Watershed Models for Predicting Nitrogen Loads from Artificially Drained Lands

Non-point sources of pollutants originate at the field scale but water quality problems usually occur at the watershed or basin scale. This paper describes a series of models developed for poorly drained watersheds. The models use DRAINMOD to predict hydrology at the field scale and a range of methods to predict channel hydraulics and nitrogen transport. In-stream changes of N load are estimated with a lumped parameter exponential decay function. The models were tested using data from a 10,000 ha eastern NC watershed. The models can be used in TMDL development and implementation procedures to target application of field scale management practices to maximize reduction in nitrogen load at the watershed scale.