DRAINMOD-GIS: A lumped parameter watershed scale drainage and water quality model

A watershed scale lumped parameter hydrology and water quality model that includes an uncertainty analysis component was developed and tested on a lower coastal plain watershed in North Carolina. Uncertainty analysis was used to determine the impacts of uncertainty in field and network parameters of the model on the predicted outflows and nitrate–nitrogen loads at the outlet of the watershed. The model, which links DRAINMOD field hydrology and a spatially distributed routing model using a kernel function, accurately predicted the outlet flows and nitrate–nitrogen loads from a lower coastal plain watershed. Model predictions were within 1% of both measured outflows and nitrate–nitrogen loads. Uncertainty analysis indicated that uncertainty in stream velocities, decay coefficient and field exports significantly contributed to the uncertainty in the predicted outlet flows, loads and mean watershed delivery ratio.