An investigation on reference crop evapotranspiration trend from 1975 to 2005 in Iran Mohammad Reza Kousari* and Hossein Ahani Management Center For Strategic Projects, Fars Agriculture Organization, Shiraz, Iran ABSTRACT: Evapotranspiration is one of the most important factors in agriculture and the hydrological cycle that can be influenced by global warming and climatic changes. In this study, the trend of reference crop evapotranspiration (ET0) computed by penman Penman-Monteith equation a ...