Computer Programs for Obtaining and 

Analyzing Daily Mean Streamflow Data 

from the U.S. Geological Survey National 

Water Information System Web Site

By Gregory E. Granato

Prepared in cooperation with the 

U.S. Department of Transportation

Federal Highway Administration

Office of Natural and Human Environment

Open-File Report 2008–1362

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Granato, G.E., 2009, Computer programs for obtaining and analyzing daily mean streamflow data from the 

U.S. Geological Survey National Water Information System Web Site: U.S. Geological Survey Open-File 

Report 2008–1362, 123 p. on CD-ROM, 5 appendixes.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Streamflow Analysis for Water-Quality Modeling...........................................................................2

Purpose and Scope ..............................................................................................................................5

Computer Programs for Obtaining and Analyzing Streamflow Data.....................................................5

Summary..........................................................................................................................................................6

Acknowledgments.........................................................................................................................................6

References Cited............................................................................................................................................7

Appendix 1. Get National Water Information System Streamflow (Q) files GNWISQ (Version 

1.0)—A program for downloading streamflow-gaging-station information and daily 

mean streamflow files from the U.S. Geological Survey National Water Information 

System Web Site ..............................................................................................................................9

Appendix 2. Make Plotting Position (MkPP Version 1.0)—A program for generating plotting 

positions, percentiles, and frequency factors from daily mean streamflow data...............27

Appendix 3. Streamflow Record Extension Facilitator (SREF Version 1.0)—A program for 

extending and augmenting available streamflow data using long-term streamflow 

records from hydrologically similar sites...................................................................................47

Appendix 4. Streamflow (Q) Statistics (QSTATS—Version 1.0)—A program for calculating 

population statistics for daily mean streamflow data retrieved from the U.S. 

Geological Survey National Water Information System Web Site ........................................91

Appendix 5. Make U.S. Environmental Protection Agency DFLOW3 batch-input files MkDF 

(Version 1.0)—A program for creating batch-input files for DFLOW3.................................124

Figures

1. Schematic diagram showing the stochastic mass-balance approach for estimating 

discharge, concentration, and loads of water-quality constituents upstream of a 

highway outfall, from the highway, and downstream of a highway-runoff outfall............3

2. Map showing spatial distribution of 2,783 selected U.S. Geological Survey streamflowgaging stations among U.S. Environmental Protection Agency (2003b) Level III 

ecoregions that have been discretized to a 15-minute grid in the conterminous 

United States .................................................................................................................................4
iv

Conversion Factors and Abbreviations

Multiply By To obtain

Area

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

cubic foot (ft3) 0.02832 cubic meter (m3) 

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

cubic foot per second per square

mile [(ft3/s)/mi2]

 0.01093 cubic meter per second per square

kilometer [(m3/s)/km2]

Abbreviations

1B3	 	 1-day 3-year biological low flow

4B3	 	 4-day 3-year biological low flow

7Q10	 	 7-day 10-year low flow

ADAPS USGS Automated Data Processing System

BCF bias correction factor 

BMP(s) best management practice(s)

CD-ROM computer disk-read only memory

dv daily value

dd data descriptor

EMC event mean concentration 

FHWA Federal Highway Administration

GNWISQ	 Get National Water Information System Streamflow (Q)

KTRLine Kendall-Theil robust line

log10 common logarithm

MkDF Make U.S. Environmental Protection Agency DFLOW3 batch input Files

MkPP	 	 Make plotting position file

MOVE maintenance of variance

NWIS National Water Information System

NWISWeb National Water Information System Web

PC Personal Computer

Q 	 	 Streamflow

QSTATS	 Streamflow (Q) Statistics

RDB relational database

ROS regression-on-order statistics

SELDM stochastic empirical loading and dilution model

SQL structured query language

SREF	 	 Streamflow Record Extension Facilitator

TMDL(s)	 Total Maximum Daily Load(s)

USGS U.S. Geological Survey
Computer programs for Obtaining and Analyzing Daily 

Mean Streamflow Data from the U.S. Geological Survey 

National Water Information System Web Site

By Gregory E. Granato

Abstract

Five computer programs were developed for obtaining 

and analyzing streamflow from the National Water Information System (NWISWeb). The programs were developed as 

part of a study by the U.S. Geological Survey, in cooperation with the Federal Highway Administration, to develop a 

stochastic empirical loading and dilution model. The programs 

were developed because reliable, efficient, and repeatable

methods are needed to access and process streamflow information and data. The first program is designed to facilitate the

downloading and reformatting of NWISWeb streamflow data.

