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Model Report

Automated Geospatial Watershed Assessment

Last Revision Date: 10/08/2009 View as PDF
General Information Back to Top
Model Abbreviated Name:

Model Extended Name:

Automated Geospatial Watershed Assessment
Model Overview/Abstract:
The Automated Geospatial Watershed Assessment (AGWA) tool is a Geographic Information Systems (GIS) interface jointly developed by the U.S. Environmental Protection Agency, the U.S. Department of Agriculture (USDA) Agricultural Research Service, and the University of Arizona to automate the parameterization and execution of the Soil and Water Assessment Tool (SWAT) and KINematic Runoff and EROSion (KINEROS2) hydrologic models. The application of these two models allows AGWA to conduct hydrologic modeling and watershed assessments at multiple temporal and spatial scales. AGWA’s current outputs are runoff (volumes and peaks) and sediment yield, plus nitrogen and phosphorous with the SWAT model. AGWA uses commonly available GIS data layers to fully parameterize, execute, and spatially visualize results from both SWAT and KINEROS2. Through an intuitive interface, users select an outlet from which AGWA delineates and discretizes the watershed using a Digital Elevation Model (DEM). The watershed model elements are then intersected with soils and land cover data layers to derive initial estimates of requisite model input parameters. AGWA can currently use STATSGO, SSURGO and FAO soils and nationally available land-cover/use data such as the National Land Cover Data (NLCD) datasets. Users are also provided the functionality to easily customize AGWA for use with any classified land-cover/use data. The chosen hydrologic model is then executed, and the results are imported back into AGWA for visual display on the spatially distributed model elements. This allows decision-makers to identify potential problem areas where additional monitoring can be undertaken or mitigation activities can be focused. AGWA can difference results from multiple simulations to examine and compare changes predicted for each alternative input scenario (e.g., climate/weather change, land-cover change, present conditions, and alternative futures). In addition, a variety of new capabilities have been incorporated into AGWA, including pre- and post-fire watershed assessment, watershed group simulations to cover all watersheds within a political or management boundary, implementation of stream buffer zones, and installation of retention and detention structures. A land-cover modification tool is provided for the development of prescribed land-cover change scenarios, with a number of options for uniform, spatially random, and patchy change to single or multiple land-cover classes. There are currently two versions of AGWA available: AGWA 1.5 for users with Environmental Systems Research Institute (ESRI) ArcView 3.x GIS software (ESRI, 2005), and AGWA 2.0 for users with ESRI ArcGIS 9.x (ESRI, 2006). Both 1.5 and 2.0 AGWA versions have been retained to reach the widest available audience.
Keywords: Hydrologic process modeling, Geographic Information Systems, erosion, watershed runoff, sediment yield, landscape change, user interface, ArcGIS, ArcView, alternative futures, scenario analysis
Model Technical Contact Information:
William G. Kepner
Landscape Ecology Branch

Developer Contact:
Shea Burns
USDA/Agricultural Research Service
Southwest Watershed Research Center
2000 E. Allen Road
Tucson, AZ 85719
520.670.6380 Ext. 162
http://www.tucson.ars.ag.gov/agwa/exit EPA

Model Homepage: http://www.epa.gov/esd/land-sci/agwa/index.htm
Substantive Changes from Prior Version: AGWA 2.0 for ArcGIS 9.x was released at the AWRA Annual Conference in Albuquerque, NM in November 12-15, 2007. AGWA 2.0 utilizes new features in ArcGIS 9.x that were not available in ArcView 3.x to make the tool more powerful, flexible, and easier to use than AGWA 1.5.
Plans for further model development: KINEROS-OPUS, a continuous physically-based model with nutrient and management options, is scheduled to be added to AGWA in 2009 to complement the existing model choices and to fill potential gaps in user needs. Additionally, an internet capable version of AGWA 2.0 (termed DotAGWA) has been developed as a proof-of-concept product for local scale applications.

User Information Back to Top
Technical Requirements
Computer Hardware
Minimum and recommended hardware configurations are dictated by the GIS software platform, ESRI ArcView 3.x for AGWA 1.5 and ESRI ArcGIS 9.x for AGWA 2.0. For specific requirements see:
http://wikis.esri.com/wiki/display/ag93bsr/ArcGIS+Desktopexit EPA (ArcGIS 9.3) and
http://support.esri.com/index.cfm?fa=knowledgebase.systemRequirements.list &PN=ArcView+3.x&PID=25&count=1&pvid=96&VID=361exit EPA (ArcView 3.x).
Compatible Operating Systems
AGWA works with the Windows 2000, ME, NT, XP, and Vista environments.
Other Software Required to Run the Model
  • For AGWA 1.5
    • ArcView 3.x
    • Spatial Analyst for ArcView 3.x
  • For AGWA 2.0
    • ArcGIS 9.x
    • Spatial Analyst for ArcGIS 9.x
    • 3D Analyst for ArcGIS 9.x (optional – only required for SWAT distributed precipitation)
    • .NET Framework 1.1 (ArcGIS 9.0 and 9.1)
    • .NET Framework 1.1 and 2.0 (ArcGIS 9.2 and 9.3)
Download Information
User registration is required for download:
http://www.tucson.ars.ag.gov/agwa/exit EPA
Using the Model
Basic Model Inputs
Using digital data in combination with the automated functionality of AGWA greatly reduces the time required to use these two watershed models. Through a robust and intuitive interface the user selects an outlet from which AGWA delineates and discretizes the watershed using the Digital Elevation Model (DEM) information. The watershed elements are then intersected with soil, land cover, and precipitation (uniform or distributed) data layers to derive the requisite model input parameters. The model is then run, and the results are imported back into AGWA for visual display.

