Evapotranspiration (ET Rating)

Category: science

The total volume of moisture lost from the soil surface combined with the water vapor transpired by the turf canopy.

Expressed in fractions of an inch per day, ET metrics dictate precision irrigation programming. Modern weather-linked irrigation controllers look at solar radiation, humidity, and wind speeds to calculate daily ET loss, replacing exactly what the lawn used.

Common Examples

• The hot, dry wind drove the daily evapotranspiration rate up to a high 0.30 inches, triggering an automated extension of the watering cycle.
• Tracking the landscape’s cumulative evapotranspiration rate stops excessive over-watering, saving millions of gallons of water annually.