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Sudan J. Agric. Res. : (2011), 17, 103 - 122 ARC, Sudan, Email: [email protected]
A software tool for appropriate design of center pivot irrigation
system
Hassan E. Alsayim1 and Amir B. Saeed2
Abstract
The experiment was conducted in the River Nile Sate, Sudan, to develop
a simulation model for designing a center pivot sprinkler irrigation
system. A Visual Basic 6.0 program was utilized in the model application
windows. The program was interactive to design a new system and/or
evaluate an already designed system. The crop water requirement and
the pipe size permitted to attain the target. The center pivot hydraulic
characteristics and its hardware specications were executed. Two center
pivot systems at Ras Elwadi farm and the Jordanian Bashair project wereused for model testing and verication during 2007/2008 season. With
respect to the hydraulic characteristics and hardware specications,
it was found that the center pivot system discharges were 318.8 m3hr-1
and 227.2 m3hr-1 for Ras Elwadi farm and Jordanian Bashair project,
respectively. The package of low drift nozzles (LDN) was 116 nozzles with
2.8 m spacing and 214 nozzles with 1.9 m spacing for Ras Elwadi farm and
Jordanian Bashair project, respectively. The ratio of actual to calculated
nozzle discharge and pressure were within the acceptable range of 0.82 to
1.13 and 0.97 to 1.17 for Ras Elwadi farm and 0.84 to 1.90 and 1.03 to 1.23for Jordanian Bashair project.
Introduction
Pressurized irrigation systems had been used since the early 1900s,
but the rst center pivot machine was developed in late 1940s. A center pivot
is a moving irrigation system with a lateral that rotates around a xed pivot
point. By mid1970s, the center pivot irrigation system had rapidly dominated
the new and expanding irrigation areas in the USA and the Middle East (Evans,
2001).Heermann and Kohl (1983) mentioned that the sprinkler irrigation systems
were designed to uniformly apply water to the soil at a rate equal to or less
than the soil intake rate. The design guidelines need to be either followed or
intentionally circumvented with appropriate design criteria when designing
and managing a center pivot irrigation system. Jorge and Pereira (2003)
depicted that a poorly designed irrigation system, even if well managed, often1 Department of Agricultural Engineering, Faculty of Agriculture, Nile Valley University, Darmali, Sudan.2 Department of Agricultural Engineering, Faculty of Agriculture, University of Khartoum, Shambat,
Sudan.
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Hassan E. Alsayim and Amir B. Saeed
results in crop yield losses and poor water productivity. Evans et al . (1997)
added that operating an irrigation system differently than assumed in the
design will alter the application rate and uniformity of coverage. Simulation
modeling of water, demand and supply is an essential analytical technique forassessing water management. Considerable research data for such conditions
and areas had been put into developed software to improve irrigation water
management. Field evaluation of sprinkler systems produced important
information to support the design in order to achieve better performance to
help farmers improve the management and maintenance of their irrigation
systems (Merriam and Keller, 1978). The eld data can easily be manipulated
through a computer model and effectively supported farmers to generate new
alternative solutions. To support design of sprinkler systems, several softwares
had been developed. Some models add graphical interfaces pay a particular
attention to the farm distribution network; others include topographical tools
to represent the elds under design. Examples of these models are:
The software SPRINKMOD developed by Andrae and Allen (1997) to
simulate pressure and discharges along the existing or newly designed
sprinkler irrigation systems.
The model ISADim developed by Abreu and Pereira (2002). It was
intended to design and/or simulate set sprinkler irrigation systems.
The model AVASPER developed by Jorge and Pereira (2003), aiming to
simulate and design sprinkler set systems.
This study was conducted to develop a center pivot simulation model (CPM)
for appropriate design of center pivot sprinkler irrigation systems.
Materials and Methods
Soil, crop and weather data for 30 years (1971 – 2000) were collected
from Atbara Meteorological Station, River Nile State. Three double ring
inltrometers were used for water inltration measurement. This data
represented the two different experimental sites of Ras Elwadi farm and the
Jordanian Bashair project, where center pivot systems were erected to irrigate
a forage crop (alfalfa) and a vegetable crop (onion) respectively. A computer
model designated (CPM) was developed during the rst season (2006/2007).
The model theoretical design characteristics were based on the collected data.
