1. General Model Information

Name: Agricultural Non-Point Source pollution model

Acronym: AGNPS

Main medium: terrestrial
Main subject: hydrology, biogeochemistry
Organization level: landscape
Type of model: not specified (2D)
Main application: research
Keywords: non-point source pollution, water quality, soil erosion, GIS, agriculture, watershed


Jaewan Yoon
Department of Civil and Environmental Engineering
KDH 135
Old Dominion University
Norfolk, VA 23529-0241
Phone: (757) 683-4724
Fax: (757) 683-5354
e-mail: yoon@cee.odu.edu


Dr. Robert A. Young
USDA-ARS North Central Soil Conservation Research Laboratory
Morris, MN 56267
Phone:612 589-3411
Fax : 612 589-3787


Model developed to examine water quality as it is affected by soil erosion from agriculture and urban areas (Young et al., 1987). It is designed to be executed at the watershed scale.

AGNPS has three major components:

  1. hydrology,
  2. soil erosion and
  3. nutrient pollution.

The hydrological function provides prediction of runoff volume and peak flow rate. The soil erosion function includes soil erosion and sedimentation. The nutrient function analyzes nitrogen, phosphorous and chemical oxygen demand concentration in the runoff and sediment.

The model requires a total of 22 parameters for execution. These include: Digital Elevation Model (DEM) aspect and slope, soil, land use, and point source information. The model calculates information on the basis of a cell. AGNPS is a single event model for a watershed no larger than several thousand square acres.

Author of the abstract:

II. Technical Information

II.1 Executables:

Operating System(s): MS-DOS, UNIX(Solaris 2.5)
UNIX: There's also AGNPS model files (program and sample I/O data) for Unix (compiled for CEE Unix Lab's Solaris 2.5) are downloadable to your Unix, NOT for MS-DOS system.

II.2 Source-code:

Programming Language(s): C, FORTRAN and Pascal

II.3 Manuals:

see: II.1

II.4 Data:

III. Mathematical Information

III.1 Mathematics

III.2 Quantities

(source of these information: AGNPS description by Jaewan Yoon)

III.2.1 Input

AGNPS Input Parameters
  1. cell number (from)
  2. receiving cell number (to)
  3. SCS curve number
  4. land slope
  5. land slope shape factor
  6. field slope length
  7. channel slope
  8. channel sideslope
  9. Manning's roughness coefficient
  10. soil erodibility factor
  11. cover and management factor
  12. support practice factor
  13. surface condition constant
  14. aspect (direction of drainage)
  15. soil texture
  16. fertilization level
  17. fertilization availability factor
  18. point source indicator
  19. gully source level
  20. chemical oxygen demand (COD) factor
  21. impoundment factor
  22. channel indicator

III.2.2 Output

Output values for the whole watershed
  1. watershed description
  2. area (acres)
  3. area of each cell (acres)
  4. characteristic storm precipitation (inches)
  5. storm energy-intensity (EI) value
Output values at the watershed outlet
  1. runoff volume (inches)
  2. peak runoff rate (cfs)
  3. fraction of runoff generated within the cell
  4. Sediment (by particle size and in total)
  5. sediment yield (tons)
  6. sediment concentration (ppm)
  7. sediment particle size distribution
  8. upland erosion (tons/acre)
  9. channel erosion (tons/acre)
  10. amount of deposition (%)
  11. sediment generated within the cell (tons)
  12. enrichment ratio
  13. delivery ratio


  1. Nitrogen
  2. sediment associated mass (lbs/acre)
  3. concentration of soluble material (ppm)
  4. mass of soluble material in runoff (lbs/acre)
  5. Phosphorous
  6. sediment associated mass (lbs/acre)
  7. concentration of soluble material (ppm)
  8. mass of soluble material in runoff (lbs/acre)
  9. Chemical Oxygen Demand
  10. concentration (ppm)
  11. mass (lbs/acre)

IV. References

Young, R., C.A. Onstad, D.D. Bosch and W.P. Anderson.1987. AGNPS: Agricultural Non-Point Source Pollution Model: awatershed analysis tool. USDA-Agricultural Research Service. ConservationResearch Report 35., U.S. Department of Agriculture, Washington, D.C.
Young R.A., C.A. Onstad, D.D. Bosch, W.P. Anderson. 1989. AGNPS: A nonpoint-source pollution model for evaluating agricultural watersheds.
Jour. of Soil and Water Conservation. v44, n2.

V. Further information in the World-Wide-Web

VI. Additional remarks

Global change implications: The model could be important forglobal change research in examining large scale erosion patterns in urban andagricultural areas. Execution of the model should occur in areassusceptible to erosion. Because is it spatially explicit, data can potentially linked to a GIS for visualization.
Author :

Last review of this document by: T. Gabele: Tue Oct 7 1997
Status of the document: updated by Markus Neteler Mar 26 1998
last modified by Tobias Gabele Wed Aug 21 21:44:39 CEST 2002

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