Description of the 2002 SPARROW Models for the Midcontinental Region of North America
The SPARROW model results displayed here represent long-term mean-annual total nitrogen and total in streams of the Midcontinental Region of North America. The simulated loads represent source inputs similar to 2002 and normalized to long-term average hydrologic conditions for the period from 1970 to through 2012.
Documentation of the SPARROW models for the Midcontinental Area of Canada and the United States
Robertson, D.M., D.A. Saad, G.A. Benoy, I. Vouk, G.E. Schwarz, and M.T. Laitta. 2019. Phosphorus and nitrogen transport in the binational Great Lakes Basin estimated using SPARROW watershed models. Journal of the American Water Resources Association 1–25. https://doi.org/10.1111/1752-1688.12792
Saad, D.A., D.M. Robertson, G.A. Benoy, and I. Vouk, 2019, SPARROW model simulated nutrient loads in streams of the Midcontinental Region of Canada and the United States, 2002 Base Year. U.S. Geological Survey, data release. Available online at: https://doi.org/10.5066/P9ODSQYB.
Vouk, I., R.S. Burcher, C.M. Johnston, R.W. Jenkinson, D.A. Saad, J.S. Gaiot, G.A. Benoy, and D.M. Robertson, 2018a. Data and procedures used to develop inputs for nutrient SPARROW models throughout the midcontinental region of Canada and the United States. National Research Council of Canada. 39 p. plus appendices. Available online at: http://doi.org/10.4224/23004810.
SPARROW Surface Water-Quality Modeling Web Pages
National Website: https://water.usgs.gov/nawqa/sparrow/
Regional Website: https://www.usgs.gov/centers/wisconsin-water-science-center/science/sparrow-watershed-modeling-great-lakes-ohio-upper?
Documentation of the modeling tool SPARROW (SPAtially Referenced Regression On Watershed
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 Midcontinent models these are NHD/NHN catchments with typical watershed size of about 2.5 square kilometers. Results can be aggregated up to larger scales for reporting: tributary outlet, HUC8/Sub-sub drainage area (typical watershed size is 3,850 square kilometers), state, or selected watersheds within the modeled area. 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. For the Midcontinent nutrient models, the drainage areas of the smallest calibration sites are typically in the range of 10 to 100 square kilometers. The uncertainty associated with incremental load and yield predictions at the catchment scale is therefore expected to be larger than the uncertainty associated with predictions at larger scales.
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The predicted mean annual load of the constituent (kilograms per year) leaving a stream reach that reflects only those sources contributed from within the incremental drainage area of that reach. The incremental load value includes the effects of in-stream attenuation processes associated with one half of the incremental reach length. Incremental drainage areas are represented here as “catchments”.
Accumulated Load (often referred to as "Total Load")
The predicted mean annual load of the constituent (kilograms per year) leaving a stream reach that reflects the accumulated mass of the constituent contributed by all sources in the total drainage area upstream of the reach outlet. The accumulated load value includes the effects of in-stream attenuation processes in all upstream reaches.
For results grouped by 8-digit HUC/Sub-sub drainage area, tributary outlet, major drainage area or state/province, aggregated load represents the sum of incremental loads for those selected areas.
The Incremental Load divided by the incremental drainage area of the reach. Units are kilograms per square kilometer per year.
The Accumulated Load divided by the total drainage area upstream of the reach outlet. Units are kilograms per square kilometer per year.
The Aggregated Load divided by the sum of the "grouped by" incremental drainage areas. Units are kilograms per square kilometer per year.
Delivered Incremental Load
Incremental load multiplied by the delivery fraction. Delivery fraction is defined below.
Delivered Accumulated Load
Incremental load multiplied by the delivery fraction. Delivery fraction is defined below.
Delivered Aggregated Load
For results grouped by 8-digit HUC/ Sub-sub drainage area, tributary outlet, major drainage area or state/province, delivered aggregated load represents the sum of delivered incremental loads for those selected areas. Delivery fraction is defined below.
Delivered Incremental Yield
The Delivered Incremental Load divided by the incremental drainage area of the reach. Units are kilograms per square kilometer per year.
Delivered Accumulated Yield
The Delivered Accumulated Load divided by the total drainage area upstream of the reach outlet or total of the “grouped by” area. Units are kilograms per square kilometer per year.
Delivered Aggregated Yield
The Delivered Aggregated Load divided by the sum of the “grouped by” incremental drainage areas. Units are kilograms per square kilometer per year.
Delivery Fraction (definition)
The fraction of the load leaving a reach that is not attenuated or removed by natural processes during downstream transport to a specified downstream target reach. A delivery fraction of 1 indicates that 100 percent of the load leaving the reach is delivered to the downstream target.
Please note: For delivered results shown here, the downstream targets represent the Great Lakes, Lake Winnipeg and the outlets of the Upper Mississippi and Ohio River Watersheds.
USGS Data Disclaimer:
Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty.
USGS Software Disclaimer:
This software has been approved for release by the U.S. Geological Survey (USGS). Although the software has been subjected to rigorous review, the USGS reserves the right to update the software as needed pursuant to further analysis and review. No warranty, expressed or implied, is made by the USGS or the U.S. Government as to the functionality of the software and related material nor shall the fact of release constitute any such warranty. Furthermore, the software is released on condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from its authorized or unauthorized use.
USGS Product Names Disclaimer:
Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
This web application functions best in Chrome, Firefox, or Safari. Internet Explorer works but with slower performance.
Link to SPARROW REST Services:
SPARROW TEST REST Services
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. (For more on the Chart features, see Data Display)
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. To read more about metric definitions visit the About section or click here
Data Display OptionsOnce the Display Filters have been chosen, there are several ways to display data about the polygons of interest in the Data Display settings.
+ SelectClicking the Select button allows individual map feature selection. Multiple features can be selected. To unselect, hold the Shift key then Click the feature to unselect it. After all features of interest have been selected, click Stop Selecting.
Show ChartClicking the Show Chart button will show a window with two tabs; Chart and Table. The information in the Chart and Table will either represent the full feature layer visible on the map, or it will represent the selection chosen from individual selecting features. This window can be repositioned to view underlying map information. The Chart tab shows a chart for the full layer visible in the map based on the filters chosen in the Data Filters section. Clicking on a the chart legend items will toggle individual sources on and off, as well as recalculating the y-axis range. Mouse over a bar to see its corresponding map feature as well as the exact value for each source.
Selected Chart SegmentTo see a magnified segment of the chart, click+drag over the chart bars. The selected features are highlighted on the map. Moving the mouse over the chart bars will give the values for each source as well as show an additional highlight to the cooresponding map feature. To return to the previous chart view, click the Reset zoom button in the top right of the chart window.
Chart OptionsThe Chart Options button contains the option to change the background transparency. Clicking Change background transparency will toggle the background transparency between transparent and not transparent.
TableThe Table tab shows a tabular representation of the chart information on the Chart tab. The table can be sorted by any column. Moving the mouse over any table row will highlight that map feature on the map. Any zooming or resetting on the Chart tab will update the Table tab's contents.
Data from the links provided below contain the SPARROW model outputs needed to reproduce the maps and model results shown here and described in Robertson and others, 2019 https://doi.org/10.1111/1752-1688.12792.
All Model Results
Calibration Site Information
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