation estimates shown are the weighted averages of those based on both gaging stations in the basin. 98 .68 1.30 90.9 .70 2.9 95 1.03 1.73 68.0 1.05 1.9 August 2.45 3.46 41.2 2.69 10.0 Average 1.17 1.90 80.0 1.27 9.5 01180600 01181000 .136 99 .51 .98 91.9 .627 23.2 98 .68 1.21 77.7 .70 2.9 95 1.03 1.63 58.3 1.05 1.9 August 2.45 2.99 22.0 2.69 10.0 Average 1.17 1.70 62.5 1.27 9.5 01180750 01180800 18.22 99 2.87 4.74 65.2 5.02 75.1 Correlation estimates shown are the weighted averages of 

those based on both gaging stations in the basin. 98 3.67 5.47 49.0 5.86 59.5

95 5.23 7.29 39.4 7.57 44.8

August 10.9 14.6 33.9 15.4 41.5

Average 5.67 8.02 46.9 8.47 55.2

01180750 01181000 .572 99 2.87 4.12 43.6 5.02 75.1

98 3.67 5.09 38.7 5.86 59.595 5.23 6.86 31.2 7.57 44.8

August 10.9 12.6 15.6 15.4 41.5

Average 5.67 7.17 32.3 8.47 55.2

Table 7. Low-flow statistics estimated using available data, the drainage-area ratio method, and regression equations; and absolute percent differences between 

the data-based estimates and estimates from the drainage-area ratio method and regression equations for stations used to analyze to applicability of the drainagearea ratio method for estimating low-flow statistics for ungaged Massachusetts streams

—Continued

Station

No.

Index

streamgaging

station

No.

Drainagearea

ratio

Low-flow 

statistic

Data-based 

estimate 

(ft3/s)

Drainage-area ratio 

method Regression equations

Remarks

Estimate 

(ft3/s)

Absolute 

percent 

difference

Estimate 

(ft3/s)

Absolute 

percent 

difference
Table 7 53

West Branch Westfield River Basin (subbasin of Westfield River Basin)—Continued

01180780 01180800 0.390 99 0.12 0.10 18.5 0.009 92.7 Correlation estimates shown are the weighted averages of 

those based on both gaging stations in the basin. 98 .14 .12 19.3 .022 84.8

95 .18 .16 13.8 .041 77.3

August .29 .31 9.1 .14 49.3

Average .18 .17 15.2 .054 76.1

01180780 01181000 .012 99 .12 .088 29.0 .009 92.7

98 .14 .11 24.8 .022 84.895 .18 .15 18.8 .041 77.3

August .29 .27 5.9 .14 49.3

Average .18 .15 19.6 .054 76.1

01180800 01181000 .031 99 .26 .23 13.1 .095 63.5

98 .30 .28 7.0 .11 62.795 .40 .38 6.0 .18 54.3

August .80 .69 13.8 .51 36.6

Average .44 .39 10.0 .22 54.3

01180821 01180800 24.57 99 2.34 6.39 173 7.1 204 Correlation estimates shown are the weighted averages of 

those based on both gaging stations in the basin. 98 2.77 7.37 166 8.40 203

95 3.53 9.83 178 10.8 205

August 5.84 19.6 236 22.1 278

Average 3.62 1.8 188 12.1 223

Table 7. Low-flow statistics estimated using available data, the drainage-area ratio method, and regression equations; and absolute percent differences between 

the data-based estimates and estimates from the drainage-area ratio method and regression equations for stations used to analyze to applicability of the drainagearea ratio method for estimating low-flow statistics for ungaged Massachusetts streams—Continued

Station

No.

Index

streamgaging

station

No.

Drainagearea

ratio

Low-flow 

statistic

Data-based 

estimate 

(ft3/s)

Drainage-area ratio 

method Regression equations

Remarks

Estimate 

(ft3/s)

Absolute 

percent 

difference

Estimate 

(ft3/s)

Absolute 

percent 

difference
54 Methods for Estimating Low-Flow Statistics for Massachusetts Streams West Branch Westfield River Basin (subbasin of Westfield River Basin)—Continued 01180821 01181000 0.771 99 2.34 5.55 137 7.1 204 98 2.77 6.86 148 8.40 203 95 3.53 9.25 162 10.8 205 August 5.84 17.0 191 22.1 278 Average 3.62 9.66 160 12.1 223 01181000 01180800 31.86 99 7.2 8.28 15.0 10.3 43.3 Statistics computed for the period corresponding to the period of record for station 01180800, 1963–77. 98 8.9 9.56 7.4 12.4 38.8 95 12.0 12.7 5.8 15.4 28.6 August 22.0 25.5 15.9 30.4 38.3 Average 12.5 14.0 11.0 17.1 37.2 Table 7. Low-flow statistics estimated using available data, the drainage-area ratio method, and regression equations; and absolute percent differences between the data-based estimates and estimates from the drainage-area ratio method and regression equations for stations used to analyze to applicability of the drainage- area ratio method for estimating low-flow statistics for ungaged Massachusetts streams

—Continued

Station

No.

Index

streamgaging

station

No.

Drainagearea

ratio

Low-flow 

statistic

Data-based 

estimate 

(ft3/s)

Drainage-area ratio 

method Regression equations

Remarks

Estimate 

(ft3/s)

Absolute 

percent 

difference

Estimate 

(ft3/s)

Absolute 

percent 

difference
Table 8 55

Table 8. Descriptions of low-flow partial-record stations used in the regression analyses—Continued

Station 

No.

Latitude

° ′ ′′

Longitude

° ′ ′′

Basin

No. Station name

Number

of measurements Gaging stations used for correlation

01073860 42 51 00 70 51 59 18 Smallpox Brook at Salisbury, Mass. 10 01101000, 01097300, 01096000, 0107300001094340 42 33 35 71 52 02 11 Whitman River near Westminster, Mass. 13 01109000, 01097300, 01105600, 01105730, 01111300, 

01111200

01094396 42 34 28 71 50 15 11 Philips Brook at Fitchburg, Mass. 10 01096000, 01097300, 01162500, 01175670, 0110100001094760 42 23 49 71 46 48 11 Waushacum Brook near West Boylston, Mass. 10 01097300, 01096000, 01111300, 0117567001095220 42 24 39 71 47 30 11 Stillwater River near Sterling, Mass. 23 01096000, 01097300, 01175670, 01162500, 0111120001095380 42 23 00 71 50 12 11 Trout Brook near Holden, Mass. 19 01175670, 01097300, 01096000, 01162500, 0111120001095915 42 34 26 71 37 43 11 Mulpus Brook near Shirley, Mass. 11 01097300, 01096000, 01162500, 0117567001095928 42 40 24 71 46 39 11 Trapfall Brook near Ashby, Mass. 18 01162500, 01175670, 01096000, 0109730001096504 42 40 03 71 33 55 11 Reedy Meadow Brook at East Pepperell, Mass. 17 01096000, 01097300, 01162500, 0110100001096505 42 41 23 71 32 54 11 Unkety Brook near Pepperell, Mass. 22 01096000, 01097300, 01162500, 0110100001096515 42 40 41 71 29 38 13 Salmon Brook at Main Street at Dunstable, Mass. 17 01162500, 01101000, 01096000, 01073000, 0109730001096805 42 21 15 71 37 40 14 North Brook near Berlin, Mass. 16 01175670, 01097300, 01162500, 0109600001096855 42 23 57 71 34 00 14 Danforth Brook at Hudson, Mass. 16 0107300, 01096000, 01175670, 01105600, 01111300, 

01111200

01096935 42 25 47 71 30 56 14 Elizabeth Brook at Wheeler Street at Stow, Mass. 12 01097300, 01096000, 01175670, 01111200, 0111130001097280 42 28 07 71 24 31 14 Fort Pond Brook at West Concord, Mass. 16 01097300, 01105600, 01109000, 01111300, 0111120001099400 42 37 29 71 19 11 14 River Meadow Brook at Lowell, Mass. 13 01097300, 01096000, 01101000, 0110560001100608 42 37 14 71 12 44 15 Meadow Brook near Tewksbury, Mass. 15 01073000, 01096000, 01097300, 01105600, 0110100001101100 42 43 31 70 54 54 16 Mill River near Rowley, Mass. 9 01101000, 01097300, 0107300001102053 42 33 34 70 56 55 18 Crane Brook at Danvers, Mass. 10 01073000, 01096000, 01097300, 01105600, 0110100001102490 42 28 16 71 10 34 18 Shaker Glen Brook near Woburn, Mass. 13 01097300, 01105600, 0110100001103015 42 25 20 71 08 59 20 Mill Brook at Arlington, Mass. 20 01097300, 01105600, 0110100001103253 42 08 27 71 25 26 20 Chicken Brook near West Medway, Mass. 22 01109000, 01073000, 01111300, 0111120001103435 42 17 13 71 18 05 20 Waban Brook at Wellesley, Mass. 11 01109000, 01097300, 01111300, 01111200, 0117567001103440 42 17 45 71 17 18 20 Fuller Brook at Wellesley, Mass. 18 01097300, 01111300, 01111200, 0110900001104960 42 11 04 71 13 29 19 Germany Brook near Norwood, Mass. 18 01111200, 01111300, 01109000, 01105730, 0110100001104980 42 10 26 71 12 31 19 Hawes Brook at Norwood, Mass. 20 01109000, 01097300, 01105600, 01105730, 01111300, 

01111200

01105100 42 09 36 71 11 47 19 Traphole Brook near Norwood, Mass. 26 01101000, 01111300, 01105730, 01105870, 0110900001105270 42 08 59 71 08 58 19 Massapoag Brook at Canton, Mass. 9 01109000, 01097300, 01105600, 01105730, 01111300, 

01111200

01105568 42 09 19 71 01 37 19 Cochato River at Holbrook, Mass. 9 01105600, 01097300, 01105730, 0110900001105575 42 11 02 71 00 42 19 Cranberry Brook at Braintree Highlands, Mass. 16 01105600, 01097300, 01105730, 01109000

Table 8. Descriptions of low-flow partial-record stations used in the regression analyses[Basin number: Number refers to figure 1. No., number]
56 Methods for Estimating Low-Flow Statistics for Massachusetts Streams 01105582 42 13 25 70 59 49 19 Monatiquot River at Braintree, Mass. 10 01105600, 01097300, 01105730, 01109000 01105630 42 12 53 70 53 06 19 Crooked Meadow River near Hingham Center, Mass. 15 01109000, 01097300, 01105600, 01105730, 01111300, 01111200 01105670 42 11 35 70 43 44 21 Satuit River at Scituate, Mass. 9 01105600, 01105730, 01105870 01105820 42 09 36 70 47 20 21 Second Herring Brook at Norwell, Mass. 15 01105600, 01105730, 01105870, 01109000 01105830 42 11 30 70 46 49 21 First Herring Brook near Scituate Center, Mass. 16 01105600, 01111200, 01111300, 01109000, 01105730 01105861 41 59 47 70 47 18 21 Jones River Brook near Kingston, Mass. 14 01105600, 01109000, 01105870, 01097300 011058839 41 46 21 70 33 46 21 Herring River at Bournedale, Mass. 12 01109000, 01158837, 01105870, 01105730 011059106 41 44 35 70 52 04 13 Mattapoisett River tributary #1 near Rochester, Mass. 13 01109000, 01105870, 01111200, 01105730 01105930 41 40 43 70 58 39 24 Paskamanset River at Turner Pond near New Bedford, Mass. 23 01109000, 01105600, 01105730, 01111200, 01106000 01105935 41 34 20 71 00 47 24 Destruction Brook near South Dartmouth, Mass. 24 01109000, 01105600, 01105870, 01105730, 01111200 01105937 41 40 55 71 01 05 24 Shingle Island River near North Dartmouth, Mass. 25 01109000, 01105600, 01105730, 01111200, 01106000 01105947 41 38 00 71 03 46 24 Bread and Cheese Brook at Head of Westport, Mass. 24 01109000, 01105600, 01105870, 01105730, 01111200, 01106000 01106460 42 02 43 70 58 17 25 Beaver Brook near East Bridgewater, Mass. 21 01109000, 01118000, 01105730, 01105870, 01111200, 01111300 01107400 41 51 55 70 54 32 25 Fall Brook near Middleboro, Mass. 36 01105600, 01111300, 01105730, 01109000 01108140 41 54 20 70 59 19 25 Poquoy Brook near North Middleboro, Mass. 16 01109000, 01105600, 01111300, 01105730

01108180 41 52 57 71 02 54 25 Cotley River at East Taunton, Mass. 14 01109000, 01105600, 01111300, 0110573001108600 41 59 11 71 14 27 25 Hodges Brook at West Mansfield, Mass. 27 01109000, 01105730, 01105870, 01111200, 01111300

01109087 41 47 57 71 03 37 25 Assonet River at Assonet, Mass. 22 01109000, 01105730, 01097300, 01111200, 0111130001109090 41 46 36 71 05 23 25 Rattlesnake Brook near Assonet, Mass. 11 01109000, 01111200, 01105730, 01118000, 01105870, 

01106000

01109225 41 46 52 71 15 03 26 Rocky Run near Rehoboth, Mass. 36 01109000, 01118000, 01111200, 01111300, 0110600001109460 42 12 20 71 50 06 12 Dark Brook at Auburn, Mass. 18 01097300, 01105600, 01109000, 01111200, 01111300, 

01175670

01111142 42 11 25 71 39 23 12 Miscoe Brook near Grafton, Mass. 11 01097300, 01105600, 01109000, 0117567001111225 42 02 40 71 37 21 12 Emerson Brook near Uxbridge, Mass. 12 01097300, 01109000, 01111300, 0117567001112190 42 05 35 71 31 11 12 Muddy Brook at South Milford, Mass. 13 01097300, 01109000, 01111300, 0117567001123140 42 06 35 72 11 51 10 Mill Brook at Brimfield, Mass. 9 01111300, 01121000, 01174900, 01175670, 01176000, 

01184490

Table 8. Descriptions of low-flow partial-record stations used in the regression analyses

—Continued

Station 

No.

