BIE 5110/6110
Sprinkle & Trickle Irrigation
Fall Semester 2004 – Exam #1
Include units in all results.
Indicate any assumptions that you might make.
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1. Preliminary Design Calculations (25 pts)
Almonds (deciduous trees, with no cover crop) have been planted in an 80acre
orchard and will be irrigated with a set sprinkler system.
The climate can be
characterized as “moderate.”
The topsoil is 2.7 ft of silty clay loam, and below that are
3.1 ft of clay loam soil.
The soil intake rate is 0.5 inch/hr.
Use an MAD value of 30%.
EC
w
is 0.47 dS/m and the estimated water application
efficiency will be E
a
= 85%.
There is no effective rain during the peakuse period.
For
these preliminary calculations, and based on the spacing of the trees, use a sprinkler
spacing of 40 ft x 50 ft.
a) Obtain the values for average W
a
, average Z, U
d
, U, and EC
e
from
the tables in Chapter 3 of the textbook.
b) Calculate the maximum net application depth per irrigation, d
x
.
c) Calculate the maximum irrigation interval, nominal irrigation
interval (whole number of days), and the net application depth per
irrigation, d
n
.
d) What is the gross depth to apply per irrigation?
e) What is the irrigation set time, S
to
, in hours?
2. Economic Pipe Size Selection (25 pts)
Suppose you applied the economic pipe sizing method.
What if you were using the
HazenWilliams equation and based all your calculations on a system capacity of 100
lps, but now you realize a calculation mistake was made, and the system capacity
should really be 115 lps.
A section flow rate, q, (threshold between two adjacent pipe sizes) was 50 lps, but now
it needs to be adjusted for the new system capacity of 115 lps.
What is the new section flow rate for this system capacity?
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Set Sprinkler Lateral Design (25 pts)
A fixed sprinkler system with buried IPSPVC (
thermoplastic pipe
) laterals is to be
designed.
The 304m long laterals will be a 0.394% (downhill) slope.
The nominal
sprinkler flow rate is 10 lpm at a pressure of 280 kPa, and the sprinkler spacing on the
laterals is 8.0 m.
Riser height is 1.0 m.
Let the allowable lateral
∆
h be equal to 20% of
h
a
.
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 Fall '03
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