Abstract:

Evapotranspiration is a crucial parameter of the hydrological cycle in agriculture, particularly in irrigated systems, because irrigation doses rely on crop water requirements, which are calculated based on evapotranspiration. Accurate assessment of evapotranspiration is a key step to achieve a proper design and management of irrigation installations. Moreover, accurate irrigation water management is required more and more to optimize efficiency, productivity and quality, as well as to mitigate water overutilization and environmental degradation.

Given the importance of evapotranspiration for different aspects of water resources management in agriculture, which affect crucial professional competences of Agricultural Engineers, e.g. design and management of irrigation installations, several subjects including these topics are scheduled in the syllabus corresponding to the Degree of Agricultural Engineering, among others, Irrigation Engineering, Agrometeorology, or Water Resources Planning.

Nevertheless, maybe given to limitation of time, lecturers traditionally just introduce the concept of evapotranspiration, and the conceptual and widely-extended approach to estimate it as the product of reference evapotranspiration, i.e. evapotranspiration from a reference surface, and a crop coefficient. Finally, the standard method for estimating reference evapotranspiration, i.e. the Penman Monteith equation, is explained. Indeed, in many situations, lecturers do not even show how to apply this equation using meteorological inputs. This method was recommended by the Food and Agriculture Organization (FAO) for reference evapotranspiration estimation and validation of other equations. However, its application is not possible in many situations, because it relies heavily on weather data that are often not available or reliable. On the other hand, estimating reference evapotranspiration with empirical and/or interpolation methods is commonly required at the local scale, because it is not possible to obtain experimental measurements or apply more accurate and robust methods. And this crucial limitation is also commonly forgotten when teaching this topic in the Degree of Agricultural Engineering. Furthermore, different new methods have been proposed in the last years taking advantage of the increasing computing possibilities offered by modern computers.

This paper aims at discussing if the topic ‘Evapotranspiration’ is being currently taught properly enough, and if the traditional procedure might be updated bearing in mind the actual application conditions that the future agricultural engineers might find in their professional practice, as well as considering the useful numerical computing tools developed in the last years.

Keywords:

Evapotranspiration, Irrigation, Agricultural Engineering, Modeling.