Ecosystems Research Division

Water quality models simulate the fate of pollutants and the state of selected water quality variables in water bodies. They incorporate a variety of physical, chemical, and biological processes that control the transport and transformation of these variables. Water quality models are driven by hydrodynamics, point and nonpoint source loadings, and key environmental forcing functions, such as temperature, solar radiation, wind speed, pH, and light attenuation coefficients. The external drivers may be specified from observed data bases, or simulated using specialized models describing, for example, the water body hydrodynamics or the watershed pollutant loading. The internal forcing functions may also be specified from databases, or calculated within the water quality model using a range of empirical to mechanistic process formulations. Examples include temperature, pH, and light attenuation.

Some water quality models focus on particular problem contexts, such as dissolved oxygen depletion or organic chemical fate. Other models are more general, and can be used to simulate different water quality problems. Similarly, some water quality models specialize in particular water body types, such as lakes or streams. Others are more general, and can be applied to several types of water bodies. Each water quality model has its own set of characteristics and requirements. The reader should thoroughly review the documentation and consider its strengths, limitations, and data requirements prior to application.

Select a Water Quality model for additional information or to download.

• WASP
• QUAL2K
• Aquatox
• EPD-RIV1

 Technical Support Center fact sheet (PDF, 2 pp., 733 KB, about PDF)

TMDL fact sheet (PDF, 2 pp., 697 KB, about PDF)