The difference between Actual Evapotranspiration (ETa) and Crop Evapotranspiration (ETc) lies in the conditions under which water is available to the plant and the environmental factors influencing water loss:

Summary:

• ETa is what actually happens in real-world, sometimes water-stressed conditions, while ETc represents the ideal scenario under optimal water supply for crops.

Qasim Ali Thanks for clarification.

I looked into the various evapotranspiration calculation methods when I developed ETCalc (https://etcalc.hydrotools.tech) and would say that the difference is not very clear. Actual Evapotranspiration can be obtained via various methods, which include but are not limited to field measurements or empirical equations. Empirical equations estimate Actual Evapotranspiration based on Potential/Reference Evapotranspiration and a coefficient. The coefficient can be fixed or vary in time (and space). I see Crop Evapotranspiration as a form of Actual Evapotranspiration, and in the case of empirical equations the coefficient mentioned above is called a crop coefficient.

There are various interpretation of the various forms of evapotranspiration, and hence you might find inconsistent or even conflicting definitions of these forms. For example, in some cases, the same formula is used but the calculated evapotranspiration form is called in some papers Potential Evapotranspiration and in others is called Reference Evapotranspiration.

For your interest I included a brief description of ETCalc below.

ETCalc (https://etcalc.hydrotools.tech) is a tool that integrates several customizable methods for calculating daily Potential Evapotranspiration (PET), Reference Evapotranspiration (ETR) and Actual Evapotranspiration (ET) based on user provided meteorological data and crop coefficients. The tool currently integrates Penman-Monteith, Thornthwaite, Blaney-Criddle, Turc, Priestley-Taylor, Hargreaves, Jensen-Haise and Abtew empirical equations.

You can check the data requirements in the User Guide using the link provided above. A few of the methods available in ETCalc require only one parameter.

Please note that ETCalc is part of the Hydrology Tool Set (HTS; https://www.hydrotools.tech), which includes several other tools for the analysis of various hydrological processes (e.g.; hydrograph separation, precipitation partitioning, crop water deficit, irrigation requirements, water budget, groundwater recharge).

Serban Danielescu thank you very much.