U.S. Department of the Interior

U.S. Geological Survey

Obtaining Streamflow Statistics for 

Massachusetts Streams on the World Wide Web

A World Wide Web application has 

been developed to make it easy to 

obtain streamflow statistics for userselected locations on Massachusetts 

streams. The Web application, named 

STREAMSTATS (available at http://

ma.water.usgs.gov/streamstats/), can 

provide peak-flow frequency, low-flow 

frequency, and flow-duration statistics 

for most streams in Massachusetts. 

These statistics describe the magnitude 

(how much), frequency (how often), 

and duration (how long) of flow in a 

stream.

The U.S. Geological Survey (USGS) 

has published streamflow statistics, 

such as the 100-year peak flow, the 

7-day, 10-year low flow, and flowduration statistics, for its datacollection stations in numerous reports. 

Federal, State, and local agencies need 

these statistics to plan and manage use 

of water resources and to regulate activities in and around streams. Engineering and environmental consulting firms, 

utilities, industry, and others use the 

statistics to design and operate watersupply systems, hydropower facilities, 

industrial facilities, wastewater treatment facilities, and roads, bridges, and 

other structures. Until now, streamflow 

statistics for data-collection stations 

have often been difficult to obtain because they are scattered among many 

reports, some of which are not readily 

available to the public. In addition, 

streamflow statistics are often needed 

for locations where no data are available. STREAMSTATS helps solve 

these problems.

STREAMSTATS was developed 

jointly by the USGS and MassGIS, the 

State Geographic Informatio

(GIS) agency, in cooperation 

Massachusetts Departments 

Environmental Managemen

Environmental Protection. T

tion consists of three major 

nents: (1) a user interface th

maps and allows users to sel

locations for which they wa

flow statistics (fig. 1), (2) a d

previously published stream

tics and descriptive informat

USGS data-collection statio

(3) an automated procedure 

mines characteristics of the 

surface area (basin) that dra

stream and inserts those cha

into equations that estimate 

flow statistics. Each of these 

nents is described and guida

using STREAMSTATS is pr

below.

USGS Fact Sh

September 20

Figure 1. View of the STREAMSTATS-user interface at start up with the map window showing town boundaries 

and data-collection stations in Massachusetts.
STREAMFLOW 

STATISTICS FOR DATACOLLECTION STATIONS

The USGS operates or has operated 

four types of streamflow-datacollection stations in Massachusetts: 

(1) continuous-record stations, 

(2) peak-flow partial-record stations, 

(3) low-flow partial-record stations, and 

(4) miscellaneous-measurement stations. A network of 74 streamgaging 

stations is currently (2000) operated in 

the State. Continuous records of 

streamflow of various length are available for these stations and for 79 

streamgaging stations that were previously operated. Networks of peak-flow 

and low-flow partial-record stations 

were previously operated throughout 

the State, although none are currently in 

operation. Streamflow and water-level 

measurements were obtained occasionally over a period of years at the partialrecord stations to determine either 

peak- or low-flow statistics for those 

stations. Streamflow data also have 

been collected at hundreds of miscellaneous-measurement stations. These 

stations were operated primarily for 

specific hydrologic studies with various 

objectives.

All streamflow data collected by the 

USGS in Massachusetts are stored in 

the USGS National Water Information 

System (NWIS) data base. This data 

base also contains descriptive information for each data-collection station. 

Data from NWIS were used to determine streamflow statistics for the 725 

stations included in the STREAMSTATS database. Many other stations 

are not in the STREAMSTATS database, either because not enough data 

were available to accurately compute 

the statistics, or the flows were affected 

by human activities.

The STREAMSTATS data base is 

much smaller and faster to operate over 

the Web than the NWIS data base. 

Descriptive information was loaded 

from NWIS into the STREAMSTATS 

data base for all stations. Descriptive 

information includes USGS station 

identification number, station name, 

station type, period of record, latitude 

and longitude, hydrologic unit code, 

major drainage basin name, directions 

to locate the station, and remarks indicating effects of human activities on the 

flow or other pertinent information 

about the station.

