July 2017 Vol.5 No.4

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Original Research Article

Comparison of Temesgen-Melesse and Abtew methods ET estimation with FAO-56 Penman-Monteith method using data of nine Class I Meteorological stations in Ethiopia

Berhanu Mengistu* and Gelana Amente

College of Natural and Computational Sciences, Haramaya University, Ethiopia

*Corresponding Author E-mail: aquamengistu@gmail.com

Accepted May 15, 2017

Abstract

Evapotranspiration is one of the essential hydrological parameter that has to be accurately estimated for appropriate water use. In this study one temperature-based method of estimating ET known as Temesgen-Melesse (TM) method and one surface radiation-based method known as Abtew method were compared with the standard FAO 56 PM method using data of nine Class-I meteorological stations, in Ethiopia. Performances of the methods were tested using parameters such as Coefficient of Efficiency (CE), Coefficient of Residual Mean (CRM), combination of coefficient of determination (R2) and slope of the linear regression, Mean Percent Error (MPE) and coefficient of variation (CV) calculated from standard deviation and mean of the data statistics. Besides, 1:1 line, 95% prediction bounds and residual plots were used to supplement the test parameters. Based on the tests, TM performed well on three of the nine sites for which there is no need for calibration. Abtew method did not do so well on all of the sites either because of over or under estimation or due to crossing of the regression line with the 1:1 line. TM method requires site-based calibration for six and Abtew method, for all the sites. When using performance test parameters, it is important to include 1:1 line and prediction bounds to get information that is not clearly obtained from the other parameters.

Keywords: ET estimation; Radiation-based ET method; Temperature-based ET method; Performance test parameters