Can a simple water quality model effectively estimate runoff-driven nutrient loads to estuarine systems? A national-scale comparison of STEPLgrid and SPARROW

This study investigated whether a simple model could scale across watersheds and effectively predict runoff-driven nutrient loading as compared to with more complex process representation. A lumped model, the Spreadsheet Tool for Estimating Pollutant Load (STEPL), was adapted use gridded data (STEPLgrid) applied 112 coastal Atlantic, Gulf, Pacific coasts of contiguous United States (U.S.) estimate annual total nitrogen (TN) phosphorus (TP) loads. STEPLgrid outputs were those SPAtially Referenced Regression on Watershed Attributes (SPARROW) model. Relative SPARROW, produced comparable estimates TN TP loads most studied its predicted similar SPARROW than TP. particularly effective at rank-ordering by indicating that useful relative comparisons diverse watersheds. • STEPL allow application large spatial scales (STEPLgrid). N P N. load. Simple models can be comparing load scenarios multiple basins.