Evaluation of pan coefficient equations in a semi-arid Mediterranean environment using the ASCE-standardized Penman-Monteith method


Reference crop evapotranspiration (ETo) is essential for irrigation, water resources management and environmental assessment. The indirect estimation of ETo is based a) on energy budget approach using meteorological data and b) pan evaporation measurements (Epan) multiplied by pan coefficients (kp) adapted to the surrounding environmental conditions. Significant interest is shown for the kp equations, which have to be tested before their use. The purpose of this study is to evaluate six different kp equations, such as those of Cuenca, Allen and Puitt, Snyder, Pereira et al., Orang, Raghuwanshi and Wallender for the summer growing season (April to October) of Thessaloniki plain in Greece, which is characterized by a semi-arid Mediterranean environment. The evaluation of the kp equations is performed by two years Epan measurements, using as reference the daily ETo values estimated by the ASCE-standardized Penman-Monteith equation (ASCE-PM) in hourly time step. The results of this study showed that Cuenca’s equation provided more accurate daily estimations. Additional analysis is performed in other methods such as those of FAO-56 and Hargreaves based on the calculation time step (hourly or daily) and their correspondence to the ASCE-PM.

Share and Cite:

G. Aschonitis, V. , Z. Antonopoulos, V. and M. Papamichail, D. (2012) Evaluation of pan coefficient equations in a semi-arid Mediterranean environment using the ASCE-standardized Penman-Monteith method. Agricultural Sciences, 3, 58-65. doi: 10.4236/as.2012.31008.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] Doorenbos, J. and Pruitt, W.O. (1977) Guidelines for predicting crop water requirements. Irrigation and Drainage Paper No. 24, (1st and 2nd Edition). Food and Agriculture Organization of the United Nations, Rome, 179 and 156 pp.
[2] Priestley, C.H.B. and Taylor R.J. (1972) On the assessment of surface heat flux and evaporation using large- scale parameters. Monthly Weather Review, 100, 81-92. doi:10.1175/1520-0493(1972)100<0081:OTAOSH>2.3.CO;2
[3] Allen, R.G. and Pruitt, W.O. (1991) FAO-24 reference evapotranspiration factors. Journal of Irrigation and Drainage Engineering, 117, 758-773. doi:10.1061/(ASCE)0733-9437(1991)117:5(758)
[4] Shuttleworth, W.J. and Wallace, J.S. (1985) Evaporation from sparse crops—An energy combination theory. Quarterly Journal of the Royal Meteorological Society, 111, 839-855. doi:10.1256/smsqj.46909
[5] Hargreaves, G.H. and Samani, Z.A. (1985) Reference crop evapotranspiration from temperature. Transactions of ASAE, 1, 96-99.
[6] Allen, R.G., Pereira, L.S., Raes, D. and Smith, M. (1998) Crop Evapotranspiration: Guidelines for computing crop water requirements. Irrigation and Drainage Paper No. 56, Food and Agriculture Organization of the United Nations, Rome, 300 pp.
[7] ASCE-EWRI (2005) The ASCE standardized reference evapotranspiration equation. Technical Committee Report to the Environmental and Water Resources Institute of the American Society of Civil Engineers from the Task Committee on Standardization of Reference Evapotranspiration. ASCE-EWRI, 1801 Alexander Bell Drive, Reston, VA 20191-4400, 173 Pages.
[8] Papamichail, D.M. and Terzidis, G.A. (1996) Assessment of the Meteorological Parameters—Effects on the Daily Penman Reference Evapotranspiration. 2nd International Symposium on Irrigation of Horticultural Crops, Chania, Acta Horticulturae, 449, 281-288.
[9] Papamichail, D.Μ. and Georgiou, P.Ε. (1999) Comparative analysis of hourly and daily estimates of reference evapotranspiration by using FAO Penman-Monteith equation. Proceedings of the 4th National Conference of the Greek Committee for Water Resources Management, Volos, 183-189 (in Greek).
[10] Ampas, V., Baltas, E. and Papamichail, D. (2006) Comparison of different methods for the estimation of the reference crop evapotranspiration in the Florida region. WSEAS Transactions on Environment and Development, 12, 1449-1454.
[11] Anadranistakis, M., Liakatas, A., Kerkides, P., Rizos, S., Gavanosis, J. and Poulovassilis, A. (2000) Crop water requirements model tested for crops grown in Greece. Agricultural Water Management, 45, 297-316. doi:10.1016/S0378-3774(99)00106-7
[12] Alexandris, S., Kerkides, P. and Liakatas, A. (2006) Daily reference evapotranspiration estimates by the “Copais” approach. Agricultural Water Management, 82, 371-386.
[13] Valiantzas, J.D. (2006) Simplified versions for the Penman evaporation equation using routine weather data. Journal of Hydrology, 331, 690-702. doi:10.1016/j.jhydrol.2006.06.012
[14] Gundekar H.G., Khodke, U.M., Sarkar, S. and Rai, R.K. (2008) Evaluation of pan coefficient for reference crop evapotranspiration for semi-arid region. Irrigation Science, 26, 169-175. doi:10.1007/s00271-007-0083-y
[15] Rahimikhoob, A. (2009) An evaluation of common pan coefficient equations to estimate reference evapotranspiration in a subtropical climate (north of Iran). Irrigation Science, 27, 289-296. doi:10.1007/s00271-009-0145-4
[16] Cuenca, R.H. (1989) Irrigation system design: An engineering approach. Prentice Hall, Englewood Cliffs, 552.
[17] Snyder, R.L. (1992) Equation for evaporation pan to evapotranspiration conversions. Journal of Irrigation and Drainage Engineering, 118, 977-980. doi:10.1061/(ASCE)0733-9437(1992)118:6(977)
[18] Pereira, A.R., Villanova, N., Pereira, A.S. and Baebieri, V.A. (1995) A model for the class-A pan coefficient. Agricultural Water Management, 76, 75-82.
[19] Orang, M. (1998) Potential accuracy of the popular non- linear regression equations for estimating pan coefficient values in the original and FAO-24 tables. Unpublished rep. California Department of Water Resources, Sacramento.
[20] Raghuwanshi, N.S. and Wallender, W.W. (1998) Converting from pan evaporation to evapotranspiration. Journal of Irrigation and Drainage Engineering, 118, 977- 980.
[21] Antonopoulos, V. and Wyseure, G. (1998). Modeling of water and nitrogen dynamics on an undisturbed soil and a restored soil after open-cast mining. Agricultural Water Management, 37, 21-40. doi:10.1016/S0378-3774(98)00040-7

Copyright © 2024 by authors and Scientific Research Publishing Inc.

Creative Commons License

This work and the related PDF file are licensed under a Creative Commons Attribution 4.0 International License.