Turf Irrigation System Runtime Calculator
This is a tool for managing turf irrigation. It will
estimate the station (zone) runtime based on the time clock
settings, environmental conditions, turf type, and average weather
(evapotranspiration).
For each station (zone) enter the precipitation rate. If this
is unknown you can estimate spray heads as 1.5-2.0 inches per hour*
and rotors as .3-.6 inches per hour*. You can click on the
buttons below to populate each zone with a estimated number.
* Rainbird 1800 12 head will apply 2.01 inches/hour at 30 psi and
12 foot spacing . Other popup spray heads are similar.
** Small rotors such as the Rainbird 42SA may apply at rates as low
as 1.8"/hr and Hunter PGJ will apply .30 "/hr in typical full circle
configuration. Pressure, nozzle selection, and spacing will
affect the precipitation rate.
Data Tables used for calculations.
- ETo Zone
- CIMIS developed 18
climate zones in California and published monthly averages for
each zone. Data is a long term average for the zone.
- Precipitation Rate
- The rate at which water is applied by the irrigation system
and commonly expressed in inches per hour. Precipitation
rate can be measured by placing a rain gauge in the lawn and watering
for a period of time. Precipitation rates can vary widely
by sprinkler system so measurement is encouraged.
- Uniformity
- All irrigation systems apply water in an uneven pattern.
The uniformity is commonly measured as
Distribution Uniformity (DU). Well designed sprinkler
systems should have values above 75%. Lower uniformity
will require longer runtimes to insure that the dry areas get adequate
water.
- Days/Week and Starts per Day
- Commonly sprinklers are commonly run multiple times per week.
Lawn watering is more effective in short duration as this reduces
runoff and watering of turf below the root zone. Enter
1 to show the total minutes per week. If you water Monday,
Wednesday, and Friday you would enter 3 days/week. If the
sprinklers start multiple times per day enter the number of starts.
- Environment
- Shaded areas require less water than those in full sun.
- Turf Type
- Cool season varieties (Ex. tall fescue, ryegrass, bentgrass,
and Kentucky bluegrass) require more water than
warm season (ex. bermudagrass, zoysiagrass, and St.
Augustinegrass).
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