SPARROW Surface Water-Quality Modeling https://water.usgs.gov/nawqa/sparrow/
Documentation of the SPARROW model for Tennessee
Hoos, A.B., Wang, S.H., and Schwarz, G.E., 2019, Adapting a regional water-quality model for local application: A case study for Tennessee, USA: Environmental Modelling & Software, https://doi.org/10.1016/j.envsoft.2019.01.001.
Roland II, V.L., 2019, Data used in the creation of total phosphorus and total nitrogen SPARROW models for the state of Tennessee: U.S. Geological Survey data release, https://doi.org/10.5066/P96RWGU0.
Documentation of the modeling tool SPARROW (SPAtially Referenced Regression On Watershed attributes)
Schwarz, G.E., A.B. Hoos, R.B. Alexander, and R.A. Smith, 2006. The SPARROW Surface Water-Quality Model: Theory, Application, and User Documentation. U.S. Geological Survey Techniques and Methods Report, Book 6, Chapter B3. https://pubs.usgs.gov/tm/2006/tm6b3/
Preston, S.D., Alexander, R.B., Woodside, M.D., and Hamilton, P.A., 2009, SPARROW MODELING—Enhancing Understanding of the Nation’s Water Quality: U.S. Geological Survey Fact Sheet 2009–3019, 6 p. https://pubs.usgs.gov/fs/2009/3019/
The relationship between the scale of reporting of model results and uncertainty: Model results can be displayed at several watershed scales. The smallest scale that could be used for reporting is the catchment scale at which model computations are made – for the Tennessee model these are RF1 catchments, typical watershed size is about 30 square miles. Results can be aggregated up to larger scales for reporting: HUC10 (typical watershed size is 200 square miles), HUC8 (typical watershed size is 1,200 square miles) or larger. The SPARROW model is, in theory, “scale independent.” However, the uncertainty associated with SPARROW predictions is expected to increase for drainage basin sizes smaller than those of stream monitoring sites used to calibrate the model.
The HUC10 watershed scale is the smallest scale chosen for reporting for the Tennessee mapper application (that is, results at the model computation scale are not reported in the Tennessee mapper). The HUC10 watershed scale is large enough to provide greater certainty of model results, because the typical HUC10 size (about 200 square miles on average for the Tennessee model domain) is larger than almost one-third of the stream monitoring sites/basins used to calibrate the model (Saad and others, 2011; Tables S1 and S3).
Delineated HUC10 boundaries in this mapper may differ from the official boundaries for these units published in the Water Boundary Dataset: A HUC10 unit is typically comprised of five or six RF1 catchments that lie completely or mostly within the HUC10 unit. Because parts of some of these catchments lie outside the official HUC10 boundary, the aggregate boundary of the group of catchments does not in all cases align with the official delineated boundary of the HUC10 from the Watershed Boundary Dataset (U.S. Department of Agriculture-Natural Resources Conservation Service, U.S. Geological Survey, and Environmental Protection Agency, 2016). Hence the drainage area load reported for some of these aggregated HUC10 units departs from the official delineated unit. In contrast, for the HUC8 aggregated units, which are typically comprised of about 40 RF1 catchments, the aggregate boundary of the group of RF1 catchments aligns well with the official delineated boundary of the HUC8.
References:
Saad, D.A., G.E. Schwarz, D.M. Robertson, and N.L. Booth, 2011. A Multi-Agency Nutrient Dataset Used to Estimate Loads, Improve Monitoring Design, and Calibrate Regional Nutrient SPARROW Models. Journal of the American Water Resources Association 47(5):933–949, doi: 10.1111/j.1752-1688.2011.00575.x. U.S. Department of Agriculture-Natural Resources Conservation Service, U.S. Geological Survey, and Environmental Protection Agency, 2016, Watershed Boundary Dataset: http://datagateway.nrcs.usda.gov [Accessed 2/2/2016].
Hydrologist
615-837-4760
abhoos@usgs.gov
https://www.usgs.gov/staff-profiles/anne-b-hoos
Hydrologist
615-837-4754
vroland@usgs.gov
https://www.usgs.gov/staff-profiles/victor-l-roland
640 Grassmere Park, Suite 100
Nashville, TN 37211
https://www.usgs.gov/centers/lmg-water
Load from (areal unit such as HUC8, HUC10, Independent Watershed, or State, or fragment of State that overlaps with the other three units) delivered to (target point on the stream network such as downstream model boundary, HUC8 outlet, HUC10 outlet) (lb/yr): The predicted mean annual load of the constituent that originates within the areal unit and reaches the target point and thus is not attenuated or removed by natural processes during stream transport.
