HYSEP: A COMPUTER PROGRAM FOR STREAMFLOW

HYDROGRAPH SEPARATION AND ANALYSIS

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 96-4040
HYSEP: A COMPUTER PROGRAM FOR STREAMFLOW

HYDROGRAPH SEPARATION AND ANALYSIS

by Ronald A. Sloto and Michèle Y. Crouse

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 96-4040

Lemoyne, Pennsylvania

1996
ii

U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Gordon P. Eaton, Director

The use of firm, trade, and brand names in this report is for identification purposes only

and does not constitute endorsement by the U.S. Geological Survey.

For additional information Copies of this report may be

write to: purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

840 Market Street Box 25286

Lemoyne, Pennsylvania 17043-1586 Denver, Colorado 80225-0286
iii

CONTENTS

Page

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

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

Purpose and scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Limitations and cautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Hydrograph-separation methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Fixed-interval method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Sliding-interval method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Local-minimum method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Program input requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Program output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Hydrograph separation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Cumulative annual base-flow distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Flow duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Seasonal flow distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Daily-values files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

How HYSEP works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

User interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Data panel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Assistance panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Instruction panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Special files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

System defaults—TERM.DAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Session record—HYSEP.LOG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Error and warning messages—ERROR.FIL . . . . . . . . . . . . . . . . . . . . . . . 17

Program options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Default settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Specifying input files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Selecting WDM file data sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Add. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Browse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Find . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Selecting program output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Data files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Graphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Modifying plot parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Selection of hydrograph-separation method. . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Execution of the base-flow separation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

References cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
iv

CONTENTS—CONTINUED

Page

Appendix 1. Annual base-flow summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Appendix 2. Monthly summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Appendix 3. Cumulative-distribution table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Appendix 4. Flow-duration table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Appendix 5. Seasonal-distribution table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Appendix 6. Special files. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

TERM.DAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

HYSEP.LOG. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

ILLUSTRATIONS

Figures 1-7.Graphs showing:

1. Daily mean streamflow and estimated base flow for

French Creek near Phoenixville, Pa., 1992 . . . . . . . . . . . . . . . . . . . . 4

2. Hydrograph analysis using the fixed-interval method for

French Creek near Phoenixville, Pa., April 1992. . . . . . . . . . . . . . . . 5

3. Hydrograph analysis using the sliding-interval method for

French Creek near Phoenixville, Pa., April 1992. . . . . . . . . . . . . . . . 6

4. Hydrograph analysis using the local-minimum method for

French Creek near Phoenixville, Pa., April 1992. . . . . . . . . . . . . . . . 7

5. Cumulative distribution function of mean annual streamflow,

estimated mean annual surface runoff, and estimated

mean annual base flow for French Creek near

Phoenixville, Pa., 1969-92 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

6. Duration of total streamflow, estimated surface runoff,

and estimated base flow for French Creek near

Phoenixville, Pa., 1969-92 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

7. Estimated mean monthly surface runoff and base flow for

French Creek near Phoenixville, Pa., 1969-92. . . . . . . . . . . . . . . . . 12

8. Basic screen layout and commands for HYSEP . . . . . . . . . . . . . . . . . . . . 14

9. Opening screen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

10. Hierarchy of menus in HYSEP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

11. Processing steps following selection of the Execute option. . . . . . . . . . . . 19

12. Browse (WSB) data-set information selection screen . . . . . . . . . . . . . . . . 21

13. Browse (WSB) data-set information screens . . . . . . . . . . . . . . . . . . . . . . . 22

14. Output options screen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

15. Graphical output screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

16. Plot modification menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

17. Plot parameter modification menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

18. Base name and date specification screen . . . . . . . . . . . . . . . . . . . . . . . . . . 29
v

TABLES

Page

Table 1. U.S. Geological Survey National Water Data Storage and

Retrieval System (WATSTORE) daily values 80-character

record ASCII format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2. WDM file data search options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3. Output file name suffixes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

APPENDIX 6 TABLES

Table 1. TERM.DAT parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

2. MENCRA values and corresponding program response . . . . . . . . . . . . 35

3. Example TERM.DAT file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

4. TERM.DAT parameters for color display

(DOS-based computers) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5. Codes used for nonprinting characters in a log file. . . . . . . . . . . . . . . . . 41

6. Description of example log file. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

CONVERSION FACTORS AND ABBREVIATIONS

Multiply By To obtain

inch (in.) 25.4 millimeter

square mile (mi 2) 2.59 square kilometer

million gallons per day (Mgal/d) 0.04381 cubic meter per second

million gallons per day per square

mile [(Mgal/d)/mi2

] 0.0169 cubic meter per second persquare kilometer

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

cubic foot per second per square

mile [(ft3

/s)/mi2] 0.01093 cubic meter per second persquare kilometer
vi
1

HYSEP: A COMPUTER PROGRAM FOR STREAMFLOW

HYDROGRAPH

SEPARATION AND ANALYSIS

By Ronald A. Sloto and Michèle Y. Crouse

ABSTRACT

HYSEP is a computer program that can be used to separate a streamflow hydrograph into baseflow and surface-runoff components. The base-flow component has traditionally been

associated with ground-water discharge and the surface-runoff component with precipitation

that enters the stream as overland runoff. HYSEP includes three methods of hydrograph

separation that are referred to in the literature as the fixed-interval, sliding-interval, and localminimum methods. The program also describes the frequency and duration of measured

streamflow and computed base flow and surface runoff. Daily mean stream discharge is used as

input to the program in either an American Standard Code for Information Interchange (ASCII)

or binary format. Output from the program includes tables, graphs, and data files. Graphical

output may be plotted on the computer screen or output to a printer, plotter, or metafile.

INTRODUCTION

Hydrograph analysis is a useful technique in a variety of water-resource investigations.

Separation of streamflow hydrographs into base-flow and surface-runoff components is used to

estimate the ground-water contribution to streamflow. Hydrograph-separation techniques also

have been used to quantify the ground-water component of hydrologic budgets and to aid in the

estimation of recharge rates. In addition, base-flow characteristics determined by hydrograph

separation of hydrographs from streams draining different geologic terranes have been used to

show the effect of geology on base flow (Sloto and others, 1991, p. 29-33). White and Sloto

(1990) analyzed streamflow hydrographs from 309 Pennsylvania streamflow-measurement

stations to estimate base-flow-frequency characteristics.

Hydrograph separation traditionally has been done manually. Two commonly used methods are

base-flow-recession methods (Olmsted and Hely, 1962; Riggs, 1963; Rorabaugh, 1963) and

curve-fitting methods (Pettyjohn and Henning, 1979; Linsley and others, 1982). Different

hydrologists using the same manual hydrograph-separation method commonly produce

different base-flow estimates. The use of a computer program removes inconsistencies inherent

in manual methods and substantially reduces the time required for hydrograph separation.

Separation of a streamflow hydrograph is based on a mathematical technique that mimics the

way that humans have been separating hydrographs, rather than on the physics of the process.

Thus, although HYSEP consistently applies various algorithms that are commonly used for

hydrograph separation, hydrograph separation remains a subjective process.

Computer hydrograph-separation methods were compared with published values determined

manually for streams in southeastern Pennsylvania by Sloto (1991). Base flows estimated with

computer methods agreed closely with those estimated by manual methods.
2

PURPOSE AND SCOPE

This report documents the streamflow hydrograph-separation and analysis program referred to

as HYSEP. HYSEP employs a character-based interface and can be used on multiple platforms.

The program separates streamflow hydrographs into base-flow and surface-runoff components

and performs frequency and duration analyses on both components. This report describes the

HYSEP program, the hydrograph-separation and analysis methods used, program design and

operation, input requirements, and program output.

The methods for streamflow hydrograph separation used in this program were adapted from

Pettyjohn and Henning (1979) and were originally incorporated in 1982 into a computer

program that used streamflow data in standard U.S. Geological Survey (USGS) daily-values

format. The version of the HYSEP program described by this report is coded so that other

methods of hydrograph separation can easily be incorporated when the methods are

computerized. Figures and appendixes in this report were produced by use of HYSEP.

LIMITATIONS AND CAUTIONS

The streamflow hydrograph-separation methods used by this program are intended to provide

estimates of base flow and surface runoff to streams. Generally, average annual estimates are

more reliable than monthly or daily estimates of base flow or surface runoff.

Base-flow estimates are affected by regulation, which changes the natural flow of a stream and

influences both base flow and surface runoff. A flood-control reservoir, for example, slowly

releases runoff after a storm, resulting in an apparent decrease in surface runoff and an apparent

increase in base flow. Regulation includes reservoir storage and releases, discharge from quarry

and mine dewatering, discharge from sewage treatment plants, and diversion for water supply.

White and Sloto (1990, p. 22) found that the effect of regulation is site specific; annual base

flows decreased for the majority of streams in the Delaware River Basin and increased for the

majority of streams in the Susquehanna and Ohio River Basins subsequent to regulation.

The accuracy of estimates of base-flow-frequency characteristics depends on the period of

record used in the analysis. Record for a station operated during a period of extreme

climatological conditions, such as mostly dry years, exhibits a bias toward the extreme. A longterm station with record representative of long-term climatological conditions provides a more

reliable base-flow estimate because extremes have less weight in the determination of base-flow

characteristics.

Input data should be carefully checked. Plotting input data provides an excellent visual check

for periods of suspect data. For large data sets, plotting the annual hydrograph to the screen for

each year of data provides a quick and efficient check on the validity of the input data and the

hydrograph separation. The use of this program to analyze data from multiple stations with long

periods of record without carefully checking the input data may result in erroneous estimates of

base flow and surface runoff. It is the responsibility of the user to correctly interpret the

usefulness of any results for the specific application.
3

HYDROGRAPH-SEPARATION METHODS

The HYSEP program uses three methods to separate the base-flow and surface-runoff

components of a streamflow hydrograph—fixed interval, sliding interval, and local minimum.

