Study of Temperature and Radiation Based Methods of Estimating Maximum Evapotranspiration with Different Probabilities

آب و خاک

Article 1, Volume 23, Issue 3, July 2009   

Document Type: Research Article

DOI: 10.22067/jsw.v0i0.2278

Authors

H. Sharifan^{* 1}; A. Alizadeh²

¹Mashhad

²Professor in Water Resources Engineering, Ferdowsi University of Mashhad, Mashhad, Iran

Abstract

Abstract
In order to estimate the reference evapotranspiration different equation is used. Validity of each methods depends upon the climate and the parameters which are used in these equations. Therefore it is necessary to calibrate these methods for any specific area and for any desired frequency. In this study common temperature and radiation based methods were used for calculating crop evapotranspiration and the results were compared with standard method of estimating reference evapotranspiration. The results showed that Jensen-Haise(J-H) method overestimate ET compare to Hargreaves-Samany(H-S) method. The difference is more in 3 days period of irrigation than 5 days period. Also for wheat and barely H-S method estimates higher value of ETc compared with J-H method. However, J-H method overestimate ETc for cotton and rice. By increasing the probability level, the difference between calculated ETc by J-H and H-S decreased significantly.

Key words: Peak water requirement, ETo, ETc, Radiation, Temperature, Probability