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

Vassilis G. Aschonitis, Vassilis Z. Antonopoulos, Dimitris M. Papamichail

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Department of Hydraulics, Soil Science and Agricultural Engineering, School of Agriculture, Aristotle University of Thessaloniki, Thessaloniki, Greece.

DOI: 10.4236/as.2012.31008                

Abstract

Reference crop evapotranspiration (ET_o) is essential for irrigation, water resources management and environmental assessment. The indirect estimation of ET_o is based a) on energy budget approach using meteorological data and b) pan evaporation measurements (E_pan) multiplied by pan coefficients (k_p) adapted to the surrounding environmental conditions. Significant interest is shown for the k_p equations, which have to be tested before their use. The purpose of this study is to evaluate six different k_p 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 k_p equations is performed by two years E_pan measurements, using as reference the daily ET_o 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.

Keywords

Pan Evaporation; Reference Evapotranspiration; ASCE-Standardized Penman-Monteith

Conflicts of Interest

The authors declare no conflicts of interest.

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