SWAT is a river basin scale model developed to quantify the impact of land management practices in large, complex watersheds. SWAT is a public domain model actively supported by the USDA Agricultural Research Service at the Grassland, Soil and Water Research Laboratory in Temple, Texas, USA. SWAT allows a number of different physical processes to be simulated in a watershed. For modeling a watershed may be partitioned into a number of sub-watersheds. This a catchment model is able to quantify the impact of land management practices on flow and water quality. The model has widespread use internationally.


SWAT was developed to predict the impact of land management practice on water, sediment and agricultural chemical yields in large complex watersheds with varying soils, land use and management conditions over long periods of time.

Latest Version SWAT2009 revision in 2011
State of Development Stable Release
Current Development Activity Active development by USDA and various research organasations.

Development Contact

Jeff Arnold - Hydraulic Engineer
+1 254 770-6502
Grassland, Soil & Water Research Laboratory, USDA-ARS
808 East Blackland Road Temple, Texas 76502 USA


Intended End Users Specialist modellers supporting land and water managers
Spatial Extents Unknown
Spatial Dimensions Unknown
Temporal Resolutions Days
Temporal Extents Years, Decades
Steady State or Dynamic Dynamic

Input & Output Data


Open/Closed Source Unknown
Licence Type

User Information

Operating Systems MS Windows
Software Needed Unknown
User Interface Please Select
Ease of Use Moderate
Use in Policy Process Plan (Policy Formulation), Do (Policy Implementation)

Comprehensive documentation of theory and I/O formats. SWAT 2009 Theoretical Documentation: SWAT 2009 Input/Output File Documentation:

Support No formal support. Training seminars are run regularly and there is an annual SWAT conference.
Users Forum Forum available

Technical Considerations

Programming Language Fortran for the main engine code. ArcSWAT is written in a .net language
Methods included for calibration and validation Calibration tools are provided in the SWATCUP tool from Eawag
Analytical Techniques Input/output
Keywords soil, water, sediment, chemical, land use, land management

SWAT Model Home Page -

An OpenMI compliant version is being developed, see

HydroModeller version available. SWAT home page -

Key References

P. W. Gassman, M. R. Reyes, C. H. Green, J. G. Arnold - The Soil and Water Assessment Tool: Historical development, applications, and the future research directions  -

Ekanayake, J.C.; Davie, T. (2005). The SWAT model applied to predicting nitrate fluxes in the Motueka catchment. Motueka Integrated Catchment Management Report Series. Landcare ICM Report No. 2004-2005/04. Landcare Research. Lincoln, New Zealand. -

Associated Case Studies

  • IDEAS - ICM Motueka Catchment

    The ICM Motueka Research Programme was a 9 year programme which commenced in July 2000 and concluded in September 2010, and whose goal was to conduct multi-disciplinary, multi-stakeholder research to provide information and knowledge that will improve the management of land, freshwater, and near-coastal environments in catchments with multiple, interacting, and potentially conflicting land uses.  The Motueka River has been used for this project.

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  • SWAT - Motueka River Watershed

    The impacts of land cover in critical water resources in the Motueka River catchment was modelled using SWAT as part of an Integrated Catchment Management (ICM) project.

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  • Other Key Case Studies

    Swat modeling of N fluxes in Motueka River International Case Studies see: