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 33
Step 9: Soil Infiltration Rate.
Your gardens soil type will determine how much water can be applied before it starts to saturate
and run off. The table below will give you a guide as to the infiltration rate of your soil.
Light and Medium soil will allow a relatively high infiltration of water however heavy soils won’t.
If you are irrigating heavy soils it will be better to break up your watering duration up into short
cycles (10-15 minute cycles every hour) so that you don’t exceed the infiltration rate of the soil.
Determining whether irrigation takes place on one day will be governed by the sites soil type
and current water restrictions. The sites soil type will determine if the Duration of Irrigation is
applied on one day or spread out over a number of days.
Light Soil – water 3 times per day
Medium Soil – water 2 times per week
Heavy Soil – water 1 time per week
Water restrictions will also determine the when watering takes place. Check with your local
water authority if watering of gardens or lawns is permitted in your area and check which days
watering can take place.
Divide the Duration of Irrigation by the number of days that watering should take place or
number of days that are allowed under water restrictions per week to determine the daily
watering time.
Example:
Plant: Warm season grass Type of System: Subsurface drip
Time of year: January Drip Discharge Rate: 1.6L/H
City: Melbourne Drip Spacing: 0.3m
Area: 200m
2
Drip Lateral Spacing: 0.3m
Appearance required: Reasonable System Efficiency: 95%
Soil Type: Medium
Step 1: Crop Factor & Evaporation Rate CF & ER)
CF= 0.4
ER = 8.8mm
Step 2: Plant Water Requirement (PWR = CF x ER)
PWR = 0.4 x 8.8
PWR = 3.52mm per day
Step 3: Weekly Water Requirement (WWR = PWR x 7)
WWR = 3.52 x 7
WWR = 24.6mm per week
Step 4: Total Water Requirement (TWR = WWR x Area m
2
)
TWR = 24.6mm x 200m
2
TWR = 4,920 Litres per week
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