Information found on this site: http://www.tvakids.com/whatistva/index.htm

Who Started TVA, and Why?

If you were carried back in time to 1933, you might not recognize most areas in the Tennessee Valley, the region that runs through seven southeastern states and surrounds the Tennessee River.

At that time, the region was in pretty bad shape compared with the rest of the United States. It was dangerous to travel on major stretches of the Tennessee River. Many of the people who lived in the Valley had no electricity and were barely getting by. Farmers were suffering because the soil where they grew their crops was poor and worn out.

To make matters worse, the entire country was in the middle of a huge economic slump known today as the Great Depression, which meant that a lot of people had no jobs. Many families in the Tennessee Valley region were unable to buy or grow enough food to stay healthy.

When our 32nd president, Franklin Delano Roosevelt, entered office in 1933, he wanted to help the people of the Tennessee Valley become more prosperous, healthy, and productive. In order to do this, President Roosevelt signed the Tennessee Valley Authority Act on May 18, 1933.

This act of Congress created the Tennessee Valley Authority (TVA), a federal corporation. The new agency was asked to tackle important problems facing the Valley, such as flooding, providing electricity to homes and businesses, and replanting forests. Other TVA responsibilities written in the act included improving travel on the Tennessee River and helping develop the region's business and farming.

Today, TVA has certainly lived up to President Roosevelt's hopes. TVA is the largest public power company in the United States. The agency also carefully runs the nation's fifth-largest river system in order to reduce flood damage, make rivers easier to travel, provide recreation, and protect water quality. The Tennessee Valley is now a great place for families to live and work.

 About Dams

People build dams to control water—to make sure the right amount is at the right place at the right time.

River water rises behind dams, forming artificial lakes called reservoirs. The stored water can be used to generate electricity or to supply water for homes and industries, for irrigation, or for navigation. Reservoirs also are good places to fish and play.

How are dams built?

Engineers use models and computers to figure out how much water a dam will have to support and how big and strong it must be. Then they can decide what sort of dam to design.

There are four main types of dams:

• Embankment dams are the most common type in the United States. They are massive structures made of earth and rock that rely on their heavy weight to resist the force of the water. A layer of clay or concrete may be used to stop leaks through gaps in the rocks. TVA’s Cedar Creek Dam is an embankment dam.
• Gravity dams are concrete dams that also hold back the water entirely by their own weight. Usually the side of the dam that faces the oncoming water is straight. Most gravity dams are expensive to build because they require so much concrete. TVA’s Norris Dam is a gravity dam.
• Buttress dams have a series of supports, or buttresses, that brace the dam on the downstream side. Buttress dams may be flat or curved. Most are made of reinforced concrete. There are no buttress dams in the TVA system.
• Arch dams are good for narrow, rocky locations. Their curved shape holds back the water in the reservoir. Arch dams are thin and require less material than any other type of dam. There are no arch dams in the TVA system.

Read more information about all the dams in the TVA system.

...what a cofferdam is? Click here for the answer

Do dams ever break?

If a dam is well designed, it will be strong enough to hold back the water behind it, whatever happens. But tragic accidents still occur, often caused by the unimaginable power of natural forces such as earthquakes, landslides, or floods.

The worst dam disaster happened over a century ago. A huge dam in Philadelphia burst in 1889, killing 10,000 people.

More recently, in 1976, the Teton Dam in Idaho broke as the reservoir behind it was being filled for the first time. Fourteen people were killed. The Teton Dam disaster resulted in new government rules to ensure that dams are safe.

Dam safety at TVA

Every TVA dam is checked regularly to make sure it that it is safe and the equipment used to operate it is working properly.

Because many of these dams were built in the 1930s, TVA has had to do a lot of work on them to make sure that they meet modern safety regulations. These ensure that TVA’s dams can stand up to the biggest flood or earthquake that we would ever expect to see in the Tennessee Valley.

