Terminology

Evaporation: It is the process during which a liquid change into gas.

Transpiration: It is the process by which water vapour leave the living plant body and enters the atmosphere.

Evapotranspiration or Consumptive use: It denotes the quantity of water transpired by plants during their growth or retained in the plant tissue plus the moisture evaporated from the surface of the soil and the vegetation. It is used to designate the losses due to evapotranspiration and the water that is used by the plants for its metabolic activities.

Potential Evapotranspiration (PET) : It is defined as the ET that occurs when the ground is completely covered by actively growing vegetation where there is optimum moisture in the soil.

Seasonal Consumptive Use (SCU): The total amount of water used in ET by cropped area during the entire growing season is called seasonal consumptive use (SCU).

Peak period consumptive use (PPCU): It is the average daily water used during the few days of the high CU of the season and expressed as mm/day.