Agricultural products are one of the major sources of food for people in many countries. So, increasing crop yield is a major challenge for governments as increasing the population. On the other hand, agricultural improvement needs to take into consideration the type of land and water available. The decrease of water availability and soil salinity are two major limiting factors in sustainable agriculture in the arid and semiarid regions. In this study, the combined effect of salinity and water stress on crop yield was simulated by developing a computer model based on a system dynamics approach. Model calibration and validation were performed using data collected from the Abshar Irrigation Network located on the hydrological Zayandehrud River. For each individual run of the model, two statistics were calculated: Root Mean Square Error and Standard Error. The averages of these indices were estimated as 2,777 kg·ha1 and 0.07 for sugar beet yield, 0.026 and 0.09 for soil moisture and finally 0.54 dS·m1 and 0.08 for salinity of the root zone, respectively. The result showed a good agreement between the simulation model and the actual data. Therefore, the model can be calibrated and used to estimate the crop yield with reasonable accuracy.
