an important component in water-balance and irrigation scheduling models.
While the FAO-56 Penman-Monteith method
has become the de facto standard for estimating reference evapotranspiration (ETo), it is a complex
method requiring several weather parameters. Required weather data are
oftentimes unavailable, and alternative
methods must be used. Three alternative ETo methods, the FAO-56
Reduced Set, Hargreaves, and Turc methods, were evaluated for use in
Mississippi, a humid region of the USA, using only measurements of air temperature.
The Turc equation, developed for use with measured temperature and solar radiation,
was tested with estimated radiation and found to provide better estimates of FAO-56 ETo than the other methods. Mean bias errors of 0.75,
0.28, and -0.19 mm, mean
absolute errors of 0.92, 0.68, and 0.62 mm,
and percent errors of 22.5%, 8.5%, and -5.7% were found for daily estimates for
the FAO-56 Reduced Set, Hargreaves,
and Turc methods, respectively.
Cite this paper
Fisher, D. and Pringle III, H. (2013) Evaluation of alternative methods for estimating reference evapotranspiration. Agricultural Sciences, 4, 51-60. doi: 10.4236/as.2013.48A008.
 Doorenbos, J. and Pruitt, W.O. (1977) Crop water requirements. FAO Irrigation and Drainage Paper No. 24, FAO, Rome.
 Allen, R.G., Pereira, L.S., Raes, D. and Smith, M. (1998) Crop evapotranspiration: Guidelines for computing crop water requirements. FAO Irrigation and Drainage Paper No. 56, FAO, Rome.
 Itier, B. (1996) Applicability and limitations of irrigation scheduling methods and techniques. Proceedings ICID/ FAO Workshop on Irrigation Scheduling: From Theory to Practice, Rome, 12-13 September 1995, Water Report No. 8, FAO, Rome.
 Hargreaves, G.H. and Samani, Z.A. (1985) Reference crop evapotranspiration from temperature. Applied Engineering in Agriculture, 1, 96-99.
 Castaneda, L. and Rao, P. (2005) Comparison of methods for estimating reference evapotranspiration in southern California. Journal of Environmental Hydrology, 13, Paper 14.
 Tabari, H. (2010) Evaluation of reference crop evapotranspiration equations in various climates. Water Resource Management, 24, 2311-2337.
 Shahidian, S., Serralheiro, R., Serrano, J., Teixeira, J., Haie, N. and Santos, F. (2012) Hargreaves and other reduced-set methods for calculating evapotranspiration. In: Irmak, A., Ed., Evapotranspiration—Remote Sensing and Modeling, InTech, Morn Hill, 59-80. doi:10.5772/725
 Lu, J., Sun, G., McNulty, S.G., and Amatya, D.M. (2005) A comparison of six potential evapotranspiration methods for regional use in the southeastern United States. Journal of the American Water Resources Association, 41, 621-633.
 Yoder, R.E., Odhiambo, L.O. and Wright, W.C. (2005) Evaluation of methods for estimating daily reference crop evapotranspiration at a site in the humid southeast United States. Applied Engineering in Agriculture, 21, 197-202.
 Douglas, E.M., Jacobs, J.M., Sumner, D.M. and Ray, R.L. (2009) A comparison of models for estimating potential evapotranspiration for Florida land cover types. Journal of Hydrology, 373, 366-376.
 Trajkovic, S. and Kolakovic, S. (2009) Evaluation of reference evapotranspiration equations under humid conditions. Water Resource Management, 23, 3057-3067.
 Tabari, H., Grismer, M.E. and Trajkovic, S. (2013) Comparative analysis of 31 reference evapotranspiration methods under humid conditions. Irrigation Science, 31, 107-117.
 Turc, L. (1961) Water requirements assessment of irrigation, potential evapotranspiration: Simplified and updated climatic formula. Annales Agronomiques, 12, 13-49.
 Allen, R.G. (2002) RefET: Reference evapotranspiration calculator. Version 2.01.17, Utah State University Foundation, Logan.
 Hargreaves, G.H. and Samani, Z.A. (1982) Estimating potential evapotranspiration. Journal of Irrigation and Drainage Engineering, 108, 223-230.
 Willmott, C.J. and Matsuura, K. (2005) Advantages of the mean absolute error (MAE) over the root mean square error (RMSE) in assessing average model performance. Climate Research, 30, 79-82. doi:10.3354/cr030079