Utah State University Extension
The goal of turfgrass irrigation is to maintain quality by replacing water lost to the atmosphere from the soil by evaporation, and from leaf surfaces by transpiration. The combination of evaporation and transpiration is referred to as evapotranspiration (Et), or simply water use.
Hill, Robert W. and Kopp, Kelly L., "Turfgrass Water Use in Utah" (2002). All Current Publications. Paper 1408.