Last year was the second wettest year on record in the Tennessee Valley, following record rains in 2018, TVA said today.
TVA said precipitation totals in the Tennessee River basin averaged nearly 15 and a half inches above normal during 2019, and included the wettest February on record when the rain-swollen river in Chattanooga rose 12 feet above its normal levels.
Darrell Guinn, manager of TVA's River Forecast center in Knoxville, said today that 2020 is also starting out wetter the normal with more than 2 inches of rain predicted in the next couple of days across TVA's 7-state region.
"Our forecasts call for wetter than normal weather in the next three months," Guinn said.
TVA uses its network of 49 dams on the Tennessee River and its tributaries to help control the flow of the Tennessee River, the fifth biggest river in the United States. Last year, TVA estimates that its flood control efforts in 2019 helped avert $1.8 billion of flood damages in the Tennessee Valley, including $1.6 billion in Chattanooga. That was the highest level of averted flood damages in the 87-year history of TVA.
Chattanooga is the drainage basin for rainfall across East Tennessee and parts of western Virginia and North Carolina and Northeast Georgia.
"Chattanooga is a bottleneck and is the most susceptible to flooding in the region," Guinn said.
Most of the benefits from TVA's flood management of the Tennessee River in 2019 came in February when more than 11 inches of rain in a couple of weeks swelled rivers and lakes in the TVA region. Although there was localized flooding in Chattanooga and some limited damages during February, TVA estimates without its dams much of Chattanooga would have been underwater, causing an estimated $1.4 billion in damages last February alone.
During the peak of the February flooding, TVA was able to store nearly 3.6 trillion gallons of water -- or more than what New York City consumes in a decade -- by holding back flows in its upstream reservoirs, some of which rose as much as 26 feet in depth during sustained rains in February.
The heavy rains last winter suspended barge traffic for weeks on the Tennessee Valley, but TVA continued to benefit from the heavy rains with extra power generation from its 29 hydroelectric dams, which provide about 10% of TVA's electricity at the lowest cost of any of the utility's power generation.
In 2019, hydro generation was 16% above normal for TVA, according to Tom Barnett, general manager of River Management for TVA.
With anywhere from 2-4 inches of rain forecast in Chattanooga today and Friday, TVA is spilling water today through its main river dams below Chattanooga at Nickajack, Guntersville, Wheeler, Wilson, Pickwick and Kentucky dams. TVA suspended spilling activity at its Chickamauga Dam on Tuesday and is using its reservoirs to help hold back rain runoff from this week's storms, Guinn said.
Although three of the six wettest years in TVA history have come in the past seven years, Barnett said TVA isn't altering its approach to flood management.
"These (rainfall totals) tend to go in cycles," he said, noting that the Tennessee Valley suffered from some of its worst drought years in the 1980s.