The Tennessee River in Chattanooga rose nearly 5 feet after the heaviest rainfall in the Tennessee Valley in nearly two years this past weekend dumped more than 5 inches over most of the Tennessee Valley.
TVA is spilling water today through most of its mainstream dams to to help draw down rain-swollen reservoirs in East Tennessee. But without those reservoirs created by TVA's network of 49 dams on the river and its tributaries, TVA projects that the heavy rains would have flooded the Tennessee River another 15 feet or so, or at least 6 feet above flood stage in Chattanooga.
"We've had a tremendous amount of rain over the past several days and in the winter months there is far more runoff than in there is the summer when temperatures are warmer and there is more vegetation to limit runoff into the river," James Everett, manager of TVA' river forecasting center in Knoxville, said Monday. "These rains demonstrate why we have our network of TVA dams and the value of how we manage the river."
TVA's upstream reservoirs such as the Norris, Fontana and Douglas reservoirs held back much of the rainfall in East Tennessee. Norris Lake rose more than 10 feet over the weekend before TVA began sluicing water through the Norris Dam to bring the lake back down to its winter level.During winter months, TVA keeps Norris and Fontana lakes down by 20 feet below the reservoirs' summertime lake levels to provide water storage capacity to protect downstream communities such as Chattanooga.
Everett said some parts of the Tennessee Valley got 6 inches of rain over the past four days. That was the biggest rainfall in the Valley since April 2016.
The National Weather Service said there is a 40 percent chance of rain today and a much greater chance of rain on Wednesday.
"We expect another inch of rain later in the week, but the worst of the rain storms seems to be behind us," Everett said.
On Monday to help lower upstream reservoirs, 88,000 cubic feet per second of water was pouring through the Chickamauga Dam and the TVA powerhouse at the dam in Chattanooga, Everett said.
At the Nickajack Dam in Marion County, 100,000 cubic feet per second of water was flowing through the dam and its generating equipment..
Contact Dave Flessner at firstname.lastname@example.org or at 757-6340.
This story was updated Feb. 12, 2018, at 10:45 p.m.