The second program is designed to facilitate graphical analysis 

of streamflow data. The third program is designed to facilitate

streamflow-record extension and augmentation to help develop

long-term statistical estimates for sites with limited data. The 

fourth program is designed to facilitate statistical analysis of 

streamflow data. The fifth program is a preprocessor to create

batch input files for the U.S. Environmental Protection Agency

DFLOW3 program for calculating low-flow statistics. These

computer programs were developed to facilitate the analysis 

of daily mean streamflow data for planning-level water-quality

analyses but also are useful for many other applications pertaining to streamflow data and statistics.

These programs and the associated documentation are 

included on the CD-ROM accompanying this report. This 

report and the appendixes on the CD-ROM describe the

implementation and use of the programs and the interpretation of results from the programs. The body of this report 

provides an overview of the five programs included on this

CD-ROM. The appendixes are the software manuals for each

program. These manuals describe statistical and numerical 

methods used to implement each program, input-file formats,

output-file formats, installation of the programs, and use of the

programs. Each appendix is written as a self-contained manual

because each program may have many uses alone or in tandem 

with other programs on the CD-ROM. Each of these programs 

uses graphical user interface that follows standard Microsoft 

Windows interface conventions.

Introduction

Streamflow information is important for many planning

and design activities including water-supply analysis, habitat 

protection, bridge and culvert design, calibration of surface 

and ground-water models, and water-quality assessments. 

Streamflow information is especially critical for water-quality

assessments (Warn and Brew, 1980; Di Toro, 1984; Driscoll 

and others, 1989; Driscoll and others, 1990, a,b). Calculation of streamflow statistics for receiving waters is necessary to estimate the potential effects of point sources such 

as wastewater-treatment plants and nonpoint sources such 

as highway and urban-runoff discharges on receiving water. 

Streamflow statistics indicate the amount of flow that may

be available for dilution and transport of contaminants (U.S. 

Environmental Protection Agency, 1986; Driscoll and others, 

1990, a,b). Streamflow statistics also may be used to indicate

receiving-water quality because concentrations of water-quality constituents commonly vary naturally with streamflow. For

example, concentrations of suspended sediment and sedimentassociated constituents (such as nutrients, trace elements, and 

many organic compounds) commonly increase with increasing 

flows, and concentrations of many dissolved constituents commonly decrease with increasing flows in streams and rivers

(O’Connor, 1976; Glysson, 1987; Vogel and others, 2003, 

2005).

Reliable, efficient and repeatable methods are needed

to access and process streamflow information and data. For

example, the Nation’s highway infrastructure includes an innumerable number of stream crossings and stormwater-outfall 

points for which estimates of stream-discharge statistics may 

be needed. The U.S. Geological Survey (USGS) streamflow

data-collection program is designed to provide streamflow

data at gaged sites and to provide information that can be used 

to estimate streamflows at almost any point along any stream

in the United States (Benson and Carter, 1973; Wahl and 

others, 1995; National Research Council, 2004). The USGS 

maintains the National Water Information System (NWIS), a 

distributed network of computers and file servers used to store
2 Computer Programs for Obtaining and Analyzing Daily Mean Streamflow Data

and retrieve hydrologic data (Mathey, 1998; U.S. Geological 

Survey, 2008). NWISWeb is an online version of this database 

that includes water data from more than 24,000 streamflowgaging stations throughout the United States (U.S. Geological 

Survey, 2002, 2008). Information from NWISWeb is commonly used to characterize streamflows at gaged sites and to

help predict streamflows at ungaged sites.