These methods can be described conceptually as three different algorithms to systematically

draw connecting lines between the low points of the streamflow hydrograph. The sequence of

these connecting lines defines the base-flow hydrograph. The techniques were developed by

Pettyjohn and Henning (1979). Hydrograph separations for the streamflow-measurement

station French Creek near Phoenixville, Pa., using the three methods are shown in figure 1. Each

method is described below.

The duration of surface runoff is calculated from the empirical relation:

N=A0.2, (1)

where N is the number of days after which surface runoff ceases, and A is the drainage area in

square miles (Linsley and others, 1982, p. 210). The interval 2N* used for hydrograph

separations is the odd integer between 3 and 11 nearest to 2N (Pettyjohn and Henning, 1979, p.

31). For example, the drainage area at the streamflow-measurement station French Creek near

Phoenixville, Pa. (USGS station number 01472157), is 59.1 mi2. The interval 2N* is equal to

5, which is the nearest odd integer to 2N, where N is equal to 2.26.

The hydrograph separation begins one interval (2N* days) prior to the start of the date selected

for the start of the separation and ends one interval (2N* days) after the end of the selected date

to improve accuracy at the beginning and end of the separation. If the selected beginning and

(or) ending date coincides with the start and (or) end of the period of record, then the start of the

separation coincides with the start of the period of record, and (or) the end of the separation

coincides with the end of the period of record.
4

FIXED-INTERVAL METHOD

SLIDING-INTERVAL METHOD

DISCHARGE, IN CUBIC FEET PER SECOND

LOCAL-MINIMUM METHOD

103

102

10

103

102

10

103

102

10

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

1992

Figure 1. Daily mean streamflow and estimated base flow for French Creek near Phoenixville, Pa., 1992.

MEASURED FLOW

ESTIMATED BASE FLOW

MEASURED FLOW

ESTIMATED BASE FLOW

MEASURED FLOW

ESTIMATED BASE FLOW
5

FIXED-INTERVAL METHOD

The fixed-interval method assigns the lowest discharge in each interval (2N*) to all days in that

interval starting with the first day of the period of record (fig. 2). The method can be visualized

as moving a bar 2N* days wide upward until the bar first intersects the hydrograph. The

discharge at that point is assigned to all days in the interval. The bar is then moved 2N* days

horizontally, and the process is repeated. The interval 2N* is 5 days in figure 2. For example,

in the interval April 5 to 9, the lowest discharge, 49 ft3/s, is assigned as the base-flow

component to every day in that interval. The assigned values are then connected to define the

base-flow hydrograph.

APRIL 1992

Figure 2. Hydrograph analysis using the fixed-interval method for French Creek near

Phoenixville, Pa., April 1992. DISCHARGE, IN CUBIC FEET PER SECOND

100

90

80

70

60

50

40

30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

SURFACE

RUNOFF

BASEFLOW
6

SLIDING-INTERVAL METHOD

The sliding-interval method finds the lowest discharge in one half the interval minus 1 day

[0.5(2N*-1) days] before and after the day being considered and assigns it to that day (fig. 3).

The method can be visualized as moving a bar 2N* wide upward until it intersects the

hydrograph. The discharge at that point is assigned to the median day in the interval. The bar

then slides over to the next day, and the process is repeated. In the interval April 16 to 20, the

lowest discharge, 42 ft3/s, is assigned to April 18, the median day in the interval (fig. 3). The

assigned daily values are then connected to define the base-flow hydrograph.

APRIL 1992

DISCHARGE, IN CUBIC FEET PER SECOND

100

90

80

70

60

50

40

30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

SURFACE

RUNOFF

BASEFLOW

Figure 3. Hydrograph analysis using the sliding-interval method for French Creek near

Phoenixville, Pa., April 1992.
7

LOCAL-MINIMUM METHOD

The local-minimum method checks each day to determine if it is the lowest discharge in one

half the interval minus 1 day [0.5(2N*-1) days] before and after the day being considered. If it

is, then it is a local minimum and is connected by straight lines to adjacent local minimums

(fig. 4). The base-flow values for each day between local minimums are estimated by linear

interpolations. The method can be visualized as connecting the lowest points on the hydrograph

with straight lines. In figure 4, local minimums occur on April 9, 15, 21, and 24.

APRIL 1992

DISCHARGE, IN CUBIC FEET PER SECOND

100

90

80

70

60

50

40

30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

SURFACE

RUNOFF

BASEFLOW

Figure 4. Hydrograph analysis using the local minimum method for French Creek near

Phoenixville, Pa., April 1992.
8

PROGRAM INPUT REQUIREMENTS

The HYSEP program accepts daily mean stream discharge as input in either of two formats:

(1) the standard USGS National Water Data Storage and Retrieval System (WATSTORE) daily

values, 80-character record American Standard Code for Information Interchange (ASCII)

format (table 1) (Williams, 1975, p. A21-A23); or (2) the binary, direct access Watershed Data

Management (WDM) file format (Flynn and others, 1995, p. 12-14). Daily-values data in the

WATSTORE format can be retrieved from the USGS WATSTORE or Automated Data

Processing System (ADAPS) data bases. Data in the WATSTORE daily values format can be

converted to the WDM format by the IOWDM program (Lumb and others, 1990, p. 163-211).

Data for 1 station in the WATSTORE daily values format and up to 300 stations in the WDM

format can be processed at one time. A minimum of 1 and a maximum of 100 years of data per

station in either format can be processed.

Table 1. U.S. Geological Survey National Water Data Storage and Retrieval

System

(WATSTORE) daily values 80-character record ASCII format

[Columns 1-24 are integers; columns 25-80 are decimal numbers]

column numeric code

 1 Format number—Daily values are designated by the number 3.

2-16 Station-identification number.

17-20 Calendar year—A four-digit number representing the calendar year.

21-22 Month—A two digit number representing the month.

23-24 Record number—A two-digit number representing the days of the month for the

data. The record number is coded as follows:

Number

01

02

03

04

Days

1-8

9-16

17-24

25-31

25-80 Daily values—Eight, seven-column fields (25-31, 32-38, 39-45, 46-52, 53-59,

60-66, 67-73, 74-80) in which daily values are coded for the days designated.

Blank fields are read as zero values.
9

PROGRAM OUTPUT

Program output options, including tables, graphs, ASCII files, and WDM data sets, are

described in the following sections. In the tables, missing values are designated by -1.0. Graphs

may be plotted on the computer screen or sent to a printer, plotter, or metafile.

HYDROGRAPH SEPARATION

The HYSEP program will produce an annual hydrograph of streamflow and estimated base flow

for each year of record processed (fig. 1). The period of record analyzed can begin with any day

of the calendar year. Tabular output from the hydrograph separation summarizes the quantity of

estimated base flow and surface runoff and the percentage of streamflow as base flow and

surface runoff. An annual summary of base flow in units of inches, cubic feet per second, and

million gallons per day per square mile is provided by default (Appendix 1). Alternatively, a

monthly summary can be selected that gives monthly values of mean streamflow (cubic feet per

second), total streamflow (inches), mean base flow (cubic feet per second and million gallons

per day per square mile), total base flow (inches), mean surface runoff (cubic feet per second),

total surface runoff (inches), and percentage of streamflow as base flow (Appendix 2).

CUMULATIVE ANNUAL BASE-FLOW DISTRIBUTION

A cumulative distribution function accumulates all of the probabilities of values less than or

equal to the value of interest. When the probability density curve (probability distribution) is

cumulated from the left, probabilities of not exceeding various magnitudes are obtained; this is

commonly referred to as a frequency curve in hydrology (Riggs, 1968, p. 1-3). Cumulative

distributions commonly are plotted on a probability scale, such that the theoretical curve is a

straight line.

Cumulative distribution functions of mean annual streamflow, estimated mean annual base

flow, and estimated mean annual surface runoff for the period of record of a station can be

tabled and plotted for any hydrograph-separation method. Mean annual base flows are arranged

in order of magnitude beginning with the smallest as number one. A Weibull plotting position

estimate of the probability (p) of an annual mean base-flow value being less than a particular

magnitude is calculated by

p = m/(n + 1), (2)

where m is the order number of the individual year in the sample, and n is the number of years

of record.

The cumulative distribution function of mean annual streamflow, estimated mean annual base

flow, and estimated mean annual surface runoff for 1969-92 for French Creek near

Phoenixville, Pa., are shown in figure 5. Estimated mean annual base flow can be printed as a

table (Appendix 3).
10

For mean annual base flow, the recurrence interval is the average interval of time during which

annual base flow will be less than a particular value. The recurrence interval is the inverse of

the cumulative probability function. Recurrence interval (T) may be calculated by

 T = (n + 1)/m = 1/p, (3)

where n is the number of years of record, and m is the order number of the individual year in

the sample.

PERCENTAGE OF TIME RUNOFF WAS LESS THAN

OR EQUAL TO INDICATED VALUE

RUNOFF, IN INCHES

40

0.5 2 5 10 20 50 70 90 95 98 99.5

36

32

28

24

20

16

12

8

4

0

TOTAL STREAMFLOW

SURFACE RUNOFF

BASE FLOW

Figure 5. Cumulative distribution function of mean annual streamflow, estimated

mean annual surface runoff, and estimated mean annual base flow for French

Creek near Phoenixville, Pa., 1969-92.
11

FLOW DURATION

A flow-duration curve is the complement of a cumulative distribution function that shows the

percentage of time specified mean daily discharges were equaled or exceeded during a given

period (Searcy, 1959). The HYSEP program plots flow-duration curves for total streamflow,

estimated base flow, and estimated surface runoff (fig. 6). A flow-duration table (Appendix 4)

can be generated for total streamflow, estimated surface runoff, and estimated base flow.

