Baseline Systems BaseStation 1000 - Manual (Page 16)

BaseStation 1000 Irrigation Controller Manual
Understanding Soak Cycling
When you set up your irrigation programs, remember that the rate at which the irrigation
application devices apply water might be very different than the rate at which the soil in your
landscape can take up that water.
Soak cycling breaks the total run time into shorter water “cycles” with “soak” periods in between to
allow time for water to soak into the soil.
Precipitation Rates vs. Infiltration Rates
The precipitation rate, which is the rate at which sprinkler heads or drip emitters apply water to the
soil, is typically measured in inches, like rainfall.
Many soils only allow water infiltration at a rate of .25 inch per hour or less, whereas most head
types put down .50 inch per hour or more (much more in the case of some spray heads).
Also remember that head spacing and overlap directly influence the total precipitation rate for any
specific zone.
Examples of Precipitation Rates for Common Sprinkler Types
Spray Heads 1.00 inch to greater than 5.00 inches per hour
Gear Driven Rotors 0.25 inch to 0.65 inch per hour
Multi-stream Rotors 0.40 inch to 0.60 inch per hour
Drip Emitters Depends on area covered, rarely exceeds infiltration rate
Estimated Infiltration Rates for Common Soil Types
Course Sand 0.75 inch to 1.00 inch per hour
Fine Sand 0.50 inch to 0.75 inch per hour
Fine Sandy Loam 0.35 inch to 0.50 inch per hour
Silt Loam 0.15 inch to 0.40 inch per hour
Clay Loam 0.10 inch to 0.20 inch per hour
As you can see from the tables above, most sprinkler heads have higher precipitation rates than the
infiltration rate of most soils.
When the irrigation schedule puts down more water than the soil can take up, the excess water will
typically run off to the lowest point, leaving some areas of the landscape, or even the entire
irrigated landscape, under watered. Standing water also evaporates at a fairly high rate, especially
in the heat of the summer months, further reducing irrigation efficiency.
Even on a perfectly designed system, it is important to match the water application rate to the
infiltration rate of your soil. You can achieve this balance by breaking a total run time for any zone
into multiple “cycles” (timed water applications) and “soaks” (timed wait periods for the water
applied in the last cycle to infiltrate into the soil before applying more water).
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