AGNPS Watershed Modeling with GIS Databases U.S. Department of Interior U.S. Geological Survey

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

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

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

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

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

Georgia Watersheds

Indiana Watershed

Washington Watershed

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

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

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

AGNPS Data Generator

Input Parameter Generation 22 parameters; varying degrees of computational development Simple, straightforward, complex

Input Parameter Generation

Details on Generation of Parameters Cell Number Receiving Cell Number SCS Curve Number Uses both soil and land cover to resolve curve number

Details on Generation of Parameters (continued) Slope Shape Factor

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)

Details on Generation of Parameters (continued) Type of Channel Uses TARDEM program Creates a Strahler steam order

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

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

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

Creating AGNPS Input, Output, and Images (continued)

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

Creating AGNPS Input, Output, and Images (continued)

Creating AGNPS Input, Output, and Images (continued)

Creating AGNPS Input, Output, and Images (continued)

Creating AGNPS Input, Output, and Images (continued)

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

AGNPS Watershed Modeling with GIS Databases U.S. Department of Interior U.S. Geological Survey