To supplement the CBP watershed model, the USGS has developed a set of spatially referenced regression models. These models can be used to provide a statistical basis to watershed modeling and to provide additional spatial detail on nutrient sources and transport processes. The method used for developing the regressions is referred to as "SPARROW" (SPAtially Referenced Regressions On Watershed attributes) (Smith and others, 1997). The SPARROW methodology has been successfully applied at the national scale for estimating total nitrogen and total phosphorus loads for streams in the continental United States (Smith and others, 1997). This report describes a separate application of SPARROW at the scale of the Chesapeake Bay watershed (fig. 1