Basin characteristics and streamflow 

statistics were entered into the 

STREAMSTATS data base for all 

stations for which these data were available. Available basin characteristics 

include drainage-basin area (the land 

surface-area that contributes streamflow 

to the location), area of stratified drift 

(coarse-grained sand and gravel areas 

where aquifers are usually located), 

area of water bodies (lakes, ponds, and 

wide streams), and area of wetlands, all 

in square miles; total length of streams, 

in miles; mean basin slope, in percent; 

and minimum, mean, and maximum 

basin elevations, in feet. Available 

peak-flow frequency statistics include 

the mean annual flood, and the 10-, 25-, 

50-, 100-, and 500-year recurrence 

interval floods. Available low-flow 

frequency statistics include the 7-day, 

2-year and the 7-day, 10-year 

recurrence interval low flows. Available 

flow-duration statistics include streamflows at selected durations exceeded 

between 99 and 1 percent of the time, 

and the August median streamflow. 

Definitions of these statistics are 

provided in the Web page for the 

application.

Not all of the streamflow statistics 

are available for all sites. Only peakflow frequency statistics are likely to be 

available for peak-flow partial-record 

stations, whereas only low-flow 

frequency and low-flow duration statistics are likely to be available for lowflow partial-record stations. Streamgaging stations may have all available 

statistics or only a portion of them. 

Miscellaneous-measurement stations 

may have any of the statistics, but most 

of them have only low-flow statistics; 

thus most of these stations have been 

grouped with the low-flow partialrecord stations in the database. In addition, many stations have few or no basin 

characteristics available. All statistics 

for the stations in the STREAMSTATS 

database were published previously in 

USGS reports, and the methods used to 

determine the statistics are described in 

those reports. Citations are provided 

along with each streamflow statistic 

served.

STREAMFLOW 

STATISTICS FOR 

LOCATIONS WHERE NO 

DATA ARE AVAILABLE

The USGS has developed equations 

that can be used to estimate various 

streamflow statistics for locations on 

Massachusetts streams where no data 

are available (Ries and Frie

The equations were derived 

sion analysis, which statistic

the streamflow statistics for 

data-collection stations to p

characteristics of the draina

for the stations. Physical ch

for a site where no data are 

can be measured and inserte

regression equations to obta

of the streamflow statistics f

Regression analysis has b

develop equations for estim

streamflow statistics in man

areas; however, use of the eq

been limited because measu

physical characteristics need

the equations has been diffic

time-consuming, and the eq

complex for some users. Hi

most physical characteristic

sured by hand from various 

process could take from sev

to days to complete for a sin

addition, many of the maps 

widely circulated, and many 

users did not possess the eq

expertise necessary to meas

values from the maps. STRE

eliminates these problems b

mating the process of measu

physical characteristics and 

equations. As a result, users 

obtain streamflow statistics 

locations within a few minu

The STREAMSTATS low

analysis procedure measure

characteristics for user-selec

tions from digital map data 

ArcView1

 GIS (Environmen

Research Institute, Inc., 199

accompanying programmin

AVENUE (Environmental S

Research Institute, Inc., 199

STREAMSTATS does not r

knowledge of how to use a G

simply select the location of 

from a map displayed in the 

face, and STREAMSTATS 

rest.

