Full Product Manual

Table Of Contents
Page 78 Appendix A
The water requirement for an individual plant is measured in gallons per day.
The formula for the water requirement for an individual plant is:
Water Requirement (GPD) = .623 x A x K
c
x PET
e
Where:
A = Area of the plant’s canopy (square feet)
K
c
= Crop coefficient (plant factor) of the plant
PET = Published daily evapotranspiration rate (inches per day)
e = Application efficiency (percentage in decimal form)
Knowing the maximum system run time helps to avoid wasted water due to run-
off or deep percolation. Keep in mind that the actual system run time will
generally be less than the maximum run time.
The formula for maximum system run time
1
is:
Maximum Run Time (hours) = 0.000361 x C x AW x D x S
2
q x e
Where:
C = Allowable water depletion (percentage in decimal form)
AW = Available Water (inches per foot)
D = Desired watering depth (inches)
S = Emitter spacing (inches)
q = Flow rate (GPH)
e = Efficiency (percentage in decimal form)
1
Developed at California Polytechnic University, Pomona by Professor Joseph Y. T. Hung, 1993.
Water Require-
ment For a Sparse
Planting Scheme
Maximum System
Run Time
®