E AP Project Summary

United States

Environmental Protection

Agency

EPANET

Users Manual

Lewis A. Rossman

Risk Reduction

Engineering Laboratory

Cincinnati, OH 45268

Research and Development

EPANET is a third generation software package for modeling water quality within drinking water distribution

systems. The program performs extended period simulation of hydraulic

and water quality conditions within

pressurized pipe networks. In addition

to substance concentration, water age

and source tracing can also be simulated. EPANET includes a graphical

user interface that runs under

Microsoft® WindowsTM and allows simulation results to be visualized on a map

of the network. EPANET is currently

being used to study such water quality

problems as chlorine decay dynamics,

source blending, effects of altered tank

operation on water age, and control of

total dissolved solids control in reclaimed water used for irrigation.

 This Project Summary was developed by EPA’s Risk Reduction Engineering Laboratory, Cincinnati, OH, to

announce key findings of the research

project that is fully documented in a

separate report of the same title (see

Project Report ordering information at

back).

Introduction

To meet regulatory requirements and

customer expectations, water utilities have

a growing need to understand better the

movement and transformation undergone

by treated water introduced into their distribution systems. Sampling alone often

provides an incomplete picture of water

quality dynamics within a system and is of

limited help when contemplating changes

in system design and operation. For these

reasons, computerized simulation models

are becoming popular and essential tools

for tracking the fate of water and its quality transformations within distribution systems.

EPANET represents a third generation

of public domain software developed by

the US Environmental Protection Agency's

Risk Reduction Engineering Laboratory for

modeling water quality within distribution

systems. The program performs extended

period simulation of hydraulic and water

quality conditions within pressurized pipe

networks. It tracks the flow of water in

each pipe, the pressure at each pipe junction, the height of water in each tank, and

the concentration of a dissolved substance

at each junction during a multi-time period

simulation. In addition to concentration,

water age and source tracing can also be

simulated.

Typical uses for the EPANET model

would include hydraulic calibration using

chemical tracers (e.g., fluoride), design of

sampling programs, chlorine decay analysis, evaluation of modified system operation (e.g., altered source utilization or tank

operation), selection of satellite treatment

locations, and use of targeted pipe cleaning and replacement to enhance water

quality.

Program Features

The EPANET package actually consists

of two programs. One performs the actual

hydraulic and water quality simulations with

EPA/600/SR-94/057 July 1994

* Mention of trade names or commercial products does

not constitute endorsement or recommendation for

use.
2

the use of data files for input and output

reports. The second program (EPANET4W) provides a graphical user interface for interactively running the simulator

and viewing its results via network maps,

data tables, and time series graphs.

Key features of the simulator include:

• modular, highly portable C language

code with no pre-set limits on size of

network,

• a simple data input format based on

a problem oriented language,

• a full-featured, extended period,

hydraulic simulator that can handle

various types of pressure and flow

regulating valves, both fixed and

variable speed pumps, and either

level- or timer-control rules on pump

and valve operation,

• an improved and more efficient

algorithm for tracking water quality

changes over time throughout a

network,

• the capability to consider water quality

reactions both within the bulk flow

and at the pipe wall.

The graphical user interface is written

in Microsoft® Visual BasicTM and operates within the WindowsTM 3.x environment on a personal computer. It allows

one to edit EPANET input files, run a

simulation, and view the results all within

a single program. Simulation output can

be visualized through:

• color-coded maps of the distribution

system with full zooming, panning,

and labeling capabilities and a slider

control to move forward or backward

through time,

• spreadsheet-like tables that can be

searched for entries meeting a

specified criterion,

• time series graphs of both predicted

and observed values for any variable

at any location in the network.

The last item proves to be an invaluable feature for network calibration.

Sample Application

Figure 1 displays a small example network that will be used to illustrate some of

EPANET’s features. Water is pumped into

the network from a surface reservoir at

Node 17 and from a well at Node 16. A

tank at Node 15 provides water storage

and flow equalization. Operation of the

reservoir pump is tied to the level of water

in the tank while the well is on a 12-houron, 12-hour-off pumping schedule. Nodal

demands follow a typical 24-hour diurnal

cycle. EPANET was used to analyze what

percent of water reaching any node in the

network throughout the day originates at

the well.

Table 1 is an abridged version of the

input data for this example. Note the liberal use of comments (text to the left of a

semicolon) to make the input more readable and tabular in nature. In the [JUNCTIONS] section, the well is treated as a

junction with a negative demand. In the

[TANKS] section, Node 15 is a tank with a

variable water level whereas Node 17 is

treated as a reservoir with a fixed water

level. The [PATTERNS] section supplies

a set of 24 hourly multipliers by which the

average nodal demands are adjusted during the day. By default, all nodes follow

this pattern unless otherwise indicated.