After the user selects a si

interest from the map, STRE

determines the drainage-bas

and area. This is done using 

combination of two sets of d

data, known as data layers. 

layer contains drainage-basi

boundaries for about 2,300 l

Massachusetts streams, an a

one set of boundaries for eve

miles of land surface in the 

other data layer is a Digital 

1

Use of trade or product names 

tion purposes only, and does not cons

ment by the U.S. Geological Survey.
Model (DEM), developed by the USGS 

at 1:25,000 scale, that consists of a 

rectangular grid of elevation points 

spaced approximately every 100 feet 

along the land surface (Elassel and 

Caruso, 1983). The DEM elevations 

correspond to elevations shown on 

1:25,000-scale USGS topographic 

quadrangle maps. If the user selects a 

site on an existing drainage-basin 

boundary, the area associated with that 

boundary is summed with areas for all 

upstream subbasins to determine the 

total drainage-basin area for that site. If 

the user selects a site not on an existing boundary, STREAMSTATS uses 

the DEM to define the boundary up to 

points at which the newly defined 

boundary coincides with existing 

boundaries. From that point, the existing boundaries are used to determine 

the total drainage-basin boundary and 

area for the site.

After STREAMSTATS determines 

the drainage-basin boundary, it then determines the remaining basin characteristics needed to solve the regression 

equations from other digital map 

layers: total length of streams, area of 

surficial stratified drift, mean basin 

slope, and hydrologic region. This 

process is more fully explained by Ries 

and Friesz (2000). STREAMSTATS 

then solves the regression equations 

and provides estimated streamflow statistics for the site to the user. Equations 

are available to estimate the 7-day, 

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

exceeded 99-, 98-, 97-, 95-, 90-, 75-, 

and 50-percent of the time; and the 

August median streamflow. STREAMSTATS also calculates prediction 

intervals at the 90-percent confidence 

level for the estimates as an indication 

of their reliability. The true values of 

the streamflow statistics for the selected sites are within the provided intervals 90 percent of the time.

MassGIS employees did much of 

the programming for the STREAMSTATS automated procedure and 

developed many of the digital map 

layers it uses. The MassGIS Watershed 

Analyst tool includes some of the 

features of this application and also 

includes several additional features. 

The Watershed Analyst tool, the map 

layers used by STREAMSTATS, and 

their descriptions are available through 

the MassGIS Web page (http://

www.state.ma.us/mgis/).

USING STREAMSTATS

The STREAMSTATS user interface 

was developed for the USGS by 

Syncline, Inc., of Cambridge, Mass. 

The user interface is a Java applet (Sun 

Microsystems, Inc., 1999) that delivers 

interactive maps to users by use of the 

Internet Map Server software extension 

to ArcView (Environmental Systems 

Research Institute, Inc., 1999). Maps 

delivered over the Web can be used to 

select sites for which streamflow statistics will be provided. The applet incorporates a map window, a map legend 

window, a map action toolbar, and a 

menu command toolbar (fig. 1).

First-time users of STREAMSTATS 

start on an introductory page, and are 

led through seven tutorial pages that 

provide instructions before they can 

start the applet. The introductory page 

also contains a link that allows users to 

view an on-line demonstration to help 

them become familiar with the application. Experienced users can bypass 

the tutorial on return visits and go to 

the main entry page for the application. 

The main entry page contains links to 

the tutorial pages for reference and a 

GO button that activates the user 

interface.

The user interface initially displays 

a map of Massachusetts in the map 

window with town boundaries and 

locations of data-collection stations 

(fig. 1). Buttons in the toolbars allow 

users to zoom in, zoom out, and pan 

to change the area displayed; to add, 

delete, and change the drawing order of 

map layers; and to identify features on 

the map. More than 100 map layers can 

be displayed to aid in locating sites of 

interest. The legend window identifies 

the displayed map layers.

The tutorial pages provide guidance 

on selecting map layers for locating 

sites. Usually, only a few map layers 

are needed. These usually include some 

combination of watershed boundaries, 

roads, stream centerlines, 1:25,000-

scale lakes and ponds (including wetlands), and digital topographic maps.