PERCENTAGE OF TIME FLOW WAS EQUALED OR EXCEEDED

FLOW, IN CUBIC FEET PER SECOND

103

0.5 2 5 10 20 50 70 90 95 98 99.5

102

10

TOTAL STREAMFLOW

SURFACE RUNOFF

BASE FLOW

Figure 6. Duration of total streamflow, estimated surface runoff, and estimated

base flow for French Creek near Phoenixville, Pa., 1969-92.
12

SEASONAL FLOW DISTRIBUTION

The HYSEP program will plot estimated mean monthly base flow and surface runoff as a bar

graph (fig. 7). The graph shows seasonal differences in base flow and surface runoff. The

estimated mean monthly base flow and surface runoff for French Creek at Phoenixville, Pa., for

1969-92 are shown in figure 7. The quantity of surface runoff exceeds that of base flow only in

June. In addition, a seasonal-distribution table (Appendix 5) can be generated for estimated

mean monthly base flow and surface runoff.

DAILY-VALUES FILES

Daily values of estimated base flow or surface runoff in the WATSTORE daily values format

(table 1) can be written to a file by selecting the appropriate program option. The ASCII file that

is generated can be used as input to other applications. AVERAGE MONTHLY DISCHARGE, IN CUBIC FEET PER SQUARE MILE

Figure 7. Estimated mean monthly surface runoff and base flow for French Creek near

Phoenixville, Pa., 1969-92.

2.5

2

1.5

1

0.5

0

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

BASE FLOW

SURFACE RUNOFF
13

HOW HYSEP WORKS

HYSEP was written to be portable and, therefore, can be used on multiple computer platforms.

Installation procedures depend on the computer platform, and specific installation instructions

are distributed with the software. Once the software is installed, type “hysep” to start the

program.

USER INTERFACE

Program interaction takes place in a screen 80 characters wide by 24 characters high. The basic

screen layout is shown in figure 8. Each screen consists of a list of available commands

displayed at the bottom and one or more boxed-in areas that are referred to as panels.

Commands are used to obtain additional information and to move between screens. The three

types of panels are data, assistance, and instruction. The data panel displayed at the top of the

screen is always present. Data panels contain menus, forms, tables, and text to permit user

interaction with the program. An assistance panel may be present depending on user or program

assignments. When present, the assistance panel is displayed below the data panel (usually as

the middle panel) and contains information, such as help messages, valid range of values, and

details on program status. The instruction panel is displayed above the available commands

when the user is expected to interact with the program. When present, the instruction panel

contains information on what keystrokes are required to interact with the program.

Each screen can be identified by a name and the path selected to reach the screen. The screen

name appears in the upper left corner of the data panel, where the words “screen name” appear

in figure 8. The first screen displayed by the program is named “Opening screen.” All

subsequent screens are named on the basis of the menu option or program sequence that caused

the current screen to be displayed. Screen names are followed by “(path)” (fig. 8), a string of

characters consisting of the first letter(s) of the menu options selected in order to arrive at the

current screen. In some cases, descriptive text may follow the path to further help identify the

screen. The path can aid in keeping track of the position of the current screen in the menu

hierarchy. For example, “Open (WFO)” indicates that the menu option Open was selected and

that the path to this screen from the “Opening screen” consisted of three menu selections—

Wdm, File, and Open.

COMMANDS

The screen commands and their associated keystrokes are described in figure 8. A subset of the

screen commands is available for any given screen. Most commands can be executed by

pressing a single function key. (The designation for a function key is “F#” where # is the number

of the function key.) All of the commands can be executed in “command mode.” Command

mode is toggled on and off by pressing the semicolon (;) key1. In command mode, any

command can be executed by pressing the first letter of the command name; for example, “o”

or “O” for the Oops command. When commands are discussed in this report, the command

name is spelled out with the function key or keystroke given in parentheses. For example,

Accept (F2) is the most frequently used command.

Use Help (F1) and Limits (F5) to obtain additional information about the current screen and

Status (F7) to obtain information on the state of the program. Cmhlp (;c) will display

information on the available commands. Use Quiet (F8) to close the assistance panel. To move

1 On some systems the F3 key and (or) the escape key (Esc) may also work.
14

Help: Accept: Prev: Limits: Status: Intrpt: Quiet: Cmhlp Oops

instruction type

F1 F4

assistance type

screen name (path)

Assistance panel

Instruction panel

Data panel

F2 F5 F7 F6 F8

HYSEP 2.0

Figure 8. Basic screen layout and commands for HYSEP.

command associated

keystrokes1

1 The function keys will execute the commands on most computer systems. On all computer systems, the semicolon key (“;”)

followed by the first letter (upper or lower case) of the command can be used to execute the commands. The F3 function key may

not be available on some systems.

description

Help F1

or ;h

Displays help information in the assistance panel. The help information is updated as the user

moves from field to field in the data panel or to a different screen. The program automatically

closes the assistance panel if a screen is displayed for which no help information is available.

Accept F2

or ;a

Indicates that you have “accepted” the input values, menu option currently highlighted, or text

message in the data panel. Selection of this command causes program execution to continue.

Cmhlp F3c

or ;c

Displays brief descriptions of the commands available on the screen.

Oops F3o

or ;o

Resets all data fields in an input form to their initial values.

Dnpg F3d

or ;d

Displays next “page” of text in data panel. Available when all of the text cannot be displayed at

one time.

Uppg F3u

or ;u

Redisplays previous “page” of text in data panel. Available after execution of Dnpg (F3d).

Prev F4

or ;p

Redisplays a previous screen. Any modifications in the data panel are ignored. Which screen is

the previous one may be ambiguous in some cases.

Limits F5

or ;l

Displays valid ranges for numeric fields and valid responses for character fields. Information on

field limits is updated as the user moves from field to field in the data panel or to a different

screen by using the arrow keys or the Enter (Return) key.

Intrpt F6

or ;i

Interrupts current processing. Depending on the process, returns the program to the point of execution prior to the current process or advances to the next step in the process.

Status F7

or ;s

Displays program status information.

Quiet F8

or ;q

Closes the assistance panel. Available when the assistance panel is open.

Xpad F9

or ;x

Opens the assistance panel as a “scratch pad.” Text entered in the scratch pad is saved in a file

called “XPAD.DAT”.
15

between screens, use Accept (F2), Prev (F4), Intrpt (F6), Dnpg (;d), or Uppg (;u). To reset the

values in the data panel, use Oops (;o). Xpad (F9) is used to save typed information in a file

called XPAD.DAT.

DATA PANEL

The four types of data panels are menu, form, table, and text. Menus offer a choice of two or

more options. Data values are entered or modified in one or more data fields of a form or table.

General or specific information, program progress, messages, and results of analyses may be

displayed in a text data panel. The data panel appears at the top of the screen (fig. 8). There are

16 rows in the data panel when the assistance panel is closed and 10 rows when the assistance

panel is open.

A single option is selected from a menu that consists of two or more options. A menu option

can be selected in two ways: (1) press the first letter (not case sensitive) of the menu option; if

more than one menu option begins with the same letter, press in sequence enough characters to

uniquely identify the option; or (2) use the arrow keys to move the cursor to the option and then

execute Accept (F2).

Forms may contain any number and combination of character, numeric, file name, or option

fields. Character fields may be a variable entry, such as a descriptive text string (case sensitive),

or they may require a specific entry, such as “yes” or “no” (not case sensitive). The text string

“none” in a field indicates that the field is undefined. Option fields are activated and deactivated

by positioning the cursor in the option field and pressing any key, such as the space bar. Use

arrow keys to move up, down, and laterally between fields. The Enter (Return) key is used to

move forward through fields. Use Accept (F2) to accept the entered or modified data and

continue with the program. Executing Oops (;o) sets all fields in the screen to their initial values.

Executing Prev (F4) will cause the data values entered on the screen to be ignored and the

previous screen to be displayed.

Tables may contain any number and combination of character, numeric, and file name columns.

As with forms, character fields may require a specific or a variable entry. Use arrow keys to

move up, down, and laterally between fields. The Enter (Return) key is used to move forward

across rows and to the next row. Some tables may contain more rows than can be displayed in

the 10 or 16 rows of the data panel. In these cases, the table is divided into multiple screens. Use

Accept (F2) to move forward through each of the screens for the table and to continue with the

program after the last screen of the table. Executing Oops (;o) sets all fields in the screen to their

initial values. Executing Prev (F4) will cause the data values entered on the screen to be ignored

and the previous screen to be displayed. Executing Intrpt (F6) will cause the data values entered

on the screen to be ignored and the remaining screens in the table to be skipped. Use Quiet (F8)

to close the assistance panel and view the 16 lines of the data panel.

A text data panel may contain a warning or error message, a tabular list of data, a progress

message for an activity that may take more than a few seconds, or other general information.

Execute Accept (F2) to continue to the next screen. In cases where the displayed text requires

more lines than the number available in the data panel, the Prev (F4), Dnpg (;d), and Uppg (;u)

commands may be used to move forward and backward (scroll) through the screens. The up and

down arrows also may be used to move through the screens. Intrpt (F6) may be available to

permit skipping the remaining screens of text.