Streamflow Analysis for Water-Quality 

Modeling

The USGS, in cooperation with the Federal Highway 

Administration (FHWA), began a study to develop the 

stochastic empirical loading and dilution model (SELDM) 

in 2003. SELDM is a water-quality model that uses available data and stochastic Monte Carlo methods to generate 

planning-level estimates of water-quality constituent concentrations, discharges, and loads from the watershed upstream 

of the highway, from the highway, and in the receiving water 

downstream from the highway discharge for storm events 

(fig. 1). This information can be used to evaluate highway

runoff as a source of constituents, the potential effects of these 

loads on receiving-water quality, and the potential effectiveness of best management practices (BMPs) to control the 

highway-runoff contribution to the downstream water discharge, constituent concentrations, and loads. Use of such a 

runoff-quality model creates a need for national, regional, and 

local estimates of streamflow statistics. The effort, time, and

expense required to collect and analyze streamflow data at a

site of interest, however, limit the availability of such data for 

any given site. Therefore, methods to develop robust planninglevel estimates of these data at unmonitored sites across the 

country would be needed. These estimates would be made on 

a regional basis with data that are available from the USGS for 

a national-scale model.

A mass-balance approach (fig. 1) commonly is applied

to estimate the concentrations and loads of water-quality 

constituents in receiving waters downstream of an urban- or 

highway-runoff outfall during storm events (Driscoll and others, 1979; Warn and Brew, 1980; Di Toro, 1984; Driscoll and 

others 1989; Driscoll and others 1990a,b). In a mass-balance 

model, the loads (the product of measured water discharge 

and concentration) of the upstream and runoff components are 

added to calculate the discharge, concentration, and load in 

the (fully mixed) receiving water downstream of the outfall.

In the application of a mass-balance model, however, statistics 

describing the frequency distributions of component discharges and concentrations are used to determine the statistics 

for downstream discharges, concentrations, and loads (Warn 

and Brew, 1980). For example, DiToro (1984) used information about probability distributions of event mean concentrations (EMCs) and storm-runoff discharges from the outfall and 

the upstream basin to develop an empirical probabilistic-dilution model for planning-level estimates of downstream EMCs 

and water discharges. DiToro (1984) based his method on the 

assumption that contributing discharges and concentrations 

are independent and lognormally distributed. Planning-level 

estimates from this model indicate the potential for exceeding water-quality criteria and, therefore, the potential need for 

more information and data that may be used to identify suitable mitigation measures.

Estimating prestorm flows and runoff from the site of

interest and the upstream basin is central to the conceptualization and implementation of a mass-balance approach for 

predicting the water discharge, constituent concentrations, and 

associated constituent loads from runoff and receiving waters 

(Warn and Brew, 1980; Schwartz and Naiman, 1999). Warn 

and Brew (1980) indicate that upstream concentrations and 

loads are correlated. Similarly, Schwartz and Naiman (1999) 

demonstrate the importance of good streamflow estimates and

the effect of the correlation between constituent concentrations and streamflow in receiving waters on the adequacy of

planning-level estimates of constituent concentrations and 

loads. Although surface runoff for the upstream watershed 

and at the site of interest would be correlated with rainfall for 

a given storm event, total upstream flow would have a lower

correlation because of the potential variation in prestorm flow.

Granato and others (2009) describe methods for developing 

planning-level estimates of background constituent concentrations by use of streamflow-based water-quality transport

curves. Estimates of upstream flow and concentration may

be used with statistics describing the population of highwayrunoff discharges and constituent concentrations (Granato 

and Cazenas, 2009) to derive mass-balance estimates of the 

population of downstream concentrations, flows, and loads in

a receiving water body.

