| An important goal for watershed management is the prevention of soil erosion and other forms of nonpoint source (NPS) pollution that adversely affect water quality. This requires that sensitive NPS areas be identified and protected using appropriate Best Management Practices (BMPs). A wide range of hydrologic models have been developed for simulating diffuse pollution transport, many of which are integrated with a geographic information system (GIS). Several models use a delivery ratio coefficient to represent what proportion of detached pollutant (sediment, nutrients, etc.) is eventually transported to the watershed outlet. Present techniques for deriving delivery ratios are of limited utility for watershed management, however, because they are either spatially lumped parameters or crude indices with little empirical basis.; This dissertation presents a new, GIS-based technique for deriving spatially distributed delivery ratios. The model, Spatially Explicit Delivery MODel (SEDMOD), estimates delivery ratios for each watershed cell by modeling the influence of six transport parameters. Parameters are derived from data readily available in digital form at large spatial scales (i.e., elevation, vegetation cover, and soil properties). SEDMOD is entirely integrated within Arc/Info, a widely used geographic information system, using a menu interface and Arc/Info's programming language.; Three companion studies were conducted to test and validate the model. The first involved applying the model to identify critical sediment source areas within a New York City water supply watershed. In this application, model behavior was explored through sensitivity analyses. The second study used long-term, measured sediment yields from six small northeastern watersheds to test SEDMOD's sediment delivery predictions. The final study used the model for predicting livestock bacterial pollution at the outlets of 12 watersheds in the Hudson River valley. Overall, the studies demonstrate the utility of SEDMOD for rapidly and systematically identifying watershed sites prone to high pollutant delivery. This information could be used by water resource professionals to identify sites so NPS pollution control measures ( e.g., BMPs, conservation easements, land acquisition and stewardship incentive programs) are applied efficiently and cost-effectively. |
