Simulation of Water Table Fluctuations and Nitrate Concentration with DRAINMOD-N Model in Paddy Rice Field (Case Study: Capic)

In this study، simulations of water table fluctuations and nitrate concentration of groundwater were investigated in paddy rice fields which were equipped with controlled drainage system. This research was done in Haraz Technology and Development center in Mazandaran province north of Iran. For simulating the qualitative and quantitative variations of groundwater surface in the drained area، DRAINMOD-N model was applied using calibrated and measured data. It was necessary to calibrate the mineralization، denitrification and dispersivity constants in acceptable range to achieve the best fitness between the measured and simulated data. Therefore، the above constants were obtained 0. 000035، 0. 4 and 5 respectively. The analysis was done in graphical and statistical modes between the measured and simulated data. The statistical comparison was done by the mean bias error (MBE)، model efficiency (EF) and correlation factor (r) indices. indices were achieved 3. 38، 0. 53، and 0. 80 for estimation of the ground water level and 0. 61، 0. 97، and 0. 99 for the estimation of nitrate concentration، respectively. The DRAINMOD-N model maybe used as a powerful model in simulation and management of water pollution in drained area for reducing the environmental risks which may be occurred in paddy rice fields.