As part of this study, data from 2,783 selected USGS 

streamflow-gaging stations across the conterminous United

States (fig. 2) were identified and analyzed to help characterize prestorm streamflow statistics. Long records (years to

decades) are commonly needed to characterize variations in 

streamflow through time. Therefore, streamflow statistics were

calculated from data available for the period 1960–2003. One 

40-year record may include about 14,610 daily mean streamflow values and require about 400,000 bytes of computer-disk

space. Hundreds to thousands of such data files are necessary to characterize national variations in streamflow because

streamflow statistics vary from site to site and are affected

by a number of natural and anthropogenic factors (Langbein, 

1949; Thomas and Benson, 1970; Poff, 1996; Lins, 1997; 

Poff and others, 2006). Assuming that the U.S. Environmental 

Protection Agency (2004b) level III ecoregions are hydrologically similar regions, each ecoregion may be used to estimate 

streamflow statistics for planning-level water-quality analyses. Automated data-collection and processing methods were 

needed to compile and analyze streamflow information and

data. Data from additional stations or data from subsequent 

years may be obtained from NWISWeb and analyzed by use 

of the tools and techniques described in the appendixes of this

report. The computer programs documented in this report also 

are applicable for many other types of hydrologic studies at a 

local, state or regional scale.
Introduction 

3

Upstream Load

Downstream Load CQUSUSConcentration Discharge C

QDSDSConcentration Discharge

CQ

HRHR

ConcentrationDischarge

Highway-Runoff Load

CDS

Cumulative

Frequency

QDS

Cumulative

Frequency

CHR

Cumulative

Frequency

QHR

Cumulative

Frequency

QHR

Cumulative

Frequency

Random Discharge

CHR

Cumulative

Frequency

Random Concentration

Concentration from Transport Curve with Random Variation Random Discharge

Random Concentration

Random Discharge

Random Concentration

US HRDS DS

US HR DS

 US HR DS

C + C = C Q Q

Q + Q = Q

Q Q

Stochastic Mass Balance for Multiple Storm Events

Mass Balance for Each Storm Event

Downstream Discharge

Downstream Concentration

Downstream Values(Derived from Mass Balance for Each Event)

(Random Variables)

Highway-Runoff Values Upstream Values

(Variables Random and/or Correlated by Transport Curve)

= +

Downstream Load

 US US HR HR DS DS Q C + Q C = Q C

CUS

QUS

C = mQ + b + e , US US i

where is the slope, is the intercept, and is the random variation. i

mbe

Figure 1. Schematic diagram showing the stochastic mass-balance approach for estimating discharge, concentration, and loads of water-quality constituents upstream of a highway outfall, from the highway, and downstream of a highway-runoff outfall. Upstream concentrations may be random, or may be related to discharge with a transport curve (with random white-noise quantified by an error term ei), highway runoff concentrations are commonly assumed to be random, and the downstream concentration is a function of the highway and upstream loads.
4 Computer Programs for Obtaining and Analyzing Daily Mean Streamflow Data 120°W 110°W 100°W 90°W 80°W 70°W 50°N 40°N 30°N Base from U.S. Geological Survey National Map Ecoregions from U.S. Environmental Protection Agency Geographic projection

Figure 2. Spatial distribution of 2,783 selected U.S. Geological Survey streamflow-gaging stations (black dots) among U.S. Environmental Protection Agency (2003b) Level III ecoregions (colored polygons) that have been discretized to a 15-minute grid in the conterminous United States (geographic projection). The selected U.S. Geological Survey streamflow-gaging stations have at least 24 years of streamflow data collected during 1960–2003 with drainage areas between 10 and 500 square miles that are not listed as being at, near, or immediately below a dam.
Computer Programs for Obtaining and Analyzing Streamflow Data 5

Purpose and Scope

This report and the appendixes on the CD-ROM describe

the implementation, use, and interpretation of results from 

five programs that were written for obtaining and analyzing

streamflow data. This report provides an overview of the five

programs included on this CD-ROM. The appendixes are the

manuals for each program. These manuals describe the statistical and numerical methods used to implement each program. 

The manuals describe input and output file formats. The

manuals also describe methods to install and use the programs. 

Each appendix is written as a self-contained software manual

because each program may have many uses alone or in tandem 

with other programs on the CD-ROM.

