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Reservoir releases improvements

Water Quality Improvements at Tributary Dams

The methods TVA uses to improve water quality below tributary dams depend on the conditions found at each site. To read about what’s being done at a particular dam, scroll down the page or choose from the list at right.

Apalachia Dam

TVA uses autoventing turbines to improve the quality of the water released from Apalachia Dam. This system allows air flow into low-pressure zones just below the turbines to create many small air bubbles. Oxygen from the bubbles is absorbed into the oxygen-poor water as it flows through the dam.

In addition, TVA releases, or pulses, water through Apalachia Dam at regularly scheduled intervals (30 minutes of generation every four hours) to keep the downstream riverbed from going dry and to sustain the health of the aquatic environment.

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Blue Ridge Dam

TVA uses an oxygen-injection system to improve the quality of water released from Blue Ridge Dam. Perforated hoses suspended above the reservoir bottom bubble gaseous oxygen into the upstream water just before it’s pulled through the dam.

A small hydroelectric turbine is also used at Blue Ridge to provide a minimum flow of water downstream when the primary turbine is not operating. This helps to keep the riverbed from drying out and to provide additional habitat for fish and other aquatic life.

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Boone Dam

TVA uses autoventing turbines to improve the quality of water released from Boone Dam. Aerating turbines use low-pressure areas to draw air into the turbine area as power is being generated. The oxygen in the air is then absorbed into the oxygen-poor water as it flows through the dam. The newest generating units at Boone were specifically designed for this purpose. The other two units were modified to draw air into the water.

This innovative technology efficiently introduces air flow into low-pressure zones just below the turbines to create many small air bubbles. Oxygen from the bubbles is absorbed into the oxygen-poor water as it flows through the dam. Operators can route the inflow of air through three different pathways into the turbine area, which makes it possible to transfer a significant amount of oxygen into the water with only a slight drop in generating efficiency.

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Chatuge Dam

TVA uses an infuser weir to improve the quality of water released from Chatuge Dam. The weir is a small dam located downstream from the powerhouse. When power is being generated, water flowing from the dam fills the pool above the weir and overflows across a deck made of steel grating. The water flows through the slots in the decking, creating a series of waterfalls that introduce air into the water. The grating helps break up the falling sheets of water, entraining more air as the water falls into the downstream pool. This entrained air creates millions of bubbles in the water below the weir, producing higher dissolved oxygen levels downstream.

The Chatuge weir also maintains a minimum flow of water downstream from the dam and weir during periods when the turbines are not operating. This is accomplished by means of special valves near the bottom of the weir that slowly releases a constant flow of water as the weir pool drains. When no hydro generation is scheduled, TVA releases water from the dam twice a day to refill the weir pool. This process helps to prevent the riverbed from drying and to provide additional habitat for fish and other aquatic life.

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Cherokee Dam

Three different systems are available at Cherokee Dam to ensure that aeration targets are met. A technology called autoventing turbines introduces air flow into low-pressure zones just below the turbines, which results in many small air bubbles. Oxygen from the bubbles is absorbed into the oxygen-poor water as it flows through the dam. Surface-water pumps are also used at Cherokee. These pumps, which resemble large, slowly turning ceiling fans, push warm, oxygen-rich surface water downward to the turbine intakes, where it is mixed with oxygen-poor water. The oxygen-rich water flows through the dam during hydropower generation.

If additional aeration is needed, TVA uses an oxygen-injection system. Perforated hoses suspended above the reservoir bottom bubble gaseous oxygen into the upstream water before it’s pulled into the dam.

TVA also releases, or pulses, water through the dam at Cherokee Dam at regular intervals to provide a minimum flow of water downstream when hydro generation is not scheduled. This helps to prevent riverbed dry-out and benefits fish and other aquatic life.

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Douglas Dam

Three different systems are used to improve the tailwater at Douglas Dam. One system is autoventing turbines, which introduces air flow into low-pressure zones just below the turbines to create many small air bubbles. Oxygen from the bubbles is absorbed into the oxygen-poor water as it flows through the dam.

Surface-water pumps are also available at Douglas. These pumps, which resemble large, slowly turning ceiling fans, push warm, oxygen-rich surface water downward to the turbine intakes where it is mixed with oxygen-poor water. The aerated water flows through the dam during hydropower generation. If additional aeration is needed, TVA uses an oxygen-injection system. Perforated hoses suspended above the reservoir bottom bubble oxygen into the water before it’s pulled into the dam.

TVA also releases, or pulses, water through the dam at Douglas at regular intervals to provide a minimum flow of water downstream when hydro generation is not scheduled. This helps to prevent riverbed dry-out and benefits fish and other aquatic life.

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Fontana Dam

TVA uses autoventing turbines to improve the quality of the water released from Fontana Dam. This technology introduces air flow into low-pressure zones just below the turbines to create many small air bubbles. Oxygen from the bubbles is absorbed into the oxygen-poor water as it flows through the dam.

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Fort Patrick Henry Dam

Dissolved oxygen levels in the water released from Fort Patrick Henry Dam are improved through the operation of the autoventing turbines upstream at Boone Dam. The system introduces air flow into low-pressure zones just below the turbines, which creates many small air bubbles. Oxygen from the bubbles is absorbed into the oxygen-poor water as it flows through the dam.