Yield from (areal unit such as HUC8, HUC10, Independent Watershed, or State, or fragment of State that overlaps with the other three units) delivered to (target point such as downstream model boundary, HUC8 outlet, HUC10 outlet) (lb/yr/acre): The load (as defined above) divided by the area of the areal unit.
Accumulated load at HUC10 outlet (lb/yr): The predicted mean annual load of the constituent at the outlet of the HUC10 that reflects the accumulated mass of the constituent contributed by all sources in the total drainage area upstream of the outlet (including all HUC10s upstream from this HUC10, if any). The accumulated load value includes the effects of in-stream attenuation processes in all upstream reaches.
Accumulated yield at HUC10 outlet (lb/yr/acre): The Accumulated Load at HUC10 outlet divided by the total drainage area upstream of the HUC10 outlet.
Load from (areal unit defined by fragment of State within the model area, or the fragment of State within a HUC10, HUC8, or Independent Watershed) within model area, lb/yr: The sum of predicted mean annual load of the constituent from all model catchments that lie within the areal unit and also that lie within the model area boundary. The summed catchment values are the incremental load for the catchment, and includes the effects of in-stream attenuation processes associated with one half of the incremental reach length.
Yield from (areal unit defined by fragment of State within the model area, or the fragment of State within a HUC10, HUC8, or Independent Watershed) within model area, lb/yr/acre: The load (as defined above) divided by the area of the areal unit.
Independent Watersheds are the large (in most cases) subwatersheds that comprise the Tennessee model area. With one exception (the “smaller tributaries to the Mississippi River”), the Independent Watersheds are delineated as the upstream drainage for each of the flow paths that exit the Tennessee SPARROW model area. The Watershed “smaller tributaries to the Mississippi River” does not have a single exit point; rather, multiple exit points where each tributary to the Mississippi River in West Tennessee discharges to the Mississippi River.
The downstream model boundary is the point where the flow path exits the Tennessee SPARROW model area boundary.
For more information about the SPARROW Tennessee Web Interface please contact 
SearchingIn addition to city, state, zip code, or general place names, USGS gaging stations and Hydrologic Unit Codes (HUCs) are also searchable.
Navigating the mapThe scroll wheel on the mouse can be used to zoom, and in the upper left area of the tool are "+" and "-" icons to zoom in and out, respectively.
Home LocationThe crosshair button will zoom the map to your location, and the home button will center the US on the map.
Opening a chartClicking on a nutrient model feature will generate a chart showing the individual sources for the selected feature. The chart also contains a button to switch to a chart of all features currently displayed.
Chart featuresClicking on a the chart legend will toggle individual sources on and off. Mouse over a bar to see its corresponding map feature as well as the exact value for each source. Dragging within the chart area allows the user to select and magnify specific segments of the chart. The selected features are also highlighted on the map. The Chart Options button contains options to download the chart data as well as toggle the background transparency.
Moving chart windowThe chart window can be repositioned to view underlying map information.
Explanation displayThe Explanation box can be expanded and collapsed
Using the ExplanationThe expanded Explanation box contains a legend for the currently selected Nutrient Model Results. The legend displays class breaks and values for the model results currently visible on the map, and updates dynamically with any change in mapped area.
Changing the basemap styleThe "Basemaps" panel allows a user to show various geographic information or landscape imagery as a background layer.
Changing or adding map layersThe "Map Layers" sidebar allows a user to add or remove layers as well as control the opacity of each individual layer.
Selecting a Nutrient ModelThe Nutrient Model can be changed at any time to view total phosphorus or total nitrogen.
Selecting an Area of Interest The Area of Interest dropdown menus can be used to customize the geographic area of the model results.
Selecting a Displayed Metric and Group Results ByYields and loads can be viewed by making changes to the Displayed Metric dropdown. The area of aggregation is controlled by the Group Results dropdown.
Show Chart, Show TableClicking these buttons will generate a chart or table for all of the features displayed on the map. Charts and Tables can also be exported and downloaded.
