Hargreaves versus Penman-Monteith under Humid Conditions
Publication: Journal of Irrigation and Drainage Engineering
Volume 133, Issue 1
Abstract
The Food and Agriculture Organization of the United Nations (FAO) has proposed using the Penman-Monteith equation as the standard for estimating reference evapotranspiration , and for evaluating other equations. The basic obstacle to using the FAO-56 Penman-Monteith equation (FAO-56 PM) widely is the required weather data which are not available in most of the stations. In such circumstances, a simple empirical Hargreaves equation (HARG) is often used. However, this equation generally overestimates at humid locations. Therefore, HARG requires local calibration. The main objective of this study is to investigate the possibility for calibrating the equation in the Western Balkans region, South East Europe through the adjustment of Hargreaves exponent (HE). Data from Palic, Sarajevo, and Nis have been used for estimating the adjusted HE. A value of 0.424 is proposed instead of the original 0.5 as one which should be used in the adjusted Hargreaves equation (AHARG) for the Western Balkan locations. The values estimated by AHARG were compared with FAO-56 PM estimates for eight humid locations (Varazdin, Zagreb, Bihac, Novi Sad, Negotin, Kragujevac, Nis, and Vranje). Estimates by AHARG were in close agreement with FAO-56 PM estimates at most of the locations. The SEE ranged from for Varazdin to for Vranje, averaging . The average overestimation was about 1%. These results strongly support the use of the adjusted Hargreaves equation at humid Western Balkan locations in the case when only the temperature data are available. Further research should be undertaken for evaluating the validity of the approach presented in this paper in other regions.
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Acknowledgments
The research reported in this paper is a part of an ongoing project titled “Model of rational management of water resources in agriculture,” sponsored by the Serbian Ministry of Science under the National Water Programme (Project No. UNSPECIFIED410022). The funding received is gratefully acknowledged. The writer is grateful to three anonymous reviewers for their useful comments and suggestions.
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Published In
Journal of Irrigation and Drainage Engineering
Volume 133 • Issue 1 • February 2007
Pages: 38 - 42
Copyright
© 2007 ASCE.
History
Received: Jun 28, 2005
Accepted: Sep 30, 2005
Published online: Feb 1, 2007
Published in print: Feb 2007
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