BIE 5110/6110
Sprinkle & Trickle Irrigation
Fall Semester 2004 – Final Exam
Include units in all results.
Indicate any assumptions that you might make.
Don’t show more than three significant digits in any of the results.
Name__________________________________
1. (35 pts) A mature citrus orchard will be drip-irrigated (drip emitters) using a single
lateral per row of trees in a 132-ha field area.
Other information:
•
Tree spacing is 6.0 x 6.0 m.
•
Peak daily ET is U
d
= 5.1 mm/day.
•
Seasonal water requirement: U = 660 mm.
•
Effective rain, peak-use period: 1.5 mm/day (average, w/ 90% probability)
•
Residual soil water in the spring: assume zero.
•
Soil water holding capacity is 175 mm/m (medium texture).
•
Irrigation water quality: EC
w
= 0.89 dS/m.
•
Root zone depth is 1.5 m.
•
Shaded area is 78%.
•
Emitter equation:
0.481
q
0.28P
=
for q in lph; and P in kPa.
•
Nominal emitter flow rate: q
a
= 3.85 lph.
•
Manufacturer’s emitter coefficient of variation: 0.0487.
•
Average wetted width at 3.85 lph: w = 2.01 m.
•
Outlets per emitter: one.
•
Use an MAD of 20%.
What you need to do:
1. Select an appropriate emitter spacing, S
e
.
2. Determine the number of emitters per tree, N
p
.
3. Calculate percent wetted area, P
w
.
4. Calculate maximum net depth to apply per irrigation, d
x
.
5. Calculate the average peak daily “transpiration” rate, T
d
.
6. Calculate the maximum irrigation interval, f
x
.
If f
x
≥
1 day, use f’ = 1day.
7. Calculate the net depth per irrigation, d
n
.
8. Select a reasonable target EU value.
9. Determine (EC
e
)
max
.
10. Determine the transmission ratio, T
r
.
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