Iran is an arid country, its average rainfall is one third of world’s rainfall while it evaporates 3 times more than the world average. Evaporation takes place from vegetation cover, from bare soil, or from water bodies. In the absence of a vegetation cover, soil surface is exposed to atmosphere which increases the rate of evaporation. Evaporation of soil moisture will not only lead to water losses even it will also increase the risk of soil salinity. The risk is increased under low annual rainfall, saline irrigation water, and deep water table. Soil and water salinity is common in arid and semiarid regions where using saline water is common under insufficient fresh water resources. This research was conducted at Ferdowsi University of Mashhad, Iran. PVC pipes with a diameter of 110 mm, and an effective height of 1 m filled with loamy sand soil was used in this study as lysimeter for calculating evaporation rate. The results showed that salinity decreased evaporation and there was a chance for better prediction of evaporation at stages I and II.

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