Utah State University Extension
The goal of garden irrigation is to maintain yield and 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. Garden water use is presented in units of inches of water per day, week or month.
Hill, Robert W., "Garden Water Use in Utah" (2002). All Current Publications. Paper 907.