2018 Tennessee River basin average rainfall breaks record
Rainfall totals for Chattanooga for 2018 ranked 13th highest on record since 1879, but other areas across the Tennessee Valley received even more rain.
TVA continues to manage this excess rainfall, and it begins in Knoxville at their River Forecast Center, where they manage the Tennessee River system with the goals of flood control, navigation, recreation, hydroelectric power, and water quality and supply all in mind.
"We're staffed around the clock, making decisions about water levels, water released from the dams to achieve the most benefit possible for all those different objectives," James Everett, Manager of TVA’s River Forecast Center, said.
The River Forecast Center manages the water flow of the Tennessee River and its tributaries through 49 dams over about 41,000 square miles.
They have approximately 150 rain gauges across the watershed. Comparing these ground truth numbers with National Weather Service data, 2018 was the wettest year on record for the average rainfall calculated across the entire river basin.
"Brand new rainfall record, the most rainfall we've ever had in the valley. We have records that go back about 130 years, and so that kept us really busy trying to manage the runoff from that heavy rainfall," Everett explained.
The official record was a basin average of 67.1 inches in 2018, breaking the record of 65.1 inches set in 1973.
"This rainfall meant that we moved spillway gates at many of our dams and sluice gates, so it kept our crews busy that work at these dams," Everett stated.
This excess rainfall is also used as fuel for the hydroelectric turbines.
"It produces very low-cost energy, clean energy. Our fuel for that power source comes from Mother Nature. That is one of the side benefits of having extra rainfall," Everett said.
TVA manages the water levels for flood control by storing water behind mountain dams and then increasing flow rates once it stops raining.
"Levels in Chattanooga, we estimate without the dams in place would have been at flood stage or above flood stage, and we were actually able to use the dams to regulate river levels many feet below flood stage in this case."
After the wettest year on record for the Tennessee River basin in 2018, TVA is still releasing water from their upstream dams with levels above normal.