The CPM model accuracy was validated by its output from the data of season
(2007/2008) as compared with the actual system design criteria. The CPM
was executed using soil, crop and weather data to obtain the theoretical design
characteristics for the intended area and crops in the two sites. The obtained
results were compared with the actual data of the two systems in the two
sites.
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A software tool for appropriate design of center pivot irrigation system
Model development
The model CPM was developed using Microsoft Visual Basic 6.0 with
Service Pack 2 and included a database in Access 2000 and was run in
Windows. The program was interactive for designing a new system and/or
for evaluation of an existing system. In the design mode, computations were
performed iteratively until design constraints were met.
Firstly, the input data were prepared and the design criteria of the center
pivot system were executed later on. Finally, the system layout report was
printed out. However, in all cases, throughout the program, “click” means to
click the left mouse button and clicking “Previous” and “Next” buttons to get
backward to the previous window or upward to the next one.
When CPM was launched from windows, then the project information was
entered, and “Open project” button to open the project le for the center pivot
system design was chosen.
Field information and water supply
This option required data inputs of total eld area, diameter or short length
of the eld, elevation, water source and maximum available water volume
from source.
Soil data
This data were collected for the analysis of soil properties viz: calculation
of total available water, selection of soil inltration family, water depletion
ratio and calculation of readily available water. Computations were based onequations proposed by Withers and Vipond (1985) as follows:
Where: Taw
is total available water (cm), θfc is soil moisture content at eld
capacity (%), θwp
is soil moisture content at permanent wilting point (%), Rd
is relative density, Drz is root zone depth (cm), Dn is readily available water
(cm) and Mad
is water depletion ratio (%).
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Meteorological data
This window was divided into two parts. The rst part was for location of
the project, which included altitude, latitude and longitude. The second part
for ETo calculation using FAO Penman-Monteith equation (3) as modied by
Allen et al. (1998) or by using class-A evaporation pan method as proposed
by Jensen (1980), equation (4).
Where: ETo is reference crop evapotranspiration (mm d-1), ∆ is slope of the
saturated vapor pressure curve, Rn is net radiation ux (MJ m-2d-1), G is
sensible heat ux into the soil (MJ m-2d-1), γ is approximately 0.059 (kPa°C-1),
T is mean air temperature (°C), U2 is wind speed (ms-1) at 2 m above the
ground, es is saturated vapor pressure (kPa), ea is actual vapor pressure (kPa),
es - ea is mean daily vapor pressure decit (kPa), kp is dimensionless, pan
coefcient and Ep is pan evaporation (mm).
Crop water requirement
In this window (Fig. 1) the user can determine peak consumptive use for
four selected crops, irrigation interval and gross water depth. These computed
performance indicators are as proposed by Merkley and Allen (2007) using
the following equations:
Hassan E. Alsayim and Amir B. Saeed
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Where: ETc is crop evapotranspiration (mm day-1), Kc is crop coefcient, ETo
is reference crop evapotranspiration rate (mmday-1), II is irrigation interval
(days), Dn is readily available water in the root zone (mm), Dg is the gross
application depth (mm) and Ea is the application efciency (%).
Fig. 1. Dialogue box for crop water requirement determination.
System revolution
The system revolution design followed the approaches proposed byAl-Ghobari (2004). In this form the simulated parameters were number of
revolutions, water depth during one revolution, available irrigation time and
one rotation time. The following equations (8, 9, 10 and 11) were used for the
aforementioned calculations:
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( )Re ................................................................................................ 9 Dg
Dg v
Nrev
=
( ) ..................................................................................................... 11Ti
Trev Nrev
=
Where: Nrev is number of revolutions, Dg is gross water depth (mm), dgmax
is maximum water depth added without causing runoff (mm), Dgrev is waterdepth during one revolution, Ti is available irrigation time for one irrigation,
Trat is readily available time (%) and II is irrigation interval.
System discharge
System discharge design followed the methodology recommended by
Merkley and Allen (2007) as follows:
Where: Q is the system discharge (l s-1), K is 2.78, A is area (ha), D is gross
daily application depth (mm), F is frequency in days per irrigation and T is
operating time, generally 20-22 (hr day-1) during the peak use period.
