The main concern in cultivating crops has always been water availability. To increase food production, water plays a major role after securing a large portion of land area. Knowledge of the factors influencing crop water use efficiency and hope to increase the efficiency has continued to be an objective in many modern studies. The gap between irrigation supply and demand is increasing from year to year as a result of an increase in population growing rate and people moving from place to place. Searching for new water may be a too difficult and very expensive process, so the shortest and easiest way is to maximize the water use efficiency throughout optimizing water use efficiency and the first step on that is determination of the actual crop water requirements.