Normandy Reservoir - Optimization of Water Releases

Bedford, Coffee, Hickman, Humphreys, Marshall, Maury, Perry and Williamson Counties, Tennessee

The Tennessee Valley Authority (TVA) is preparing an Environmental Assessment (EA) to address its proposal to modify how TVA measures flow targets of water releases from Normandy Dam into the Duck River. Under the Proposed Action, TVA would begin releasing water to meet a target at the Shelbyville, TN gage (28 miles downstream of the dam) that is based on the average flows at Shelbyville over the course of a week (through 2400 hours on Sunday) rather than releasing flows to maintain the Shelbyville flow target “instantaneously” (measured during one instant in time).

TVA is not proposing to modify the reservoir guide curve of Normandy Reservoir or change the minimum flows released from the dam.

In addition, TVA would maintain a new minimum instantaneous flow requirement to augment the weekly average flow target; TVA would be required to meet this minimum instantaneous flow requirement even if the average flow for any day or combination of days of the week was considerably higher than the weekly target.

The draft EA was made available for public review and comment on May 29, 2024. TVA plans to complete its review of the proposal by the end of 2024. 

The Normandy Reservoir/Duck River region experienced severe drought conditions during 2007 and 2008. As a result, TVA and the Tennessee Duck River Development Agency (TDRDA), which represents seven water utilities serving approximately 250,000 people and industries in the region, have been working collaboratively with numerous consulting agencies and stakeholders to reduce the potential negative effects of drought conditions in the future.

Optimization of Normandy Reservoir Releases

Under current operation of Normandy Reservoir, TVA provides instantaneous flow (flows specified for a fixed period of time) of 155 cfs from June through November, and 120 cfs from December through May, 28 river miles downstream at Shelbyville. In addition, TVA’s current guidelines for Normandy Reservoir stipulate pool elevations of 875 feet from June through November, and 864 feet for flood control from December through May. TVA also maintains a minimum flow from Normandy Dam of 40 cfs year round.

In 2013, the TDRDA developed an Optimization of Normandy Reservoir Releases (ONRR) report to assess water release modifications to precisely meet flow targets at Shelbyville, with the goal of preserving water and storage in Normandy Reservoir. A main recommendation of the ONRR was to implement a weekly average flow target at Shelbyville, instead of the current instantaneous flow targets. This recommendation is the basis for the proposed action in the draft EA. Under the proposal, TVA would revise its flows as follows:

• Weekly average flow of 120 cfs (measured at midnight on Sunday) for the period of December 1 through May 31, with a minimum instantaneous flow threshold of 100 cfs during this period;
• Weekly average flow of 155 cfs (measured at midnight on Sunday) for the period of June 1 through November 30, with a minimum instantaneous flow threshold of 135 cfs during this period.

The proposed action would provide TVA with greater flexibility to meet operational goals during normal conditions while continuing to meet key operational goals related to water quality, aquatic habitat, and water supply. The proposal also has the potential to assist TVA and its partners in addressing drought conditions in the watershed that may affect water supply in the region.

Public Involvement

During the 30-day public review and comment period, which concluded June 28, 2024, TVA invited the public to review and comment on the draft EA. The comments submitted during this period are currently being reviewed by TVA and will be considered as the analysis is completed.

TVA hosted a virtual webinar on June 13, 2024, to provide information about the proposal. A recording of the virtual webinar can be viewed by clicking the link below.

Public Virtual Webinar - Recording (6/13/2024)