Full Product Manual

To calculate the K
c
values, simply multiply each plant’s species factor, density
factor, and microclimate factor. Round this number to the nearest tenth, and
record it in the “K
c
” column of the worksheet.
➌ Calculate
Water Require-
ment for Dense
Plantings
➌ Calculate Water
Requirement for
Individual Plants
in a Sparse
Hydrozone
The water requirement for individual plants in a sparse planting scheme is
measured in gallons per day (GPD). To calculate the water requirement for an
individual plant, you must first calculate the area of the plant’s root zone. You
can approximate the area of the root zone by using the area of the plant’s canopy.
Plant Diameter
For each plant, enter into the worksheet the diameter of the plant’s mature
canopy. That means that if immature plants are currently in place, you will need
to estimate how big they will grow as they mature. For the water requirement
calculation, you should estimate the diameter of the plant’s canopy in feet.
EXAMPLE:
Assume the PET for our site is 0.35 inches per day (an arbitrary number
selected for this example). Previously, we calculated a K
c
of 0.5. To deter-
mine the water requirement, multiply these two figures together (0.35 x 0.5
= 0.175). The water requirement for the base plant under these circum-
stances is .175 inches per day.
After rounding to the nearest tenth, you find that the water requirement for
this site is 0.2 inches per day.
The water requirement for the base plant in a densely planted hydrozone is
measured in inches per day. To calculate the water requirement in inches per day,
the formula is:
Water Requirement (inches per day) = K
c
× PET
EXAMPLE
You’re designing for a hydrozone that includes only sparsely planted shrubs
that require a great deal of supplemental water. Therefore, the species factor
is high (0.7), and the density factor is low (0.5). The hydrozone is adjacent to
the street, and it is surrounded by cement walkways, so you’ve assigned it a
high microclimate factor (1.3).
To calculate K
c
you multiply:
0.7 x 0.5 x 1.3 = 0.455
After rounding to the nearest tenth, you find that the K
c
for this shrub is 0.5.
Enter this number in the “K
c
” box on your worksheet.
Page 24 Chapter 4
K
c
Once you have collected all the information about the plants in the hydrozone,
and assigned the values for species, density, and microclimate factors, you can
calculate the K
c
for each plant. K
c
indicates the plant’s need for water as it relates
to the established PET rate in the area.
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