Pivot lateral design
In the “Pivot lateral Design” window (Fig. 2), the output design criteria for
the system with one pipe size or two pipes size are lateral inner diameter andsystem discharge adjusted to the calculated diameter. The calculations were
carried out as proposed by Keller and Bliesner (1990) as follows:
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Where: d is inside diameter of the main line (m), Q is system discharge
(m3 sec-1), V is water ow velocity (V ≤ 2 m sec-1) and p is 227
or 3.14.
Fig. 2. Window for pivot lateral diameter and system discharge for Ras
Elwadi farm.
Application rateThe calculation of maximum application rate and application time for
specic sprinkler was major functions of this window. The calculation
procedure used was suggested by Al-Ghobari (2004) as follows:
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Where: AR is the average application rate over width W (mm min -1 for ETc
in mm day-1), k is 60, Q is system discharge, Re is the fraction of applied
water that reaches the soil surface, Oe is the fraction of water that does not
leak from the system pipes, R is effective radius (m), Ram is the maximum
application rate, Tw is application time (min), Dw is sprinkler wetted diameter
at the distance (r) from the pivot (m) and Trev is revolution time (min).
Sprinklers (nozzles) conguration
This window (Fig. 3) represents types of sprinklers (nozzles) and rain guns
used for center pivot systems and their hydraulic characteristics to help the
designer in selecting proper sprinklers. The sprinklers (nozzles) conguration
and selection followed the approaches proposed by King and Kincaid (1997).
Fig. 3. User interface for sprinklers selection.
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Hydraulic characteristics and hardware specications
Simulation of hydraulic system includes determination of friction losses
on the sprinkler line, determination of operating head (pressure) in the
pivot point, distribution of operating pressure along the lateral, sprinklers(nozzles) operating pressure and nozzle size and color (Fig. 4). The hydraulic
characteristics design followed the approaches proposed by Keller and Bliesner
(1990) and Merkley and Allen (2007) as the following equation:
Where: Hf is the friction losses (m), K is 16.42(10)4, F is 0.555 for a center
pivot with a “large” number of outlets and no end gun, Q is the ow rate (L
s-1), C is a roughness coefcient, d is the pipe inside diameter (cm) and R is the
pipe length (m). The determination of sprinklers (nozzles) operating pressure,
nozzle size and discharge was carried out using the following equations as
suggested by Al-Ghobari (2004):
Where: Psp is sprinkler operating pressure (kPa), Pf is friction losses on the
pivot lateral (kPa), r is nozzle spacing from the pivot point (m), R is sprinkler
line length (m), Pe is pressure required in the end of the sprinkler line (kPa),
dsp is nozzle diameter (mm), Qsp is nozzle discharge (L s-1), Ss is sprinklers
spacing (m), Q is system discharge (L s-1) and K is a unit conversion of 10000
in metric units of L s-1
, m, and L s-1
ha-1
.
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System report
This window is for assembly of output data for the system design, which
consists of three reports (Figs. 5a, 5b and Table 1).
Data collection and analysisThe climate data from Atbara meteorological station included rainfall data,
mean maximum and mean minimum temperatures, mean relative humidity,
mean sunshine, wind speed and evaporation. Monthly means for 30 years
(1971 – 2000) were presented in Table 2.
* Dark color
Fig. 4. User interface for hydraulics and hardware specications along the
sprinkler line.
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Soil physical properties for the two sites were obtained from samples
analyzed in Hudeiba Research Station laboratory. The soil in both sites
was classied as sandy clay loam. Using the method proposed by Saxton
et al
. (2006), soil moisture contents at eld capacity and permanent wilting point were determined as 30.6 and 19.6, respectively. Eight sprinklers were
randomly selected along the sprinkler line to measure the sprinkler discharge
and pressure as recommended by Code of Practice for Irrigation Evaluation
(2006).
Results and Discussion
The simulation model CPM was used to determine the center pivot system
design criteria. Table (3) shows the results of irrigated area, readily available
water, reference evapotranspiration, crop evapotranspiration, irrigation intervaland application depth. For Ras Elwadi farm, they were 43.7 ha, 11.9 ha, 49 mm,
8.11 mm day-1, 8.9 mm day-1, 6 days and 70 mm, respectively. While for the
Jordanian Bashair project, they were 55.4 ha, 15.1 ha, 49 mm, 8.11 mm day-1,
9.3 mm day-1, 6 days and 70 mm, respectively. Reference evapotranspiration
was determined using the modied (FAO) Penman-Monteith equation, then
the parameters of crop evapotranspiration, irrigation interval and application
depth were calculated and exhibited in Fig. 1.
