Calibration of SWAP Model for Simulating Crop Yield, Biological Yield and Soybean Water Use Efficiency

Document Type : Research Paper


1 Assistant Professor, Department of Water Sciences and Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.

2 Young Researchers Club, Science and Research Branch, Islamic Azad University, Tehran, Iran.


     SWAP model is called an agro-hydrological, agronomical-hydrological and eco-hydrological model. In this research, SWAP model was studied for estimation of soybean crop yield, biological yield and available moisture percentage in soil during growing season. In this study, first of all results were sensitivity analyzed and calibrated based on soybean cultivation for four furrow irrigation scenarios in agronomical years 2008-2009. Then it was validated based on field results in agronomical year 2009-2010. The results of this study showed that this model simulated crop yield better than biological yield. Also sensitivity analysis of the model showed that SWAP model is sensitive to input data of residual moisture and saturation hydraulic conductivity and with the least variation in soil input including saturation hydraulic conductivity and residual moisture, output results varied greatly. Based on statistical analyses, with a lot of existing variables, SWAP model can estimate the soil moisture, leaf area index, water use efficiency and crop yield well because in all cases coefficients of determination are higher than 0.8 (are equal to 0.86, 0.87, 0.89 and 0.93 respectively) and root mean square error is less than standard deviation of data and mean comparison T-test did not show significant differences between the simulated and measured amounts.