Latitude

° ′ ′′

Longitude

° ′ ′′

Basin

No. Station name

Number

of measurements Gaging stations used for correlation
Table 8 57

01123161 42 06 25 72 11 36 10 Wales Brook at Brimfield, Mass. 10 01121000, 01174000, 01175670

01123200 42 03 41 72 09 45 10 Stevens Brook at Holland, Mass. 22 01176000, 01175670, 01171500, 01187300, 0112100001124390 42 09 16 71 54 47 10 Little River at Richardson Corners, Mass. 18 01175670, 01176000, 01111200, 01111300, 0112100001162900 42 33 52 72 00 43 7 Otter River at Gardner, Mass. 18 01162500, 01165500, 01174000, 01174900, 01175670, 

01096000

01163298 42 35 49 72 05 28 7 Trout Brook at Route 20, near Baldwinville, Mass. 9 01096000, 01169000, 01170100, 0117490001164300 42 41 14 72 10 39 7 Lawrence Brook at Royalston, Mass. 14 01096000, 01162500, 01174500, 0117567001165090 42 38 45 72 15 25 7 West Branch Tulley River at North Orange, Mass. 9 01096000, 01162500, 01174500, 0117567001165250 42 32 17 72 14 51 7 Riceville Brook near South Athol, Mass. 9 01096000, 01162500, 01174500, 01175670, 0117010001167200 42 41 15 72 32 43 6 Fall River at Bernardston, Mass. 16 01169000, 01170100, 01169900, 0116250001168300 42 38 12 72 56 10 3 Cold River near Zoar, Mass. 31 01169000, 01333000, 01169900, 0117010001168400 42 37 28 72 54 27 3 Chickley River near Charlemont, Mass. 22 01170100, 01169900, 01169000, 0133300001168650 42 36 47 72 46 10 3 Clesson Brook near Shelburne Falls, Mass. 24 01169000, 01169900, 01170100, 01333000, 0117150001169600 42 32 45 72 43 15 3 Bear River near Conway, Mass. 17 01169000, 01169900, 01170100, 01171500, 0133300001169800 42 29 16 72 44 47 3 Poland Brook near Burkville, Mass. 15 01169000, 01169900, 01170100, 01333000, 0117150001169801 42 43 15 72 44 37 3 South River at North Poland Road near Burkville, Mass. 11 01169000, 01169900, 01170100, 01333000, 0117150001170575 42 31 23 72 32 24 6 Sawmill Brook near Montague, Mass. 9 01162500, 01171500, 01169900, 01174900, 0117450001171947 42 16 33 72 30 31 6 Bachelor Brook At Granby, Mass. 10 01171500, 01174900, 01175670, 01176000, 0118449001171970 42 15 08 72 34 26 6 Stony Brook at Morgan Street at South Hadley, Mass. 10 01169900, 01171500, 01174900, 01175670, 01176000,

01181000

01172810 42 26 15 72 02 26 8 Canesto Brook near Barre, Mass. 10 01175670, 01162500, 01176000, 0117490001173420 42 14 53 72 15 59 8 Muddy Brook at Ware, Mass. 9 01176000, 01175670, 01174900, 0117450001173450 42 14 56 72 15 53 8 Flat Brook near Ware, Mass. 15 01162500, 01096000, 01171500, 01174900, 0117567001175710 42 19 39 72 02 18 8 Five Mile River near North Brookfield, Mass. 11 01174500, 01174900, 01175670, 01176000

01175850 42 15 50 72 09 33 8 Mill River at West Brookfield, Mass. 12 01171500, 01176000, 01175670, 0117490001175890 42 13 31 72 10 12 8 Naultaug Brook at Warren, Mass. 14 01162500, 01174900, 01175670, 0117600001176100 42 10 13 72 15 41 8 Blodgett Brook near West Brimfield, Mass 15 01171500, 01176000

01176200 42 09 41 72 16 08 8 Kings Brook at West Brimfield, Mass. 14 01171500, 01176000, 01184490, 01121000

01176300 42 07 43 72 15 31 8 Foskett Mill Stream near Fentonville, Mass. 17 01171500, 01176000, 01184490, 0112100001176415 42 05 35 72 18 44 8 Chicopee Brook at Route 32, South Monson, Mass 10 01121000, 01174900, 01175670, 0118449001176780 42 08 52 72 24 00 8 Twelvemile Brook near North Wilbraham, Mass. 8 01176000, 01175670, 01171500, 01184490, 0112100001177360 42 05 06 72 28 50 6 South Branch Mill River at Porter Road near East 

Longmeadow, Mass.

10 01176000, 01175670, 01174900, 01174500, 01184490

Table 8. Descriptions of low-flow partial-record stations used in the regression analyses—Continued

Station 

No.

Latitude

° ′ ′′

Longitude

° ′ ′′

Basin

No. Station name

Number

of measurements Gaging stations used for correlation
58 Methods for Estimating Low-Flow Statistics for Massachusetts Streams 01178200 42 28 41 72 59 09 4 Westfield Brook at East Windsor, Mass. 17 01169900, 01181000, 01171500, 01180500, 01169000 01178300 42 26 50 72 51 29 4 Swift River at Swift River, Mass. 18 01169900, 01181000, 01171500, 01180500 01178490 42 24 02 72 52 36 4 West Branch at West Chesterfield, Mass. 8 01169000, 01169900, 01181000, 01187300 01179900 42 25 21 72 59 19 4 Trout Brook at West Worthington, Mass. 9 01169900, 01171500, 01181000 01180650 42 19 56 73 05 09 4 Shaker Mill Brook at Becket, Mass. 9 01169900, 01171500, 01181000, 01199050 01183210 42 07 05 72 48 01 4 Munn Brook near Westfield, Mass. 9 01187300, 01181000, 01171500, 01184490, 01188000 01184200 42 02 31 72 14 00 6 Still Brook near West Agawam, Mass. 18 01171500, 01181000, 01174900, 01175670, 01184490, 01121000 01184277 42 02 54 72 27 16 6 Scantic River near Hampden, Mass. 9 01174900, 01175670, 01176000, 01184490 01184855 42 09 40 73 04 19 5 West Branch Farmington River near Otis, Mass. 10 01187300, 01171500, 01188000, 01181000, 01199050 01185490 42 06 03 73 05 43 5 Clam River near West New Boston, Mass. 14 01181000, 01187300, 01188000 01186300 42 02 37 73 08 13 5 Sandy Brook near Sandisfield, Mass. 14 01181000, 01187300, 01188000, 01180500, 01199050, 01197000 01197120 42 26 28 73 17 47 2 South West Branch Housatonic River at Pittsfield, Mass. 12 01197000, 01333000, 01181000, 01169900 01197140 42 22 51 73 15 26 2 Yokun Brook near Lenox, Mass. 18 01169900, 01181000, 01199050, 01333000 01197180 42 17 59 73 12 53 2 Greenwater Brook at East Lee, Mass. 14 01197000, 01181000, 01187300, 01188000 01197230 42 16 13 73 15 06 2 Hop Brook near South Lee, Mass. 14 01181000, 01187300, 01188000, 01169900, 01199050 01198060 42 09 17 73 26 51 2 Fenton Brook near South Egremont, Mass. 17 01181000, 01187300, 01188000, 01999050

01198160 42 05 26 73 14 40 2 Umpachene River at Southfield, Mass. 17 01181000, 01188000, 01199050

01198200 42 03 11 73 19 35 2 Konkapot River at Ashley Falls, Mass. 34 01181000, 01199050, 01198000, 0119850001331380 42 33 40 73 09 06 1 South Brook at Windsor Road at Cheshire, Mass. 14 01169000, 01169900, 01197000, 0133300001332900 42 40 38 73 12 39 1 Hopper Brook at Hopper Road near South 

Williamstown, Mass.

15 01169000, 01169900, 01333000

01333100 42 41 16 73 13 50 1 Hemlock Brook near Williamstown, Mass. 14 01333000, 0133200001359967 42 32 19 73 20 01 1 Kinderhook Creek at Hancock, Mass. 9 01197000, 01333000, 01199050, 01198000

Table 8. Descriptions of low-flow partial-record stations used in the regression analyses

—Continued

Station 

No.

Latitude

° ′ ′′

Longitude

° ′ ′′

Basin

No. Station name

Number

of measurements Gaging stations used for correlation
Table 9 59

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50

01073860 Streamflow 0.17 0.18 0.23 0.28 0.33 0.38 0.44 0.51 -- -- 0.34 0.15 0.23

Variance .00303 .00229 .00118 .00063 .00058 .00079 .00124 .00270 -- -- .00061 .01182 .00123Standard error 12.7 11.1 7.9 5.8 5.6 6.5 8.1 12.0 -- -- 5.7 25.4 8.1Years 27.2 27.9 31.3 37.3 37.6 30.2 19.6 8.0 -- -- 17.9 3.5 5.5

01094340 Streamflow 1.05 1.33 2.21 3.78 5.40 7.53 10.0 13.0 -- -- 5.82 .89 2.29

Variance .0096 .00706 .00353 .00175 .00146 .00185 .00269 .00384 -- -- .00152 .01182 .00376Standard error 22.9 19.5 13.7 9.7 8.8 9.9 12.0 14.3 -- -- 9.0 25.4 14.2Years 17.2 19.3 26.7 36 37.1 29.5 19.9 13.6 -- -- 21.7 3.5 7.1

01094396 Streamflow .44 .58 1.04 1.69 2.20 2.95 -- -- -- -- 2.34 .34 1.08

Variance .0093 .00636 .00301 .00241 .00262 .00339 -- -- -- -- .00279 .01167 .00373Standard error 22.5 18.5 12.7 11.3 11.8 13.5 -- -- -- -- 12.2 25.3 14.1Years 19.6 25.1 37.9 33.3 25.5 19.8 -- -- -- -- 15.8 5.8 13.2

01094760 Streamflow .082 .12 .22 .43 .64 .98 1.42 1.95 3.53 -- .67 .056 .23

Variance .0061 .00468 .00272 .0016 .00133 .00141 .00176 .00228 .00381 -- .00141 .01201 .00481Standard error 18.1 15.9 12.1 9.2 8.4 8.7 9.7 11.0 14.3 -- 8.7 25.6 16.1Years 27.4 28.2 30.2 31.8 31.9 31.1 29.1 26.4 19.9 -- 26.1 13.4 17.3

01095220 Streamflow 1.23 1.65 2.79 4.39 5.99 7.97 10.1 12.7 19.6 28.9 6.42 1.06 2.73

Variance .00109 .0009 .00061 .00042 .00034 .00028 .00026 .00026 .0003 .00037 .00035 .00271 .00138Standard error 7.6 6.9 5.7 4.7 4.2 3.9 3.7 3.7 4.0 4.4 4.3 12.0 8.6Years 42.8 43.5 44 43.9 43.8 43.8 43.7 43.1 41.9 40.2 38.4 25.4 26.1

01095380 Streamflow .061 .10 -- -- .83 1.35 2.09 3.06 -- -- .94 .051 .22

Variance .00681 .00472 -- -- .00079 .0012 .00195 .00289 -- -- .00093 .01092 .00357Standard error 19.2 15.9 -- -- 6.5 8.0 10.2 12.4 -- -- 7.0 24.4 13.8Years 35.6 39 -- -- 49.6 43.8 37.1 31.2 -- -- 41.2 13.4 20.8

01095915 Streamflow .44 .61 1.09 1.82 2.52 3.52 4.77 6.16 10.7 17.4 2.73 .39 1.06

Variance .00454 .00338 .0018 .001 .00078 .0008 .00102 .00135 .00252 .00403 .00083 .00973 .00408Standard error 15.6 13.4 9.8 7.3 6.4 6.5 7.4 8.5 11.6 14.7 6.6 23.0 14.8Years 35.5 36.4 38.2 39.7 39.9 39.1 36.7 33.9 26.4 20.6 34 19.8 21.1

01095928 Streamflow .030 .054 .16 .36 .65 1.15 1.82 -- -- -- .74 .020 .16

Variance .00463 .00336 .00204 .00182 .0021 .00276 .00352 -- -- -- .00236 .01072 .00479Standard error 15.8 13.4 10.4 9.8 10.6 12.1 13.7 -- -- -- 11.2 24.2 16.0Years 38.8 41.8 43.5 40.4 36.6 32.4 28.6 -- -- -- 29.6 22.5 28.1