Users must first zoom in to select a 

location for which they want streamflow information. When the location of 

interest is a data-collection station, 

users should select the Station Lookup 

button, then click their left mouse 

button on the station symbol on the 

map to get streamflow statistics and descriptive information for the station 

from the data base. The map scale of an 

entire river basin is usually sufficient 

for selecting data-collection 

When the location of intere

data-collection station, user

select the Low-Flow Analy

then click their left mouse b

point on a centerline stream 

mates of the statistics for th

Users must first zoom in to 

greater than 1:5,000 and th

streams must be activated i

window before the Low-Flo

button is selected.

STREAMSTATS output 

a separate Web browser wi

opens automatically. This w

tains a table of previously p

formation for data-collectio

The window contains a ma

legend, measured basin cha

estimated streamflow statis

prediction intervals for the 

for sites where no data are 

(fig. 2). The map shows the 

basin boundary for the sele

any previously delineated b

aries within the map area, a

centerline streams within th

boundary. Users should car

spect the map and the meas

characteristics for the site to 

the basin delineation appea

Incorrect delineations occa

occur when selected sites a

flat areas such as wetlands 

bodies, and near stream con

Moving the selected point a 

tance upstream or downstre

original location will often 

these problems. Users can u

Web browser to print the in

displayed by STREAMSTA

LIMITATIONS OF 

STREAMSTATS

The equations used in th

STREAMSTATS low-flow 

procedure provide estimate

streamflow. If human activi

dam regulation and water w

substantially affect the timi

tude, or duration of flows a

location, the estimates from 

tions should be adjusted by 

account for those activities

flow analysis procedure can 

locations of data-collection 

streams that are affected by 

activities to obtain estimate

streamflow conditions for t

Users should not assume, h

the differences between the 

estimates (data base and lo

analysis) are equivalent to t
Figure 2. Example output from the STREAMSTATS low-flow analysis 

procedure, including a map of the drainage basin determined for the userselected site, a map legend, and a table of estimated streamflow statistics.

human activities on streamflow at the s

cause there are errors associated with b

estimates.

STREAMSTATS provides an error 

when the basin characteristics for a sel

are outside the ranges of those for the s

to develop the regression equations. Es

be obtained for these sites, but predicti

are not provided. The program does no

estimates for sites on major rivers with 

basins that extend into areas outside of 

Massachusetts where data for running 

STATS are not available.

The regression equations in STREA

do not apply in the eastern part of the B

Bay Basin, the southern part of the Sou

Shore Basin, on Cape Cod, or the Islan

the data available in these areas were i

for use in the regression analyses. Flow

streams in these areas, shown as the So

Coastal region in the Hydrologic Regi

layer, are highly affected by regulation

or cranberry bogs. In addition, the regi

lain almost entirely by coarse-grained 

drift. Surface-water drainage boundari

monly do not coincide with contributin

ground water for streams in the region

REFERENCES CITED

Elassel, A.A., and Caruso, V.M., 1983, U

cartographic standards: digital elevati

U.S. Geological Survey Circular 895

Environmental Systems Research Institu

1996a, Using ArcView GIS: Redland

350 p.

Environmental Systems Research Institu

1996b, AVENUE, Customization and 

Development for ARCVIEW: Redlan

239 p.

Environmental Systems Research Institut

ArcView Internet Map Server: at http

www.esri.com/software/arcview/exte

imsext.html, accessed 10/7/99

Ries, K.G., III, and Friesz, P.J., 2000, Me

estimating low-flow statistics for Mas

streams: U.S. Geological Survey Wat

Investigations Report 00-4135.

Sun Microsystems, Inc., 1999, What is th

Platform?: at http://java.sun.com/nav/

index.html, accessed 10/7/99

FOR MORE INFORMATION

http://ma.water.usgs.gov

U.S. Geological Survey

MA-RI District Office

10 Bearfoot Road

Northborough, MA 01532

telephone: (508) 490-5000

facsimile: (508) 490-5068

—By Kernell G. Ries III and Peter A. Stee

U.S. Geological Survey; Aleda Freeman, 

and Raj Singh, of Syncline, Inc.