The [OPTIONS] section indicates that the

file EXAMPLE.MAP contains X-Y coordinates and labels for the system map. It

also requests that a trace of source water

emanating from Node 16 (the well) be

made. If a chemical analysis had been

chosen instead, then additional input data

sections would be used to specify initial

concentrations throughout the network,

concentrations in the source waters, and

reaction rate coefficients.

Figure 2 shows what the Windows version of EPANET would look like after the

input file has been opened. At this point

the input data could be edited and then

analyzed with the simulator. Figure 3

shows the display after a simulation has

been made. The nodes and links on the

map are actually color-coded to emphasize the different levels of the current view

variable, which in this case is percent of

water from the well at Node 16 (i.e., %

N16). The Browser panel on the right of

the display controls the node and link view

variable, displays the current values of

these variables for any node or link, and

sets the simulation time. Any choices made

in the Browser cause the map to be updated. Other variables besides water quality can also be viewed. These include

demand, elevation, hydraulic grade, and

pressure for nodes and diameter, flow,

velocity, and head loss for links.

Figure 4 illustrates the creation of a

time series graph for % of well water reaching Node 5. To generate this graph, one

merely had to click the mouse on Node 5

on the map (or select it from the Browser)

and select the Graph command from the

menu across the top of the display. Another graphing option allows prerecorded

data (from SCADA systems or field sampling) to be superimposed on a graph.

This feature is especially useful for model

calibration.

Figure 5 illustrates the creation of a

table showing results for all nodes in the

network at hour 12 of the simulation. The

bottom of the display shows how a query

was formed to search this table for all

nodes where the flow from the well was

above 50%. Similar kinds of queries can

be done visually by modifying the map

legend so that items meeting the search

criterion appear in a particular color.

In addition to screen displays, EPANET

can also print out the contents of any

window or copy the contents to the Windows clipboard. The map in Figure 1 was

printed directly from EPANET.

Current Uses

EPANET is currently being used to study

a variety of water quality related issues in

distribution systems. These include:

• chlorine decay dynamics,

• source blending and trihalomethane

propagation

• the effect of altered tank operation on

water quality and age

• control of total dissolved solids in

blending reclaimed water with

groundwater for irrigation.

The EPANET program should provide

water managers with a useful tool for understanding and analyzing water quality

behavior within distribution systems.
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Well

Reservoir

Tank

Example Network

1

17

2

4

8

3

5 7

9

15

16

10

14

6

12

13

11

Figure 1. Example water distribution network.
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Table 1. Excerpt of EPANET input file.

[TITLE]

EXAMPLE NETWORK

[JUNCTIONS]

; ID ELEV. DEMAND PATTERN

;---------------------------------------------------------------------------------------

1 340 0

2 350 90

3 360 70

<Nodes 4 - 13 not shown>

14 380 80

16 380 -400 3 ;WELL

[TANKS]

; INIT MIN MAX

; ID ELEV. LEVEL LEVEL LEVEL DIAM

;-------------------------------------------------------------------------------------------------------------

15 470 48 35 50 60

17 340

[PIPES]

; ID NODE1 NODE2 LENGTH DIAM C-FACTOR

;----------------------------------------------------------------------------------------------------------

1 1 2 1800 16 100

2 2 4 1600 12 100

3 2 3 2900 8 100

<Remaining pipes not shown>

[PUMPS]

; ID NODE1 NODE2 HEAD FLOW

;---------------------------------------------------------------------------------------

20 17 1 200 1000

[CONTROLS]

LINK 20 OPEN IF NODE 15 BELOW 42

LINK 20 CLOSED IF NODE 15 ABOVE 49

[PATTERNS]

; ID FACTORS

;-------------------------------------------------------------------------------------------------

1 1.0 1.6 1.5 1.4 1.2 1.2

1 1.2 1.1 1.0 1.0 1.1 1.2

1 1.3 1.2 1.1 1.0 1.0 0.8

1 0.6 0.5 0.4 0.4 0.5 0.7

<Remaining patterns not shown>

[OPTIONS]

MAP EXAMPLE.MAP

QUALITY TRACE 16

[TIMES]

DURATION 24

[END]
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Figure 2. View of example input data.

Figure 3. View of network map and browser.
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Figure 5. Example table query.

Figure 4. Example time series graph.

8 items found - display them?

Search of Hour 12 Node Table
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Lewis A. Rossman (also the EPA Project Officer) is with the U.S. Environmental Protection Agency's Risk Reduction Engineering Laboratory (see

below).

The complete report consists of a manual and diskette.

Manual—(Order No. PB94-165610AS; Cost: $27.00, subject to change)

Diskettes & Manual—(Order No. PB94-501673/AS; Cost: $90.00, subject

to change) will be available only from:

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

Telephone: 703-487-4650

The EPA Project Officer can be contacted at:

Risk Reduction Engineering Laboratory

U.S. Environmental Protection Agency

Cincinnati, OH 45268

United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

Official Business

Penalty for Private Use

$300

EPA/600/SR-94/057

BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35