Hydroelectric Power

Hydroelectric power, or hydroelectricity, is generated by the force of falling water. (Hydro comes from the Greek word for water.) It’s one of the cleanest sources of energy, and it’s also the most reliable and costs the least. That means that TVA’s hydroelectric power plants are able provide electricity at a reasonable cost to families, schools, farms, factories, and businesses.

How does hydroelectric power work?
Water is needed to run a hydroelectric power-generating unit. The water is held behind a dam, forming an artificial lake, or reservoir. The force of the water being released from the reservoir through the dam spins the blades of a giant turbine. The turbine is connected to the generator that makes electricity as it spins. After passing through the turbine, the water flows back into the river on the other side of the dam.

TVA uses water to make electricity at 29 hydroelectric dams and one pumped-storage power plant (at Raccoon Mountain near Chattanooga, Tennessee). Together these plants produced about 13.9 million megawatt hours of electricity in 2004, enough electricity to power nearly one million homes for a year.

How TVA Stops Floods

The best time to stop a flood is before it starts, right? That’s exactly what TVA tries to do.

TVA uses 35 dams to reduce flood damage by holding back the water from heavy rains in reservoirs. These “flood-storage” reservoirs (usually located on “tributary rivers”—rivers that run into the main Tennessee River) do most of the work in controlling floods.

Big storms — the ones that can cause flooding — are most likely to hit the Tennessee Valley in the winter and early spring. So, to make room for this water in the flood-storage reservoirs, TVA lowers their water levels by January 1 each year. The water in tributary reservoirs can rise and fall as much as 60 feet per year.

When a storm hits, TVA holds the water back by closing the gates of the dams in areas where it is raining. When the rain stops and the danger of downstream flooding is over, TVA lets the water out at a gradual rate to get ready for the next storm.

As you might expect given how much it rains, there were lots of floods in the Tennessee Valley before TVA dams were built. These floods washed away the topsoil, causing problems for farmers. Even worse, hundreds of people died and thousands more lost their homes and farms. The city of Chattanooga, Tennessee, would flood about once a year. Click here to find out why.

Today, TVA’s system of dams and reservoirs prevents about $224 million in flood damage along the Tennessee, Ohio, and Mississippi Rivers every year.

Dams and Water Quality

When people build a dam on a river, it changes the water quality. Some of these changes are good, but others can cause problems.

At dams that produce hydroelectric power, these problems can really affect the fish and other animals that live in the “tailwater” area. That’s the stretch of river on the downstream side of the dam, where the water comes out when electricity is being produced.

Keeping water in the riverbed

When water is flowing through the dam to make electricity, there is plenty of water in the tailwater area. But when the equipment that makes the electricity is shut off, the riverbed can dry out, sometimes for several miles below the dam, which is bad news for fish—as you can imagine!

In 1991 TVA decided to do something about this problem. At some dams, TVA built small dams, called “weirs,” which hold back some of the water when electricity is being generated, then slowly empty when generation stops.

At other dams, TVA turns the equipment used to make electricity on and off throughout the day to make sure that there is always enough water flowing through the dam to keep the tailwater area from drying out.

...what fish need, besides water, to stay alive? Click here for the answer

What is stratification?

Oxygen is another big problem in the tailwater area below some dams, especially dams that form very deep reservoirs. That’s because the water used to spin the turbines at these dams comes from the lower part of the upstream reservoir. This water usually doesn’t have much oxygen in it during late summer and autumn because of a natural process called “stratification.”

Maybe you’ve never heard this word before, but if you’ve ever jumped into a reservoir on a hot summer day, you’ve probably felt the effects of stratification. The deeper you go, the colder the water feels; then you pop back up to the warmer surface water that’s been heated by the sun’s rays.

Because of the difference in temperature, the surface water and the bottom water of deep reservoirs don’t mix, so the bottom water becomes trapped. It doesn’t have any contact with the air, which means there’s no way to replace the oxygen that is used up as plants die, settle to the bottom, and decay. By late summer or fall, sometimes there’s no oxygen in the water near bottom at all.

