Agriculture Reference
In-Depth Information
Assuming overlapping factor,
F
0.7 (higher for windy condition)
Taking a manufacturer rated wetting diameter for mainline and lateral sprinkler
as 12 m and 10 m, respectively, we get
S
m
=
=
12 (1 - 0.7/2)
=
7.8
S
l
=
10 (1 - 0.7/2)
=
6.5
10
-7
m/h
Application rate,
I
=
Q
A
/
A
=
(0.1074
×
3600)/250,000
=
4.296
×
=
1.5468 mm/h, which is less than the soil infiltration rate.
Here, assuming
I
=
2 mm/h (to minimizing evaporation loss in windy climate)
=
×
×
×
=
Putting the values,
q
[7.8
6.5
(2/1,000)]
(1,000/60)
1.69 l/min
A
S
m
×
250, 000
7.8
(5) Number of sprinklers,
n
=
S
l
=
6.5
=
4,930.9
≈
4,931 nos
×
Note
: The above calculation is for fixed lateral. If moving lateral is used, no. of
laterals should be based on the maximum working /pump operating period.
Note that each setting requires 4 h for the above calculation, so 16/4
=
4
settings can be operated if 16 h is the working period.
Besides, number of laterals should be based on the dimension of the land,
lateral size available in the market, etc.
(6) Power required (motor capacity required),
P
(KW)
Q
(m
3
/s)
×
×
=
9.81
H
T
(m)
0.1074 m
3
/s
Here,
Q
=
H
T
=
H
m
+
H
f
+
H
r
+
H
s
+
H
sf
H
m
=
pressure head required to operate the sprinklers at minimum required
pressure (m)
=
28.37 m (
=
40 psi) (assuming)
H
f
=
total frictional head in the lines (m)
≈
5% of
H
m
=
1.71 m (assum-
ing/estimating)
H
r
=
maximum riser height from the pump level (m)
=
1.5 m (assuming)
H
s
=
suction head (vertical difference between pump level and source water
level after drawdown) (m) (if needed)
=
0 (assuming that water is pumped
from the supply canal)
H
sf
=
friction head loss in suction line (if suction line exists)
=
0
Thus,
H
T
=
31.26 m
32.94 KW
(7) Summary design parameters are as follows:
Taking for fixed laterals:
Pump capacity:
Q
t
=
Thus,
P
=
0.1074
×
9.81
×
31.26
=
0.1074 m
3
/s
Irrigation period
=
4h
Motor capacity:
P
32.94 KW
Lateral spacing along mainline:
S
m
=
=
7.8 m
Sprinkler spacing along lateral:
S
l
=
6.5 m
=
Number of total sprinklers:
n
4,931 nos (Ans.)
Relevant Journals
-
Agricultural Water Management
-
Irrigation Science
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