Modeling

The Water District has developed reservoir water quality models for each of its four major reservoirs as well as watershed models for the sub-basins within each reservoir's watershed.

Reservoir Models (WASP Model)

The Water District is using the USEPA's Water Quality Analysis Program (WASP) to simulate the biological, chemical, and physical reactions that occur in each of its four major reservoirs.   The WASP models help TRWD to:

• Predict the effect of hydrologic changes on the quality of the water (such changes include lake drawdowns and diversions to lakes from other watersheds)
• Predict the water quality benefits of Best Management Practices (BMPs) implemented within reservoir watersheds
• Predict impacts from point source discharges (both actual and proposed)

The Water District has linked the reservoir (WASP) and watershed (SWAT) models to determine the water quality impacts of activities such as farming and ranching practices, drought/flood conditions, and non-point source Best Management Practices.

Watershed Models (SWAT Model)

For each reservoir's watershed, the Water District is utilizing the USDA's Soil and Water Assessment Tool (SWAT) model to determine the runoff volumes and sediment and chemical mass loadings for multiple watershed sub-basins.

The SWAT model uses the GRASS Geographic Information System (GIS) to store and manage data such as farming; soil type, land use, topography, crop growth, precipitation, and other physical characteristics of the watershed.

Linking the Reservoir and Watershed Models

The watershed (SWAT) models have been linked to their respective reservoir (WASP) models to provide a comprehensive tool for water quality management of these vital water supply facilities.