Consumptive use is defined as the amount of water needed to meet the water loss through evapotranspiration. It generally applies to a crop but can be extended to a field, farm, project or even a valley. Consumptive use is generally measured as volume per unit area or simply as the depth of water on the irrigated area.
Knowledge of consumptive use helps determine irrigation requirement at the farm which should,
obviously, be the difference between the consumptive use and the effective precipitation.