Methodology¶
Reference evapotranspiration (ETo)¶
The derivation of ETo had developed over many years with several different equations. The latest and hopefully last variant is derived from the Penman-Montieth equation.
Extensive documentation on the methods and concepts can be found in the UN-FAO 56 paper [1]
Hargreaves¶
The derivation for the Hargreaves equation can also be found in the UN-FAO 56 paper.
The History and Evaluation of Hargreaves Evapotranspiration Equation [2] is a more detailed description and background of the Hargreaves method.
References¶
- 1
Allen, R. G., Pereira, L. S., Raes, D., & Smith, M. (1998). Crop evapotranspiration-Guidelines for computing crop water requirements-FAO Irrigation and drainage paper 56. FAO, Rome, 300(9), D05109.
- 2
Hargreaves, G. and Allen, R. (2003). History and Evaluation of Hargreaves Evapotranspiration Equation. Journal of Irrigation and Drainage Engineering. Vol. 129, Issue 1 (February 2003).