The evaluation of Drainmod-S model for simulating the water table fluctuations and salt concentration in soil profiles in Paddy fields areas with a shallow water table and saline

In this research, the Drainmod-S model, which is specific for regions with shallow and saline water table, was used for water table changes and salt determination of salt concentration in paddy fields. This research was performed as a physical model (lysimeter) in meteorological research center of college of agriculture and natural resources, university of Tehran in 2017. The complete randomized design consists of two main treatments with fresh and shallow water table (FSG), as the control treatment, and in the presence of saline and shallow water table (SSG(, respectively. After evaluating the model for water table, the amount of MBE, RMSE, NRMSE, d and R2 for FSG treatment were obtained 0.18 cm, 7.48 cm, 23.41%, 0.86 and 0.63, respectively and for FSG treatment were obtained 0.69 cm, 7.25 cm, 21.06%, 0.83 and 0.53, respectively. These results showed a good simulation of the model and a relative correlation between measured and estimated data. Also, the parameters of MBE, RMSE, NRMSE, d and R2 were calculated to evaluate the efficient of model for estimating the salt concentration changes in three different areas of the soil. The average of these parameters at different soil depths for FSG treatment was 0.02 dS/m, 0.1 dS/m, 4/61%, 0.9 and 0.87, respectively. The above parameters in SSG treatment were calculated as 0.07 dS/m, 0.24 dS/m, 2.78%, 0.94 and 0.89, respectively. At the end, the model was simulated for the real paddy fields (Miankale lands in Behshahr region). In general, the comparison of measured and estimated water table and soil salinity showed that the Drainmod-S model is able to use as a general guide for prediction and simulation of water table and soil salinity changes.