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14[Streamflow is in cubic feet per second; variance is in units of base-10 logarithms; standard error is in percent. No., number; --, station not used in analysis because standard error of estimate was too large or it was an outlier]
60 Methods for Estimating Low-Flow Statistics for Massachusetts Streams 01096000 Streamflow 6.40 7.80 11.0 15.0 18.0 22.0 27.0 32.0 48.0 69.0 19.0 6.52 11.7 Variance .00005 .00004 .00003 .00002 .00002 .00002 .00002 .00001 .00001 .00001 .00007 .00467 .00256 Standard error 1.6 1.5 1.3 1.1 1.0 1.0 .9 .9 .8 .8 2.0 15.8 11.7 Years 47 47 47 47 47 47 47 47 47 47 47 47 47 01096504 Streamflow .26 .31 .45 .63 .77 .92 1.08 1.25 1.60 2.00 .81 .24 .46 Variance .00307 .00207 .00078 .00029 .00032 .00056 .00092 .00138 .00242 .00359 .00037 .00405 .00095 Standard error 12.8 10.5 6.4 3.9 4.1 5.5 7.0 8.6 11.4 13.9 4.4 14.7 7.1 Years 26.9 31.1 46.5 65.1 57.5 40.7 27.3 18.7 10 6.7 36.8 9.4 18.3 01096505 Streamflow .50 .64 .97 1.41 1.82 2.34 2.89 3.50 4.98 6.80 1.94 .46 .97 Variance .0027 .00203 .00118 .00071 .00057 .00056 .00064 .00078 .00123 .00181 .00057 .00395 .00161 Standard error 12.0 10.4 7.9 6.1 5.5 5.5 5.8 6.4 8.1 9.8 5.5 14.5 9.3 Years 36.9 38.9 43.1 46.8 48 46.3 42.3 37.4 27.9 21.1 34.8 15.8 18.4 01096515 Streamflow 2.55 3.06 4.32 5.98 7.41 9.18 11.2 13.3 18.6 25.0 7.76 2.34 4.49 Variance .00262 .00196 .00114 .00081 .00081 .00096 .00125 .00162 .00261 .00378 .00084 .00337 .00132 Standard error 11.8 10.2 7.8 6.6 6.6 7.1 8.2 9.3 11.8 14.2 6.7 13.4 8.4 Years 34.9 37.1 42.2 41.7 37.1 31.6 25.5 20.5 12.6 8.5 21.7 8.3 11.8 01096805 Streamflow .65 .77 1.19 1.85 2.62 3.50 4.53 5.61 8.34 11.7 2.73 .54 1.09

Variance .00413 .00327 .00177 .00095 .00078 .00091 .00125 .0017 .00287 .00408 .00084 .00687 .00287Standard error 14.9 13.2 9.7 7.1 6.4 7.0 8.2 9.5 12.4 14.8 6.7 19.3 12.4Years 29.1 29.4 32 35.6 38.3 38.6 32.1 26.7 19.7 16.4 32 11.2 13.3

01096855 Streamflow .16 .18 .26 .39 .50 .65 .82 1.02 -- -- .53 .14 .25

Variance .00549 .00408 .00206 .00119 .00121 .00162 .00239 .00337 -- -- .00129 .00728 .00247Standard error 17.2 14.8 10.5 8.0 8.0 9.3 11.3 13.4 -- -- 8.3 19.8 11.5Years 18.5 20.6 27.8 32.9 30 23.4 16 11.3 -- -- 18.5 4.4 7.4

01096910 Streamflow .040 .060 .10 .15 .24 .34 .47 .69 1.30 2.20 .22 -- --

Variance .00039 .00032 .00025 .00019 .00016 .00014 .00013 .00012 .00011 .00010 .00088 -- --Standard error 4.5 4.2 3.6 3.2 2.9 2.7 2.6 2.5 2.4 2.4 6.8 -- --Years 11 11 11 11 11 11 11 11 11 11 11 -- --

01096935 Streamflow .91 1.07 1.54 2.39 3.19 4.05 5.24 6.69 10.5 -- 3.36 .76 1.55

Variance .00726 .0056 .00307 .00136 .00082 .00068 .00089 .00141 .00312 -- .00078 .0098 .00348Standard error 19.8 17.4 12.8 8.5 6.6 6.0 6.9 8.7 12.9 -- 6.4 23.1 13.6Years 16.1 17.1 21.7 29.9 34.3 36.2 30.9 23.9 12.8 -- 26.6 3.6 6.1

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14

—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
Table 9 61

01097280 Streamflow 1.11 1.33 1.78 2.60 3.42 4.40 5.49 6.77 -- 13.0 3.65 0.89 1.83

Variance .00382 .00292 .00176 .0009 .00063 .00062 .00079 .00113 -- .00316 .00063 .00574 .002Standard error 14.3 12.5 9.7 6.9 5.8 5.7 6.5 7.8 -- 13.0 5.8 17.6 10.3Years 21.6 22.7 26 32 34.9 33.7 29 22.9 -- 10 25.6 4 7.2

01097300 Streamflow .19 .29 .71 1.40 2.10 3.10 4.10 5.20 7.90 12.0 2.30 .12 --

Variance .00012 .00010 .00008 .00006 .00005 .00004 .00004 .00004 .00003 .00003 .00036 .01480 --Standard error 2.5 2.3 2.0 1.8 1.6 1.5 1.5 1.4 1.3 1.3 4.4 28.6 --Years 32 32 32 32 32 32 32 32 32 32 32 32 --

01099400 Streamflow 1.17 1.61 2.54 4.22 5.93 8.28 11.0 14.2 -- -- 6.52 .98 2.45

Variance .01153 .0081 .00399 .00175 .00128 .00151 .00221 .00322 -- -- .00134 .01505 .00483Standard error 25.1 20.9 14.6 9.7 8.3 9.0 10.9 13.1 -- -- 8.4 28.8 16.1Years 16.8 19.1 24.7 33 37.8 39.6 28.3 19.6 -- -- 27.6 3.8 7

01100608 Streamflow .18 .24 .36 .55 .73 .96 1.23 1.52 -- -- .78 .15 .36

Variance .00535 .00387 .00218 .00148 .00154 .00196 .00262 .00343 -- -- .00162 .0071 .00248Standard error 17.0 14.4 10.8 8.9 9.1 10.2 11.8 13.5 -- -- 9.3 19.6 11.5Years 29.8 32 37 39.9 34.8 26.5 18.9 14.1 -- -- 19.7 4.6 7.6

01100700 Streamflow .15 .22 .41 .60 .78 1.10 1.40 1.80 3.20 4.90 .67 .15 .36

Variance .00033 .00028 .00021 .00016 .00014 .00012 .00011 .00010 .00009 .00009 .00046 .01102 .00605Standard error 4.2 3.9 3.4 2.9 2.7 2.5 2.4 2.3 2.2 2.2 5.0 24.5 18.1Years 11 11 11 11 11 11 11 11 11 11 11 11 11

01101000 Streamflow -- -- -- -- -- -- 6.00 8.70 15.0 23.0 -- -- --

Variance -- -- -- -- -- -- .0000322 .0000298 .0000271 .00003 -- -- --

Standard error -- -- -- -- -- -- 1.3 1.3 1.2 1.2 -- -- --Years -- -- -- -- -- -- 50 50 50 50 -- -- --

01101100 Streamflow .45 .53 .77 1.20 1.55 1.93 2.32 2.81 3.76 4.75 1.64 .39 .81

Variance .00337 .00254 .00128 .0006 .00059 .0008 .00113 .00164 .00271 .00382 .00066 .00537 .00188Standard error 13.4 11.6 8.3 5.6 5.6 6.5 7.8 9.3 12.0 14.3 5.9 17.0 10.0Years 31.9 33.2 37.3 42 40.7 36.5 31.1 25.4 18.7 15 31.4 12.3 18.9

01102053 Streamflow .46 .49 .57 .69 .78 .94 1.13 1.36 2.00 2.85 .84 -- .58

Variance .00104 .00074 .00038 .00026 .00031 .00045 .00067 .00091 .00154 .00224 .00035 -- .00066Standard error 7.4 6.3 4.5 3.7 4.1 4.9 6.0 7.0 9.1 10.9 4.3 -- 5.9Years 28.6 30.8 35.6 38.1 35.9 30.9 24.6 19.9 11.7 7.8 26.7 -- 16.6

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
62 Methods for Estimating Low-Flow Statistics for Massachusetts Streams 01102490 Streamflow 0.19 0.24 0.36 0.58 0.77 0.99 1.20 1.45 -- -- 0.83 0.17 0.37 Variance .0044 .00321 .00172 .00108 .00121 .00167 .00223 .00293 -- -- .00134 .00623 .00217 Standard error 15.4 13.1 9.6 7.6 8.0 9.4 10.9 12.5 -- -- 8.4 18.3 10.8 Years 26.6 28.1 32.6 35.8 31.9 25.8 20.6 16.2 -- -- 22 8.3 12.6 01103015 Streamflow .45 .57 .87 1.29 1.64 2.04 2.41 2.79 3.60 4.48 1.76 .38 .84 Variance .00441 .00326 .00172 .00087 .00064 .00061 .00071 .00087 .00135 .00194 .00064 .00618 .00227 Standard error 15.4 13.2 9.6 6.8 5.8 5.7 6.1 6.8 8.5 10.2 5.8 18.3 11.0 Years 20.7 22.3 26.8 31.9 33.7 33 30.2 26.4 19.6 15 27.2 5.8 9.3 01103253 Streamflow .26 .32 .46 .72 .99 1.36 1.86 2.53 4.18 6.41 1.04 .18 .48 Variance .00185 .00146 .00098 .00062 .00052 .00055 .0007 .00097 .00168 .00252 .00056 .00408 .00176 Standard error 9.9 8.8 7.2 5.7 5.3 5.4 6.1 7.2 9.5 11.6 5.5 14.8 9.7 Years 34.6 34.8 36.8 38.2 38.7 37.2 33.7 29.6 23.3 19.3 31.1 11.8 15.6 01103435 Streamflow .25 .33 .51 .96 1.46 2.05 2.94 4.68 10.1 -- 1.51 .13 .54 Variance .00867 .00685 .00442 .00236 .00167 .00142 .00147 .00207 .0042 -- .00164 .01605 .00612 Standard error 21.7 19.2 15.4 11.2 9.4 8.7 8.8 10.5 15.0 -- 9.3 29.8 18.2 Years 22.3 22.7 23.9 27.7 29.3 29.7 28.7 25.3 19.3 -- 24.9 7.1 10.2 01103440 Streamflow .15 .19 .30 .50 .70 .95 1.27 1.70 2.74 -- .74 .11 .31

Variance .00397 .00309 .00192 .00129 .00117 .0013 .00162 .00215 .00349 -- .00121 .00675 .00259Standard error 14.6 12.9 10.1 8.3 7.9 8.3 9.3 10.7 13.7 -- 8.0 19.1 11.8Years 29.7 30.6 33.9 35.2 34.1 31.6 27.8 23.5 16.7 -- 24.7 7.8 12.4

01104960 Streamflow .10 .13 .19 .28 .37 .49 .63 .81 1.19 1.66 .40 .079 .19

Variance .00237 .00196 .00139 .00092 .0007 .00057 .00053 .00054 .00068 .00093 .00069 .00369 .00176Standard error 11.2 10.2 8.6 7.0 6.1 5.5 5.3 5.4 6.0 7.0 6.1 14.1 9.7Years 27 27.1 28.1 29.7 31 32 32.5 32.1 28.6 24.4 23.9 7.8 9.6

01104980 Streamflow .38 .47 .67 1.05 1.51 2.07 2.71 3.60 5.85 8.93 1.71 .29 .66

Variance .00214 .00179 .0013 .00085 .00059 .00043 .00033 .00027 .00028 .00042 .00058 .00418 .00206Standard error 10.7 9.8 8.3 6.7 5.6 4.8 4.2 3.8 3.9 4.7 5.5 15.0 10.5Years 25.6 25.6 26.1 27.2 28.3 29.1 29.7 29.9 29.1 27.3 24.7 11.2 11.2

01105100 Streamflow -- -- -- 1.86 2.04 2.26 -- 2.84 3.40 3.99 2.13 -- --

Variance -- -- -- .00011 .00009 .00009 -- .00012 .00018 .00025 .0001 -- --Standard error -- -- -- 2.4 2.2 2.2 -- 2.5 3.1 3.6 2.3 -- --Years -- -- -- 33.4 33.3 33 -- 30.4 25.1 20.7 26.3 -- --

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14

—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
Table 9 63

01105270 Streamflow -- -- -- -- -- 2.43 2.87 3.50 -- -- 2.10 -- --

Variance -- -- -- -- -- .00332 .00292 .00304 -- -- .00392 -- --Standard error -- -- -- -- -- 13.3 12.5 12.7 -- -- 14.5 -- --Years -- -- -- -- -- 17.2 17.2 16.7 -- -- 10.4 -- --

01105568 Streamflow 0.12 0.15 0.25 0.38 0.53 -- -- -- -- -- -- 0.093 0.25

Variance .00773 .00535 .003 .00266 .00357 -- -- -- -- -- -- .01132 .00366Standard error 20.5 17.0 12.7 11.9 13.8 -- -- -- -- -- -- 24.9 14.0Years 25.8 27.9 29.9 25.5 19.3 -- -- -- -- -- -- 4.6 7.3

01105575 Streamflow .015 .025 .062 .13 .22 .33 .47 .64 1.16 1.87 .25 .009 .055

Variance .00805 .0064 .00424 .00293 .00237 .00205 .00192 .00192 .00221 .00272 .00233 .01309 .00627Standard error 20.9 18.6 15.1 12.5 11.2 10.5 10.1 10.1 10.9 12.1 11.1 26.8 18.4Years 24.9 25.2 26.2 27 27.4 27.7 27.9 27.8 26.1 23.7 23.4 9 10.5

01105582 Streamflow -- -- -- -- 6.92 9.83 12.4 -- -- -- 8.15 -- --

Variance -- -- -- -- .00399 .00357 .00349 -- -- -- .00371 -- --Standard error -- -- -- -- 14.6 13.8 13.7 -- -- -- 14.1 -- --Years -- -- -- -- 31.3 30.2 33.4 -- -- -- 24.5 -- --

