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Estimating actual crop water requirement and irrigation schedule are essential for designing of the irrigation systems, storage construction and water conveyance structures. Many models have developed for estimating crop water requirement. Although most of these methods need different climatic parameters, providing and forecasting all of these parameters always are not available. Most of the time, some of these forecasted parameters are incorrect, through of these the maximum and minimum temperature are more accurate. In addition, temperature is the most affective factor on evapotranspiration in and and semi-arid region. In this paper, ET-HS has been presented which after calibration by regional factors, could be predicted the time of irrigation. This model only needs daily maximum and minimum temperature for this prediction.