AGNPS Watershed Modeling with GIS Databases

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AGNPS Watershed Modeling with GIS Databases
Second Federal Interagency Hydrologic Modeling
Conference
Las Vegas, NV 28 Jul - 1 Aug 2002
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AGNPS Watershed Modeling with GIS Databases

• Michael P. Finn
• E. Lynn Usery
• Douglas J. Scheidt
• Thomas Beard
• Sheila Ruhl
• Morgan Bearden
• U.S. Geological Survey
• Mid-Continent Mapping Center
• Rolla, MO

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Outline

• Introduction
• Study Areas
• GIS Databases for Parameter Extraction
• AGNPS Parameter Generation
• Creating AGNPS Input, Output, and Images
• Results

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Objectives

• Use GIS databases as input to AGNPS Pollution
  Model
• Demonstrate automatic extraction of input
  parameters
• Create a tool for generating input, executing the
  model, and analyzing output

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Introduction

• Agricultural NonPoint Source (AGNPS) Pollution
  Model USDA lead agency
• AGNPS operates on a cell basis and is a
  distributed parameter, event-based model
• AGNPS requires 22 input parameters
• Elevation, land cover, and soil data served as
  the base of extraction for the input

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Study Areas

• Four Watersheds
• Little River, GA
• Piscola Creek, GA
• Sugar Creek, IN
• EL68D Wasteway, WA
• Watershed Boundaries
• NAWQA Boundary
• GIS Weasel

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Georgia Watersheds
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Indiana Watershed
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Washington Watershed
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GIS Databases for Parameter Extraction

• USGS 30-m DEMs
• USGS 30-m National Land Characteristics Data
• Augmented with recent Landsat TM data
• Soil databases from USDA soil surveys
• Scanned separates, rectified, vectorized, and
  tagged
• Resampled the 30-m data to 60, 120, 210, 240,
  480, 960, and 1920 meters
• 210-m roughly matches 10 acre grid size

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AGNPS Parameter Generation

• AGNPS Data Generator
• Input parameter generation
• Details on generation of parameters
• Extraction methods

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AGNPS Data Generator

• Created to provide interface between GIS software
  (Imagine) and AGNPS
• Developed interface for Imagine 8.4, running on
  WinNT/ 2000

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AGNPS Data Generator
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Input Parameter Generation

• 22 parameters varying degrees of computational
  development
• Simple, straightforward, complex

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Input Parameter Generation
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Details on Generation of Parameters

• Cell Number
• Receiving Cell Number
• SCS Curve Number
• Uses both soil and land cover to resolve curve
  number

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Details on Generation of Parameters (continued)

• Slope Shape Factor

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Details on Generation of Parameters (continued)

• Slope Length
• A concern max value should be 300 ft.
• Parameters 10, 11, 12, 14, 15, 16, and 17
• Uses Spatial Modeler to look up attributes from
  soils or land cover
• Example p10 is Overland Mannings Coefficient
• Parameters 13, 18, 19, 20, and 21
• Hard coded on advice from experts
• Example p13 is Practice Factor (conservation)
  coded to 1 (worst case)

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Details on Generation of Parameters (continued)

• Type of Channel
• Uses TARDEM program
• Creates a Strahler steam order

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Extraction Methods

• Used object-oriented programming and macro
  languages
• C/ C and EML
• Manipulated the raster GIS databases with Imagine
• Extracted parameters for each resolution for both
  boundaries using AGNPS Data Generator

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Creating AGNPS Input, Output, and Images

• Input Data File Creation
• Format generated parameters into AGNPS input file
• Use a stacked image file to create AGNPS data
  file (.dat) -- ASCII

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Creating AGNPS Input, Output, and Images
(continued)

• Output Image Creation
• AGNPS Creates a nonpoint source (.nps) file
• ASCII File like the input tabular/ numerical form

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Creating AGNPS Input, Output, and Images
(continued)
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Creating AGNPS Input, Output, and Images
(continued)

• Output Image Creation (continued)
• Combined .nps file with Parameter 1 to create
  multidimensional images
• Users can graphically display AGNPS output
• Process create image with n layers, fill
  layers with AGNPS output data, set projection and
  stats for image
• Multi-layered (bands) images per model event

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Creating AGNPS Input, Output, and Images
(continued)
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Creating AGNPS Input, Output, and Images
(continued)
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Creating AGNPS Input, Output, and Images
(continued)
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Creating AGNPS Input, Output, and Images
(continued)
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Results

• Collaboration continues to quantify the impact of
  spatial resolution on model results
• Demonstrated the use of GIS databases as sources
  in watershed modeling, particularly with AGNPS
• Demonstrated methods of automatic extraction of
  AGNPS input parameters from GIS databases
• Showed implications of results for 4 watersheds
• Demonstrated the practicality of AGNPS Data
  Generator as an AGNPS GIS interface

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AGNPS Watershed Modeling with GIS Databases
Second Federal Interagency Hydrologic Modeling
Conference
Las Vegas, NV 28 Jul - 1 Aug 2002