Assessing SWAT+ Performance in Simulating Drainage Water Management and Parameter Transferability for Watershed-Scale Applications.

[Display omitted] • SWAT+ effectively simulates Drainage Water Management (DWM) • Field-scale annual DWM tile flow reduction varies by approximately ± 26 % • Zone of Influence defines areal extent of field scale model parameterization. • DWM adoption viable for 34 % of croplands surrounding the SWAT+ calibrated site. Drainage Water Management (DWM) is widely implemented to mitigate nutrient outflow from tile-drained croplands. However, the performance of process-based hydrological models in simulating DWM remains untested. This study aimed to assess the Soil and Water Assessment Tool (SWAT+) in simulating daily tile flow for a paired DWM field site in eastern South Dakota. Additionally, it sought to develop a method for determining the transferability of field-scale model parameterization to the surrounding watershed. Field-scale SWAT+ yielded satisfactory results during the calibration period (2016–2017) (East: NSE = 0.82, PBIAS = -26.8, RSR = 0.42; West: NSE = 0.75, PBIAS = -30.5, RSR = 0.5) and validation period (2018) (East: NSE = 0.71, PBIAS = -17, RSR = 0.55; West: NSE = 0.81, PBIAS = -4.6, RSR = 0.44) for each half of the experimental site. Further, ten-year SWAT+ simulations for the calibrated site showed an average annual reduction of 6.5 ± 1.7 mm in tile flow across the field due to DWM. Additionally, the study utilized remotely sensed Evapotranspiration to demonstrate that the calibrated site's model parametrization could be transferred to only 28 % to 46 % of surrounding croplands each year. Overall, the implications of the study extend beyond South Dakota, making the proposed research applicable to other geographical regions with tiled croplands as well. [ABSTRACT FROM AUTHOR]