Understanding River Temperatures Saves Ratepayers Money

What does Tennessee River water temperature have to do with your power bill? A lot. Find out why.

Early in the morning, a flotilla of boats containing TVA engineers fan out across Wheeler Lake in northern Alabama. Their mission is not to respond to a problem, but to deploy sensors at various points in the water column. These devices will gather data so TVA can make better decisions in order to protect the ecosystem and save ratepayers money.

Daniel Saint, TVA civil engineer for the company’s River Forecast Center is on one of those boats. Saint and his fellow engineers are executing a complex plan. They are making a 3D water-temperature model of the lake—an integral part of the Tennessee River watershed—so TVA can better forecast water temperatures throughout the year.

“People understand that water temperature affects wildlife,” says Saint. “What folks may not realize is that water temperature can also have a positive or negative affect on their power bill.”


The Tennessee Valley Authority is the largest public utility in the United States. As a public utility, the company’s ratepayers fund the organization, which is responsible for holding rates as low as is feasible.

“Since there are no shareholders, TVA passes costs and savings directly back to the Valley’s local power companies, and ultimately to the person paying their power bill,” Saint explains. “Getting data to be more efficient will allow [TVA] to reduce costs.”

How so? TVA’s Browns Ferry Nuclear Plant draws cooling water from the lake. TVA hopes improved temperature data will enable the company to when—and when not—to make use of expensive cooling systems, ultimately cutting the cost of producing electricity.

“It costs a lot of money to operate our cooling towers at Browns Ferry,” says Saint. “With seven cooling towers at the plant, we can avoid a lot of costs to the rate payers if we can safely avoid running them.”

Data-Driven Cost Cutting

While TVA continually collects data and updates its river temperature database, technological advancements including 3D data collection and modeling technology can produce improved forecasting models that were unavailable just a few years ago, Saint notes.

“3D technology makes this study different than any other data we’ve gathered so far,” says Saint. “The models we are creating are more precise, and we can duplicate the study in order to reduce costs at all of our TVA facilities along the river.”

Saint explains that with the 3D temperature model the company will “more precisely know when to turn on the cooling towers to improve both plant and environmental safety,” and when to turn them off to “avoid unnecessary costs to the ratepayers.”

TVA also wants to collect temperature data to ensure that heated water discharged by Browns Ferry does not impact the river's ecosystem.

According to TVA and the United States Geological Survey, 96 percent of the water pulled from the Tennessee River goes back into the river. Saint hopes the data will help TVA understand how the temperature of returned water affects the river, and how the company can adjust its operations.

“At the end of the day, it’s all about making better decisions for our ratepayers and being better stewards of the river and its ecosystem,” he concludes.

TVA. Lasers. Spaghetti?

Today, TVA surveyors deploy the latest technology—3-D laser scanning—capable of mapping the spaghetti of piping and conduits in engineering spaces with millimeter accuracy. Read more about 3-D laser scanning.