Such as any other element, water also is evaporated. But since water plays a key role in our life on earth, its evaporation is very important in many aspects in different scientific fields. Water vapor is the main source of many atmospheric activities. It has an important role in the hydrologic cycle and water budget which is considered as the main solution of different water management problems. Evaporation has the core role in hydro-climatologic studies, watershed management, dams and water reservoirs designing. Evaporation is the most important parameter in irrigation programming and many other agricultural activities. It is important not only to prevent loosing water in drought but also to manage the consumption of water by plants, since it is the main source of loosing of water by plants through transpiration from stomata. Evaporation is most considered by agronomists in arid and semi-arid regions because limitation water availability is very restricted and evaporation is extremely high. It is also an important parameter in wet climates, when the need for investigation into its role in the water balance has been appreciated for a long time (Lemeur and Zhang, 1990).