Computer Programs for Obtaining and 

Analyzing Streamflow Data

Five computer programs were developed for obtaining 

and analyzing NWISWeb streamflow data. These computer

programs were conceived and written to facilitate the analysis 

of daily mean streamflow data for planning-level water-quality

analyses but also are useful for many other applications for 

streamflow data and statistics. These computer programs

include:

1. Get National Water Information System Streamflow (Q)

files (GNWISQ Version 1.0)—A program for individual

or batch download of streamflow-gaging-station information and daily mean streamflow files;

2. Make Plotting Position file (MkPP Version 1.0)—A

program for generating plotting positions and normal 

scores for daily mean streamflow files from the USGS

NWISWeb site;

3. Streamflow Record-Extension Facilitator (SREF Version 1.0)—A program for extension or augmentation of

available streamflow data by using long-term streamflow

records at hydrologically similar sites. 

4. Streamflow (Q) Statistics (QSTATS Version 1.0)—A program for calculating population statistics for streamflow

data; and 

5. Make U.S. Environmental Protection Agency DFLOW3 

batch input files (MkDF Version 1.0)—A program to

facilitate mass processing of daily mean streamflow files

by the U.S. Environmental Protection Agency (2004a) 

DFLOW3 computer program for estimating design 

streamflows for use in water-quality standards and Total

Maximum Daily Load (TMDL) waste-load allocations.

The computer programs are documented on the CD-ROM 

accompanying this report. Each of these Visual Basic programs has a graphical user interface that follows standard 

Microsoft Windows interface conventions.

The GNWISQ program was developed to facilitate the 

process for downloading streamflow-gaging-station information and daily mean streamflow data files from the USGS

NWISWeb site. The GNWISQ program has an individual-file

mode to retrieve information and data for one streamflowgaging-station. The program also has a batch-file mode to

retrieve information and data for multiple streamflow-gagingstations. The program also has the capability to reformat the 

current (2006) NWISWeb text-file format to an earlier, more

consistent, NWISWeb text-file format. The program provides

error files to document any problems that may occur. The

output from the GNWISQ program can be used to facilitate 

hydrologic-data analysis with multiple programs in individual 

or batch mode.

The MkPP program was developed to facilitate visual 

analysis of daily mean streamflow data. Hydrologic analysis

of streamflow data may be improved by visual inspection of

a probability plot or flow-duration curve of the data values.

The program was designed to sort the data and provide a 

condensed file of the plotting positions, percentiles, normal

frequency factors, Pearson Type III frequency factors, and 

associated data. The program reads daily-value data files that

have been downloaded from the USGS NWISWeb site and 

reformatted to a common format with GNWISQ. The output 

file from the MkPP program can be used to facilitate rapid

production of probability plots and flow-duration curves using

simple spreadsheet or graphing software commonly available 

on most personal computers. 

The SREF program was developed to provide an estimated long-term record of daily mean streamflows (record

extension) or long-term estimates of streamflow statistics

(record augmentation) at sites with limited data. SREF can 

be used to extend or augment limited data from a partialrecord site or short-term streamflow-gaging-station by using

data from a representative long-term continuous-record 

streamflow-gaging-station. Record extension and augmentation are based on the assumption that long-term streamflow

records from hydrologically similar sites can be used to estimate values at a site of interest with limited data. The SREF 

program implements the maintenance of variance extension

type 1 (MOVE.1) methods described by Hirsch (1982) and the 

maintenance of variance extension type 3 (MOVE.3) method

described by Vogel and Stedinger (1985). The program also 

facilitates record extension with a single or multisegment

regression model developed by use of the nonparametric 

Kendall-Theil Robust Line (KTRLine) program (Granato, 

2006). The program provides graphical displays of the data, 

regression lines and residual statistics to facilitate the analytical process. The program outputs a file of paired data values

and a file with regression statistics. The user may output files

containing an estimated record of daily mean streamflow data

and files containing estimates of selected long-term statistics

for the site of interest.

