United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-94/057 July 1994
EPA Project Summary
EPANET
Users Manual
Lewis A. Rossman
EPANET is a third generation soft-
ware package for modeling water qual-
ity within drinking water distribution
systems. The program performs ex-
tended 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 simu-
lated. EPANET includes a graphical
user interface that runs under
Microsoft® Windows™ and allows simu-
lation 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 re-
claimed water used for irrigation.
This Project Summary was devel-
oped by EPA's Risk Reduction Engi-
neering 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 dis-
tribution systems. Sampling alone often
* Mention of trade names or commercial products does
not constitute endorsement or recommendation for
use.
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 qual-
ity transformations within distribution sys-
tems.
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 junc-
tion, 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 analy-
sis, evaluation of modified system opera-
tion (e.g., altered source utilization or tank
operation), selection of satellite treatment
locations, and use of targeted pipe clean-
ing 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
-------
the use of data files for input and output
reports. The second program (EPA-
NET4W) provides a graphical user inter-
face 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 Basic™ and oper-
ates within the Windows™ 3.x environ-
ment 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 invalu-
able feature for network calibration.
Sample Application
Figure 1 displays a small example net-
work 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-hour-
on, 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 lib-
eral use of comments (text to the left of a
semicolon) to make the input more read-
able and tabular in nature. In the [JUNC-
TIONS] 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 dur-
ing the day. By default, all nodes follow
this pattern unless otherwise indicated.
The [OPTIONS] section indicates that the
file EXAMPLE.MAP contains X-Y coordi-
nates 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 ver-
sion 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 empha-
size 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 up-
dated. Other variables besides water qual-
ity 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 reach-
ing 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. An-
other graphing option allows prerecorded
data (from SCADA systems or field sam-
pling) 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 Win-
dows 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 un-
derstanding and analyzing water quality
behavior within distribution systems.
-------
Example Network
Tank
Reservoir
Figure 1. Example water distribution network.
-------
Table 1. Excerpt of EPANETinput file.
[TITLE]
EXAMPLE NETWORK
[JUNCTIONS]
; ID
ELEV.
DEMAND PATTERN
1 340 0
2 350 90
3 360 70
14 380 80
16 380 -400
;WELL
[TANKS]
ID
15
17
ELEV.
470
340
INIT
LEVEL
48
MIN
LEVEL
35
MAX
LEVEL
50
DIAM
60
[PIPES]
ID
NODE1
NODE2 LENGTH
DIAM
C-FACTOR
1 1 2 1800 16 100
2 2 4 1600 12 100
323 2900 8 100
[PUMPS]
ID
20
NODE1
17
NODE2
1
HEAD
200
FLOW
1000
[CONTROLS]
LINK20 OPEN IF NODE 15 BELOW42
LINK20 CLOSED IF NODE 15 ABOVE 49
[PATTERNS]
; ID FACTORS
1 1.0
1 1.2
1 1.3
1 0.6
1.6
1.1
1.2
0.5
1.5
1.0
1.1
0.4
1.4
1.0
1.0
0.4
1.2
1.1
1.0
0.5
1.2
1.2
0.8
0.7
=Remaining patterns not shown=
[OPTIONS]
MAP EXAMPLE.MAP
QUALITY TRACE 16
[TIMES]
DURATION 24
[END]
-------
3 EPANET-EXAMPLE.INP(Input) EjD
Eile Edit Bun Report Q-aph Map fflindow Help
• Q Input Data P
EXAMPLE NETWORK
[JUNCTIONS]
; ID ELEV. DEMAND PATTERN
1 340 0
2 350 90
3 360 70
4 330 SO
5 350 30
6 380 60
7 370 40
8 350 50
9 370 70
10 390 50
dfe
HI
4
Ready
Figure 2. View of example input data.
EPANET- EXAMPLE. INP( Input)
Edit fiun Reporl Qraph Map Window Help
Map
-••'**"««"-
%N1 6
S..
»40.
»60.
V
TANK
• RESERVOIR
_LL
-Nodes '
Model
Ji
0.00
rTime-
I Hour 12 I
EXAMPLE NETWORK
Figure 3. View of network map and browser.
-------
EPANET-EXAMPLE.INP( Input)
Ella Edit Bun
Roporl
Mop Window Help
d.
Map
TANK
• RESERVOIR
60.00
50.00
40.00
30.00
20.00
10.00
0,00
%N16!orNode 5
Browser
Nodes
I Nodes
|%N16
| 0.00
1*1
1*1
1
0.
10. 15.
Hour
20.
25.
EXAMPLE NETWORK
Figure 4. Example time series graph.
EPANET-EXAMPLE.INP(lnput)
Hour 12 Node Table
340.00
350.00
360.00
330.00
350.00
380.00
370.00
350.00
370.00
390.00
420.00
477.51
477.51
475.36
478.03
47521
471.33
477.22
500.11
505.71
491.75
487.75
5938
55.25
49.99
64.14
54.25
39.57
46.46
65.04
58.80
44.09
23.36
0.00
19.03
0.00
5.04
52.48
59.41
63.45
5.04
5.04
70.07
100.00
117.00
91.00
65.00
39.00
78.00
52.00
85.00
91 .00
65.00
143.00
Search of Hour 12 Node Table
Demand
Elevation
Grade
Proseur
8 items found - display them?
Figure 5. Example table query.
-------
Lewis A. Rossman (also the EPA Project Officer) is with the U.S. Environ-
mental 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
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-94/057
------- |