01105600 Streamflow .20 .29 .48 .83 1.20 1.70 2.20 2.71 4.10 5.40 1.40 .16 .44

Variance .00010 .00008 .00006 .00005 .00004 .00004 .00003 .00003 .00003 .00003 .00029 .00525 .00288Standard error 2.3 2.1 1.8 1.6 1.5 1.4 1.3 1.2 1.2 1.2 3.9 16.8 12.4Years 30 30 30 30 30 30 30 30 30 30 30 30 30

01105630 Streamflow .35 .46 .73 1.08 1.40 1.92 2.50 3.19 -- -- 1.55 .27 .71

Variance .00368 .00234 .00104 .00069 .00083 .00145 .00231 .00336 -- -- .001 .0061 .00145Standard error 14.0 11.2 7.4 6.1 6.6 8.8 11.1 13.4 -- -- 7.3 18.1 8.8Years 24.9 28.4 34.6 35.2 31.1 23.3 16.6 12.1 -- -- 20.2 5.3 11.6

01105670 Streamflow .14 .17 .23 .30 .36 .43 .50 .58 -- -- .41 -- --

Variance .00729 .00492 .0026 .00145 .00134 .00169 .00226 .00316 -- -- .00147 -- --Standard error 19.9 16.3 11.8 8.8 8.4 9.5 11.0 13.0 -- -- 8.8 -- --Years 13.8 15.9 19.4 22.7 22.3 19.5 15.8 11.2 -- -- 15.4 -- --

01105820 Streamflow .047 .071 .14 .26 .41 .62 -- -- -- -- .53 .033 .14

Variance .0107 .0073 .00371 .00218 .00226 .00315 -- -- -- -- .00279 .01612 .00485Standard error 24.2 19.9 14.1 10.8 11.0 13.0 -- -- -- -- 12.2 29.9 16.1Years 27.5 29.8 35.1 37.8 37.2 32.1 -- -- -- -- 24.2 5.7 10.1

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
64 Methods for Estimating Low-Flow Statistics for Massachusetts Streams 01105830 Streamflow -- 0.021 0.043 0.085 0.14 0.23 0.34 0.49 0.95 1.60 0.17 0.010 0.044 Variance -- .00427 .00322 .0024 .00195 .00164 .00146 .00136 .00137 .00152 .00191 .00796 .00437 Standard error -- 15.1 13.1 11.3 10.2 9.3 8.8 8.5 8.5 9.0 10.1 20.8 15.3 Years -- 31.9 32 31.8 31.9 32 32.2 32.2 31.3 29.6 26.1 11.4 11.6 01105861 Streamflow 0.60 .79 1.23 1.81 2.38 2.97 3.93 5.09 -- -- 3.11 .49 1.24 Variance .00343 .00238 .00148 .00154 .00194 .00252 .0035 .00469 -- -- .00261 .00525 .00192 Standard error 13.5 11.3 8.9 9.1 10.2 11.6 13.7 15.9 -- -- 11.8 16.8 10.1 Years 39.8 41.3 41.3 34.5 28.6 24.5 19.7 15.6 -- -- 16.4 9.2 13.1 011058839 Streamflow -- -- -- 5.95 -- 8.45 -- -- -- 10.6 -- -- -- Variance -- -- -- .00298 -- .00284 -- -- -- .0028 -- -- -- Standard error -- -- -- 12.6 -- 12.3 -- -- -- 12.2 -- -- -- Years -- -- -- 44.4 -- 38.3 -- -- -- 15.6 -- -- -- 011059106 Streamflow .090 .11 .15 .22 .32 .41 .52 .64 -- -- .41 .076 .15 Variance .00611 .00509 .00368 .00267 .0022 .00196 .00176 .00144 -- -- .00225 .00819 .00413 Standard error 18.1 16.5 14.0 11.9 10.8 10.2 9.7 8.8 -- -- 11.0 21.1 14.9 Years 22.8 23.2 24.8 25.4 24.4 22.6 21.3 21.6 -- -- 14.4 4.4 5.4 01105930 Streamflow .41 .54 .91 1.53 2.29 3.34 4.63 -- -- -- 2.71 .32 .94

Variance .00391 .00308 .00196 .00122 .00092 .00083 .00091 -- -- -- .00093 .00592 .00266Standard error 14.5 12.8 10.2 8.1 7.0 6.6 7.0 -- -- -- 7.0 17.9 11.9Years 36.1 36.2 37.7 38 38.1 37.7 36.5 -- -- -- 31.7 10.3 13

01105935 Streamflow -- .48 -- .98 -- -- -- -- -- 4.27 -- -- --

Variance -- .00101 -- .00041 -- -- -- -- -- .00076 -- -- --Standard error -- 7.3 -- 4.7 -- -- -- -- -- 6.4 -- -- --Years -- 36.8 -- 38.2 -- -- -- -- -- 26.3 -- -- --

01105937 Streamflow .085 .13 .28 .60 1.05 1.76 2.80 4.25 8.78 -- 1.29 .062 .28

Variance .00491 .00395 .00257 .00155 .00111 .00093 .00097 .00117 .00183 -- .00114 .00818 .00382Standard error 16.2 14.5 11.7 9.1 7.7 7.0 7.2 7.9 9.9 -- 7.8 21.1 14.3Years 35.6 35.6 36.8 37.7 38.3 38.5 38.1 36.6 31.6 -- 34 12.5 15

01105947 Streamflow .18 .26 .47 .82 1.21 1.65 2.24 3.04 5.21 8.41 1.52 .14 .46

Variance .00693 .00543 .00356 .00231 .00176 .00156 .00151 .00166 .00239 .00347 .00161 .00919 .00396Standard error 19.3 17.1 13.8 11.1 9.7 9.1 9.0 9.4 11.3 13.6 9.3 22.3 14.6Years 25.8 27 30.2 32.8 33.8 33 30.8 27.7 22.1 17.4 24.7 5.1 6.9

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
Table 9 65

01106000 Streamflow 0.070 0.080 0.12 0.30 0.63 1.20 2.20 3.40 6.50 9.20 0.65 0.054 0.15

Variance .00016 .00013 .00010 .00008 .00007 .00006 .00005 .00005 .00004 .00004 .00050 .01015 .00557Standard error 2.9 2.7 2.3 2.0 1.9 1.8 1.7 1.6 1.5 1.5 5.2 23.5 17.3Years 37 37 37 37 37 37 37 37 37 37 37 37 37

01106460 Streamflow .40 .50 .74 1.10 1.44 1.81 2.26 2.80 3.99 5.66 1.64 .34 .76

Variance .00162 .00112 .00063 .00057 .00075 .00106 .00146 .00194 .00293 .00415 .0009 .00259 .0009Standard error 9.3 7.7 5.8 5.5 6.3 7.5 8.8 10.2 12.5 14.9 6.9 11.8 6.9Years 42.5 45.5 48.6 45.2 37.9 29.5 22.2 16.8 10.9 7.9 21.8 8.2 14.9

01107000 Streamflow .020 .030 .070 .17 .32 .60 1.00 1.60 3.70 5.50 .19 -- --

Variance .00059 .00050 .00038 .00029 .00025 .00022 .00020 .00018 .00017 .00016 .00179 -- --Standard error 5.6 5.1 4.5 3.9 3.6 3.4 3.2 3.1 3.0 2.9 9.8 -- --Years 11 11 11 11 11 11 11 11 11 11 11 -- --

01107400 Streamflow -- 2.06 -- 3.76 4.64 5.72 6.86 -- -- -- 5.01 1.32 2.73

Variance -- .00058 -- .00033 .00027 .00023 .0002 -- -- -- .00028 .00137 .00075Standard error -- 5.5 -- 4.2 3.8 3.5 3.3 -- -- -- 3.9 8.5 6.3Years -- 35.3 -- 35.3 35.5 35.8 36.5 -- -- -- 31.2 16.8 17

01108140 Streamflow -- -- -- 3.21 3.78 4.42 5.13 5.89 7.45 8.96 4.02 -- --

Variance -- -- -- .00033 .00035 .00047 .00067 .00093 .00154 .00217 .0004 -- --Standard error -- -- -- 4.2 4.3 5.0 6.0 7.0 9.1 10.8 4.6 -- --Years -- -- -- 42.2 39.3 33.2 25.7 19.4 11.8 8.5 25.9 -- --

01108180 Streamflow .60 .75 1.07 1.48 1.90 2.41 2.99 3.64 -- -- 2.09 .47 1.06

Variance .00307 .00213 .00116 .0008 .00091 .00131 .0019 .00263 -- -- .00106 .00495 .00147Standard error 12.8 10.7 7.9 6.5 7.0 8.3 10.1 11.8 -- -- 7.5 16.3 8.8Years 27.9 30.1 34.9 36.3 32.7 26 19.3 14.3 -- -- 20.8 5.8 10.4

01108600 Streamflow .036 .058 .14 .32 .61 1.05 -- -- -- -- .90 .025 .15

Variance .00441 .00311 .00186 .0018 .00252 .0035 -- -- -- -- .00329 .00896 .00354Standard error 15.4 12.9 10.0 9.8 11.6 13.7 -- -- -- -- 13.3 22.1 13.8Years 49.5 49.4 49.5 47.9 45.3 40.8 -- -- -- -- 32.2 19.5 25.9

01109087 Streamflow .84 1.11 1.84 2.99 4.22 5.95 7.98 10.4 16.3 24 4.67 .62 1.91

Variance .00367 .0031 .00221 .00155 .0012 .00093 .00077 .00067 .00062 .00069 .00116 .00578 .00294Standard error 14.0 12.9 10.9 9.1 8.0 7.0 6.4 6.0 5.7 6.1 7.9 17.6 12.5Years 27.5 27.2 27.7 28.2 28.9 29.8 30.7 31.4 31.6 30.4 22.9 8.8 10.1

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
66 Methods for Estimating Low-Flow Statistics for Massachusetts Streams 01109090 Streamflow 0.14 0.19 0.34 0.58 0.86 1.24 1.80 2.53 -- -- 1.04 0.11 0.34 Variance .00509 .00371 .00212 .00149 .00157 .00213 .00305 .00418 -- -- .00185 .00716 .00254 Standard error 16.5 14.1 10.6 8.9 9.1 10.7 12.8 15.0 -- -- 9.9 19.7 11.6 Years 29.1 31.6 36.5 38.7 35.3 28.1 20.9 15.7 -- -- 22.2 5.6 10 01109200 Streamflow -- -- .090 .16 .29 .48 .78 1.50 3.40 5.00 .26 -- -- Variance -- -- .00008 .00006 .00005 .00005 .00004 .00004 .00004 .00003 .00037 -- -- Standard error -- -- 2.1 1.8 1.7 1.6 1.5 1.4 1.4 1.4 4.4 -- -- Years -- -- 10 10 10 10 10 10 10 10 10 -- -- 01109225 Streamflow .083 .11 .19 .35 .55 -- -- -- 3.95 6.60 .60 .065 .20 Variance .00687 .00591 .00452 .00315 .00238 -- -- -- .00167 .00214 .00228 .00893 .00487 Standard error 19.3 17.8 15.6 13.0 11.3 -- -- -- 9.4 10.7 11.0 22.0 16.2 Years 33.9 33.8 34.3 35.4 36.6 -- -- -- 34.3 29.2 24.9 6.5 7.2 01109460 Streamflow 1.11 1.36 1.97 2.94 3.84 4.74 5.48 6.29 8.36 10.9 4.13 .94 -- Variance .00366 .00289 .00176 .00097 .00066 .00054 .0005 .00049 .00066 .00102 .00063 .00480 -- Standard error 14.0 12.4 9.7 7.2 5.9 5.4 5.2 5.1 5.9 7.4 5.8 16.1 -- Years 17.7 18.5 21.3 25.5 28.2 29.2 29.6 29.5 24.9 18.2 21.4 3.4 -- 01111142 Streamflow .068 .11 .21 .36 .52 -- -- -- -- -- -- -- .20

Variance .01236 .00839 .00405 .00349 .00422 -- -- -- -- -- -- -- .00554Standard error 26.0 21.3 14.7 13.7 15.0 -- -- -- -- -- -- -- 17.3Years 20.2 23.6 28.5 27.4 23.3 -- -- -- -- -- -- -- 9.3

01111200 Streamflow 2.10 2.50 3.20 4.50 6.10 7.90 10.0 13.0 20.0 29.0 6.80 1.80 3.23

Variance .00010 .00008 .00006 .00005 .00004 .00004 .00003 .00003 .00003 .00003 .00016 .00290 .00159Standard error 2.3 2.1 1.8 1.6 1.5 1.4 1.3 1.3 1.2 1.2 2.9 12.4 9.2Years 28 28 28 28 28 28 28 28 28 28 28 28 28

01111225 Streamflow .78 .90 1.15 1.49 1.78 2.12 2.46 2.79 3.46 4.18 1.80 .63 1.19

Variance .001 .00071 .00039 .00035 .00048 .00074 .00106 .00141 .00215 .00297 .00051 .00212 .00066Standard error 7.3 6.1 4.5 4.3 5.0 6.3 7.5 8.7 10.7 12.6 5.2 10.6 5.9Years 29 31 34.7 31.6 25.7 19.4 14.6 11.4 7.8 5.8 18.3 8.2 14.7

