Application of SSURGO Data to Statewide TOPMODEL and SPARROW Stream System Modeling.

SPARROW (SPAtially Referenced Regression on Watershed Attributes) uses water-quality data in a statistically based land-use and land-attribute model that incorporates source and delivery variables in order to estimate contaminant loads for non-monitored streams.  In Kentucky, a statewide SPARROW model is available for mean annual nitrogen and phosphorus loads using 1992 data as a baseline.  This model is based on a combination of spatial data, with resolutions varying from 100 m² to 25 km², and a stream network with a mean watershed size of 6.0 km².  The resolution of the input data limits the applicability of the model to watersheds where the total drainage area is on the order of several hundred km².  One such watershed is Floyds Fork (743 km²), east of Louisville.  Current issues of concern in the watershed include phosphorus, nitrogen, pathogens, and sediment.  The current SPARROW model only addresses relative nutrient contributions for the six largest stream segments within Floyds Fork.  However, an improved monitoring network, combined with a finer spatial data resolution, will address nutrient contributions in the smaller tributaries, as well as enabling an understanding of sediment contributions.  We will discuss the development of the model for smaller watersheds, how it is being used to design TMDL criteria, and how this local model relates to the national and regional SPARROW modeling efforts.