Graham Sustainability Institute

Soil & Water Assessment Tool (SWAT)

October 2016

The Soil and Water Assessment Tool (SWAT) is a spatially referenced watershed model used to simulate the impacts of land use, land management, and climate on water quantity and quality. This graphic illustrates the general processes associated with developing and applying SWAT models. Learn more: SWAT FAQ

SWAT was developed by researchers within the U.S. Department of Agriculture, Agricultural Research Service (USDA, ARS) in the mid-1990s, and the model has undergone continual review and expansion since it was first developed. As a result, the model is extremely well-documented in a detailed user manual and contains over 1000 peer-reviewed journal articles that describe applications and enhancements. This physical model uses mathematical equations to represent watershed processes such as hydrology, soil erosion, crop growth, and nutrient cycling on the land and in the stream network on a daily time scale. SWAT is spatially-referenced to a specific watershed or sub-watershed. Within the model, the smallest spatial units are the hydrologic response units (HRUs) which generally have uniform soil type, land use, and slopes.

Keywords: Soil and Water Assessment Tool, land use, land management, climate, water quantity and quality, model, U-M Water Center