01111300 Streamflow .50 .66 1.00 1.80 2.60 3.90 5.60 7.60 12.0 18.0 2.40 .25 1.16

Variance .00013 .00011 .00008 .00006 .00005 .00005 .00004 .00004 .00004 .00004 .00034 .01227 .00674Standard error 2.6 2.4 2.1 1.8 1.7 1.6 1.5 1.5 1.4 1.4 4.2 25.9 19.1Years 29 29 29 29 29 29 29 29 29 29 29 29 29

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14

—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
Table 9 67

01112190 Streamflow 0.19 0.24 0.36 0.57 0.78 1.05 1.37 1.74 2.56 -- 0.79 0.14 0.39

Variance .00505 .00396 .0025 .00167 .00155 .00178 .00227 .00292 .00446 -- .00162 .00877 .00326Standard error 16.5 14.6 11.6 9.4 9.1 9.7 11.0 12.5 15.5 -- 9.3 21.8 13.2Years 23.5 24.1 26.1 27.4 26.7 24.5 20.9 17.2 12 -- 19.5 6.2 9.6

01123140 Streamflow 1.44 1.64 2.16 2.84 3.54 4.28 4.89 5.67 7.40 -- 3.85 1.29 2.20

Variance .00342 .00253 .00133 .00079 .00081 .00116 .00159 .00222 .00378 -- .00096 .00439 .00138Standard error 13.5 11.6 8.4 6.5 6.6 7.9 9.2 10.9 14.2 -- 7.1 15.3 8.6Years 14.9 17 23.1 28 25.9 19.1 15.3 10.8 5.9 -- 12.6 2.4 5.3

01123161 Streamflow -- -- -- 1.38 2.22 2.99 -- -- -- -- 2.25 -- --

Variance -- -- -- .00342 .00207 .00272 -- -- -- -- .00227 -- --Standard error -- -- -- 13.5 10.5 12.1 -- -- -- -- 11.0 -- --Years -- -- -- 30.5 33.4 29 -- -- -- -- 28.2 -- --

01123200 Streamflow .10 .15 .28 .50 .79 -- -- -- 4.04 6.64 .78 .086 .25

Variance .002 .00145 .00083 .00059 .00063 -- -- -- .00228 .00328 .00066 .00325 .00141Standard error 10.3 8.8 6.6 5.6 5.8 -- -- -- 11.0 13.2 5.9 13.2 8.7Years 51.1 52.8 55.6 56.6 55.1 -- -- -- 31.2 24.9 45.6 17 21.1

01124390 Streamflow .26 .33 .50 .84 1.25 1.77 2.4 3.23 -- -- 1.38 .20 .52

Variance .00789 .00618 .00394 .00247 .00207 .00218 .00263 .00341 -- -- .00206 .01033 .00422Standard error 20.7 18.3 14.5 11.5 10.5 10.8 11.8 13.5 -- -- 10.5 23.7 15.0Years 23.9 25.6 30.8 34.6 33.3 29.5 25 20.6 -- -- 20.8 4.3 6.1

01162500 Streamflow -- -- -- -- -- -- -- -- -- 17.0 -- .45 --

Variance -- -- -- -- -- -- -- -- -- .00001 -- .00357 --Standard error -- -- -- -- -- -- -- -- -- .8 -- 13.8 --Years -- -- -- -- -- -- -- -- -- 76 -- 76 --

01162900 Streamflow 2.79 3.33 4.61 6.33 8.18 10.1 12.2 14.3 19.5 25.0 8.32 2.57 4.52

Variance .00106 .00085 .00057 .00041 .00036 .00038 .00043 .0005 .00072 .00097 .00037 .00148 .00076Standard error 7.5 6.7 5.5 4.7 4.4 4.5 4.8 5.2 6.2 7.2 4.4 8.9 6.4Years 37.5 38 38.9 39 38.1 36.3 33.6 30.5 24.2 19.8 28.2 11.7 12.4

01163250 Streamflow .94 1.56 2.29 3.16 3.67 4.65 5.72 7.06 10.3 -- 4.02 .90 2.07

Variance .00201 .00136 .00065 .00043 .00054 .00089 .00147 .00221 .00409 -- .00061 .00324 .0012Standard error 10.4 8.5 5.9 4.8 5.4 6.9 8.8 10.9 14.8 -- 5.7 13.2 8.0Years 33.5 35.6 40 42.5 40.6 34.1 26.2 19.9 12 -- 28.4 10.2 15.5

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
68 Methods for Estimating Low-Flow Statistics for Massachusetts Streams 01164300 Streamflow 0.35 0.52 1.02 1.77 2.65 3.80 5.11 -- -- -- 2.87 0.32 1.01 Variance .00965 .0069 .00389 .00274 .00265 .00309 .00382 -- -- -- .00274 .01163 .0046 Standard error 22.9 19.3 14.4 12.1 11.9 12.9 14.3 -- -- -- 12.1 25.2 15.7 Years 27 29.7 34.9 35.9 33.2 28.1 22.9 -- -- -- 21.6 8.1 10.9 01165090 Streamflow .15 .20 -- -- -- -- -- -- -- -- -- -- -- Variance .00941 .00641 -- -- -- -- -- -- -- -- -- -- -- Standard error 22.6 18.6 -- -- -- -- -- -- -- -- -- -- -- Years 22 26.4 -- -- -- -- -- -- -- -- -- -- -- 01165250 Streamflow -- -- .52 .96 1.28 1.98 -- -- -- -- -- -- .50 Variance -- -- .00159 .00124 .00165 .00259 -- -- -- -- -- -- .0043 Standard error -- -- 9.2 8.1 9.4 11.8 -- -- -- -- -- -- 15.2 Years -- -- 46.9 43.9 39.2 34.2 -- -- -- -- -- -- 25.1 01165500 Streamflow .70 .87 -- -- -- -- -- -- 7.40 10.0 -- -- -- Variance .00005 .00004 -- -- -- -- -- -- .00001 .00001 -- -- -- Standard error 1.6 1.4 -- -- -- -- -- -- .8 .8 -- -- -- Years 65 65 -- -- -- -- -- -- 65 65 -- -- -- 01166105 Streamflow .99 1.10 1.40 2.00 2.50 2.90 3.40 4.00 5.10 6.30 2.60 -- --

Variance .00030 .00025 .00019 .00015 .00012 .00011 .00010 .00009 .00008 .00008 .00133 -- --Standard error 4.0 3.6 3.2 2.8 2.6 2.4 2.3 2.2 2.1 2.1 8.4 -- --Years 5 5 5 5 5 5 5 5 5 5 5 -- --

01167200 Streamflow 1.91 2.43 3.48 5.21 6.58 7.71 8.66 9.61 -- -- 6.63 1.46 2.89

Variance .0011 .00097 .00088 .00094 .00103 .00109 .00113 .00112 -- -- .00107 .00225 .00144Standard error 7.6 7.2 6.8 7.1 7.4 7.6 7.8 7.7 -- -- 7.5 11.0 8.8Years 42.2 42.1 41.1 38.6 36.2 34.7 34.1 34.2 -- -- 27.8 20.9 17.5

01168300 Streamflow 1.97 2.39 3.27 4.70 6.11 7.77 9.72 12.3 17.8 25.3 6.36 1.69 3.05

Variance .00071 .00055 .00036 .00024 .00021 .00024 .0003 .00041 .00066 .001 .00024 .00127 .00063Standard error 6.1 5.4 4.4 3.6 3.3 3.6 4.0 4.7 5.9 7.3 3.6 8.2 5.8Years 43.8 44.1 45.7 47.2 47.5 46.4 44.2 41.6 36 30.8 41.6 16.9 18.7

01168400 Streamflow -- 4.06 5.05 6.52 7.91 9.44 11.1 13.1 17.1 22.2 8.14 3.24 4.84

Variance -- .00057 .0003 .00019 .00025 .00041 .00063 .00096 .00165 .00252 .00028 .0012 .00045Standard error -- 5.5 4.0 3.2 3.6 4.7 5.8 7.1 9.4 11.6 3.9 8.0 4.9Years -- 49.2 55.5 61 56.4 45.6 35.3 26.6 17 11.9 39.1 8.1 12

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14

—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
Table 9 69

01168650 Streamflow -- -- 4.39 5.55 6.57 7.72 8.94 10.3 13.3 17.1 6.78 2.89 4.25

Variance -- -- .00028 .0002 .00026 .0004 .0006 .00087 .00149 .00228 .00028 .00096 .00036Standard error -- -- 3.9 3.3 3.7 4.6 5.6 6.8 8.9 11.0 3.9 7.1 4.4Years -- -- 68 76 67.1 50.7 36.6 26.2 15.2 10 37.1 7.7 11.3

01169000 Streamflow 9.20 11.0 15.0 21.0 27.0 33.0 40.0 49.0 68.0 92.0 27.4 8.46 13.9

Variance .00004 .00004 .00003 .00002 .00002 .00002 .00001 .00001 .00001 .000012 .00007 .00118 .00065Standard error 1.5 1.4 1.2 1.1 1.0 .9 .9 .8 .8 .8 2.0 7.9 5.9Years 57 57 57 57 57 57 57 57 57 57 57 57 57

01169600 Streamflow .80 .96 1.29 1.80 2.32 2.92 3.62 4.48 6.41 9.07 2.41 .70 1.20

Variance .0012 .00082 .00041 .00025 .00034 .00058 .00092 .0014 .00244 .00376 .00039 .00179 .00063Standard error 8.0 6.6 4.7 3.6 4.2 5.5 7.0 8.6 11.4 14.2 4.5 9.8 5.8Years 44.5 46.8 52.3 60.5 56.6 45.4 35.6 27.5 17.9 12.7 39.7 8.8 13.7

01169800 Streamflow .22 .29 .44 .69 .96 1.32 1.78 2.42 4.12 -- 1.02 .19 .39

Variance .00155 .00108 .00059 .00047 .00066 .00103 .00156 .00226 .00389 -- .00075 .0026 .00103Standard error 9.1 7.6 5.6 5.0 5.9 7.4 9.1 11.0 14.4 -- 6.3 11.8 7.4Years 40.7 42 45.5 49.2 47.1 41.2 34.2 27.9 18.7 -- 35.9 11.2 16.3

01169801 Streamflow 2.41 2.75 3.44 4.24 4.95 5.79 6.69 7.77 9.98 12.8 5.07 2.17 3.10

Variance .00017 .00011 .00007 .00008 .00013 .0002 .0003 .00043 .00069 .00103 .00016 .00051 .00021Standard error 3.0 2.4 1.9 2.1 2.6 3.3 4.0 4.8 6.1 7.4 2.9 5.2 3.3Years 33.6 34.1 36.1 39.4 37.2 32.1 27.4 23.6 18.3 15 28.4 14.5 17.9

01169900 Streamflow 3.70 4.32 5.70 7.40 9.10 11.0 13.0 16.0 22.0 30.0 9.60 3.32 5.37

Variance .00007 .00006 .00004 .00003 .00003 .00003 .00002 .00002 .00002 .00002 .00014 .00165 .00091Standard error 1.9 1.8 1.5 1.3 1.2 1.2 1.1 1.1 1.0 1.0 2.7 9.4 6.9Years 30 30 30 30 30 30 30 30 30 30 30 30 30

01170100 Streamflow -- 7.10 8.80 12.0 14.6 17.6 21.0 26.0 36.0 49.0 15.0 4.81 7.61

Variance -- .00007 .00005 .00004 .00003 .00003 .00003 .00002 .00002 .00002 .00013 .00179 .00098Standard error -- 1.9 1.6 1.4 1.3 1.2 1.2 1.1 1.1 1.1 2.6 9.8 7.2Years -- 29 29 29 29 29 29 29 29 29 29 29 29

01170575 Streamflow 3.80 4.20 5.33 6.50 7.48 8.60 9.79 11.0 13.7 -- 7.73 3.48 5.05

Variance .00253 .00181 .00088 .00066 .00082 .00118 .00172 .00235 .00399 -- .00088 .00323 .00105Standard error 11.6 9.8 6.8 5.9 6.6 7.9 9.6 11.2 14.6 -- 6.8 13.1 7.5Years 22.7 24.9 31.4 29.2 23.2 16.3 11 7.7 4.2 -- 13.5 2.3 3.8

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
70 Methods for Estimating Low-Flow Statistics for Massachusetts Streams 01171500 Streamflow 6.70 7.80 10.0 14.0 17.0 21.0 25.0 29.0 40.0 55.0 18.0 6.31 10.0 Variance .00004 .00003 .00002 .00002 .00002 .00001 .00001 .00001 .00001 .00001 .00007 .00087 .00048 Standard error 1.4 1.3 1.1 1.0 .9 .9 .8 .8 .7 .7 2.0 6.8 5.0 Years 57 57 57 57 57 57 57 57 57 57 57 57 57 01171800 Streamflow .55 .63 .79 1.10 1.40 1.70 2.00 2.30 3.60 4.80 1.50 .46 .89 Variance .00019 .00016 .00012 .00010 .00008 .00007 .00006 .00006 .00005 .00005 .00039 .00883 .00485 Standard error 3.2 2.9 2.6 2.3 2.1 1.9 1.8 1.8 1.7 1.7 4.5 21.9 16.1 Years 11 11 11 11 11 11 11 11 11 11 11 11 11 01171947 Streamflow 1.61 1.97 3.06 4.62 6.02 7.42 8.75 10.5 14.7 20.4 6.96 1.49 3.03 Variance .00386 .00301 .00169 .00102 .00088 .0009 .00101 .00121 .00188 .00282 .00086 .00477 .00195 Standard error 14.4 12.7 9.5 7.4 6.8 6.9 7.3 8.0 10.0 12.3 6.8 16.0 10.2 Years 34.2 35.7 39.8 42.7 44.4 45.4 44.1 40.5 31.9 24.4 34.1 8.3 11 01171970 Streamflow .85 1.11 1.91 3.38 5.12 7.17 9.62 -- -- -- 5.65 -- -- Variance .00851 .00637 .00333 .00189 .0021 .00291 .00402 -- -- -- .00226 -- -- Standard error 21.5 18.5 13.3 10.0 10.6 12.5 14.7 -- -- -- 11.0 -- -- Years 24.1 26.7 34.1 41.6 34.3 25.4 18.9 -- -- -- 20.9 -- -- 01172810 Streamflow 1.38 1.55 2.05 2.64 3.18 3.69 4.19 4.70 -- -- 3.36 1.29 2.02