Center pivot sprinkler irrigation modelCPM version 1.0.0
System design report
Project data:
Project No.1 :. Project Name: Ras Elwadi farm.
Engineer (Designer): Mamoon.
Project location:
Country: Sudan. Latitude: 17°40
Longitude: 33° 58 Altitude: 346.5 m.
Field Information and water supply:Total eld area: 55.56 ha. Irrigated area: 43.7 ha.
None irrigated area: 11.86 ha.
Maximum available water from source: Well is ________ m3/day.
Soil:
Soil Type: Silty loam soil. Readily available water: 49 mm.
Crop/s Water requirements with application efciency of 70%.
Fig. 5a. System report of project data.
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System discharge:
System type:Without rain gun.
System discharge: 318.6 m3/hr.
Rain gun discharge:_____ m3/hr (if existent).
Main line design:
Main line length: 372.7 m. Main line (Pipe) diameter. Manufacturing:
162.05 mm.
Spans (Towers) No.: 9. Spans (Towers) Spacing: 38 m.
Over hang length: 30.7 m. Rain gun wetted Radius: m.
(if existent).
Application rate:
System application rate: 102.8 mm/hr.
Maximum application rate: 130.8 mm/hr.Sprinklers selection:
Sprinkler (Nozzle) type: Low drift and multiple spray head.
Sprinklers spacings:1.9 m.
Fig. 5b. System report of system discharge.
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T a b l e 1 . S y s t e m r e p o r t ( s a m p l e ) f o r h y d r a u l i c s c h a r a c t e r i s t i c s a n d h a r d w a r e s p e c i
c a t i o n s a l o n g t h e s p r i n k l e r l i n e .
N
o z z .
N
o .
S p a c i n g
f r o m
p r e v i o u s
( m )
D i s t a n c e
f r o m
p i v o t
p o i n t
( m )
S p r i n k l e r
d i s c h a r g e
( L / s )
S p r i n k l e r
d i s c h a r g e
( g p m ) +
S p r i n k
l e r
o p e r a t i n g
p r e s s u
r e
( p s i )
S p r i n k l e r
o p e r a t i n g
p r e s s u r e
( k p a )
N o z z l e
d i a m e t e r
( m m )
N
o z z l e
d
i a m e t e r
(
T H 6
4
i
n c h )
N o z z l e s i z e a n d
c o l o r
I r r i g a t e d
a r e a
( h a )
1
4 6 . 8
4 6 . 8
2 . 7
9 3
4 4 . 2 7 5
3 8 . 2
2 6 3 . 4
1 2 . 6
3
1 . 7
3 2 Y e l l o w
1 . 3
7 7
2
2 . 8
4 9 . 6
0 . 1
7 7
2 . 8 0 6
3 8 . 1
2 6 2 . 4
3 . 2
8
. 1
8 . 5 L a v e n d e r *
0 . 0
8 7
3
2 . 8
5 2 . 4
0 . 1
8 7
2 . 9 6 4
3 7 . 9
2 6 1 . 4
3 . 3
8
. 3
8 . 5 L a v e n d e r *
0 . 0
9 2
4
2 . 8
5 5 . 2
0 . 1
9 7
3 . 1
2 3
3 7 . 8
2 6 0 . 4
3 . 4
8
. 6
9 G r a y
0 . 0
9 7
5
2 . 8
5 8 . 0
0 . 2
0 7
3 . 2
8 1
3 7 . 6
2 5 9 . 4
3 . 5
8
. 8
9 G r a y
0 . 1
0 2
6
2 . 8
6 0 . 8
0 . 2
1 7
3 . 4 4 0
3 7 . 5
2 5 8 . 5
3 . 5
8
. 8
9 G r a y
0 . 1
0 7
7
2 . 8
6 3 . 6
0 . 2
2 7
3 . 5
9 8
3 7 . 3
2 5 7 . 5
3 . 6
9
. 1
9 . 5 G r a y *
0 . 1
1 2
8
2 . 8
6 6 . 4
0 . 2
3 7
3 . 7
5 7
3 7 . 2
2 5 6 . 5
3 . 7
9
. 3
9 . 5 G r a y *
0 . 1
1 7
9
2 . 8
6 9 . 2
0 . 2 4 7
3 . 9
1 5
3 7 . 1
2 5 5 . 5
3 . 8
9
. 6
1 0 T u r q u o i s e
0 . 1
2 2
1
0
2 . 8
7 2 . 0
0 . 2
5 7
4 . 0 7 4
3 6 . 9
2 5 4 . 6
3 . 9
9
. 8
1 0 T u r q u o i s e
0 . 1
2 7
1
1
2 . 8
7 4 . 8
0 . 2 6 7
4 . 2 3 2
3 6 . 8
2 5 3 . 6
3 . 9
9
. 8
1 0 T u r q u o i s e
0 . 1
3 2
1
2
2 . 8
7 7 . 6
0 . 2
7 7
4 . 3 9 1
3 6 . 6
2 5 2 . 7
4 . 0
1
0 . 1
1 0 . 5 T u r q u o i s e *
0 . 1
3 7
*
D a r k c o l o r . + : G a l l o n s p e r m i n u t e .
