Journal of Applied Sciences1812-56541812-5662Asian Network for Scientific Information10.3923/jas.2011.2599.2605KangrangAnongritPhumphanAnujitHomwuttiwongSahalaphCompliewSudarat1220111114This study proposed a fuzzy sets model for computing ET_{o} using only a few basic hydrological parameters including temperature, humidity and wind speed. Genetic algorithm technique was applied to calibrate membership function condition of fuzzy sets model. The proposed model was applied to determine the ET_{o} of 5 Meteorological Stations in Thailand. The daily data of the stations were used in the study. Results showed that the fuzzy-GAs model can be used to calculate the ET_{o}, given only the basic hydrological parameters; temperature, humidity and wind speed. The obtained ET_{o} of the proposed model closed to the ET_{o} of the accepted Penman-Monteith equation. Furthermore, the results presented that the Genetic algorithm calibration provided the optimal condition of membership function.]]>Allen, R.G., L.S. Pereira, D. Raes and M. Smith,1998Allen, R.G., W.O. Pruitt, J.L. Wright, T.A. Howell and F. Ventura et al.,2006Chang, F.J., J.S. Lai and L.S. Kao, 2003Chow, V.T., D.R. Maidment and L.W. Mays,2003Doorenbos, J. and W.O. Pruitt,1977Goldberg, D.E.,1989Hormwichian, R., A. Kangrang and A. Lamom,2009Irmak, A., S. Irmak and D.L. Martin,2008Jairaj, P.G. and S. Vedula,2000Jang, J.S.R., C.T. Sun and E. Mizutani,1997Jensen, M.E., R.D. Burman and R.G. Allen,1990Kangrang, A. and C. Chaleeraktrakoon,2007Kangrang, A. and C. Chleeraktrakoon,2008Lu, J., F. Wu and G. Zhang,2007Panigrahi, D.P. and P.P. Mujumda,2000Ross, T.J.,1995Saruwatari, N. and A. Yomota,1995Shrestha, B.P., L. Duckstein and E.Z. Stakhiv,1996Wardlaw, R. and M. Sharif,1999