ISY-99i/ISY-26 INSTEON:Evapotranspiration and Irrigation
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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).
- In most climates, this will result in watering every few days.
- Rain may offset some of the water use/loss, resulting in less frequent watering.
- Calculations performed once every 24 hours are sufficient for this tracking.
- There's some amount of allowed depletion (based on the plant types, root lengths, etc.).
- This depletion will not typically happen in a single day.
- What is varied is when to water, not how much.
Irrigation with Evapotranspiration
- A running balance is used to decide when to irrigate.
- It's not necessary to exactly replace all the water which has left the soil (i.e. zero-out the balance).