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T a b l e 2 . C l i m a t o l o g i c a l n or m a l s 1 9 7 1 –2 0 0 0 ,A t b ar a S t a t i o n ,L a t .1 7 ° 4 0 / N ,L o n g . 3 3 ° 5
8 / E ,A l t . 3 4 5 m .
M on .
Ai r t e m p e r a t ur e i nº C
M e a n
d r y
t e m p .
Br i gh t
s un s h i n e
d ur a t i on
R e l a t i v e
h umi d i t y
%
R a i nf a l l i nm
m
E VAP .
pi t c h
mm
Wi n d
m e a n
s p e e d
a t 2 m
M .P .D
M a xi m um
Mi ni m um
N o . of r a i n d a y s
M e a n
H S T *
M e a n
L S
T *
º C
Hr s .
%
M e
a n
> = 0 .1
> =1 . 0
> =1 0 . 0
J a n .
2 9 . 8
3 9 .1
1 4 .2
6 . 3
2 2 . 0
9 . 9
8 8
3 6
0 . 0
0 . 0
0 . 0
0 . 0
1 3 . 5
4 . 9 7
F e b .
3 1 . 8
4 1 .4
1 5 .1
5 . 5
2 3 .4
1 0 . 3
9 0
3 1
0 . 0
0 . 0
0 . 0
0 . 0
1 5 . 0
4 . 9 7
M a r c h
3 5 . 7
4 5 . 7
1 8 .4
1 0 . 8
2 7 . 0
1 0 .1
8 4
2 4
0 . 0
0 . 0
0 . 0
0 . 0
1 8 .1
4 . 9 7
A pr .
4 0 . 0
4 6 . 3
2 2 .1
1 5 . 0
3 1 .1
1 0 . 6
8 5
2 3
0 .4
0 .2
0 .1
0 . 0
2 0 .1
4 .2 6
M a y
4 2 . 6
4 7 . 5
2 6 . 5
1 8 . 9
3 4 . 5
9 . 8
7 5
2 3
3 .2
0 . 7
0 . 5
0 .1
2 0 .4
3 . 5 5
J un .
4 3 .2
4 8 . 0
2 8 . 0
2 1 . 6
3 5 . 6
8 . 6
6 5
2 2
1 . 0
0 . 3
0 .2
0 . 0
2 0 . 7
3 . 5 5
J ul .
4 1 .2
4 7 . 7
2 7 . 3
1 9 . 5
3 4 . 3
8 . 7
6 5
3 2
1 5 .1
1 .4
1 . 3
0 .4
1 9 . 0
4 .2 6
A u g .
4 0 . 6
4 6 . 5
2 6 . 9
1 9 . 5
3 3 . 8
8 . 6
6 7
3 7
2 6 . 5
2 .2
2 . 0
0 . 9
1 8 . 0
4 .2 6
S e p .
4 1 . 6
4 7 . 6
2 7 .4
2 0 . 0
3 4 . 5
8 . 6
7 1
3 2
8 . 6
1 .1
1 . 0
0 . 3
1 8 . 5
4 .2 6
O c t .
3 9 . 7
4 4 . 5
2 5 .2
1 6 . 0
3 2 . 5
9 . 8
8 3
3 1
3 . 0
0 . 5
0 . 5
0 .1
1 7 .4
3 . 5 5
N o v .