TVA also releases water through the dam at Fort Patrick Henry at regular intervals, a process called pulsing, to provide a minimum flow of water downstream when hydro generation is not scheduled. This helps to keep the riverbed from drying out and benefits fish and other aquatic life.

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Hiwassee Dam

Two different systems are available at Hiwassee Dam to ensure that aeration targets are met. In a technology called autoventing turbines, air flow is introduced into low-pressure zones just below the turbines to create many small air bubbles. Oxygen from the bubbles is absorbed into the oxygen-poor water as it flows through the dam.

If additional aeration is needed, TVA uses an oxygen-injection system. Perforated hoses suspended above the reservoir bottom bubble oxygen into the water before it’s pulled through the dam.

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Norris Dam

TVA uses autoventing turbines to improve the quality of water released from Norris Dam. This innovative technology efficiently introduces air flow into low-pressure zones just below the turbines to create many small air bubbles. Oxygen from the bubbles is absorbed into the oxygen-poor water as it flows through the dam. Operators can route the inflow of air through three different pathways into the turbine area, which makes it possible to transfer a significant amount of oxygen into the water with only a slight drop in generating efficiency.

If additional aeration is needed, TVA uses an oxygen-injection system. Perforated hoses suspended above the reservoir bottom bubble oxygen into the water before it is pulled into the dam.

A re-regulating weir is also used at Norris to provide some aeration and to maintain a minimum flow of water downstream of the weir between periods of hydroelectric generation. The weir stretches across the river from bank to bank on both sides of Hibbs Island, about two miles downstream from Norris Dam. A timber-crib structure that’s built out of six-inch timbers and filled with loose rock, the weir creates a pool that is filled when power is being generated and then gradually drains through low-level valved pipes when the turbines are shut off. The valved pipes allow a constant downstream flow from the weir as the pool drains. That process maintains a minimum flow of water downstream of the dam and weir, which helps to prevent riverbed dry-out and benefits fish and other aquatic life.

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Nottely Dam

Two different systems are used to improve the quality of water released from Nottely Dam. Air blowers force air into the water flowing through the dam. If additional aeration is needed, TVA uses an oxygen-injection system. Perforated hoses suspended above the reservoir bottom bubble oxygen into the water before it is pulled into the dam.

A small hydroelectric turbine is also used at Nottely to provide a minimum flow of water downstream when the primary turbine is not operating. This helps to prevent riverbed dry-out and benefits fish and other aquatic life.

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South Holston Dam

Two different systems are used at South Holston Dam to ensure that aeration targets are met. Most of the aeration is provided by a labyrinth weir located below the dam. It consists of wooden walls made of interlocking timbers in a repeating “W” design and held in place by reinforced-concrete piers and midspan supports. The water gains oxygen as it plunges over the top of the 7.5-foot weir walls, much as it would in a natural waterfall.

The South Holston weir also serves to maintain a minimum flow of water downstream of the dam. During periods when the turbines are not operating, valved pipes located near the bottom of the weir allow controlled drainage of the weir pool. When no hydro generation is scheduled, TVA releases water through the turbines twice a day to refill the weir pool. This helps to prevent riverbed dry-out and benefits fish and other aquatic life.

Additional aeration is created by autoventing turbines, a technology in which air flow is introduced into low-pressure zones just below the turbines to create many small air bubbles. Oxygen from the bubbles is absorbed into the oxygen-poor water as it passes through the turbine area.

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Tims Ford Dam

At Tims Ford Dam, TVA uses two large air blowers to protect conditions in the tailwater. These blowers force air into the water as it passes through the dam. If additional aeration is needed, TVA uses an oxygen-injection system. Perforated hoses suspended above the reservoir bottom bubble oxygen into the water before it is pulled into the dam.

To maintain a consistent flow of water in the downstream riverbed when hydroelectric generation is shut off, TVA releases water through the sluiceway at the dam. The sluiceway and/or spillway consists of vertical slots in the dam that can be opened to release water from Tims Ford Reservoir without passing it through the penstock and turbine area.

Tracking water temperatures on the Elk River

TVA monitors water temperatures in the Elk River closely so that it can adjust the operation of Tims Ford Dam to protect the diversity of aquatic life, including a cold-water trout fishery and endangered species and sport fish that require warm water. Read more.

 

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Watauga Dam

TVA uses autoventing turbines to improve the quality of the water released from Watauga Dam. This technology introduces air flow into low-pressure zones just below the turbines to create many small air bubbles. Oxygen from the bubbles is absorbed into the oxygen-poor water as it flows through the dam.

TVA releases water from Watauga Dam at regular intervals to provide a seasonal minimum flow below Wilbur Dam. This continuous flow helps to prevent riverbed dry-out and benefits fish and other aquatic life.

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Wilbur Dam

TVA releases water through Wilbur Dam at regular intervals, called pulsing, or runs one of the smaller hydro units to keep the downstream riverbed from going dry and to help sustain the health of the aquatic life.

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Tributary dams

To see what TVA is doing about the problems of low oxygen concentrations and low flows at tributary dams, choose from the list below.

Main-river dams

View information on improvements at main-river dams.

Improvement technologies

For an explanation of the technologies mentioned on this page, go to Boosting Oxygen Concentrations and Maintaining a Wetted Riverbed.

           
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