Possum Kingdom Lake – using computer models to keep it clean

Possum Kingdom Lake has a well-deserved reputation for clean water because the Brazos River Authority has worked to protect what nature gave it – a pristine quality due to depth and geology.

The attractiveness of the lake as a water source, residential community and recreational playground also poses risks to that purity. Consequently, BRA has launched a water quality modeling project to preserve the cleanliness as population grows and development expands.

“This project fits perfectly into BRA’s longstanding mission to protect the water resources in the Brazos River Basin,” said Tiffany Malzahn, chief environmental officer for BRA. “It is innovative and forward-looking.”

The project will develop a toolkit of computer models that enable BRA to make decisions based on scientific data about how water quality might be impacted by changes in land use in surrounding areas. First, a baseline will be established by assessing current and past water quality in the study area, which is shown in the map below.

Then two models will be developed:

• A watershed model to assess the results of potential changes in land use, such as ranch land being developed into residential areas.
• A lake model that will combine the watershed model results with other data such as river flow, water levels, temperature, and nutrients that have seasonal patterns.

The complete model toolkit will evaluate how future scenarios might change the lake’s water quality and whether planning efforts might reduce pollution risks. These advanced, decision-support tools will allow BRA to take action to protect the lake as residential and industrial density increase.

“We know that development is going to happen, and these digital models will provide the data we need to make informed decisions,” said Randall McCartney, Regional Lake Operations Manager.

The lake area is a popular destination for water recreation, hiking, and camping. Also, Texas’ population is forecast to increase and that means once rural areas such as Palo Pinto County will draw the attention of both industry and land developers.

The lake’s limestone basin, canyon formation and low levels of suspended matter make it exceptionally clean, but also sensitive to changes in land use around the lake and upstream in the Upper Brazos River watershed.

During the course of the project, feedback from stakeholders will be considered and incorporated as appropriate. Stakeholders include homeowners, businesses, water suppliers, cities and regulatory agencies.

“Many of our local stakeholders have already provided useful input into lakeside development along with their concerns for water quality,” said Malzahn.

An External Science Advisory Panel will review and provide input on key assumptions, decisions, and recommendations from stakeholders and regulatory agencies. It will provide quality assurance and control for the project.

The models will be calibrated so that estimated probabilities align with historical data and actual occurrences.

The project was launched and October 2024 and is being led by a consultant team headed by Hazen/Aqua Strategies Inc. It is expected to last three years.

“This project enables BRA to proactively look at the changes that are expected to happen over the next 10, 20, or 30 years,” said Malzahn, adding that “the scientific methodology offers an important opportunity to analyze key environmental variables as a part of the overall decision-making process.”