T E C H L I N E A S ™ D E S I G N G U I D E
NETAFIM @BCL@C40BDC65.doc 21/12/2009 32
Step 5: Determine the Gross Water Requirement (GWR)
Determining the Total Water Requirement (TWR) for your garden (step 4) does not make
allowance for water lost due to the efficiency (Ef%) of your irrigation system. It is accepted that
applying water to the root zone is more efficient than spraying water over the entire garden
area and as such is indicated by a value (%) in the following table.
Gross Water Requirement (GWR) is calculated by dividing the Total Water Requirement (TWR)
by the System Efficiency (Ef%).
GWR = TWR ÷ Ef%
Step 6
: Determine your drip systems Application Rate (AR) from the table below according to
the drip discharge rate and respective drip and dripperline spacing.
If your spacing differs from the selection above you can calculate the Application Rate (AR) with
the following formula.
Drip Discharge (L/H)
AR = ---------------------------------------------------
Drip Spacing (m) x Dripperline Lateral (m)
Step 7
: Determine Total Zone Flow by multiplying the Application Rate (AR) by the Area (m
2
)
that is being irrigated.
TZF = AR x Area (m
2
)
Step 8
: Determine the Duration of Irrigation (D) by dividing the Gross Water Requirement
(GWR) by the Total Zone Flow (TZF).
D = GWR ÷ TZF
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