Continuous calculations of evapotranspiration (LE) using eddy covariance method and energy budget were performed over more than one year above the heterogeneous canopy of an arid oasis ecosystem in the central Syrian desert. Irrigation practice was traditional flooding with a 28 days turn of water delivery. The work focuses on seasonal variations of energy budget over a 2 years period with emphasis on effects of rainfall, wind speed and radiative budget on evapotranspiration. Maximum evapotranspiration was only 5mm/day. Even under irrigation practices, winter rainfall seems to have an important impact on LE: comparisons of two situations in June 2002 and June 2003 showed an increase of 13% in values of LE/Rn-G. Maximum averaged hourly values of evapotranspiration were found for wind speed values closed to 3m/s. This suggests that when the evaporative demand from the air (or vapour pressure deficit (vpd) ) is increasing above a certain limit, the vegetation closes its stomata and reduces transpiration. Results from the energy balance closure showed significant differences in the slope of H+LE against Rn-G relationships between cold and hot month which was explained by specific radiative budget of desert areas.