Using EPANET for irrigation system design

EPANET
FOR PRESSURIZED PIPE SYSTEMS

WHAT IS IT?
“EPANET is a Windows computer program
that performs extended period simulation
of hydraulic and water-quality behavior
within pressurized pipe networks. A
network can consist of pipes, nodes (pipe
junctions), pumps, valves and storage
tanks or reservoirs.”

WHO DEVELOPED IT?
Water Supply & Water Resources Section of the
Environmental Protection Agency (Lewis Rossman)

WHERE CAN I GET IT?
EPANET AND MANUAL CAN BE DOWNLOADED AT
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IT HAS USDA CCE CERTIFICATION
ADVANTAGES OF USING EPANET:
•
SURVEY DATA CAN BE READ INTO PROGRAM (A LITTLE EDITING IN EXCEL)
•
ALL CALCULATIONS ARE DONE INTERNALLY AND QUICKLY
•
GRAPHICS, SUMMARY OUTPUT TABLES
•
EASY TO CHECK OTHER PERSONS WORK
•

CHANGES ARE QUICK AND EASY
•
UNLIMITED NETWORK SIZE AND COMPLEXITY (LOOPED SYSTEMS, ETC.)
•
ERROR CHECKING AND WARNINGS
DISADVANTAGES OF USING EPANET:
•
HAVING TO LEARN THE PROGRAM (CAN TAKE SOME TIME).

Program components
•
Lets check out the various components
with a simple example.
•
A gravity pipe running from a diversion to
a pond

EXAMPLE PUMPED SYSTEM PROBLEM
We are installing a pump in a stream to pump water to an on-farm
irrigation system. After analyzing the on farm system,
we have determined that the peak crop water requirement is 350 gpm
and the pressure requirement at the turnout is 60 psi. The location
of the pump and pipeline have already been surveyed. PVC pipe will
be used. Pump site elevation = 3500 ft
Determine the:
1. Pump selection to deliver the flow and pressure to the turnout
2. Pressure rating of the pipe
3. Daily electrical costs to run the pump

GPS Survey Pro Exported Text File

EPANET NETWORK INPUT FILE (*.inp)

Import file

P U M P
P U M P M O T O R
W A T E R T O W I R E E F F I C I E N C Y
D E S I G N P A R A M E T E R S
T D H = 2 0 0 f t
Q = 4 0 0 g p m
V F D
M e t e r
6 0 - 8 0 % e f f .
8 0 - 9 0 % e f f .
9 5 - 9 8 % e f f .
E x a m p l e :
T D H = 2 0 0 f t
Q = 4 0 0 g p m
P u m p E f f i c i e n c y ( f r o m c u r v e ) = 7 5 %
P u m p M o t o r E f f i c i e n y ( a s s u m e d ) = 8 5 %
N O V F D d r i v e t o p u m p ( s e t m o t o r r p m = 3 6 0 0 )
W H P = ( 2 0 0 x 4 0 0 ) / 3 9 6 0 = 2 0 . 2 0 h p
B H P = 2 0 . 2 / 7 5 % = 2 6 . 9 4 h p
E H P = 2 6 . 9 4 / 8 5 % = 3 1 . 6 9 h p
W a t e r t o w i r e E f f i c i e n c y ( p u m p i n g p l a n t e f f . ) = 7 5 % x 8 5
%
= 6 4 %
A s s u m e y o u d r a w t h r o u g h t h e m e t e r 3 0 h p ( 2 2 . 3 8 K w ) f o r 1 d a y .
A s s u m e t h e c o s t o f e l e c t r i c i t y = $ 0 . 0 5 / K w - h r

T o r u n t h e p u m p f o r 2 4 h o u r s :
2 2 . 3 8 K w x 2 4 h o u r s x $ 0 . 0 5 / K w - h r = $ 2 6 . 8 6

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From Berkeley Pump Selection Software, Q = 350 gpm, TDH = 215 ft

Power, hydraulic (water) : 18.97 hp
Power, brake : 26.90 hp
Minimum recommended driver rating set @ : 30.00 hp / 22.37 kW

Electronic Variable Frequency Drives (VFD’s)
“control the speed and torque of an AC electric motor by varying the frequency
and voltage of the electricity supplied to the motor. They replace inefficient,
energy robbing controls such as control valves, pressure reducing valves, etc.”

Why Use VFD’s?
From Pump Affinity Laws (constant impeller diameter):
P1/P2= (N1/N2)
3
P = Power
N= Speed (rpm)
Initially we have a 10 hp pump running at 3600 rpm to meet demand and
pressure requirements in our piping system. Demand declines and the
VFD lowers the pump speed to 3200 rpm. What are the power savings?
P1 = 10 hp
N1 = 3600 rpm
N2 = 3200 rpm
P2 = 7 hp
An 11.1% speed decrease results in a 30% decrease in power
Consumption! Small speed decreases result in large energy savings.

The Real Cost of Electricity-Whats On Your Bill!
**Demand Charge is based on the highest average 15 minute power usage for
the billing period. Demand charge kicks in at > 15 kw usage. (pacific power)
Example Bill

Pump Example

Summary of Pipeline/Irrigation Projects
Using GIS Survey EPANET
1) Conduct the GPS survey of water levels, pumps, pipelines,
sprinkler locations, etc.
2) Export the data from Survey Pro to a text format.
3) Read the exported text file into Excel and manipulate it into
The EPANET input format.
4) Import the nodes into EPANET
5) Draw the pipe network and begin the simulation

Sprinkler Simulation EPANET

Emitter-Sprinkler Orifice Equation
q = C p
y

q = emitter flow rate
C = discharge coefficient
p = pressure
y
= pressure exponent
y
= 0.5 for sprinklers/nozzles


Calculate the Emitter Coeficients for the Varying Nozzles
For the rainbird 30H (SBN-3) with plug @ 50 psi:
9/64” nozzle, C = q/p

0.5
= 4.1 gpm/ 50
0.5
= 0.580
5/32” nozzle, C = 0.707
11/64” nozzle, C = 0.863
3/16” nozzle, C = 1.018
Change the emitter coefficient in EPANET to change the
Sprinkler/nozzle.

Questions ?