3 4 . 9
4 0 . 7
2 0 .1
1 1 . 7
2 7 . 5
1 0 .2
9 0
3 6
0 . 0
0 . 0
0 . 0
0 . 0
1 4 . 7
4 .2 6
D e c .
3 1 .1
3 8 . 5
1 6 . 0
6 . 5
2 3 . 6
9 . 7
8 8
4 0
0 . 0
0 . 0
0 . 0
0 . 0
1 3 .2
4 .2 6
Y e a r
3 7 . 7
4 8 . 0
2 2 . 3
5 . 5
3 0 . 0
9 . 6
7 9
3 1
5 7 . 7
6 . 7
5 .4
1 . 8
1 7 .4
-
S o ur c e : S u d a
nM e t r o l o g i c a l A u t h or i t y ,A t b ar a S t a t i o n .
* : H S T : H i g h e s t s t a t i o n t e m p er a t ur e .
* : L S T : L o w e s t s t a t i o n t e m p er a t ur e .
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Table 3 shows sample calculations as CPM Model output. Regarding the
hydraulic characteristics and hardware specications, it was found that the
center pivot system discharges were 318.8 m3 hr -1 and 227.2 m3 hr -1 for Ras
Elwadi farm and the Jordanian Bashair project, respectively (Fig. 2). Onthe other hand, the packages of Low-drift nozzles (LDN) were 116 nozzles
with 2.8 m spacing and 214 nozzles with 1.9 m spacing for Ras Elwadi farm
and the Jordanian Bashair project, respectively. Tables (4 and 5) exhibit the
ratio of actual (measured) to calculated nozzle locations along the sprinkler
line, nozzle discharge, nozzle pressure and nozzle size and color through the
sprinkler line. The columns titled VND and VNP in aforementioned tables
represent the ratio of actual to calculated nozzle discharge and nozzle pressure,
respectively. VND and VNP for Ras Elwadi farm were within the range of
0.82 to 1.13 and 0.97 to 1.17, respectively. For the Jordanian Bashair project
VND and VNP were between 0.84 to 1.90 and 1.03 to 1.23, respectively. The
obtained results indicated that the variation in nozzle discharge were within
11% and 19% and the variation in nozzle pressure was within 11% and 12%
for Ras Elwadi farm and the Jordanian Bashair project, respectively. These
variations may be attributed to the systems performance which was directly
inuenced by inadequate nozzle pressure; nozzles wear and water leakage
through spans connections.
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Table 3. Sample calculations of the design criteria, for the tow center pivot
sprinkler systems.
Design criteria Ras Elwadi farm Jordanian Bashair project
Irrigated areaTotal eld (A) = R 2
A=3.14Í(745.4/2)2/10000 =
43.7 ha
Total eld (A) = R 2
A = 3.14Í(840/2)2/10000
= 55.4 ha
Readily available
water
Equations (1 and 2)
(Total available water )
Taw = (30.6 –
19.6)/100Í1.49Í60Í10 =
98 mm
(Readily available water) Dn =
98Í
0.5 = 49 mm
(Total available
water) Taw = (30.6 –
19.6)/100Í1.49Í60Í10
= 98 mm
(Readily available water)
Dn = 98Í
0.5 = 49 mm
Reference
evapotranspiration
Equation (3)
ETo = 8.11 mm day-1 ETo = 8.11 mm day-1
Crop water
requirements
Equation (5)
For Kc = 1.1
ETcrop (Alfalfa) = 8.11Í1.1=
8.9 mm day-1
For Kc = 1.15
ETcrop (Onion) =
8.11Í1.15= 9.3mm day-1
Irrigation interval
Equation (6)
II = 49/8.9 = 5.5 ≈ 6 days II = 49/9.3 = 5.3 ≈ 6 days
Application depth
Equation (7)
Dg = 49/0.7 = 70 mm
Dg is gross water depth.
Dg = 49/0.7 = 70 mm
Dg is gross water depth.
System discharge
(Q)
Equations (12 and 13)
Q = 43.7Í
70Í
10/115.2 =265.5 m3 hr-1
Q adjusted to selected
diameter, velocity method
162.05Í3600Í(3.14Í1.52
)0.5/4/1000 = 318.8 m3 hr-1 =
1403.6 gpm
Q = 55.4Í
70Í
10/115.2 =336.6 m3 hr-1
Q adjusted to selected
diameter, velocity method
162.05Í3600Í(3.14Í1
.52)0.5/4/1000 = 227.2 m3
hr-1 = 1000.3 gpm
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T a b l e 4 . H y d r a u l i c s c h a r a
c t e r i s t i c s a n d h a r d w a r e
s p e c i c a t i o n s - a c t u a l
a n d c a l c u l a t e d a s C P M
o u t p u t
f o r R a s E l w a d i f a r m .