ASSISTANCE PANEL

The assistance panel provides information to help the user enter data in the data panel or to allow

note taking during a program session. The panel appears in the middle of the screen below the

data panel. A name corresponding to the type of assistance being provided is displayed in the
16

upper left corner of the panel, where the words “assistance type” appear in figure 8. The Help

(F1), Limits (F5), Status (F7), Cmhlp (;c), and Xpad (F9) commands open the assistance panel.

The program may open the assistance panel to display status information. Help and Limits

provide information about the screen and data fields; Status provides information about the

current process; Cmhlp provides information about the available commands; and Xpad provides

a “note pad” for making notes in the file XPAD.DAT. Use Quiet (F8) to close the assistance

panel.

Assistance panels display four lines at a time. In cases where the assistance information is

greater than four lines, the cursor moves into the assistance panel. Use the up and down arrow

keys to scroll through the information. If available, the Page Down and Page Up keys may be

used to page through the information. Use the command mode toggle (;) to put the cursor back

in the data panel.

INSTRUCTION PANEL

The instruction panel provides information on how to interact with the current screen, such as

how to enter data or how to advance to another screen. This panel appears at the bottom of the

screen just above the screen commands (fig. 8). The instruction panel is present whenever the

program requires input from the user. Up to four lines of text are displayed in an instruction

panel. If an invalid keystroke is entered, the information in the instruction panel is replaced with

an error message. In this case, the panel name (upper left hand corner) changes from the usual

“INSTRUCT” to “ERROR.” Once a valid keystroke is entered, the Instruct panel is redisplayed.

SPECIAL FILES

Three files are associated with the interaction between the user and the program. System

defaults that control how the program operates can be overridden by setting parameters in the

optional TERM.DAT file. A session record is written to the HYSEP.LOG file each time the

program is run; all or parts of this file can be used as input to the program at a later time. Error

and warning messages, as well as some additional information, may be written to the file

ERROR.FIL.

System Defaults—TERM.DAT

Certain aspects of the appearance and operation of the program are controlled by parameters

within the program. These parameters specify things such as the computer system type, graphic

output type, terminal type, program response to the Enter key, and colors. Each parameter is set

on the basis of the preferences of users who tested the program. The preset values can be

overridden by creating a TERM.DAT file in the directory where the program is initiated (the

current working directory). The available parameters and the format of the TERM.DAT file are

described in Appendix 6. If a TERM.DAT file does not exist in the current directory, the

message “optional TERM.DAT file not opened, defaults will be used” is displayed briefly when

the program starts. If the TERM.DAT file is present, the message “reading users system

parameters from TERM.DAT” is displayed.

Session Record—HYSEP.LOG

The keystrokes entered during a program session are recorded in the HYSEP.LOG file. Each

time the program is run, a HYSEP.LOG file is created; if one already exists in the current

directory, it is overwritten. All or part of this file can be used as input to the program as a means

of repeating the same or similar tasks. To do this, first save the HYSEP.LOG file under a

different name. Modify the file to contain only the sequence of commands that need to be

repeated. Then, at any point in a subsequent program session, press the “@” key and a small file

name panel appears. Then, type the name of the log file and press the Enter key. Appendix 6

describes the use and format of the HYSEP.LOG file.
17

Error and Warning Messages—ERROR.FIL

Any error or warning messages produced during a program session are written to the

ERROR.FIL file. Each time the program is run, an ERROR.FIL file is created; if one already

exists in the current directory, it is overwritten. Diagnostic and summary reports also may be

written to this file. Examine ERROR.FIL if an unexpected program response is encountered.

PROGRAM OPTIONS

Typing “hysep” at the operating system prompt starts the program. The Opening screen shown

in figure 9 will appear. The data panel contains the Opening screen menu options, and the

instruction panel explains how to select the menu items. The following options are available:

Card Choose the Card option to specify an input file that contains daily streamflow

values in WATSTORE daily values format.

Wdm Choose the Wdm option if the input data are in a WDM format file.

Output Choose this menu item to specify the format and content of the printed output,

which can contain summary tables of the hydrograph separation and analysis.

Computed daily base flow and surface runoff also can be selected for output

in the WATSTORE or WDM formats.

Plots Choose this option to specify plots and graphical output devices.

Method Choose this option to specify the hydrograph-separation method.

Execute This option is chosen after an input data file has been specified, all desired

tabular and graphical output options have been defined, and the hydrographseparation method has been chosen. Choosing this option initiates execution

of the hydrograph separation.

Query Select Query to display information on who to contact for technical support.

Return Choose this option to terminate the program.

Figure 9. Opening screen.
18

The Return option is included on almost all menu screens. On menus other than the Opening

screen menu, choosing the Return option will return to the previous menu. Return performs the

same function as the Prev (F4) command on forms and tables.

The overall structure of the program and the processing steps that take place upon selection of

the Execute option are diagramed in figures 10 and 11.

DEFAULT SETTINGS

At a minimum, the Card or Wdm option must be chosen to specify the input data file before the

Execute option can be chosen. If no other menu options are chosen, the hydrograph separation

will be performed by use of the following default settings: (1) the fixed-interval hydrographseparation method will be used, (2) a hydrograph of total flow and estimated base flow will be

displayed on the screen for each year of data processed, and (3) an annual summary table will

be included in the print file if 3 or more years of data from the same station are processed.

HYSEP

Card Wdm Output Plots Method Execute

File Select

Open Close Summarize Add Drop List Clear Sort Browse Find Input Output

Query

Fixed Local Sliding

Figure 10. Hierarchy of menus in HYSEP.

(see figure 11)
19

Yes

No

Figure 11. Processing steps following selection of the Execute option.

Is drainage

area included

in data set?

Were

frequency

distribution, flow

duration, or seasonal

distribution plots

requested?

Has entire

period of data

been processed?

Was

graphical

hydrograph

requested?

Execute Option

Specify base name for

output files and period of

data to be processed.

One year’s worth

of data processed.

Have all stations

been processed?

Specify

drainage area.

Graphical

hydrograph

generated.

Yes

Requested

plots

generated.

Yes

No

Yes

No

Return to

Opening

screen.

No

No Yes
20

SPECIFYING INPUT FILES

If input data are in a WATSTORE daily values format file,

Choose the Card option by typing “c”, or execute Accept (F2) while the Card option is

highlighted.

Type the name of the input data file on the file name screen [Card (C)] that appears.

Execute Accept (F2) to open and read the file.

If input data are stored in a WDM format file,

Choose the Wdm option.

Choose File from the Wdm (W) menu to specify the name of the WDM file. The File

(WF) menu will appear containing operations that can be performed on a WDM file,

including opening, closing, or summarizing the contents of the file. The Close option is

used to close the current WDM file so that another file can be opened. The Summarize

option displays general information on the WDM file.

Choose Open and type the name of the WDM file on the file name screen [Open (WFO)]

that appears.

Execute Accept (F2) to open the file.

Choose Return to return to the Wdm (W) menu.

Choose Select to specify the stations—stored as numbered data sets in the WDM file—

to be included as input to the HYSEP program.

SELECTING WDM FILE DATA SETS

The Select (WS) menu contains options for manipulating the data-set buffer. This buffer is an

array that contains the number of each data set selected for use in the hydrograph analysis. Upon

first reaching this menu, the buffer will be empty. Data-set numbers can be added to the buffer

by choosing the Add, Browse, or Find options.

Add

If the data-set numbers for the stations in the WDM file are known, the data-set numbers may

be added directly to the buffer by use of the Add option. To add data-set numbers directly to the

buffer,

Choose Add.

Type in the data-set numbers on the Add (WSA) screen, one per line.

Execute Accept (F2).

Up to 24 data-set numbers may be entered. Repeat the above steps to add more than 24 data-set

numbers to the buffer. Up to 300 data sets may be selected as input to the HYSEP program.

Browse

Choose the Browse option from the Select (WS) menu to scan through the WDM file to view

the data sets currently stored. A screen containing two character input fields will appear

(fig. 12). The source of data to be browsed is specified in the first input field. The entire WDM

1

2

3

1

2

3

4

5

6

1

21

3
21

file or just the currently selected data sets are browsed by specifying “WDM” or “BUFFER,”

respectively. The contents of the second input field indicate what data-set information is to be

included on the screen. The assistance window shown in figure 12 describes the types of

information that can be viewed; the Browse (WSB) screen after the Help (F1) command was

executed is shown in figure 12.

Upon Accepting the Browse (WSB) screen, one of the three screens shown in figure 13 will

appear, depending on which type of data-set information was selected. Data-set number and

type and time-series type are displayed on all three screens. “TS”, representing “time series,”

must be the data-set type of all WDM data sets used as input to the HYSEP program. The string

displayed under the time-series type column (“Tstype”) will generally be “FLOW,” “BFLO,”

or “SRNF” indicating that the data set contains daily streamflow, estimated base-flow, or

surface-runoff values, respectively. If “na” appears in any column, that data-set information was

not available.

Figure 12. Browse (WSB) data-set information selection screen.
22

Figure 13. Browse (WSB) data-set information screens.
23

Find

Choosing the Find option will display a menu of data-set characteristics [Find (WSF)] for which

values can be specified and used in searching the WDM file. To find data sets in the WDM file

on the basis of data-set characteristics,

Choose Find and, from the Find (WSF) menu, select one or more of the options shown

in table 2.

After setting the search options, choose Execute to perform the search.

Once data sets have been selected by use of the Add, Browse, or Find options, several operations

can be performed on the data-set buffer by choosing other menu options:

List displays the contents of the buffer

Sort reorders the data-set numbers into ascending order

Drop eliminates a specific data-set number from the buffer

Clear removes all data-set numbers from the buffer

Output stores the data-set numbers in a file for later retrieval

Input retrieves data-set numbers from a file and places them in the buffer

To return to the Opening screen, choose Return from the Select (WS) menu and then choose

Return from the Wdm (W) menu.

