Tailwater Improvements

Hydropower producers are faced with two environmental problems that can affect the area downstream from a dam, called the tailwater: low concentrations of dissolved oxygen in the water released through the dam during generation, and dry riverbeds that can result when hydropower is shut off.

Since the early 1990s, TVA has spent about $60 million to address these problems. In the first stage of the improvement effort, TVA installed equipment to increase dissolved oxygen concentrations below 16 dams. At the same time, TVA made operational changes and installed additional equipment to ensure minimum water flows through its dams.

TVA has since completed a second round of improvements. Oxygen systems have been installed or enhanced at nine projects, and two new autoventing turbines have been installed at Boone Dam. The additional oxygenation capacity will help offset the increased oxygen demands associated with delaying the seasonal drawdown of TVA reservoirs until Labor Day. The delayed drawdown is part of a new operating policy approved by the TVA Board in June 2004.

Link to the pages below to learn more about TVA’s successes in addressing these two areas.

Boosting oxygen concentrations

Learn why low-oxygen conditions can occur below hydropower dams and find out about the different technologies that TVA is using to address this problem at specific locations.

Maintaining a wetted riverbed

Learn how generating electricity can affect water flow below hydropower dams and find out what TVA is doing to maintain wetted habitat in the riverbeds below its dams.