poster - International Conference of Agricultural Engineering

4. Conclusions
Hargreaves equation can provide relatively accurate estimations of daily ET 0 at
weather stations where only air temperature acquisition is available and under the
semiarid conditions of the studied zone (SE Spain).
Because of the empirical nature of the Hargreaves equation, a single universal
calibration of this equation would be difficult to achieve. However, the approach
outlined in this paper could likely be applied in other semiarid regions to obtain
appropriate local calibrations of the Hargreaves equation.
Obtained results indicate that Hargreaves equation is precise enough for daily
estimations of ETo in the studied zone, without the requirement of a previous
calibration.
It would be necessary to extend this study to a higher number of stations in order to
calibrate at local or regional scale.
References
Allen, R.G., Pereira, L.S., Raes, D. Smith, M., 1998. Crop evapotranspiration. Guidelines for
computing crop water requirements. FAO Irrigation and Drainage, paper nº. 56, FAO,
Rome.
Doorenbos, J., Pruitt, W.O., 1975. Crop water requirements. FAO Irrigation and Drainage
Paper nº 24. Roma.
Hargreaves, G.H., Samani, Z.A., 1985. Reference crop evapotranspiration from temperature.
Appl. Eng. Agric. 1(2), 96–99.
López-Urrea, R., Martín de Santa Olalla, F., Fabeiro, C., Moratalla, A., 2006. An evaluation
of two hourly reference evapotranspiration equations for semiarid conditions. Agric. Water
Manage. 86, 277-282.
Acknowledgements
This work has been partially supported by the PPII10-0319-8732 project “Determinación de
las funciones de producción y necesidades hídricas de los cultivos utilizando radiometría de
campo, imágenes de satélite y el modelo Aquacrop” (Ministry of Education and Science from
the Government of Castilla la Mancha, Spain).