October Reservoir System Update

TVA provides monthly updates on the operation of TVA-managed reservoirs by e-mail. To sign up for future updates, provide feedback, change your e-mail address, or have your address removed from this distribution list, please send an e-mail request to reservoirupdate@tva.com.

Rain and runoff

Most of September was dry in the eastern Tennessee Valley, but the rainfall total for the month ended up above normal thanks to two days of steady rain at month’s end. Eastern Valley rainfall for the year totaled 31.7 inches at the end of September, which is 7.4 inches below normal.

Runoff (the amount of water that reaches the river system when it rains instead of being absorbed into the ground) is currently 87 percent of normal in the eastern Valley.

Reservoir elevations

On average, the elevation of tributary storage reservoirs decreased by about five feet during the month of September as TVA continued the annual drawdown to winter flood-damage-reduction levels. Tributary reservoirs were slightly higher than normal on Oct. 1, but comfortably below their flood-guide elevations. (Flood-guide elevations reflect the amount of storage allocated in tributary reservoirs for flood-damage reduction during different times of the year. The operating objective is to keep the reservoir level at the dam at or below this elevation to be ready for flood events. A reservoir may rise above its flood-guide elevation as a result of large inflows, but the water level is lowered to the flood-guide elevation as soon as it can be done without increasing downstream flood damage.)

Blue Ridge Reservoir is a special case. TVA began a deep drawdown on Blue Ridge in mid-July. The reservoir is being lowered to an elevation between 1620 and 1630 feet above sea level—compared to its normal winter flood-damage-reduction level of 1668—as part of a project to rehabilitate the 79-year-old dam. Get an update on this project below.

Reservoirs along the main Tennessee River—Fort Loudoun, Watts Bar, Chickamauga, Nickajack, Guntersville, Wheeler, Wilson, Pickwick, and Kentucky—were all within their normal operating ranges on Oct. 1.

1 Water elevation at the dam in feet above mean sea level
2 Flood guide elevations show the amount of storage allocated for flood damage reduction during different times of the year. The amount of storage varies with the potential flood threat. Flood-guide elevations are lowest from Jan. 1 through mid March because winter storms are generally larger, occur more frequently, and produce more runoff. Flood-guide elevations increase between mid-March and June 1 as the risk of flooding decreases. They are highest from June 1 through Labor Day to support summer reservoir recreation. After Labor Day, TVA begins the unrestricted drawdown to Jan. 1 flood-guide elevations.

Reservoir operations

Since Labor Day, TVA river operations have focused primarily on two objectives, according to David Bowling, manager of TVA’s River Forecast Center in Knoxville. “We are working to lower reservoir elevations to winter flood-damage-reduction leve