Variance .0047 .00352 .00176 .00108 .00113 .00149 .00202 .00268 -- -- .00122 .0055 .00191Standard error 15.9 13.7 9.7 7.6 7.8 8.9 10.4 12.0 -- -- 8.1 17.2 10.1Years 13.4 14.6 21.7 25.8 20 13.9 9.8 7.1 -- -- 11.1 1.7 3.1

01173260 Streamflow -- -- .040 .15 .34 .56 .88 1.40 2.60 3.60 .26 -- --

Variance -- -- .00058 .00045 .00038 .00033 .00030 .00028 .00025 .00025 .00288 -- --Standard error -- -- 5.6 4.9 4.5 4.2 4.0 3.9 3.7 3.6 12.4 -- --Years -- -- 9 9 9 9 9 9 9 9 9 -- --

01173420 Streamflow 2.37 2.68 3.69 4.96 6.08 7.40 8.82 10.2 13.5 17.1 6.47 2.17 3.56

Variance .00319 .00251 .00136 .00075 .00055 .0005 .00061 .00079 .00133 .00199 .00054 .00398 .00165Standard error 13.1 11.6 8.5 6.3 5.4 5.2 5.7 6.5 8.4 10.3 5.4 14.6 9.4Years 22 22.8 27.2 31.7 34.8 36.9 33.7 28.9 20 14.4 29.5 4.3 6.1

01173450 Streamflow .22 .27 .44 .71 1.03 1.37 1.78 2.22 3.58 5.33 1.09 .20 .42

Variance .00133 .00105 .00062 .00044 .00048 .0006 .00077 .00097 .00159 .0023 .00053 .00239 .00111Standard error 8.4 7.5 5.7 4.8 5.0 5.6 6.4 7.2 9.2 11.1 5.3 11.3 7.7Years 37 37.9 39.7 41 40.4 37.9 34.7 31.4 24.2 19 32.1 15.3 17.7

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14

—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
Table 9 71

01174000 Streamflow 0.020 0.050 0.14 0.31 0.56 0.81 1.14 1.55 2.50 3.60 0.50 -- --

Variance .00014 .00011 .00009 .00007 .00006 .00005 .00004 .00004 .00004 .00004 .00052 -- --Standard error 2.7 2.5 2.1 1.9 1.7 1.6 1.5 1.5 1.4 1.4 5.3 -- --Years 34 34 34 34 34 34 34 34 34 34 34 -- --

01174050 Streamflow .16 .19 .27 .50 .91 1.21 1.57 1.91 2.98 4.44 1.85 -- --

Variance .00170 .00143 .00108 .00084 .00071 .00062 .00056 .00052 .00047 .00046 .00369 -- --Standard error 9.5 8.7 7.6 6.7 6.1 5.8 5.5 5.3 5.0 4.9 14.0 -- --Years 2 2 2 2 2 2 2 2 2 2 2 -- --

01174565 Streamflow .90 1.00 1.40 2.09 2.94 4.10 5.49 6.15 8.12 11.9 3.24 -- --

Variance .00010 .00008 .00006 .00005 .00004 .00004 .00003 .00003 .00040 .000026 .00028 -- --Standard error 2.3 2.1 1.8 1.6 1.5 1.4 1.3 1.3 4.6 1.2 3.8 -- --Years 2 2 2 2 2 2 2 2 2 2 2 -- --

01174900 Streamflow .11 .13 .21 .34 .52 .72 1.00 1.30 2.10 3.00 .55 0.092 0.18

Variance .00009 .00008 .00006 .00005 .00004 .00003 .00003 .00003 .00003 .00003 .00026 .00523 .00287Standard error 2.2 2.0 1.8 1.6 1.4 1.3 1.3 1.2 1.2 1.2 3.7 16.8 12.4Years 35 35 35 35 35 35 35 35 35 35 35 35 35

01175670 Streamflow .28 .35 .61 1.10 1.80 2.60 3.40 4.30 6.70 9.40 1.90 .23 .56

Variance .00009 .00008 .00006 .00005 .00004 .00003 .00003 .00003 .00003 .00003 .00026 .00523 .00287Standard error 2.2 2.0 1.8 1.6 1.4 1.3 1.3 1.2 1.2 1.2 3.7 16.8 12.4Years 35 35 35 35 35 35 35 35 35 35 35 35 35

01175710 Streamflow .32 .42 .82 1.52 2.18 3.10 4.14 5.34 8.49 -- 2.52 .30 .83

Variance .0092 .00729 .00431 .00274 .0024 .00253 .00286 .00319 .00394 -- .00239 .01102 .00527Standard error 22.4 19.9 15.2 12.1 11.3 11.6 12.4 13.1 14.5 -- 11.3 24.5 16.8Years 32.1 32.3 34.9 36.3 33.8 32.3 30.5 29 26.3 -- 25.5 8.4 8.8

01175850 Streamflow 1.05 1.24 1.83 2.70 3.69 4.72 5.78 6.92 9.80 13.2 3.96 .97 1.81

Variance .00107 .00086 .0005 .00031 .0003 .00036 .00047 .0006 .00095 .00136 .00034 .00174 .00081Standard error 7.5 6.8 5.2 4.1 4.0 4.4 5.0 5.6 7.1 8.5 4.2 9.6 6.6Years 36.1 37 39 40.2 40.2 39.1 36.5 32.9 25.7 20.6 33.1 12.4 15

01175890 Streamflow .12 .16 .30 .48 .66 .86 1.08 1.35 2.06 3.03 .74 .10 .29

Variance .00383 .00288 .00153 .00088 .00066 .00061 .00067 .00082 .00134 .00207 .00063 .00493 .00194Standard error 14.3 12.4 9.0 6.8 5.9 5.7 6.0 6.6 8.4 10.5 5.8 16.3 10.2Years 37.9 41.4 49.3 52.1 50.2 50.7 50.9 48.9 40.4 31.3 43.9 10.3 16.4

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
72 Methods for Estimating Low-Flow Statistics for Massachusetts Streams 01176000 Streamflow 16.0 20.0 30.0 42.0 52.0 65.0 78.0 93.0 126 168 65.0 15.8 32.8 Variance .00002 .00002 .00001 .00001 .00001 .00001 .00001 .00001 .00001 .00001 .00005 .00124 .00068 Standard error 1.1 1.0 .9 .8 .7 .7 .6 .6 .6 .6 1.7 8.1 6.0 Years 83 83 83 83 83 83 83 83 83 83 83 83 83 01176100 Streamflow -- -- .82 1.47 1.97 -- -- -- -- -- -- .11 .91 Variance -- -- .00542 .00402 .00409 -- -- -- -- -- -- .01378 .00608 Standard error -- -- 17.1 14.7 14.8 -- -- -- -- -- -- 27.5 18.1 Years -- -- 60.2 61.1 57.1 -- -- -- -- -- -- 11.8 16 01176200 Streamflow .74 .89 1.18 1.58 1.94 2.30 2.59 2.95 3.81 4.97 2.08 .69 1.22 Variance .00105 .00078 .00048 .00036 .00037 .00045 .00055 .00068 .00103 .00153 .00041 .0015 .00064 Standard error 7.5 6.4 5.0 4.4 4.4 4.9 5.4 6.0 7.4 9.0 4.7 8.9 5.8 Years 40.3 41.7 45 45.2 42.1 37 31.5 26.9 20.2 15.6 30.9 10.4 14 01176300 Streamflow -- -- -- 3.48 3.90 4.30 4.61 4.97 5.79 6.74 4.09 -- -- Variance -- -- -- .00015 .00018 .00024 .0003 .0004 .00068 .00106 .00022 -- -- Standard error -- -- -- 2.8 3.1 3.6 4.0 4.6 6.0 7.5 3.4 -- -- Years -- -- -- 53.1 48 40.3 33.6 27.4 17.7 11.8 27.6 -- -- 01176415 Streamflow 3.31 3.58 4.26 5.02 5.78 6.48 6.93 7.61 9.08 10.5 6.05 3.11 4.17

Variance .00072 .00055 .00029 .00015 .00012 .00016 .00021 .0003 .00057 .0009 .00014 .00100 .00038Standard error 6.2 5.4 3.9 2.8 2.5 2.9 3.3 4.0 5.5 6.9 2.7 7.3 4.5Years 25.2 26.9 31.4 34.3 32.6 28.7 24.9 21 14.1 9.5 27.2 4.7 7.9

01176780 Streamflow 1.75 2.10 3.00 4.20 5.41 6.76 7.70 9.16 13.1 -- 6.42 1.68 3.18

Variance .0066 .00497 .00274 .00138 .00091 .00088 .00105 .00137 .00265 -- .00091 .00764 .00271Standard error 18.9 16.3 12.1 8.6 7.0 6.8 7.5 8.5 11.9 -- 7.0 20.3 12.0Years 17 18.5 23.2 29.1 31.5 29.8 26 22.1 14.2 -- 21.1 2.8 5.1

01177360 Streamflow 2.74 2.97 3.61 4.32 4.95 5.58 5.91 6.50 7.79 9.25 5.57 -- --

Variance .00272 .00207 .00112 .00057 .00038 .00036 .00041 .00055 .00103 .00176 .00041 -- --Standard error 12.1 10.5 7.7 5.5 4.5 4.4 4.7 5.4 7.4 9.7 4.7 -- --Years 12.1 13.3 17 22.3 26.1 27.2 24.2 20.3 12.6 7 19 -- --

01178200 Streamflow .62 .79 1.16 1.82 2.43 3.21 4.11 5.20 8.18 12.6 2.55 .54 1.11

Variance .00089 .00064 .00043 .00041 .00054 .00077 .00107 .00144 .00234 .00345 .0006 .00166 .0007Standard error 6.9 5.8 4.8 4.7 5.4 6.4 7.5 8.8 11.2 13.6 5.6 9.4 6.1Years 58.8 61 59.3 55.3 52.1 47.6 42.6 37.9 29.5 23.3 40.6 18.8 23.6

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14

—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
Table 9 73

01178300 Streamflow 1.51 1.90 2.87 4.37 5.68 7.36 9.33 11.6 -- -- 5.91 1.32 2.71

Variance .00194 .00135 .00086 .00081 .00114 .00172 .00246 .00334 -- -- .00126 .00309 .00115Standard error 10.2 8.5 6.8 6.6 7.8 9.6 11.5 13.4 -- -- 8.2 12.9 7.8Years 56.5 60 58.3 52.2 46.4 38.6 31.3 25.8 -- -- 30.8 10.2 15.6

01178490 Streamflow .73 1.06 1.99 -- -- -- -- -- -- -- 4.77 .59 1.67

Variance .00796 .00533 .00253 -- -- -- -- -- -- -- .0017 .01096 .00386Standard error 20.8 16.9 11.6 -- -- -- -- -- -- -- 9.5 24.5 14.4Years 29.6 31.3 35.3 -- -- -- -- -- -- -- 30 5.5 9

01179900 Streamflow -- -- .21 .55 1.04 1.74 2.97 -- -- -- 1.04 -- --

Variance -- -- .00422 .00215 .00168 .00184 .00248 -- -- -- .00205 -- --Standard error -- -- 15.0 10.7 9.5 9.9 11.5 -- -- -- 10.5 -- --Years -- -- 52.5 55.4 56.5 55.9 54.1 -- -- -- 51.4 -- --

01180000 Streamflow .070 .080 .11 .16 .22 .28 .38 .53 0.86 1.20 .21 .058 .11

Variance .00013 .00011 .00008 .00006 .00005 .00005 .00004 .00004 .00004 .00003 .00022 .00306 .00168Standard error 2.6 2.4 2.1 1.8 1.7 1.6 1.5 1.4 1.4 1.3 3.4 12.8 9.5Years 28 28 28 28 28 28 28 28 28 28 28 28 28

01180500 Streamflow 2.90 -- 5.30 8.20 11.0 15.0 19.0 24.0 36.0 50.0 11.2 1.40 5.33

Variance .00004 -- .00003 .00002 .00002 .00002 .00001 .00001 .00001 .00001 .00009 .00326 .00179Standard error 1.5 -- 1.2 1.0 1.0 .9 .9 .8 .8 .8 2.1 13.2 9.8Years 79 -- 79 79 79 79 79 79 79 79 79 79 79

01180650 Streamflow .30 .37 .55 .86 1.28 -- -- -- -- -- 1.31 .24 .55

Variance .00922 .00646 .00338 .00193 .00272 -- -- -- -- -- .0029 .01298 .0039Standard error 22.4 18.7 13.4 10.1 12.1 -- -- -- -- -- 12.4 26.7 14.5Years 26.4 30.8 41.3 51.7 41.7 -- -- -- -- -- 29.3 3.1 5.6

