Two computer models CRIWAR, (Crop Irrigation Water Requirement) and SWATRE, (Soil Water Actual Transpiration Rate Extented) were used to estimate the evaporation and consequently the water requirement of Zea mays L. For this reson corn seeds were planted in lysemeter in 3 replicates and irrigated in specific time and amounts. Water balance in the lysimeter was calculated according to input/output parameters. Meteorological data such as, mean daily temperature, mean relative humidity, wind speed, sum radiation, day length, percentage of cloudless and soil physical parameters such as soil moisture content prior to irrigation, and also plant parameters needed for the computer mode’s were used to predict the evapotranspiration rate on the basis of 10 days intervals.
According to the results obtained from execution of the two models and the lysimeter, the CRIWAR predicts better results compared to the SWATRE model. Although, SWATRE model has different options such as ability to evaluation the ground water level, hydraulic relation in soil and etc., the results obtained by this model have too much deviation from the measured data and therefore the model needs some modification to be used.
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