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AGNPS Watershed Modeling with GIS Databases. Second Federal Interagency Hydrologic Modeling Conference. Las Vegas, NV 28 Jul - 1 Aug 2002. AGNPS Watershed Modeling with GIS Databases. Michael P. Finn E. Lynn Usery Douglas J. Scheidt Thomas Beard Sheila Ruhl Morgan Bearden

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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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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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Input Parameter Generation

  • 22 parameters; varying degrees of computational development

    • Simple, straightforward, complex



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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 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 Manning’s 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)

  • 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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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


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