Using simulation models to improve irrigation water application

The soil water and crop models can be used at increasing efficient use of the allocated irrigation water. This study was carried out to compare a number of these models and evaluate using in such a purpose. Field measurements were conducted for three growing seasons on winter wheat and cotton crops at the experimental station of University college of Aboureyhan, located at the region of Varamin in Iran. A measuring system including data acquisition system using a mini data logger for meteorology and soil water content parameters was to be adapted. The measurements were done in a high time resolution; 15 min average values, and are a good data base for the applied water balance models. The selected models/algorithms for water-balance calculation were parameterized and tested based on the measured data from field tests. The model testing study showed the models are most useful for application in irrigation scheduling and the water productivity can be significantly improved using the simple simulation models such FAO & Allen algorithm, CROPWAT and WOFOST Models. The comparison of the simulations showed also reasonable good results for irrigation scheduling and the performance of these models was similar to more complex ones. The application of the more sophisticated models (CERES, SWAP) strongly depends on available input data and model validation. They can be very useful however, as the extended range of system outputs widen their applicability also for other agro-meteorological planning activities. The results indicated all models could help reduce the amount of needed water considerably, with almost no loss in yield.