Model inputs and estimated total nitrogen and total phosphorus loads used in the development of Mississippi SPARROW models, 2018 base year

Degradation of water quality from nutrient pollution continues to be a challenge for water resource managers. The development of effective management strategies begins with tools that facilitate an understanding of nutrient sources and transport. SPARROW (SPAtially Referenced Regression On Watershed attributes) is a spatially explicit model platform that correlates water-quality observations with sources and transport-related properties of the watershed to predict constituent loads for streams and catchments. Several large-scale regional SPARROW models have been previously developed by the USGS that predict nutrient loads for large portions of the U.S. (see https://www.usgs.gov/mission-areas/water-resources/science/sparrow-mapp…). However, relatively smaller-scaled and more focused, state-based SPARROW models may also be of particular benefit to state and local resource managers related to assessment of total maximum daily loads, nutrient criteria, and prioritizing nutrient reduction strategies, etc.

For this study, the USGS Lower Mississippi-Gulf Water Science Center, in cooperation with Mississippi Department of Environmental Quality (MDEQ), developed state-based SPARROW models for Mississippi using RSPARROW software (Alexander and Gorman Sanisaca, 2019). Mississippi SPARROW models were developed by utilizing published input datasets of nutrients sources and delivery variables compiled from the Midwest (Saad and Robertson, 2020) and Southeast regional SPARROW models (Roland and Hoos, 2020).  These source and delivery variables included land characteristics (urban coverage), instream and reservoir attenuation, and various sources of nitrogen and phosphorus (atmospheric deposition, point-sources, fertilizer/manure application, geologic material, etc.) from the period of 1999 through 2014. Updated load estimates were then calculated using streamflow and nutrient data for the period of 2005 through 2020 from USGS streamgages throughout Mississippi and portions of Alabama, Georgia, Tennessee, North Carolina, and Virginia. Load estimates were used to calibrate total nitrogen and total phosphorus SPARROW models for the base year of 2018.

Included datasets:
ms_sparrow_data1.csv (model input data file "data1")
ms_sparrow_catchments.zip (catchment shapefile)
ms_sparrow_reaches.zip (stream reach shapefile)
ms_sparrow_output_TN.csv (total nitrogen model results - predicted loads and yields)
ms_sparrow_output_TP.csv (total phosphorus model results - predicted loads and yields)

Please note: The spatial footprint of these datasets includes calibration sites, stream reaches, and catchments that extend outside of the state of Mississippi; however, the associated report by Roland and Gain (2025) and web-based mapper (https://sparrow.wim.usgs.gov/sparrow-mississippi/) only include model results for stream reaches and catchments that are within or drain into the state of Mississippi. Also, attributes of "waterid" and "originalWaterid" within the input data1 and output files, respectively, correspond with "COMID" attribute within the catchment and reach shapefiles.