In the present study, DRAINMOD-NII model was calibrated for the years 2018–2019 and validated for the period 2019–2020 over the two cropping years. The model simulations were statistically evaluated by comparing the measured drain flows and nitrate-nitrogen (NO3-N) with the model simulated drain outflows and nitrate loss. The study results depicted closer agreement between the simulated and observed results for both the calibration and validation periods. The Root Mean Square Error (RMSE) of

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... drainage rate was 8.88 cm more than observed data, 15.41, 0.53 and 0.57 cm were the values recorded for PBIAS, modelling efficiency (NSE) and R2. The similar parameter values for nitrogen load were recorded to be 0.14, 2.76, 0.84 and 0.88 respectively during the calibration period for rice wheat system. The model was statistically tested during the validation period also, confirming DRAINMOD-NII has the capability to simulate nitrogen losses from the area subjected to subsurface drainage system.