1

2

Table 2. WDM file data search options

search

option usage

Type Specify the data-set type for the search. Although many WDM data-set

types are available, only time-series data sets can be used as input to the

HYSEP program.

Number Specify a range of data-set numbers to search.

Attributes Enter values of data-set attributes for the search. Data-set attributes are

ancillary values and include station-identification number, latitude,

longitude, drainage area, and basin slope, among many others. On-line

help information on all WDM data-set attributes is available.

Subset Choose this option to perform the search operation only on those data sets

already in the buffer, thus selecting a subset of the currently selected data

sets. Choosing Subset turns this option “on”; no screens are displayed by

choosing Subset. Once Subset is chosen, all searches performed will

result in a subset of the selected data sets. This option is turned “off” only

by returning to the previous menu and choosing Find again.
24

SELECTING PROGRAM OUTPUT

Tables

Choosing the Output option from the Opening screen will display a form containing output

options (fig. 14). The five options on the upper left side of the screen refer to tables that can be

included in the print file. In the default program setting, the print file will always contain an

annual summary for the hydrograph separation if 3 or more years of data are processed. The first

month of the summary can be specified by typing in the abbreviation for the month. The Limits

(F5) command will list the valid abbreviations for each month.

A monthly summary for the hydrograph separation and frequency, flow-duration, and seasonaldistribution tables can be included in the print file by typing “yes” or “y” in the corresponding

input fields. The frequency, flow-duration, and seasonal-distribution tables are produced only

if 3 or more years of data are processed.

The two options on the lower left side of the Output (O) options screen (fig. 14) modify the units

of values included in the print file tables. If “ENGLISH” units are chosen, the units listed on the

next line define the units used in a predefined column (shaded columns in Appendixes 1, 2, and

3) in the monthly and annual summaries and in the frequency table. The English units that can

be chosen are included on the screen as option fields that are toggled on or off by pressing any

key. An “X” in the box to the left of one of the units indicates which units will be used. At least

one of the units must be specified to Accept (F2) this screen and continue.

All values in the print file can be converted to metric units by specifying “METRIC” in the

“Units” input field. The metric units used in the predefined column (shaded columns in

Appendixes 1, 2, and 3) are fixed regardless of the English unit chosen on the second line.

Figure 14. Output options screen.
25

Data Files

The options on the upper right side of the Output (O) options screen describe the forms of

computed output that can be produced. Daily values of estimated base flow and surface runoff

can be written to a file in the WATSTORE format or stored as data sets in the input WDM file.

The data-set number assigned to each of these computed data sets will be the next free number

on the WDM file following the input data set from which it was computed. If you have not

specified a WDM file as the input data file, the WDM output options are not available and will

not appear on the screen. WDM output is saved only to the input WDM file.

Graphs

Selecting the Plots option on the opening screen brings up a form containing graphical output

options (fig. 15). Four plots can be produced:

1. a frequency-distribution plot of annual values,

2. a flow-duration plot of daily values,

3. a seasonal bar chart of mean monthly flows, and

4. an annual hydrograph of total flow and estimated base flow.

The annual hydrograph is produced for each year of data processed; the other three plots are

produced when 3 or more years of data from one station are processed. For each plot, two of

four possible output devices may be chosen. These are specified under the “Device1” and

“Device2” headings and include the monitor screen, a laser or dot matrix printer, a pen plotter,

or a metafile.

Figure 15. Graphical output screen.
26

By default, total streamflow, estimated base flow, and estimated surface runoff will be included

in the frequency-distribution and flow-duration plots. Enter “no” or “n” for the input fields

corresponding to these curves to eliminate them from the plots. Average monthly base flow and

surface runoff can be plotted in the seasonal bar chart or base flow and surface runoff as a

percentage of the average monthly flow can be shown.

The query, “Do you want to modify the plots?” is included to streamline the process of

producing graphical output. If the response is left as “NO,” the plots will be produced by use of

the default plot parameters. If the response is changed to “YES,” plot parameters, such as axes

types, labels, minimum Y-axis value, maximum Y-axis value, plot size, title, and the color and

line or symbol type for each curve, can be modified. Extra text can be added to each plot. Plot

parameters need be specified only for the first time each plot is selected; all subsequent plots

produced will include the modifications made to the first plot of that type.

The values for modified plot parameters generally are retained between each execution of the

hydrograph separation. For example, if a set of stations is processed multiple times using

different hydrograph-separation methods, a specific line type or color need be specified only

once for each type of plot selected during the first execution of the hydrograph separation.

However, there are specific instances when the values for modified plot parameters are not

retained. Whenever a new station is processed, the plot title will be reassigned using the station

name associated with the streamflow data. If the units specified under Output (O) are changed

between executions of the hydrograph separation, y-axis labels that specify the units of the data

plotted also will be reassigned. For the frequency-distribution and flow-duration plots, curve

specifications such as line type or color and the curve labels used in the plot explanation will be

reassigned default values when the curves to be plotted differ from those last plotted.

When the modification option is set to “YES,” the menu shown in figure 16 will be displayed.

Regardless of the type of plot being produced, the menu displayed will be identical to the one

shown in figure 16; only the screen name will differ to reflect the plot type.

The Modify and Replot options can be chosen multiple times to change plot characteristics and

re-create the plot. Once Done is chosen, the most recently modified plot parameters are used for

all subsequent plots of that type.

Figure 16. Plot modification menu.
27

Modifying Plot Parameters

Choosing Modify from the menu shown in figure 16 will display the menu shown in figure 17.

Each menu option allows modification of the following plot characteristics.

Device This option for choosing an alternate output device has been disabled within

the HYSEP program because output devices are specified on the Plots (P)

form.

Axes Axes types, such as arithmetic, logarithmic, or probability, can be specified.

Additional axes, such as a right y-axis or an auxiliary axis, can be added or

eliminated.

Titles The plot title and all axes labels can be modified.

Curves Curve characteristics, such as color, line type, or symbol used, can be

changed. The axis against which each curve is plotted also can be modified.

The label for the explanation can be changed.

Min/Max The minimum and maximum value plotted on each axis can be modified. If

the minimum and maximum values are changed so that some points are no

longer plotted, several options are available to indicate where those points

would have been plotted, or those points can be omitted entirely.

Extra Text may be added to the graph. The placement of that text, the number of

lines of text, and the number of characters per line of text can be specified.

The location of the explanation can be moved.

Size The plotting space dimensions, axes lengths, location of origin within the

plotting space, and size of text lettering can be modified. If the HYSEP

program is run on a computer using the X Window System, the position of

the graphics window on the monitor can be modified.

Figure 17. Plot parameter modification menu.
28

SELECTION OF HYDROGRAPH-SEPARATION METHOD

By default, the fixed-interval hydrograph-separation method is used. To select another

separation method,

Choose Method.

Select a hydrograph-separation method from the menu options displayed.

EXECUTION OF THE BASE-FLOW SEPARATION

Before choosing Execute from the Opening screen menu, an input data file must be specified;

and unless the default settings are being used, tabular and graphical output options and the

hydrograph-separation method must be specified. After choosing Execute, the Execute (E)

drainage area screen will appear only if the drainage area was not included in the input file.

After entering the drainage area and pressing the Enter key, the screen in figure 18 will appear

for each station to be processed.

Specify a base name for output files. Appropriate suffixes will be added to distinguish

each type of file as shown in table 2.

Specify the dates of the data to be processed.

Execute Accept (F2).

Once Accept (F2) is executed on the base name and date specification screen, text screens

describing the progress of the analysis will be displayed.

Each output file that is produced is assigned a name containing the base name specified on the

Execute (E) station screen with a descriptive suffix appended. The base name can be modified

each time this screen appears so that the output files for each station can be distinguished from

one another. Alternatively, the same base name can be used for all stations processed during the

same execution of the hydrograph separation to distinguish different sets of stations processed

together or to distinguish output produced when different hydrograph-separation methods or

output options were chosen. If the same base name is used for all stations processed, one print

file will be produced that contains output for all of the stations. If a distinct base name is used

for each station, separate print files will be produced.

When multiple output files of the same type are produced using the same base name, sequence

numbers are appended to the base name to distinguish the files from one another. For example,

“.prt” is the file name suffix used to denote the print file; if the hydrograph separation is

executed 10 times using the same base name, 10 print files will be produced having the names:

basename.prt, basename2.prt, ... , basename10.prt. If frequency distribution plots are produced

for each hydrograph separation and the printer is chosen as the output device on a system where

PostScript graphical output is placed in a file, 10 files will be produced with the names:

basenamefq.ps, basenamefq2.ps, ... , basenamefq10.ps.

The Intrpt (F6) command is available on the base name and date specification screen. Executing

the Intrpt (F6) command will return the program to the Opening screen, terminating execution

of the hydrograph separation. This is helpful if you have selected multiple stations for

processing and determine that you do not want to complete the hydrograph separation for all the

stations.

1

2

1

2

3
29

Table 3. Output file name suffixes

tabular/computed

data output file suffix appended to base name

Print file .prt

Surface runoff, WATSTORE format .sro

Base flow, WATSTORE format .bsf

graphical output file1 suffix appended to base name

Printer2 Plotter3 Metafile4

Frequency distribution plot fq.ps fq.hpgl fq.cgm

Flow-duration plot fd.ps fd.hpgl fd.cgm

Seasonal bar chart sb.ps sb.hpgl sb.cgm

Hydrograph of base-flow separation hy.ps hy.hpgl hy.cgm

1 Whether graphical output is placed in a file or sent directly to an output device is dependent on

the software library used to implement the Graphical Kernel System (GKS). Graphical output placed in a

file will be appropriately formatted for the intended output device. The output file name will be composed

of the user-specified base name and the suffix corresponding to the plot type and file format unless the

output file name is fixed by the graphics software library. The README documentation that accompanies

the program gives more information on system-dependent aspects of graphics generation.

