Modeling the hydrologic influence of subsurface tile drainage using the National Water Model

The calibrated NWM with tile drainage (CalibTD) showed enhanced accuracy with higher event hit rates and lower false alarm rates than Calib. CalibTD showed better performance in high-flow estimations as TD increased streamflow peaks (14%), volume (2.3%), and baseflow (11%). Regional water balance analysis indicated that TD significantly reduced surface runoff (-7% to -29%), groundwater recharge (-43% to -50%), evapotranspiration (-7% to -13%), and soil moisture content (-2% to -3%).

However, TD significantly increased soil profile lateral flow (27.7%) along with infiltration and soil water storage potential. Overall, our findings highlight the importance of incorporating the TD process into the operational configuration of the NWM.