Universal Devices ISY-994i Series, User Manual

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Figure 256: Program Condition Window
17 Irrigation Notes
Example programs can be found in section: 11.4 Irrigation Timer Programs
17.1 Evaporation and Irrigation
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17.1.1 What is Evapotranspiration
•
ET is an approximation of the amount of water leaving the soil via a combination of
evaporation and transpiration (a fancy word for plants drinking it up).
•
The goal of an ET-aware irrigation system is to approximately (despite all the
appearance of precision, we have to remember this) replace this water.
•
It does this by tracking the water used/lost from the soil until a threshold is reached
(where the plants would starve for water if much more left without replacement).
84 (Universal Devices)