2 Suffix .ps denotes a PostScript file.

3 Suffix .hpgl denotes a Hewlett Packard Graphics Language file.

4 Suffix .cgm denotes a Computer Graphics Metafile.

Figure 18. Base name and date specification screen.
30

SUMMARY

HYSEP is a computer program that can be used to separate a streamflow hydrograph into baseflow and surface-runoff components. Three methods of hydrograph separation are currently

implemented: fixed interval, sliding interval, and local minimum. These methods can be

described conceptually as three different algorithms to systematically draw connecting lines

between the low points of the streamflow hydrograph. The sequence of these connecting lines

defines the base-flow hydrograph. The program also creates graphs showing the frequency and

duration of measured streamflow and computed base flow and surface runoff.

The HYSEP program accepts daily mean stream discharge as input in either of two formats:

(1) standard USGS WATSTORE daily values in an 80-character record ASCII format or

(2) binary, direct access WDM System file format. Data for up to 300 stations in the WDM

format can be processed at one time. A minimum of 1 and a maximum of 100 years of data per

station in either format can be processed.

Program output options include tables, graphs, data files, and WDM data sets. All values in the

print files can be in English or metric units. Graphical output may be plotted on the computer

screen or output to a printer, plotter, or metafile. An annual hydrograph of total streamflow and

estimated base flow can be plotted for each year of record processed. The year can begin with

any day. Printed output for the hydrograph separation provides information on the quantity of

estimated base flow and surface runoff and on the percentage of streamflow as base flow and

surface runoff on an annual or monthly basis.

Frequency distributions of mean annual streamflow, estimated mean annual base flow, and

estimated mean annual surface runoff for the period of record of a station can be plotted and

printed for any hydrograph-separation method. The program estimates a cumulative probability

distribution. Flow-duration curves can be plotted and a flow-duration table can be printed for

total streamflow, estimated base flow, and estimated surface runoff. A bar graph can be plotted

and a seasonal-distribution table can be printed for mean monthly estimated base flow and

surface runoff. Daily values of estimated base flow and surface runoff can be written to a file in

the WATSTORE format or stored as data sets in the input WDM file.

Program interaction takes place in a screen 80 characters wide by 24 characters high, which is

made up of three types of boxed-in areas referred to as panels. The data panel, displayed at the

top of the screen, contains menus, forms, tables, and text to permit user interaction with the

program. The assistance panel, when present, is displayed below the data panel and contains

text information, such as help messages, valid range of values, and details on program status.

The instruction panel is displayed at the bottom of the screen and contains information on what

keystrokes are required to interact with the program. Beneath the panels is a list of commands

for obtaining additional information and moving between screens.

At a minimum, the input data file must be specified before executing the hydrograph separation.

If no other program options are chosen, the hydrograph separation will be performed using the

following default settings: (1) the fixed-interval hydrograph-separation method will be used, (2)

a hydrograph of total flow and estimated base flow will be displayed on the screen for each year

of data processed, and (3) an annual summary table will be included in the print file if 3 or more

years of data are processed.
31

REFERENCES CITED

Flynn, K.M., Hummel, P.R., Lumb, A.M., and Kittle, J.L., Jr., 1995, User’s manual for

ANNIE, version 2, a computer program for interactive hydrologic data

management: U.S. Geological Survey Water-Resources Investigations Report

95-4085, 211 p.

Linsley, R.K., Kohler, M.A., and Paulhus, J.L., 1982, Hydrology for engineers

(3rd ed.): New York, McGraw-Hill, 508 p.

Lumb, A.M., Kittle, J.L., Jr., and Flynn, K.M., 1990, Users manual for ANNIE, a

computer program for interactive hydrologic analyses and data

management: U.S. Geological Survey Water-Resources Investigations Report

89-4080, 236 p.

Olmsted, F.H., and Hely, A.G., 1962, Relation between ground water and surface

water in Brandywine Creek Basin, Pennsylvania: U.S. Geological Survey

Professional Paper 417-A, 21 p.

Pettyjohn, W.A., and Henning, Roger, 1979, Preliminary estimate of ground-water

recharge rates, related streamflow and water quality in Ohio: Ohio State

University Water Resources Center Project Completion Report Number 552, 323

p.

Riggs, H.C., 1963, The base-flow recession curve as an indicator of ground

water: International Association of Scientific Hydrology Publication 63,

p. 352-363.

———1968, Frequency curves: U.S. Geological Survey Techniques of WaterResources Investigations, book 4, chap. A2, 15 p.

Rorabaugh, M.I., 1963, Estimating changes in bank storage and ground-water

contribution to streamflow: International Association of Scientific Hydrology

Publication 63, p. 432-441.

Searcy, J.K., 1959, Flow-duration curves: U.S. Geological Survey Water-Supply

Paper 1542-A, 33 p.

Sloto, R.A., 1991, A computer method for estimating ground-water contribution to

streamflow using hydrograph-separation techniques: U.S. Geological Survey

Water-Resources Investigations Report 90-4162, p. 101-110.

Sloto, R.A., Cecil, L.D., and Senior, L.A., 1991, Hydrogeology and ground-water

flow in the carbonate rocks of the Little Lehigh Creek Basin, Lehigh County,

Pennsylvania: U.S. Geological Survey Water-Resources Investigations Report

90-4076, 83 p.

White, K.E., and Sloto, R.A., 1990, Base-flow-frequency characteristics of selected

Pennsylvania streams: U.S. Geological Survey Water-Resources Investigations

Report 90-4160, 67 p.

Williams, O.O., 1975, Daily values data entry and computation (program H475)—

section A of chapter IV of WATSTORE user’s guide: U.S. Geological Survey

Open-File Report 75-426.
32
33

APPENDIXES
34

APPENDIX 1. ANNUAL BASE-FLOW SUMMARY

[Alternate English units can be used for the values in the shaded column. All values can be converted to equivalent

metric units. See the section “Selecting Program Output”; in, inches; ft3/s, cubic feet per second; Mgal/d/mi2, million

gallons per day per square mile; %, percent]

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

Annual base-flow summary

French Creek near Phoenixville, Pa.

Station ID = 1472157

Drainage area = 59.10 square miles

Local minimum method

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

Year starts in January

Year ends in December

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

Period ending in

----------

 ft3/s

---------

Mgal/d/

 mi2

----------

 % of

stream-

 flow

----------

1969 6.201 27.00 0.295 64.75

1970 11.007 47.92 0.524 65.22

1971 13.665 59.49 0.651 54.91

1972 18.018 78.23 0.855 57.95

1973 16.380 71.31 0.780 61.17

1974 12.380 53.90 0.589 69.33

1975 16.123 70.20 0.768 61.88

1976 11.115 48.26 0.528 65.00

1977 10.803 47.03 0.514 56.59

1978 17.554 76.43 0.836 60.50

1979 17.561 76.46 0.836 55.70

1980 11.288 49.01 0.536 72.41

1981 5.517 24.02 0.263 63.37

1982 10.327 44.96 0.492 58.01

1983 15.474 67.37 0.737 57.42

1984 18.516 80.40 0.879 60.81

1985 8.375 36.46 0.399 61.21

1986 10.247 44.61 0.488 60.83

1987 10.354 45.08 0.493 61.44

1988 12.085 52.47 0.574 60.77

1989 15.437 67.21 0.735 65.61

1990 11.975 52.14 0.570 63.55

1991 10.751 46.81 0.512 72.08

1992 8.191

---------

35.56

--------

0.389

---------

63.64

--------

median 11.632 50.58 0.553 61.32
35

APPENDIX 2. MONTHLY SUMMARY

[Alternate English units can be used for the values in the shaded column. All values can be converted to equivalent

metric units. See the section “Selecting Program Output”; ft3/s, cubic feet per second; in, inches; BF, base flow; %,

percent; Mgal/d/mi2, million gallons per day per square mile]

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

Hydrograph separation by the local minimum method

French Creek near Phoenixville, Pa.

Station ID = 1472157

Drainage area = 59.10 square miles

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

Period ending in 1969 interval = 5 days

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

 Mean

stream-

 flow

(ft3/s)

-------

 Mean

 base

 flow

(ft3/s)

--------

-

 Mean

surface

runoff

(ft3/s)

--------

 Total

streamflow

 (in)

-------

-

Total

 base

 flow

 (in)

--------

-

Total

surface

runoff

 (in)

--------

 BF/

stream-

 flow

 (%)

--------

-

 Base

 flow

(Mgal/d/

 mi2)

--------

-

Jan. 42.87 31.56 11.32 0.836 0.616 0.221 73.60 0.345

Feb. 42.18 36.37 5.81 0.743 0.641 0.102 86.22 0.398

Mar. 57.45 41.56 15.89 1.121 0.811 0.310 72.34 0.454

Apr. 46.60 36.88 9.72 0.880 0.696 0.184 79.14 0.403

May 28.55 21.99 6.56 0.557 0.429 0.128 77.01 0.240

June 19.30 14.53 4.77 0.364 0.274 0.090 75.29 0.159

July 94.13 28.06 66.07 1.836 0.547 1.289 29.81 0.307

Aug. 30.39 24.18 6.20 0.593 0.472 0.121 79.58 0.264

Sept

.

