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What is AGNPS
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AGricultural Non-Point Source Pollution Model (AGNPS) is a joint USDA-Agricultural Research Service and -Natural Resources Conservation Service system of computer models developed to predict non point source pollutant loadings within agricultural watersheds. It contains a continuous simulation, surface runoff model designed to assist with determining BMPs, the setting of TMDLs, and for risk & cost/benefit analyses. The set of computer programs consist of: (1) input generation & editing as well as associated databases; (2) the "annualized" science & technology pollutant loading model for agricultural-related watersheds (AnnAGNPS); (3) output reformatting & analysis;  and (4) the integration of more comprehensive routines (CCHE1D) for the stream network processes;  (5) a stream corridor model (CONCEPTS);   (7) an instream water temperature model (SNTEMP); and (8) several related salmonid models (SIDO, Fry Emergence, Salmonid Total Life Stage, & Salmonid Economics). Not all of the models are electronically linked but there are paths of common input/output that, with the use of standard text editors, can be linked.

"Download a Powerpoint 2002 overview of AGNPS"

AGNPS System Diagram
AGNPS System

The input programs include: (1) a GIS-assisted computer program (TOPAZ with an interface to AGNPS) to develop terrain-following cells with all the needed hydrologic & hydraulic parameters that can be calculated from readily available DEM's; (2) an input editor to initialize, complete, and/or revise the input data; and (3) an AGNPS-to-AnnAGNPS converter for the input data sets of the old single-event versions of AGNPS (4.03 & 5.00).

AnnAGNPS includes up-to-date technology (e.g., RUSLE & pesticides) as well as the daily features necessary for continuous simulation in a watershed.

Outputs related to soluble & attached nutrients (nitrogen, phosphorus, & organic carbon) and any number of pesticides are provided. Water and sediment yield by particle size class and source are calculated. A field pond water & sediment loading routine is included for rice/crawfish ponds that can be rotated with other land uses. Nutrient concentrations from feedlots and other point sources are modeled. Individual feedlot potential ratings can also be derived using the model.

The application of CCHE1D for stream networks and CONCEPTS for stream corridors include more detailed science for the channel hydraulics, morphology, and transport of sediments and contaminants.