N
N P L
N N S
D F P P
( m )
A N D
( L / s )
C N D
( L / s )
V N D
%
N P A
K p a
( P s
i )
N P C
K p a
( P s i )
V N P
%
A N S C
( 6 4 T h i n c h )
a n d c o l o r
C N S
C
( 6 4 T
h i n c h )
a n d c o l o r
2
0
4
1 0 0 . 4
0 . 3 2
4
0 . 3
5 8
0 . 9
1
2 6 1
. 8
( 3 8
)
2 4 5 . 2
( 3 5 . 6 )
1 . 0 7
1 1 Y e l l o w
1 2 R
e d
3
6
4
1 4 5 . 6
0 . 4 2
4
0 . 5
2
0 . 8
2
2 6 1
. 8
( 3 8
)
2 3 2 . 3
( 3 3 . 7
)
1 . 1 3
1 2 . 5 R e d *
1 4 . 5
B l u e *
5
1
3
1 8 8
0 . 5 9
4
0 . 6 7 1
0 . 8
9
2 6 1
. 8
( 3 8
)
2 2 3 . 3
( 3 2 . 4 )
1 . 1 7
1 5 . 5 D B r o u n *
1 6 . 5
O r a n g e *
6
7
3
2 3 8 . 8
0 . 7 9
2
0 . 8
3 3
0 . 9
5
2 4 8 ( 3 6
)
2 1 8 . 2
( 3 1 . 6 )
1 . 1 4
1 7 D
G r e e n
1 8 . 5
P u r p l e *
8
4
4
2 8 1 . 2
0 . 9 1
3
1 . 0 0 4
0 . 9
1
2 3 4
. 3
( 3 4
)
2 1 9 . 6
( 3 1 . 8
)
1 . 0 7
1 9 B l a c k
2 0 T u r q
1
0 2
4
3 3 2
1 . 1 8
8
1 . 1
8 5
1 . 0
0
2 3 4
. 3
( 3 4
)
2 3 0 . 9
( 3 3 . 5
)
1 . 0 1
2 2 M a r o o n
2 1 . 5
M u s t a r d *
1
1 1
1 3
3 5 7 . 2
1 . 3 1
9
1 . 2
7 5
1 . 0
3
2 3 4
. 3
( 3 4
)
2 4 1 . 2
( 3 5 )
0 . 9 7
2 3 . 5 C r e a m *
2 2 M
a r o o n
1
1 5
1 7
3 6 8 . 4
1 . 4 8
4
1 . 3
1 5
1 . 1
3
2 3 4
. 3
( 3 4
)
2 4 1 . 2
( 3 5 . 8
)
0 . 9 8
2 5 Y e l l o w
2 2 . 5
M a r o o n *
N N
P L : N o z z l e n u m b e r o n p i v o t l a t e r a l .
N N S : N o z z l e n u m b e r o n s p a n .
D F P P : D i s t a n c e f r o m p i v o t p o i n t .
A N
D : A c t u a l n o z z l e d i s c h a r g e .
C N D : C a l c u l a t e d n o z z l e d i s c h a r
g e .
V N D : V a r i a n c e i n n o z z l e d
i s c h a r g e , r a t i o o f a c t u a l t o c a l c u l a t e d ( % ) .
N P A : N o z z l e p r e s s u r e a c t u a l .
N P C : N o z z l e p r e s s u r e c a l c u l a t e d .
V N P : V a r i a n c e i n n o z z l e p r
e s s u r e , r a t i o o f a c t u a l t o c a l c u l a t e d ( %
) .
A N
S C : A c t u a l n o z z l e s i z e ( 6 4 T h i n c h ) a
n d c o l o r .
C N
S C : C a l c u l a t e d n o z z l e s i z e ( 6 4 T h i n c h ) a n d c o l o r .
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T a b l e 5 .
