Sensitivity analysis of the DRAINWAT model applied to an agricultural watershed in the lower coastal plain, North Carolina, USA
The DRAINWAT, DRAINmod for WATershed model, was selected for hydrological modelling to obtain water table depths and drainage outflows at Open Grounds Farm in Carteret County, North Carolina, USA. Six simulated storm events from the study period were compared with the measured data and analysed. Simulation results from the whole study period and selected rainfall events assured that the DRAINWAT model reasonably predicted the water table depths and drainage outflow events even though it underestimated outflows in very dry period after 24 April, 2001. The potential evapotranspiration by various calculation methods was found to be the most sensitive parameter in this study. The other three parameters (maximum surface depressional storage, Manning's channel roughness coefficient, and channel bedslope) were not significantly (á = 0.05) sensitive to the cumulative outflow as expected. The DRAINWAT model may be a useful tool for water management in flat agricultural areas with high water table if it can be calibrated properly with reliable measurements.