21.70 19.02 2.68 0.410 0.359 0.051 87.65 0.208

Oct. 22.48 19.96 2.53 0.439 0.389 0.049 88.76 0.218

Nov. 43.10 19.72 23.38 0.814 0.372 0.441 45.75 0.216

Dec. 50.48

-------

-

30.48

--------

20.01

--------

-

0.985

-------

-

0.595

--------

-

0.390

--------

-

60.37

--------

-

0.333

--------

41.70 27.00 14.70 9.577 6.201 3.376 64.75 0.295
36

APPENDIX 3. CUMULATIVE-DISTRIBUTION TABLE

[Alternate English units can be used for the values in the shaded column. All values can be converted to equivalent

metric units. See the section “Selecting Program Output”; cum dist, cumulative distribution; in, inches; Mgal/d/mi2,

million gallons per day per square mile]

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

Annual base-flow summary ordered by frequency

French Creek near Phoenixville, Pa.

Station ID = 1472157

Drainage area = 59.10 square miles

Local minimum method

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

Year starts in January

Year ends in December

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

 Cum

 dist

-------

 in

-------

Mgal/d/

 mi2

-----------

year

---------

 4.0 5.517 0.263 1981

 8.0 6.201 0.295 1969

12.0 8.191 0.389 1992

16.0 8.375 0.399 1985

20.0 10.247 0.488 1986

24.0 10.327 0.492 1982

28.0 10.354 0.493 1987

32.0 10.751 0.512 1991

36.0 10.803 0.514 1977

40.0 11.007 0.524 1970

44.0 11.115 0.528 1976

48.0 11.288 0.536 1980

52.0 11.975 0.570 1990

56.0 12.085 0.574 1988

60.0 12.380 0.589 1974

64.0 13.665 0.651 1971

68.0 15.437 0.735 1989

72.0 15.474 0.737 1983

76.0 16.123 0.768 1975

80.0 16.380 0.780 1973

84.0 17.554 0.836 1978

88.0 17.561 0.836 1979

92.0 18.018 0.855 1972

96.0 18.516 0.879 1984
37

APPENDIX 4. FLOW-DURATION TABLE

Flow duration table for total flow, local minimum method

 at French Creek near Phoenixville, Pa. (1969-1992)

Lower

Class

Cases equal or

exceeding lower

limit and less

than upper limit

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

Cases equal or

 exceeding lower

class limit

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

limit

--------

Cases

---------

Percent

-----------

Cases

-----------

Percent

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

0.00 0 0.00 8766 100.00

6.90 0 0.00 8766 100.00

7.90 5 0.06 8766 100.00

9.10 6 0.07 8761 99.94

10.00 29 0.33 8755 99.87

12.00 88 1.00 8726 99.54

14.00 147 1.68 8638 98.54

16.00 178 2.03 8491 96.86

18.00 373 4.26 8313 94.83

21.00 366 4.18 7940 90.58

24.00 600 6.84 7574 86.40

28.00 464 5.29 6974 79.56

32.00 517 5.90 6510 74.26

37.00 566 6.46 5993 68.37

43.00 447 5.10 5427 61.91

49.00 551 6.29 4980 56.81

57.00 586 6.68 4429 50.52

66.00 540 6.16 3843 43.84

75.00 654 7.46 3303 37.68

87.00 498 5.68 2649 30.22

100.00 568 6.48 2151 24.54

120.00 195 2.22 1583 18.06

130.00 303 3.46 1388 15.83

150.00 308 3.51 1085 12.38

180.00 152 1.73 777 8.86

200.00 126 1.44 625 7.13

230.00 129 1.47 499 5.69

270.00 78 0.89 370 4.22

310.00 64 0.73 292 3.33

360.00 54 0.62 228 2.60

410.00 42 0.48 174 1.98

470.00 28 0.32 132 1.51

540.00 25 0.29 104 1.19

630.00 21 0.24 79 0.90

720.00 14 0.16 58 0.66

830.00 12 0.14 44 0.50

950.00 6 0.07 32 0.37

1100.00 8 0.09 26 0.30

1300.00 4 0.05 18 0.21

1500.00 8 0.09 14 0.16

1700.00 1 0.01 6 0.07

1900.00 2 0.02 5 0.06

2200.00 2 0.02 3 0.03

2600.00 0 0.00 1 0.01

3900.00 0 0.00 1 0.01

5200.00 0 0.00 0 0.00

100000.00 0 0.00 0 0.00
38

 Flow duration table for surface runoff, local minimum method

 at French Creek near Phoenixville, Pa. (1969-1992)

Lower

Class

Cases equal or

exceeding lower

limit and less

than upper limit

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

Cases equal or

 exceeding lower

class limit

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

limit

--------

Cases

---------

Percent

-----------

Cases

-----------

Percent

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

0.00 2130 24.30 8766 100.00

0.10 8 0.09 6636 75.70

0.12 1 0.01 6628 75.61

0.13 8 0.09 6627 75.60

0.15 7 0.08 6619 75.51

0.18 10 0.11 6612 75.43

0.20 16 0.18 6602 75.31

0.23 12 0.14 6586 75.13

0.27 13 0.15 6574 74.99

0.31 63 0.72 6561 74.85

0.36 22 0.25 6498 74.13

0.41 39 0.44 6476 73.88

0.47 56 0.64 6437 73.43

0.54 51 0.58 6381 72.79

0.63 113 1.29 6330 72.21

0.72 72 0.82 6217 70.92

0.83 79 0.90 6145 70.10

0.95 143 1.63 6066 69.20

1.10 129 1.47 5923 67.57

1.30 124 1.41 5794 66.10

1.50 144 1.64 5670 64.68

1.70 92 1.05 5526 63.04

1.90 159 1.81 5434 61.99

2.20 197 2.25 5275 60.18

2.60 139 1.59 5078 57.93

2.90 212 2.42 4939 56.34

3.40 165 1.88 4727 53.92

3.90 202 2.30 4562 52.04

4.50 202 2.30 4360 49.74

5.20 199 2.27 4158 47.43

6.00 213 2.43 3959 45.16

6.90 184 2.10 3746 42.73

7.90 222 2.53 3562 40.63

9.10 124 1.41 3340 38.10

10.00 239 2.73 3216 36.69

12.00 201 2.29 2977 33.96

14.00 204 2.33 2776 31.67

16.00 166 1.89 2572 29.34

18.00 200 2.28 2406 27.45

21.00 167 1.91 2206 25.17

24.00 189 2.16 2039 23.26

28.00 169 1.93 1850 21.10

32.00 168 1.92 1681 19.18

37.00 150 1.71 1513 17.26

43.00 125 1.43 1363 15.55

49.00 152 1.73 1238 14.12

57.00 133 1.52 1086 12.39

66.00 96 1.10 953 10.87

75.00 105 1.20 857 9.78

87.00 76 0.87 752 8.58

100.00 121 1.38 676 7.71
39

120.00 36 0.41 555 6.33

130.00 74 0.84 519 5.92

150.00 79 0.90 445 5.08

180.00 39 0.44 366 4.18

200.00 60 0.68 327 3.73

230.00 51 0.58 267 3.05

270.00 33 0.38 216 2.46

310.00 39 0.44 183 2.09

360.00 24 0.27 144 1.64

410.00 23 0.26 120 1.37

470.00 20 0.23 97 1.11

540.00 21 0.24 77 0.88

630.00 12 0.14 56 0.64

720.00 12 0.14 44 0.50

830.00 5 0.06 32 0.37

950.00 4 0.05 27 0.31

1100.00 8 0.09 23 0.26

1300.00 6 0.07 15 0.17

1500.00 3 0.03 9 0.10

1700.00 1 0.01 6 0.07

1900.00 4 0.05 5 0.06

2200.00 0 0.00 1 0.01

3400.00 0 0.00 1 0.01

4500.00 0 0.00 0 0.00

100000.00 0 0.00 0 0.00
40

 Flow duration table for base flow, local minimum method

 at French Creek near Phoenixville, Pa. (1969-1992)

Lower

Class

Cases equal or

exceeding lower

limit and less

than upper limit

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

-

Cases equal or

 exceeding lower

class limit

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

limit

--------

Cases

---------

Percent

-----------

Cases

----------

-

Percent

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

-

0.00 0 0.00 8766 100.00

6.90 0 0.00 8766 100.00

7.90 7 0.08 8766 100.00

9.10 15 0.17 8759 99.92

10.00 64 0.73 8744 99.75

12.00 176 2.01 8680 99.02

14.00 303 3.46 8504 97.01

16.00 259 2.95 8201 93.55

18.00 410 4.68 7942 90.60

21.00 501 5.72 7532 85.92

24.00 813 9.27 7031 80.21

28.00 531 6.06 6218 70.93

32.00 596 6.80 5687 64.88

37.00 672 7.67 5091 58.08

43.00 478 5.45 4419 50.41

49.00 567 6.47 3941 44.96

57.00 673 7.68 3374 38.49

66.00 623 7.11 2701 30.81

75.00 606 6.91 2078 23.71

87.00 538 6.14 1472 16.79

100.00 430 4.91 934 10.65

120.00 123 1.40 504 5.75

130.00 156 1.78 381 4.35

150.00 156 1.78 225 2.57

180.00 29 0.33 69 0.79

200.00 22 0.25 40 0.46

230.00 12 0.14 18 0.21

270.00 5 0.06 6 0.07

310.00 1 0.01 1 0.01

360.00 0 0.00 0 0.00

100000.00 0 0.00 0 0.00
41

APPENDIX 5. SEASONAL-DISTRIBUTION TABLE

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

French Creek near Phoenixville, Pa.