H y d r a u l i c s c h ar a c t e r i s t i c s
a n d h ar d w ar e s p e c i c a t i o
n s - a c t u a l a n d c a l c u l a t e d
a s C P M o u t p u t f or J or d a n i a n
B a s h
a i r pr o j e c t .
N NP L
N N S
DF P P
( m )
A ND
( L / s )
C ND
( L / s )
V ND
%
NP AK p a
( P s i )
NP C
K p a
( P s i )
V NP
%
A N S C
( 6 4 T h i n c h )
a n d c ol or
C N S C
( 6 4 T h i n c h )
a n d c ol or
2 2
2
4 5 . 7
0 . 0 8 2
0 . 0 6 2
1 . 3 2
1 3 1 . 0 0 5
( 1 9 )
1 0 6 . 9
( 1 5 . 5 )
1 .2 3
6 . 5 Y e l l o w
1 2 R e d
3 8
1 8
7 6 .1
0 .1 2 0
0 .1 0 3
1 .1 7
1 1 7 .2 1 5
( 1 7 )
1 0 6 . 9
( 1 5 . 5 )
1 .1 0
8 L a v e n d e r
1 4 . 5 Bl u e *
6 2
2 0
1 2 2 . 7
0 .1 8 8
0 .1 6 7
1 .1 3
1 1 7 .2 1 5
( 1 7 )
1 0 6 . 9
( 1 5 . 5 )
1 .1 0
1 0 T ur q u oi s e
1 6 . 5 Or a n g e *
8 4
2 0
1 6 5 . 5
0 .2 2 8
0 .2 2 5
1 . 0 1
1 1 7 .2 1 5
( 1 7 )
1 0 6 . 9
( 1 5 . 5 )
1 .1 0
1 1 Y e l l o w
1 8 . 5 P ur pl e *
1 2 0
6
2 3 6 . 6
0 .2 8 5
0 . 3 2 2
0 . 8 9
1 1 0 . 3 2 ( 1 6 )
1 0 6 . 9
( 1 5 . 5 )
1 . 0 3
1 2 . 5 R e d *
2 0 T ur q
1 4 5
6
2 8 5 . 3
0 . 3 2 7
0 . 3 8 8
0 . 8 4
1 1 0 . 3 2 ( 1 6 )
1 0 6 . 9
( 1 5 . 5 )
1 . 0 3
1 3 . 5 Wh i t e *
2 1 . 5 M u s t a r d
*
1 6 3
2 4
3 1 9 . 5
0 .4 0 0
0 .4 3 4
0 . 9 2
1 2 4 .1 1
( 1 8 )
1 0 6 . 9
( 1 5 . 5 )
1 .1 6
1 4 . 5 Bl u e *
2 2 M a r o on
2 1 3
2 4
4 1 7 .1
1 . 0 8 0
0 . 5 6 7
1 . 9 0
1 2 4 .1 1 ( 1 8 )
1 0 6 . 9
( 1 5 . 5 )
1 .1 6
1 8 P ur pl e
2 2 . 5 M a r o on*
N NP L : N ozz
l e n um b e r on pi v o t l a t e r a l .
N N S : N ozzl e n um b e r on s p a n .
DF P P : Di s t a n c e f r om pi v o t p oi n t .
A ND : A c t u a l n ozzl e d i s c h a r g e .
C ND : C a l c ul a t e d n ozzl e d i s c h a r g e .
V ND : V a r i a n c e i nn ozzl e d i s c h a r g e ,r a t i o of a c t u a l t o c a l c ul a t e d ( % ) .
NP A : N ozzl e
pr e s s ur e a c t u a l .
NP C
: N ozzl e pr e s s ur e c a l c ul a t e d .
V NP : V a r i a n c e i nn ozzl e pr e s s ur e ,r a t i o of a c t u a l t o c a l c ul a t e d ( % ) .
A N S C : A c t u a l n ozzl e s i z e ( 6 4 T h i n c h ) a n d c ol or .
C N S C : C a l c u
l a t e d n ozzl e s i z e ( 6 4 T h i n c h ) a n d c ol or .
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Conclusion
The Center Pivot Model (CPM), which is a computer technology, could1-
successfully be used to assess appropriate center pivot system design
and performance.
The execution of the simulated system using the viable alternatives2-
will help the engineers and practitioners to understand the operational
mechanism of the center pivot system and taking appropriate measures
for improvement.
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Hassan E. Alsayim and Amir B. Saeed