SWAT (Soil & Water Assessment Tool)
Criterion | Explanation |
General Description | SWAT (Soil & Water Assessment Tool) is a river basin scale model developed to quantify the impact of land management practices in large, complex watersheds. SWAT is public domain software actively supported by the USDA Agricultural Research. It is a hydrology model with the following components: weather, surface runoff, return flow, percolation, evapotranspiration, transmission losses, pond and reservoir storage, crop growth and irrigation, groundwater flow, reach routing, nutrient and pesticide loading, and water transfer. The model's webpage is at: https://swat.tamu.edu/ |
Model Domain | The model domain is flexible, as specified by user. |
Developer | USDA Agricultural Research Service (ARS) and Texas A&M AgriLife Research |
Hardware computing requirements | Windows; 2GB free space if using 32-bit system |
Code language | FORTRAN for scientific code; Python and Javascript for user interface |
Original application | The original application of the SWAT model was for agriculture. SWAT was developed to predict impacts of land management practices on water, sediment and pollutant yields from watersheds. The model simulates physical processes associated with water movement, sediment erosion, crop growth and nutrient cycling. |
Public/proprietary and cost | The model is in the public domain; no cost. |
Physically or empirically based | The model is physically based. |
Mathematical methods used | The following mathematical methods are used by SWAT:
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Input data requirements | Watershed input files with routing and land parameters defined, precipitation, temperature, solar radiation, wind speed, relative humidity, potential evapotranspiration, weather forecast, land cover/plant growth, pesticide, fertilizer, urban pollutant build-up/washoff, septic, subbasin, pond/wetland, water use, soil chemical and physical characteristics, and main water channel parameters files. The model also requires water quality files associated with QUAL2E transformations in main channels and streams. |
Outputs | Flow (surface runoff, lateral flow contribution to streams, groundwater, water percolation, drainage tile, stored soil water, actual and potential evapotranspiration, water yield) and water quality (sediment yield, nitrate loadings, plant uptake of N, soluble and organic phosphorus loadings, ammonia distributions in flow and solids and changes in bacterial loadings) by sub-catchbasin; There are several graphical user interfaces (GUIs) available, both GIS based (ArcGIS extension) and non-GIS based. |
Pre-processing and post-processing tools | Several pre- and post-processing tools are available, both in the public domain and for purchase. |
Representation of uncertainty | Offers automated method for uncertainty analysis/auto-calibration. Use SWAT-CUP as a calibration/uncertainty or sensitivity program. |
Prevalence | The model is widely used in the research and commercial fields, with several hundred peer-reviewed publications. |
Ease of use for public entities | The model requires training to use; however, there is much support available, through training and active user groups. The hardware/software requirements are easily obtained. |
Ease of obtaining information and availability of technical support | Product information available online. User support available from user groups and development team. |
Source code availability | Yes, the source code is available for download. |
Status of model development | The SWAT model has undergone active development. A completely revised version of the SWAT model called SWAT+ has been released in 2018. SWAT+ provides a more flexible spatial representation of interactions and processes within a watershed. |
Challenges in integration | Challenges to integration are few, given the open source code and active user community. Spatial variation is specified on the hydrologic response unit (HRU) level. The temporal scale is an hourly time step. |