AGNPS is a tool for use in evaluating the effect of management decisions impacting a watershed system. The AGNPS system is a direct update of the AGNPS 98 & 2001 system of modules containing many enhancements.

The term "AGNPS" now refers to the system of modeling components instead of the single event AGNPS, which was discontinued in the mid-1990's. These enhancements have been included to improve the capability of the program and to automate many of the input data preparation steps needed for use with large watershed systems.

New to AnnAGNPS Version 4.00, the model includes a newly developed ephemeral gully feature, an automated runoff calibration feature, enhance tile drainage features to describe controlled drainage or surface tile inlet management options, and more input and output options. The AGNPS Arcview interface has been better integrated with the components needed to develop AnnAGNPS datasets. The capabilities of RUSLE, used by USDA-NRCS to evaluate the degree of erosion on agricultural fields and to guide development of conservation plans to control erosion, have been incorporated into AnnAGNPS. The capability of importing RUSLE2 databases into AnnAGNPS is also now available.  This provides a watershed scale aspect to conservation planning. The channel network evolution model has been updated and enhanced as CCHE1D, and the stream corridor model CONCEPTS, has been developed for analysis of reaches within a stream network, for watersheds that require a more comprehensive evaluation of the stream system, when channel evolution, erosion, or in-stream structures produce problems that the simplified channel system of AnnAGNPS is not designed for.  An updated output processor now provides convenient compilation of loadings at any point in the watershed on an event, monthly or annual basis.

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; and (2) an input editor to initialize, complete, and/or revise the input data.

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.