  • Digital elevation model (DEM) for watershed delineation and discretization
  • STATSGO, SSURGO, or FAO soils for parameterization
  • Classified land cover for parameterization
  • Multi-year daily precipitation for SWAT
  • Event-based precipitation for KINEROS2
Basic Model Outputs
  • Plane
    • Infiltration (mm or in)
    • Runoff (mm or m3)
    • Sediment yield (kg/ha)
    • Peak flow (m3/s or mm/hr)
    • Peak sediment discharge (kg/s)
    • Mass balance error (%)

  • Channel
    • Infiltration (m3/km or ac-ft/mi)
    • Runoff (mm or m3)
    • Sediment yield (kg)
    • Peak flow (m3/s or mm/hr)
    • Peak sediment discharge (kg/s)
    • Channel scour (mm/m2)
    • Mass balance error (%)


  • Subwatershed
    • Precipitation (mm)
    • ET (mm)
    • Percolation (mm)
    • Surface runoff (mm)
    • Transmission loss (mm)
    • Water yield (mm)
    • Sediment yield (t/ha)
    • Organic Nitrogen (kg/ha)
    • Organic Phosphorous (kg/ha)
    • Mineral Phosphorous (kg/ha)
    • Nitrate (kg/ha)
    • Soluble Phosphorous (kg/ha)

  • Channel
    • Transmission loss (m3/s)
    • Sediment yield (tons)
    • Runoff (m3//day)
    • Sediment concentration (mg/kg)
    • Organic Nitrogen (kg)
    • Organic Phosphorous (kg)
    • Nitrate (kg)
    • Ammonium (kg
    • Nitrite (kg)
    • Mineral Phosphorous (kg)
User Support
User's Guide Available?
Other User Documents
Fact sheet: http://www.epa.gov/nerlesd1/land-sci/agwa/pdf/agwa_fact_sheet_2-0.pdf
TMDL application: http://www.epa.gov/nerlesd1/land-sci/agwa/pdf/tmdl_fs_2-0.pdf
Brochure: http://www.epa.gov/nerlesd1/land-sci/agwa/pdf/brochure_2-0.pdf
Quality Assurance Plan: http://www.epa.gov/nerlesd1/land-sci/agwa/pdf/qaqc2-0.pdf
Design Documentation: http://www.epa.gov/nerlesd1/land-sci/agwa/archive/agwa_design.pdf
Publications and Posters: http://www.epa.gov/nerlesd1/land-sci/agwa/pubs.htm
Availability of User Support
Yes, but limited (available via Help Forum)
http://www.tucson.ars.ag.gov/agwa/index.php?option=com_fireboard&Itemid=33exit EPA
User Qualifications
Some college background and experience in geographic information systems and watershed hydrology or natural resource/watershed management.

Model Science Back to Top
Problem Identification
AGWA was designed with the following objectives in mind:
  • provide a simple, direct, and repeatable method for hydrologic model parameterization;
  • be useful for scenario and alternative futures simulation work at multiple scales;
  • use only basic, widely obtainable GIS data

The application of AGWA allows users to conduct hydrologic modeling and watershed assessments at multiple temporal and spatial scales:

  • SWAT: a river basin scale model developed to quantify the impact of land management practices in large, complex watersheds.
  • KINEROS2: A distributed-parameter, event-based rainfall-runoff-erosion model (this model is being coupled with OPUS to form a continuous model with nutrient and carbon cycling, common pesticides, and common cultivated and range management practices)

AGWA’s current outputs are runoff (volumes and peaks) and sediment yield, plus nitrogen and phosphorous.

Summary of Model Structure and Methods
The AGWA tool is an extension for the ESRI ArcView and/or ArcGIS software that uses geospatial data to parameterize two watershed runoff and erosion models: KINEROS2, and SWAT. AGWA is a modular program that is designed to be run in a step-wise manner.


Model Evaluation
Key Limitations to Model Scope
SWAT and KINEROS2 documentation should be carefully reviewed to fully understand model limitations. SWAT is a daily time step model and employs the concept of hydrologic response units (HRU). Explicit position of land uses, and best management practices for computing runoff-runon effects are not directly treated with HRUs. KINEROS2 is an event-based model and must therefore be provided initial soil moisture conditions. It must also be supplied with sub-daily rainfall data, preferably in 15 min. intervals or less. Both models cannot treat backwater effects in flow routing.
Case Studies
Kepner, W.G., D. J. Semmens, M. Hernandez, and D.C. Goodrich. 2008. Evaluating Hydrological Response to Forecasted Land-Use Change. Chapter 15, The North American Land Cover Summit, Association of American Geographers, Washington, DC, 275-292, (2008).

Kepner, W., Hernandez, M., Semmens, D., and Goodrich, D. 2008. The Use of Scenario Analysis to Assess Future Landscape Change on a Watershed Condition in the Pacific Northwest (USA). Use of Landscape Sciences for the Assessment of Environmental Security. Springer, The Netherlands, ISBN 978-1-4020-6588-0. pp. 237-261.

Kepner, W.G., D.J. Semmens, S.D. Bassett, D.A. Mouat, and D.C. Goodrich. 2004. Scenario Analysis for the San Pedro River, Analyzing Hydrological Consequences of a Future Environment (13 pp, 2.6MB). Journal of Environmental Monitoring and Assessment. 94: 115-127.

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