 The QSTATS program was developed to facilitate statistical analysis of daily mean streamflow data for one station or

multiple stations. The program reads daily-value data files that
6 Computer Programs for Obtaining and Analyzing Daily Mean Streamflow Data

have been downloaded from the USGS NWISWeb site and 

reformatted to a common format with GNWISQ. The program 

can be used to calculate the average, standard deviation, skew, 

and median of daily mean streamflow values in arithmetic and

common logarithmic (Log10) space. The program provides 

the option to calculate probability weighted moments and 

L-moments in arithmetic and Log10 space. The program also 

calculates the total number of daily mean streamflow values,

the number of gaps in the record (each of which may be one 

day to several decades long), and the fraction of zero flows

recorded in the data file.

The MkDF program was developed to facilitate creation 

of batch input files for the U.S. Environmental Protection

Agency (2004a) DFLOW3 program. The program reads 

daily-value data files that have been downloaded from the

USGS NWISWeb site and reformatted to a common format 

with GNWISQ. The program was designed to create DFLOW 

input files automatically from a list of USGS streamflowgaging station numbers because streamflow stations must

be manually specified within the DFLOW3 interface. The

DFLOW3 program was developed to calculate water-qualitydesign streamflow statistics. Low-flow statistics including the

1-day 3-year biological low flow (1B3) and the 4-day 3-year

biological low flow (4B3) are known as water-quality-design

streamflows because low-flow statistics represent a streamflow

with a specified exceedance frequency that is used for setting

water-quality criteria and TMDL waste-load allocations. These 

low-flow statistics may also be used with estimates of runoff

from a watershed to estimate the potential for water-quality 

exceedances from stormwater runoff that occurs during lowflow periods.

Summary

Reliable, efficient, and repeatable methods are needed to

access and process streamflow information and data because

streamflow information is important for many planning and

design activities including water-supply, habitat protection, 

bridge and culvert design, and water-quality assessments. 

The U.S. Geological Survey (USGS) in cooperation with the 

Federal Highway Administration developed five computer

programs as part of the effort to develop the stochastic empirical loading and dilution model because streamflow information is especially critical for water-quality assessments. These 

computer programs were conceived and written to facilitate 

the analysis of daily mean streamflow data for planning-level

water-quality analyses but also are useful for many other 

applications pertaining to streamflow data and statistics.

Streamflow data and information are available to the

public on the USGS NWISWeb site, and these five computer programs were developed to facilitate streamflow data

analysis. The GNWISQ program can be used to download files

containing streamflow-gaging-station information and daily

mean streamflow data from the NWISWeb site. The MkPP

program can be used to produce statistics for visual analysis of 

daily mean streamflow data. The SREF program can be used

to augment or extend limited data from a partial-record site

or short-term streamflow-gaging station by using data from a

representative long-term continuous-record streamflow-gaging

station. The QSTATS can be used for statistical analysis of 

daily mean streamflow data. The MkDF program can be used

to create batch input files for the U.S. Environmental Agency

DFLOW3 program.

These five computer programs are documented on the

CD-ROM accompanying this report. This report and the 

appendixes on the CD-ROM describe the implementation and

use of the programs and the interpretation of results from the 

programs. The body of this report provides an overview of 

the five programs on this CD-ROM. The appendixes are the

manuals for each program. These manuals describe the statistical and numerical methods used to implement each program, 

input-file formats, output-file formats, installation of the

programs, and use of the programs. Each appendix is written

as a self-contained manual because each program may have 

many uses alone or in tandem with other programs on the CDROM. Each of these Visual Basic programs has graphical user 

interface that follows standard Microsoft Windows interface 

conventions.

Acknowledgments

The author thanks several subject-matter experts within

the USGS who were instrumental in the effort to develop and 

deploy this suite of computer programs. Elizabeth Ahearn, 

Gardner Bent, Sara Brandt, Ken Eng, Julie Kiang, William H. 

Kirby, Gene Parker, and Marla Stuckey of the USGS provided 

input and technical reviews that helped the author improve 

these computer programs and the associated manuals. Patricia 

Cazenas of the Federal Highway Administration, Gene Parker, 

and Marla Stuckey provided technical and editorial feedback 

that helped the author improve this report.
References Cited 7

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