The Tennessee Valley Authority says their dozens of dams are holding back the most rainfall the Tennessee River basin has seen from January through March since 1891.
The TVA last week in a release said 24.61 inches in those three months have helped fill TVA’s 49 dams with about 2.2 trillion gallons of water, breaking the recorded rainfall record set in 1891, when the basin saw 23.95 inches. That water eventually flows into west Kentucky, through Kentucky Lake and Lake Barkley, and into the Ohio River.
TVA River Operations Support Manager Darrell Guinn said while the record rainfall is causing the authority to act more cautiously with the release of water, all the dams and reservoirs are designed to hold back even more rain than the current situation. Yet, the rainfall isn’t the only factor for which TVA officials have to account.
“When you have wet periods, your ground moisture, your ground’s saturated. So your runoff rate is going to be higher. Runoff is what actually makes it into the river system,” Guinn said. “With a close eye on the forecast, and with updates from the National Weather Service, we stay ahead of it and prepare ahead of time and mitigate as much flood damage as we can.”
The TVA estimates 12.6 million gallons of water in the form of runoff have been managed, helping prevent almost $1 billion in potential damages to agriculture and structures. Guinn said it’s hard to determine if the record rainfall is an anomaly, or a part of a larger trend.
“I do think extremes seem to be getting stretched from dry periods to wetter periods,” Guinn said. “But as far as being able to predict year after year we’re going to see these totals, I don’t think the data is there yet.”
A brief on climate change from the U.S. The Environmental Protection Agency in 2016 reported Tennessee’s annual rainfall was increasing, with a higher potential for future flooding and droughts.
Guinn also said the TVA is working with other federal agencies to manage the water releases out of Kentucky Dam and Barkley Dam, to ultimately help control flood levels in vulnerable cities downstream, including Cario, Illinois. Ohio River levels have fallen slightly at Cairo since March 31, when the river peaked at 52 feet, about 20 feet above flood stage.
“Cairo has crested, and they’re beginning to fall. It will be a slow fall, as much of the Ohio Valley has received above normal rainfall as well,” Guinn said. “It’s really hard to predict a timeframe when everything will be back to normal, because it depends if we’ll continue to see above-normal rainfall.”
The TVA expects summer pool levels in Kentucky Lake and Barkley Lake to peak about three feet above normal as the authority manages flood control operations.