01180800 Streamflow .26 .30 .40 .54 .74 1.00 1.30 1.60 2.50 3.40 .80 .21 .34

Variance .00021 .00018 .00013 .00010 .00009 .00008 .00007 .00006 .00006 .00006 .00051 .00329 .00181Standard error 3.3 3.0 2.7 2.3 2.1 2.0 1.9 1.8 1.8 1.7 5.2 13.3 9.8Years 14 14 14 14 14 14 14 14 14 14 14 14 14

01181000 Streamflow 7.10 8.90 12.0 18.0 24.0 30.0 38.0 46.0 70.0 96.0 23.0 5.79 11.0

Variance .00005 .00004 .00003 .00002 .00002 .00002 .00002 .00001 .00001 .00001 .00010 .00155 .00085Standard error 1.6 1.4 1.3 1.1 1.0 1.0 .9 .9 .8 .8 2.3 9.1 6.7Years 60 60 60 60 60 60 60 60 60 60 60 60 60

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
74 Methods for Estimating Low-Flow Statistics for Massachusetts Streams 01183210 Streamflow 2.95 4.43 7.26 8.77 10.5 11.7 12.2 13.3 15.4 16.8 11.9 1.94 7.44 Variance .00249 .00175 .00096 .00065 .00051 .00054 .00064 .00085 .00169 .00313 .00058 .0035 .00117 Standard error 11.5 9.7 7.1 5.9 5.2 5.4 5.8 6.7 9.5 12.9 5.5 13.7 7.9 Years 45.3 48.3 54.1 51.5 46.8 41.2 35.5 31.4 23.7 16.9 36.4 8.4 14.6 01184200 Streamflow .48 .57 .78 1.12 1.47 1.83 2.17 2.55 3.52 4.70 1.56 .43 .78 Variance .00076 .00064 .0005 .00043 .00044 .0005 .00057 .00065 .00088 .00116 .00047 .00113 .00067 Standard error 6.4 5.8 5.2 4.8 4.8 5.2 5.5 5.9 6.8 7.9 5.0 7.8 6.0 Years 38.8 38.7 37.9 36.5 34.3 31.5 28.6 26 21.1 17.6 25.4 10.9 10.4 01184277 Streamflow 1.41 2.25 4.32 6.36 7.82 8.90 9.46 10.2 11.5 -- 8.44 -- 4.21 Variance .00239 .00184 .00094 .00055 .00058 .00085 .00117 .00165 .00294 -- .00075 -- .00128 Standard error 11.3 9.9 7.1 5.4 5.5 6.7 7.9 9.4 12.5 -- 6.3 -- 8.3 Years 31.3 32.3 36.9 39.3 36.9 31.6 26.2 21.5 14.5 -- 27.3 -- 11.8 01184855 Streamflow 3.13 4.03 5.94 8.50 11.5 14.9 18.6 22.9 -- -- 12.0 2.70 5.81 Variance .00349 .00249 .00148 .00106 .00113 .00148 .00199 .00264 -- -- .00119 .00456 .00174 Standard error 13.7 11.5 8.9 7.5 7.8 8.9 10.3 11.9 -- -- 8.0 15.6 9.6 Years 32.6 35.1 39 39.9 36.5 30.5 24.2 19.2 -- -- 23.7 4.8 7.3 01185490 Streamflow 2.17 2.99 -- -- -- -- -- -- -- -- 10.3 1.75 4.47

Variance .00643 .00432 -- -- -- -- -- -- -- -- .00315 .00847 .00317Standard error 18.6 15.2 -- -- -- -- -- -- -- -- 13.0 21.4 13.0Years 45.1 49.8 -- -- -- -- -- -- -- -- 24.2 6.4 9.5

01186300 Streamflow .51 .70 1.17 1.83 2.55 3.38 4.34 5.49 8.76 -- 2.61 .40 1.11

Variance .00346 .00241 .00126 .00082 .00084 .00108 .00146 .00195 .00328 -- .00089 .00493 .0016Standard error 13.6 11.3 8.2 6.6 6.7 7.6 8.8 10.2 13.2 -- 6.9 16.3 9.2Years 39.6 42.9 51.1 54.1 49.3 41.3 32.9 26.3 16.7 -- 34.3 6.7 12.1

01187400 Streamflow .30 .40 .50 .80 1.00 1.60 2.20 3.00 5.00 7.20 -- .24 .46

Variance .00012 .00010 .00008 .00006 .00005 .00004 .00004 .00004 .00003 .00003 -- .00435 .00239Standard error 2.5 2.3 2.0 1.8 1.6 1.5 1.4 1.4 1.3 1.3 -- 15.3 11.3Years 31 31 31 31 31 31 31 31 31 31 -- 31 31

01197015 Streamflow 1.20 1.30 1.40 1.60 2.17 2.70 3.60 4.40 8.34 9.90 2.35 -- --

Variance .00117 .00098 .00074 .00057 .00048 .00043 .00039 .00036 .00032 .00031 .00066 -- --Standard error 7.9 7.2 6.3 5.5 5.1 4.8 4.5 4.4 4.2 4.1 5.9 -- --Years 2 2 2 2 2 2 2 2 2 2 2 -- --

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
Table 9 75

01197120 Streamflow 1.63 1.96 2.76 4.15 5.57 7.16 9.05 11.3 -- -- 5.90 1.45 2.67

Variance .00225 .00164 .00083 .00068 .00101 .0016 .00238 .00337 -- -- .00118 .00325 .00118Standard error 11.0 9.3 6.6 6.0 7.3 9.2 11.3 13.4 -- -- 7.9 13.2 7.9Years 39.7 41.2 47.1 44.2 35.1 27.7 21.8 17.2 -- -- 22.9 7.1 13.5

01197140 Streamflow .16 .21 .36 .63 .95 1.39 1.94 -- -- -- 1.02 .12 .34

Variance .00692 .00528 .00328 .00216 .00209 .00258 .00343 -- -- -- .00219 .00957 .00391Standard error 19.3 16.8 13.2 10.7 10.6 11.7 13.5 -- -- -- 10.8 22.8 14.5Years 37.5 39.2 42 44.9 43.3 38.4 31.4 -- -- -- 29.8 6.4 8.6

01197180 Streamflow -- 1.85 2.25 2.68 3.13 3.54 4.00 4.43 5.45 6.47 3.13 1.49 2.17

Variance -- .00057 .00035 .00032 .00042 .00059 .00082 .00107 .00174 .00245 .00043 .00111 .00042Standard error -- 5.5 4.3 4.1 4.7 5.6 6.6 7.5 9.6 11.4 4.8 7.7 4.7Years -- 52.8 60.9 54.8 42.3 31.7 23.3 17.8 10.9 7.8 25.3 7 9.8

01197230 Streamflow 1.70 2.09 2.84 -- 4.91 6.06 7.26 8.63 11.9 15.5 4.98 1.50 2.77

Variance .00088 .00062 .00043 -- .00063 .0009 .0012 .00156 .00239 .00328 .00067 .00138 .00062Standard error 6.8 5.7 4.8 -- 5.8 6.9 8.0 9.1 11.3 13.2 6.0 8.6 5.7Years 47.6 49.7 49.4 -- 37.8 30.6 24.3 19.6 13.3 10.1 26.4 11.9 15

01197300 Streamflow .010 .020 .060 .21 .38 .55 .83 1.10 1.60 2.40 .47 -- --

Variance .00064 .00053 .00040 .00031 .00026 .00023 .00021 .00020 .00018 .00017 .00275 -- --Standard error 5.8 5.3 4.6 4.1 3.7 3.5 3.3 3.2 3.1 3.0 12.1 -- --Years 9 9 9 9 9 9 9 9 9 9 9 -- --

01198000 Streamflow 3.20 3.70 4.70 6.40 8.50 12.0 15.0 19.0 30.4 42.0 9.10 3.11 --

Variance .00014 .00012 .00009 .00007 .00006 .00005 .00005 .00004 .00004 .00004 .00020 .00320 --Standard error 2.7 2.5 2.2 1.9 1.8 1.7 1.6 1.5 1.4 1.4 3.3 13.1 --Years 21 21 21 21 21 21 21 21 21 21 21 21 --

01198060 Streamflow -- -- -- -- -- -- -- -- -- -- -- .017 .092

Variance -- -- -- -- -- -- -- -- -- -- -- .01321 .00643Standard error -- -- -- -- -- -- -- -- -- -- -- 26.9 18.6Years -- -- -- -- -- -- -- -- -- -- -- 11.2 12.6

01198160 Streamflow .68 .80 1.03 1.34 1.67 2.00 2.33 2.70 3.57 4.50 1.70 .59 1.02

Variance .00142 .00111 .0008 .00069 .00078 .00097 .00122 .00152 .0023 .00313 .00081 .00212 .00101Standard error 8.7 7.7 6.5 6.1 6.4 7.2 8.1 9.0 11.1 12.9 6.6 10.6 7.3Years 44.6 46.2 46.9 45.3 40.4 34.9 29 24.2 16.7 12.9 29 9.6 11.2

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
76 Methods for Estimating Low-Flow Statistics for Massachusetts Streams 01198200 Streamflow -- -- 19.1 24.5 29.6 35.7 41.3 47.4 61.0 75.9 30.6 -- -- Variance -- -- .00017 .00014 .00012 .00011 .0001 .0001 .0001 .00011 .00013 -- -- Standard error -- -- 3.0 2.7 2.5 2.4 2.3 2.3 2.3 2.5 2.6 -- -- Years -- -- 37.3 36.9 36.6 36.2 35.8 35.3 34.3 33.3 31.8 -- -- 01331380 Streamflow .48 .54 .72 .96 1.17 1.44 1.78 2.16 3.20 -- 1.22 .44 .70 Variance .00343 .00253 .00131 .00069 .00058 .0007 .00107 .00159 .00288 -- .00061 .00446 .00169 Standard error 13.5 11.6 8.3 6.1 5.5 6.1 7.5 9.2 12.4 -- 5.7 15.5 9.5 Years 39.7 41.4 46.1 51.8 52.8 49.4 42.6 35.7 25.1 -- 40.8 7 10 01331400 Streamflow .17 .27 .57 1.10 1.60 2.00 2.60 3.37 5.20 7.30 1.90 -- -- Variance .00044 .00037 .00028 .00022 .00018 .00016 .00015 .00014 .00012 .00012 .00209 -- -- Standard error 4.8 4.4 3.9 3.4 3.1 2.9 2.8 2.7 2.6 2.5 10.6 -- -- Years 10 10 10 10 10 10 10 10 10 10 10 -- -- 01332000 Streamflow 5.70 6.50 8.50 11.0 14.4 19.0 23.0 -- -- 49.0 14.0 5.21 7.77 Variance .0000409 .0000343 .000026 .0000201 .000017 .0000149 .0000135 -- -- .00001 .0000834 .0007938 .0004359 Standard error 1.5 1.3 1.2 1.0 .9 .9 .8 -- -- .8 2.1 6.5 4.8 Years 58 58 58 58 58 58 58 -- -- 58 58 58 58 01332900 Streamflow -- -- -- 1.67 2.01 2.70 -- -- -- 7.98 2.13 1.34 1.45

Variance -- -- -- .00029 .00026 .00032 -- -- -- .00166 .00029 .00202 .00086Standard error -- -- -- 3.9 3.7 4.1 -- -- -- 9.4 3.9 10.4 6.8Years -- -- -- 57.1 56.6 54.4 -- -- -- 33.4 49.7 19.2 23.6

01333000 Streamflow 4.80 5.60 7.80 11.0 14.0 18.2 23.0 27.0 36.0 48.0 15.0 4.57 8.19

Variance .00005 .00004 .00003 .00002 .00002 .00002 .00002 .00001 .00001 .00001 .00009 .00171 .00094Standard error 1.6 1.4 1.2 1.1 1.0 .9 .9 .9 .8 .8 2.2 9.5 7.1Years 47 47 47 47 47 47 47 47 47 47 47 47 47

01333100 Streamflow -- -- -- -- -- -- 1.26 1.67 2.68 4.29 -- .10 .22

Variance -- -- -- -- -- -- .00111 .00136 .00201 .00295 -- .00564 .00301Standard error -- -- -- -- -- -- 7.7 8.5 10.4 12.6 -- 17.4 12.7Years -- -- -- -- -- -- 45.9 43.8 39.4 34.9 -- 16.1 17.7

01359967 Streamflow 2.43 2.75 3.66 4.74 4.94 5.11 5.77 6.80 9.09 11.3 4.96 2.29 3.74

Variance .00291 .00214 .00093 .00051 .00057 .00041 .0005 .00088 .00214 .00354 .00057 .00366 .00099Standard error 12.5 10.7 7.0 5.2 5.5 4.7 5.2 6.8 10.7 13.8 5.5 14.0 7.3Years 24.4 27.2 42.4 57.5 28.7 21.4 19.3 16.1 9.6 6.6 17.3 4 9.9

Table 9. Streamflow statistics, variances, standard errors, and years of record for stations included in the regression analyses; streamflow statistics are computed from daily records for streamgaging stations and estimated for low-flow partial-record stations; equivalent years of record for low-flow partial-record stations are computed from equation 14

—Continued

Station

No. Statistic

Flow-duration percentile August 

median

7-Day, 

10-year

low flow

7-Day,

2-year

low flow 99 98 95 90 85 80 75 70 60 50
Table 10 77

Table 10. Basin characteristics for stations used in the regression analyses—Continued

Station No. Drainage

area

Total

stream

length

Mean

basinslope

Stratifieddrift area Area of water bodies Area of wetlands Minimum basin elevation Mean basin elevation Maximum basin elevation Region