 Station ID = 1472157

Drainage area = 59.10 square miles

Local minimum method

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

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

Month

---------

Base flow

(inches)

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

Runoff

(inches)

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

January 1.221 0.496

February 1.832 1.345

March 1.949 0.667

April 1.998 0.975

May 1.427 0.558

June 1.200 1.569

July 0.959 0.447

August 0.641 0.507

September 0.608 0.396

October 0.604 0.208

November 1.000 0.928

December 1.336 0.716
42

APPENDIX 6. SPECIAL FILES

Three files are associated with the interaction between the user and the program. The optional

TERM.DAT file is used to change some aspects of how the program operates. The

HYSEP.LOG file records keystrokes entered during a program session. Error and warning

messages are written to the ERROR.FIL file if problems arise during a program session. The

ERROR.FIL file also can contain messages that document the processing sequence of the

program.

A TERM.DAT file is used to override the default values of parameters that define the

configuration of the computer system and the user’s preferences. The program looks for a

TERM.DAT file in the current directory. The parameters include terminal type, the program

response to the Enter key, and graphics options. Table 1 describes the TERM.DAT parameters

showing the default values as set for DOS-based computers, for DG/UX-based (Data

General/UNIX) computers, and for other UNIX-based computers. A parameter is overridden by

specifying its keyword and the new value in the TERM.DAT file. One record is used to define

each parameter, with the keyword beginning in column 1 and the value beginning in column 8.

Many of the TERM.DAT parameters control graphical output, such as the specification of a

graphics device, text font, symbol size, and background color. The values assigned to the

graphics parameters depend on the software library used to implement the Graphical Kernel

System (GKS). For information on overriding the graphics parameters on DOS-based

computers, see the README file distributed with the program. For other computer platforms,

see the README documentation that accompanies the program and the GKS library

documentation for your system.

The value of the MENCRA parameter and the data panel type control how the program

responds when the Enter key is pressed. Table 2 describes the program response for the various

combinations of MENCRA values and data panel type. The default value for the MENCRA

parameter is "NEXT."

Table 3 shows an example TERM.DAT file that overrides the default BLACK background

color of the graphics display. The parameter BCOLOR is set to OTHER and the parameters

BGRED and BGBLUE are set to 40 and 60, respectively. The resulting graphics screen display

background will be a shade of purple. In addition to the parameters described in table 1, there

are five parameters that can be used to set the foreground and background colors of parts of the

program screen on DOS-based computers. These parameters are listed in table 4.

TERM.DAT
43

Table 1. TERM.DAT parameters

[GKS, Graphical Kernel System]

parameter

keyword

default values

valid

values description

dos dg/ux other

unix

TRMTYP PC VT100 VT100 PC

VT100

OTHER

Terminal type.

MENCRA NEXT NEXT NEXT NONE

DOWN

NEXT

Program response to Enter key.

USRLEV 0 0 0 0 to 2 User experience level: 0=lots,

1=some, 2=none.

GRAPHS YES YES YES NO

YES

Is a software library for graphics

generation available?

GKSDIS 1 1100 4 0-99991 GKS code number for workstation

type for display terminal.

GKSPRT 2 102 4 0-99991 GKS code number for workstation

type for printer device.

GKSPLT 3 7475 4 0-99991 GKS code number for workstation

type for pen plotter.

GKSMET 4 24 4 0-99991 GKS code number for metafile.

GKPREC CHAR STROKE CHAR STRING

CHAR

STROKE

Text precision.

GKSCFT 1 1 1 -9999 to 99991 Text font for screen.

GKPRFT 1 -2808 1 -9999 to 99991 Text font for printer.

GKPLFT 1 1 1 -9999 to 99991 Text font for plotter.

BCOLOR BLACK BLACK BLACK WHITE

BLACK

OTHER

Background color of graphics screen

display.

BGRED 0 0 0 0 to 100 Percent red for background of

graphics screen display if

BCOLOR=OTHER.

BGREEN 0 0 0 0 to 100 Percent green for background of

graphics screen display if

BCOLOR=OTHER.

BGBLUE 0 0 0 0 to 100 Percent blue for background of

graphics screen display if

BCOLOR=OTHER.

PBCOLR WHITE WHITE WHITE WHITE

BLACK

Foreground color of graphics screen

display.

SYMSIZ 100 100 100 1 to 10000 Symbol size ratio in hundredths.

TXTEXF 133 100 100 0 to 200 Text expansion factor in hundredths.

TXTCHS 0 0 0 0 to 200 Text character spacing in hundredths.

1 Refer to GKS documentation and README file supplied with the program to determine valid

values for these parameters.
44

Table 2. MENCRA values and corresponding program response

mencra

data

panel

contents

program response when enter is pressed

NEXT menu Same as if Accept (F2) were executed; the highlighted menu option is selected

and the program advances to the next screen.

form For all but the last field on the form, causes the cursor to advance to the next

field. For the last field on the form, the response is the same as for Accept

(F2)—the program advances to the next screen. (Note: usually the rightmost,

lowest field is the "last" field in the form. Occasionally, however, it is not!)

table For each row, the cursor advances across the fields in the row. For all but the

last row, the cursor advances from the last field in the row to the first field of

the next row. For the last row, the cursor advances to the beginning of the last

row. (Use Accept (F2) to advance to the next page of the table.)

text Same as if Accept (F2) were executed—the program advances to the next

screen.

NONE menu No effect—it is ignored.

form Cursor is advanced to the next field. When the cursor is in the last field, the cursor cycles back to the first field.

table For each row, the cursor advances across the fields in the row. For all but the

last row, the cursor advances from the last field in the row to the first field of

the next row. For the last row, the cursor advances to the beginning of the last

row. (Use Accept (F2) to advance to the next page of the table.)

text No effect—it is ignored.

DOWN menu Same as if the down arrow were pressed; the highlight bar moves to the next

menu option. When the highlight bar is on the last menu option, it returns to

the first menu option.

form Cursor is advanced to the next field. When the cursor is in the last field, the cursor cycles back to the first field.

table For each row, the cursor advances across the fields in the row. For all but the

last row, the cursor advances from the last field in the row to the first field of

the next row. For the last row, the cursor advances to the beginning of the last

row. (Use Accept (F2) to advance to the next page of the table.)

text No effect—it is ignored.

Table 3. Example TERM.DAT file

BCOLOR OTHER

BGRED 40

BGREEN 0

BGBLUE 60

Table 4. TERM.DAT parameters for color display (DOS-based computers)

parameter

keyword

default

value

allowable

values1 description

CLRFRS 15 0 to 15 Standard foreground color.

CLRBKS 1 0 to 15 Standard background color.

CLRFRE 7 0 to 15 Foreground color for error messages in instruction panel.

CLRBKE 4 0 to 15 Background color for error messages in instruction panel.

CLRFRD 14 0 to 15 Color of first letter of commands in command mode.

1 0, black; 1, blue; 2, green; 3, cyan; 4, red; 5, magenta; 6, brown; 7, light gray; 8, dark gray; 9,

bright blue; 10, bright green; 11, bright cyan; 12, bright red; 13, bright magenta; 14, yellow; 15, white
45

A file named HYSEP.LOG is created each time the program is run. This file contains the

sequence of keystrokes entered during a program session. It may be used as an input to the

program in a later session. To keep the sequence of keystrokes, you must rename the file

because the program will overwrite any file named HYSEP.LOG. Keystrokes of nonprinting

keys, such as the backspace and function keys, are represented in the file by special codes. Table

5 lists each code and its definition. Menu options are chosen in one of two ways—either press

the first letter(s) of a menu option, or position the cursor with the arrow keys and then Accept

(F2). Using the first method will make the log file easier to interpret and modify. Using the letter

"x" for making option selections also will help. Table 6 contains an annotated example log file

for a program session that opens a WDM file and gets a summary of the contents of the file.

Log files can be used to easily repeat a task, or they can be modified to perform a similar task.

A log file may contain all of the keystrokes required for a complete program session, or it may

contain the keystrokes for part of a program session. For example, all of the keystrokes needed

to plot the results of a hydrograph separation can be saved and then reused for the next

hydrograph separation. A subset of a session might consist of the keystrokes required to select

a particular set of data sets; this log file would be used whenever that set of data was needed.

A log file may be entered at any point in the program by typing "@"; in the small panel that

appears, type the name of the log file. The program will run using the input from the file just as

if it were being typed in. The program and the log file must be synchronized; if the keystrokes

in the log file get out of sync with the program, the program response may produce

unpredictable results. A common cause of synchronization problems involves output files. If an

output file did not exist when the log file was generated and does exist when the log file is read

by the program, the program may ask if it is OK to overwrite the existing file. Because the

keystrokes required to answer this question are not in the log file, the program will probably do

something unexpected.

HYSEP.LOG
46

Table 5. Codes used for nonprinting

characters in a log file

code user’s

keystroke

associated

command

#227 ; or Esc1

#208 Backspace

#213 Return or Enter

#301 ↑

#302 ↓

#303 →

#304 ←

#307 Page Up

#308 Page Down

#401 F1 Help

#402 F2 Accept

#403 F3

#404 F4 Prev

#405 F5 Limits

#406 F6 Intrpt

#407 F7 Status

#408 F8 Quiet

#409 F9 Xpad

1 The Escape key is only functional on DOS-based

computers.

Table 6. Description of example log file

line contents explanation

1 fotest.wdm The File option was selected from the Opening screen menu. The

Open option was selected from the File (F) screen menu. The file

name test.wdm was entered in the Open (FO) screen.

2 #402 Accept, function key F2, was executed, causing the test.wdm file to

be opened.

3 s The Summarize option was selected from the File (F) screen menu.

4 #402 After the summary of the contents of the test.wdm file had been

viewed, Accept, function key F2, was executed.

5 rr The Return option was selected from the File (F) screen menu. The

Return option was selected from the Opening screen menu.