The use of geographic information system facilities to estimate the evapotranspiration in Iraq according to Thornthwaite adjusted formula

Iraq is facing water shortage problems due to various factors, globally ( Global warming) and regionally ( GAP project) and locally ( improper water resources management projects). In this search the global warming influence on the annual mean value of temperature and yet on the annual mean value of the evapotranspiration for more than three decades has been studied. The climate of Iraq is influenced by its location between the subtropical aridity of the Arabian desert areas and the subtropical humidity of the Arabian Gulf. The relative ascension of temperature degrees in the recent decades was the main factor in relative humidity decrement which increase the evapotranspiration values, since that utilizing a temperature-based method as in this search is the best choice to obtain realistic results. The increment in the annual mean value for maximum, minimum, and air temperature for each decade comparing with the previous one is about (1-3) % which yield an increment in the Evapotranspiration values of the millenniums decade comparing with the eighties one of about (35- 60) % for some southern Iraqi administratives, while it is about (13-15) % in some northern ones.