01073860 1.83 4.21 0.84 1.80 0.00 0.00 22 65 108 001094340 21.7 38.6 4.57 3.78 .77 .70 670 1,000 1,340 001094396 15.8 32.3 6.41 1.40 .25 .40 567 1,050 1,580 001094760 7.41 12.7 3.81 1.62 .52 .23 423 615 806 001095220 30.4 50.7 5.80 5.41 .47 .80 403 1,150 2,000 001095380 6.79 11.6 3.99 1.95 .02 .41 532 806 1,080 001095915 15.7 23.6 3.02 4.53 .50 .02 241 312 403 001095928 5.89 13.3 4.93 .66 .02 .22 482 893 1,300 001096000 64.4 125 5.07 17.1 .40 1.35 252 855 1,500 001096504 1.92 3.26 1.93 1.52 .02 .30 181 300 428 001096505 6.84 12.7 2.28 4.62 .02 .52 177 332 514 001096515 18.2 30.7 2.86 11.3 .91 .36 174 234 397 001096805 15.4 42.6 4.54 3.43 .15 .57 216 450 701 001096855 6.62 18.5 3.71 1.76 .05 .57 234 446 661 001096910 1.61 2.99 3.66 .18 .00 .00 298 441 582 001096935 17.2 42.4 3.92 5.55 .37 .71 205 422 640 001097280 24.9 57.4 2.28 7.70 .49 1.56 126 295 470 001097300 12.9 33.7 2.39 7.45 .09 .96 158 314 463 001099400 25.6 48.1 2.01 15.8 .47 1.60 98 249 403 001100608 4.09 10.2 1.37 2.17 .13 .12 104 229 354 001100700 5.54 10.1 2.78 1.72 .07 .21 95 213 334 001101000 21.4 56.4 5.52 9.92 .50 2.16 32 193 354 001101100 7.70 25.6 4.67 5.51 .07 .56 26 130 252 001102053 2.72 4.88 1.99 1.72 .01 .02 26 96 167 001102490 3.05 5.06 3.21 .34 .01 .04 50 202 364 001103015 5.35 10.5 3.21 2.26 .05 .13 15 194 377 001103253 7.23 18.5 2.29 1.09 .06 .36 172 306 445 001103435 10.2 19.0 1.81 6.24 .50 .48 110 236 370 001103440 3.91 7.03 1.58 2.35 .01 .47 118 214 336 001104960 2.37 4.18 1.65 .67 .07 .10 113 213 334 0

Table 10. Basin characteristics for stations used in the regression analyses[Flows are in cubic feet per second; areas are in square miles; lengths are in miles; slopes are in percent; elevations are in feet. Region: 0 is eastern; 1 is western; No., number; -- , no data]
78 Methods for Estimating Low-Flow Statistics for Massachusetts Streams 01104980 8.64 15.5 2.27 2.20 0.46 0.31 59 222 396 0 01105100 3.40 5.84 3.03 1.96 .01 .05 79 271 484 0 01105270 10.4 29.4 2.50 6.45 .72 .73 104 284 490 0 01105568 4.31 6.53 1.30 2.04 .05 .05 118 180 241 0 01105575 1.72 1.79 2.13 .00 .01 .09 115 182 259 0 01105582 27.4 48.7 2.33 10.8 1.01 1.86 59 330 630 0 01105600 4.47 8.03 1.27 1.50 .00 .26 75 137 200 0 01105630 4.91 10.9 1.63 3.64 .06 .21 29 104 180 0 01105670 1.61 2.47 .81 .15 .00 .06 6 65 124 0 01105820 3.17 6.09 1.14 .77 .05 .28 42 154 221 0 01105830 1.72 3.19 .61 .08 .00 .20 62 131 200 0 01105861 4.74 7.92 1.06 4.22 .06 .00 39 94 170 0 011058839 6.87 5.34 2.21 6.87 1.10 .02 42 118 193 0 011059106 2.58 3.46 .61 1.64 .02 .50 52 70 88 0 01105930 8.09 17.4 1.24 3.63 .16 2.40 75 155 236 0 01105935 2.64 5.76 1.82 1.44 .01 .43 41 109 179 0 01105937 8.59 15.3 1.52 3.27 .02 .76 70 170 270 0 01105947 9.25 18.3 .90 1.43 .01 1.03 19 155 296 0

01106000 7.99 17.6 1.51 .18 -- -- 10 178 227 001106460 8.94 17.3 1.50 3.30 .19 .91 55 175 259 001107000 4.71 9.61 1.10 .88 .04 .25 118 209 301 001107400 9.30 15.4 1.04 7.21 .45 1.32 49 111 173 001108140 8.20 16.0 1.09 6.98 .18 .89 32 82 131 001108180 7.48 11.6 .96 3.69 .05 .61 15 92 183 001108600 3.83 11.4 .96 2.49 .01 .19 124 214 305 001109087 20.7 37.0 1.42 9.37 .15 2.53 27 138 249 001109090 4.22 6.19 1.81 1.51 .03 .11 23 172 326 001109200 4.33 9.25 .32 2.78 .02 .42 101 160 255 001109225 7.21 11.6 1.11 2.85 .02 1.18 19 109 200 001109460 11.1 31.1 3.46 2.91 .51 .44 491 680 869 0

Table 10. Basin characteristics for stations used in the regression analyses

—Continued

Station No. Drainage

area

Total

stream

length

Mean

basinslope

Stratifieddrift area Area of water bodies Area of wetlands Minimum basin elevation Mean basin elevation Maximum basin elevation Region
Table 10 79

01111142 5.67 11.7 3.98 1.30 0.05 0.65 350 505 659 001111200 27.8 69.9 4.43 8.45 .27 1.77 247 424 659 001111225 7.26 17.2 3.15 2.60 .08 .19 270 456 641 001111300 16.0 30.0 3.14 4.60 -- -- 348 572 773 001112190 6.17 16.2 3.38 .95 .02 .17 200 371 587 001123140 13.8 39.2 6.33 3.27 .17 .57 652 943 1,250 001123161 6.57 15.3 5.96 1.88 .16 .24 653 915 1,180 001123200 4.39 12.9 4.63 .18 .02 .20 690 986 1,290 001124390 8.58 28.5 3.82 .00 .16 .50 564 828 1,090 001162500 19.2 13.9 3.68 2.01 .01 .52 851 1,280 1,870 101162900 19.2 32.2 2.82 6.17 .45 1.19 913 1,110 1,310 101163298 7.22 10.9 3.09 2.59 .09 .21 834 995 1,160 101164300 15.6 26.8 4.06 2.80 .54 .73 856 1,360 1,880 101165090 14.1 20.8 7.64 1.45 .05 .18 560 977 1,400 101165250 7.08 11.2 4.34 1.45 .16 .17 623 961 1,300 101165500 12.1 15.0 6.93 1.92 .14 .17 511 999 1,620 101166105 5.24 10.6 7.39 1.24 .00 .05 478 983 1,300 101167200 22.3 38.6 10.6 1.15 .05 .03 395 858 1,400 101168300 29.6 57.0 11.0 .20 .17 .20 751 1,940 2,830 101168400 27.1 55.5 12.1 .91 .14 .13 613 1,790 2,510 101168650 18.1 36.7 11.1 2.17 .04 .07 483 1,330 1,900 101169000 89.8 175 9.70 5.41 .08 .20 475 1,350 2,230 101169600 10.5 21.4 8.49 1.06 .01 .01 587 1,070 1,550 101169800 6.69 13.6 8.22 .24 .02 .07 776 1,310 1,700 101169801 15.6 31.2 8.72 1.89 .09 .08 820 1,280 1,830 101169900 24.1 48.1 9.45 3.20 .10 .08 485 1,150 1,830 101170100 41.3 84.2 9.52 1.48 .01 .03 475 1,360 2,400 101170575 21.7 39.7 6.86 4.43 .32 .10 296 907 1,300 101171500 54.0 100 6.91 9.52 .53 .54 141 848 1,690 101171800 5.56 9.17 5.20 2.04 .03 .11 209 514 829 1

Table 10. Basin characteristics for stations used in the regression analyses—Continued

Station No. Drainage

area

Total

stream

length

Mean

basinslope

Stratifieddrift area Area of water bodies Area of wetlands Minimum basin elevation Mean basin elevation Maximum basin elevation Region
80 Methods for Estimating Low-Flow Statistics for Massachusetts Streams 01171947 18.4 34.4 3.46 8.20 0.25 1.31 292 394 797 1 01171970 18.8 31.2 1.41 10.9 .10 .88 167 401 643 1 01172810 12.7 17.8 3.61 2.47 .03 .59 713 1,010 1,310 1 01173260 4.62 4.01 1.66 .00 .03 .58 927 1,070 1,220 1 01173420 19.0 33.4 5.44 4.54 .25 1.23 432 699 986 1 01173450 6.60 10.8 4.27 1.00 .02 .46 432 699 986 1 01174000 3.39 7.97 6.53 .07 .01 .00 730 1,000 1,300 1 01174050 5.03 6.29 4.60 .72 .17 .25 706 931 1,220 1 01174565 12.5 27.9 7.47 1.94 .08 .04 593 823 1,040 1 01174900 2.89 5.99 5.96 .02 .00 .01 539 860 1,160 1 01175670 8.69 16.74 5.46 1.11 .21 .30 650 864 1,080 1 01175710 13.8 28.8 3.87 2.16 .43 .83 664 908 1,150 1 01175850 11.5 25.6 4.67 1.93 .08 .52 613 880 1,160 1 01175890 3.55 7.68 5.64 0.67 .01 .09 609 857 1,100 1 01176000 149 319 4.51 31.7 4.36 8.28 387 792 1,220 1 01176100 9.34 20.8 4.88 2.86 .03 .52 373 775 1,220 1 01176200 3.96 4.91 7.07 1.08 .01 .17 373 684 1,040 1 01176300 6.57 8.76 8.54 1.41 .05 .13 408 806 1,210 1

01176415 15.3 18.9 5.80 3.54 .32 .28 396 819 1,260 101176780 13.6 22.0 5.57 2.83 .08 .26 260 647 1,050 101177360 6.92 12.5 3.20 4.57 .03 .54 243 332 850 101178200 11.1 19.2 5.79 .22 .01 .10 1,360 1,860 2,300 101178300 22.9 38.8 4.86 .80 .17 .48 961 1,410 1,870 101178490 12.3 26.0 5.78 .26 .01 .00 747 1,410 2,070 101179900 6.46 6.78 5.34 .19 .01 .07 1,460 1,830 2,120 101180000 1.74 2.54 9.72 .00 .01 .15 637 1,010 1,340 101180500 52.8 97.8 8.50 1.50 .46 .51 412 1,320 2,240 101180650 6.35 13.21 4.74 .00 .01 .11 1,220 1,700 2,140 101180800 2.95 6.98 4.76 .12 .05 .03 1,280 1,550 1,820 101181000 94.0 161 8.78 3.91 1.15 1.30 393 1,320 2,240 1

Table 10. Basin characteristics for stations used in the regression analyses

—Continued

Station No. Drainage

area

Total

stream

length

Mean

basinslope

Stratifieddrift area Area of water bodies Area of wetlands Minimum basin elevation Mean basin elevation Maximum basin elevation Region
Table 10 81

01183210 22.2 43.2 8.39 5.02 0.28 0.29 209 829 1,460 101184200 5.27 13.6 2.79 3.00 .04 .31 190 387 583 101184277 24.4 49.6 7.70 5.58 .07 .25 399 786 1,210 101184855 30.3 42.7 5.26 2.42 .92 1.39 1,160 1,620 2,120 101185490 29.1 46.8 6.69 .19 .71 .89 -- -- -- 101186300 9.87 15.9 3.83 .59 .09 .79 1,280 1,540 1,810 101187400 7.37 12.2 11.0 .70 -- -- 573 1,120 1,400 101197015 10.6 20.8 11.1 .54 .01 .04 1,110 1,790 2,630 101197120 20.4 36.2 8.09 .11 .40 .56 1,020 1,600 2,210 101197140 5.95 7.50 8.59 .03 .03 .37 969 1,550 2,160 101197180 7.62 8.91 12.4 .78 .16 .18 1,060 1,660 2,260 101197230 22.2 25.6 10.7 2.79 .19 .46 846 1,400 1,960 101197300 2.18 1.87 9.29 .01 .02 .11 990 1,370 1,840 101198000 51.0 76.6 9.49 5.13 .38 .32 688 1,290 2,060 101198060 2.91 3.19 19.0 .08 .00 .00 774 1,400 2,030 101198160 8.46 18.9 6.22 .27 .05 .27 1,010 1,490 1,850 101198200 61.0 94.0 6.78 10.6 1.23 1.28 682 1,440 2,110 101331380 7.03 12.8 10.5 .02 .00 .02 979 1,640 2,260 101331400 7.68 9.60 8.19 .21 .01 .09 1,160 1,690 2,250 101332000 40.9 58.5 13.5 3.10 -- -- 830 1,950 3,080 101332900 6.70 8.21 24.6 .22 .00 .00 766 2,080 3,480 101333000 42.6 73.2 18.5 4.90 .03 .00 629 2,020 3,480 101333100 5.25 10.1 19.4 .44 .00 .00 837 1,540 2,800 101359967 14.1 21.4 17.6 1.39 .02 .05 979 1,580 2,550 1

Table 10. Basin characteristics for stations used in the regression analyses—Continued

Station No. Drainage

area

Total

stream

length

Mean

basinslope

Stratifieddrift area Area of water bodies Area of wetlands Minimum basin elevation Mean basin elevation Maximum basin elevation Region