Spreadsheet Tool for Estimating Pollutant Loads (STEPL)
Questions or Comments?
- nutrient and sediment loads from different land uses, and
- the load reductions that would result from the implementation of various best management practices (BMPs).
- watershed surface runoff;
- nutrient loads, including nitrogen, phosphorus, and 5-day biological oxygen demandbiological oxygen demandAn indirect measure of the concentration of biologically degradable material present in organic wastes. It usually reflects the amount of oxygen consumed in five days by biological processes breaking down organic waste. (BOD5); and
- sediment delivery based on various land uses and management practices.
For each watershed, the annual nutrient loading is calculated based on the runoff volume and the pollutant concentrations in the runoff water, as influenced by factors such as the land use distribution and management practices.
The annual sediment load (sheet and rill erosion only) is calculated based on the Universal Soil Loss Equation (USLE)Universal Soil Loss EquationAn equation used to predict the average rate of erosion of an area on the basis of the rainfall, soil type, topography, and management measures of the area. and the sediment delivery ratio. The sediment and pollutant load reductions that result from the implementation of BMPs are computed using the known BMP efficiencies.
Model Download and Documentation
(Last updated: 03/15/2018)
- STEPL 4.4 Spreadsheet Model for 10 Watersheds (Microsoft Excel 2016) (.zip) - Note: This download includes STEPL version 4.4 that is fully functional for modeling up to 10 watersheds at a time. It does not require users to have Administrator Rights for installing STEPL on their computers.
- STEPL 4.4 Full Installation Package (.zip) - Note: This download contains a 'setup.exe' file that installs STEPL version 4.4 for full functionality on a customizable number of watersheds; however, it requires Administrator Rights for model installation.
- STEPL 4.4 BMP Calculator (.zip)
- STEPL 4.4 Updates and New Features (PDF) - This documentation highlights the new features of STEPL version 4.4.
- STEPL 4.4 User’s Guide (PDF) - This is the complete model documentation for STEPL version 4.4.
Note: This update includes new BMP types (cropland and pastureland) and this version of STEPL has been upgraded to be compatible with Windows 10 and Excel 2016. It is also compatible with Windows 7 and Excel 2013.
(Last updated: 01/16/2017)
- STEPL 4.3b Installation Package (.zip) - Note: This download contains a 'setup.exe' file that installs STEPL version 4.3 for full functionality on a customizable number of watersheds; however, it requires Administrator Rights for model installation.
Note: This version of STEPL has been upgraded to be compatible with Windows 10 and Excel 2013.
The Input Data Server for STEPL uses the ArcGIS Viewer for Flex 2.1. You must have Adobe Flash Player version 10.1 or higher installed to use the data server.
- More stable GIS platform using a simple and modern Web 2.0-style user interface.
- Additional map layers:
- Street map.
- Aerial map.
- Elevation map.
- Boundaries and places.
- State and County boundaries.
- Watershed boundary dataset (HUC12, HUC10, HUC8, HUC6, HUC4, and HUC2).
- NHDplus catchments.
- NHDplus flowlines and waterbodies.
- Updated datasets:
- 2011 Landuse area distribution at the Subwatershed (HUC12) level.
- 2012 Agricultural animal count at the Subwatershed (HUC12) level.
- Access the Input Data Server for STEPL (Note: requires Adobe Flash Player version 10.1.0 or greater)
- View the Guide for Using the Input Data Server for STEPL
- Video: EPA STEPL 4.4 Training Webinar (March 20, 2018)
- EPA STEPL 4.4 Training Slides (PDF) (March 20, 2018)
- EPA STEPL 4.3 Training Workshop, Washington D.C. (.zip) (August 25, 2015)
- Audio archive of Wisconsin STEPL 4.3 training (August 5, 2014) (University of Wisconsin - Cooperative Extension) Exit