Full Product Manual

Table Of Contents
Page 48 Chapter 6
3.Determine Irrigation Interval
The first task in determining the irrigation interval is to compare your calculated
system run time per day to the maximum run time.
In most cases the calculated run time per day will be less than the maximum run
time, and you can use the following formula to determine the maximum irriga-
tion interval:
EXAMPLE:
You are irrigating to a depth of 9 inches with 1 GPH emitters in medium soil.
Your calculated run time is 66 minutes per day. The maximum run time (from
Table 6-3) is 45 minutes. You must irrigate twice each day for 33 minutes each
time to total the required 66 minutes.
If the calculated run time is more than the maximum run time, you will need to
run your system more than once each day. Depending on the capability of your
controller and how much more time you need, you can determine how many
times to run the system each day to provide adequate water without wasting any
due to deep percolation. In general, you should probably be able to irrigate just
twice each day in these cases.
EXAMPLE:
You are irrigating to a depth of 18 inches in coarse soil with 1.0␣ GPH emit-
ters. The calculated run time per day is 19 minutes. The maximum run time
is 62 minutes. Using the formula, you determine that the maximum irrigation
interval should be 3.26 days. You round this down to the nearest day, and
irrigate at least every third day.
You now have all the information you need to decide your irrigation schedule
for this hydrozone. If you water daily, you will run your system for 19
minutes. Or you might choose to water every other day for 38 minutes (2 ¥
19). If you choose to water on the maximum interval of three days, you must
water for 57 minutes (3 x 19). To avoid runoff, split this longer watering time
into multiple cycles.
Maximum Irrigation Interval (days) = Maximum Run Time
Calculated Run Time Per Day
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