You’ve probably figured out the problem already: when this low-oxygen water passes through the dam in the process of producing electricity, it affects the amount of oxygen in the tailwater area and the health of the animals that live there.

TVA tackled this problem at the same time it decided to do something to keep the riverbed from drying out. The solution involved a lot of research. TVA installed different kinds of equipment at 16 dams to add oxygen to the water—from huge fans that push the oxygen-rich surface water down to the reservoir bottom to hoses that hang just above the reservoir bottom with holes that create millions of tiny bubbles as oxygen is pumped into the hoses from a tank on the land.

Want to know more? Read about tailwater improvements on the TVA Web site.

Ancient fish return

A fish that first appeared in Valley waters more than 350 million years ago, before the dinosaurs, is making a comeback, thanks to better water quality below TVA dams and other clean water improvements.

Hundreds of young lake sturgeon have already been released into the French Broad River below TVA’s Douglas Dam as part of a 10-year restoration effort.

Lake sturgeon once thrived throughout the Tennessee River system until water pollution, overfishing, and changes in habitat resulted in near-extinction.

These fascinating fish usually live 50 to 100 years. The largest lake sturgeon ever recorded weighed 310 pounds and was a little over eight feet long.

Sturgeon photo by Todd Stailey

What TVA Does

Have you ever wondered what TVA does? The answer is — many different things.

TVA is the largest public power company in the United States. It’s called “public” because it’s owned by the U.S. government, unlike most companies that are owned by individual people or investors. Through its many plants that make electricity, TVA supplies power to about 8.8 million people in the southeastern United States.

In addition to producing power for many Americans, TVA also manages the nation’s fifth-largest river system. The Tennessee River flows 652 miles from east Tennessee down into Alabama and back up into Kentucky, where it joins the Ohio River. All along the Tennessee River, TVA employees work to reduce the dangers of flooding, make it possible for boats to travel safely, and keep the water clean.

In the 41,000-square-mile area drained by the Tennessee River, TVA also operates some of the country’s best outdoor recreation areas. Although TVA was first set up in 1933 as an agency supported by Americans’ tax dollars, today it runs all of its programs and pays its employees with the money it earns by making and selling electricity.

So, the next time you turn on a computer, drink from the school water fountain, or go fishing on a TVA reservoir, you will know what part TVA plays in helping everybody in the Valley lead a better life.

How TVA dams and locks make navigation possible

Quick! Name some ways TVA dams benefit people in the Tennessee Valley.

Flood damage reduction, power production, recreation—those are the ones that come to mind first.

But “promoting navigation” was actually the very first purpose mentioned in the TVA Act of 1933, which spelled out exactly how the new agency was to manage the river. Navigation has been important to the welfare of the Valley ever since.

If it weren’t for those barges moving up and down the river, we would be paying more for all kinds of products. Anything made from materials shipped in large quantities—grain, stone and gravel, iron and steel, lumber, coal, and chemicals, for example—would cost more. Why? Because they’d have to be shipped by rail or truck, which would cost over $550 million a year more than moving them by barge.

One barge can carry as much stuff as 60 trucks, so there’d be a lot more 18-wheelers on the road, too. Using barges helps keep our highways safer and reduces fuel use, air pollution, and the number of tires going to landfills.

A river highway

TVA built nine dams along the main Tennessee River to create a 652-mile long river highway. TVA operates these dams to make sure the water all along the way is at least 11 feet deep—enough to float even the heaviest barge.

Before these dams were built, the water was too shallow for barges to travel very far up the Tennessee River. In fact, in dry years, you could cross the river near Muscle Shoals, Alabama, without even getting your feet wet—if you didn’t slip off the rocks!

The main-river dams form a “staircase” of quiet, pooled water and controlled current along the entire length of the Tennessee River. But how do boats get around the dams?

Every dam has a lock—a canal for raising and lowering boats—which allows boats to pass around the dam and to deal with the difference in elevation between Knoxville, Tennessee, and Paducah, Kentucky. Paducah is 513 feet lower than Knoxville.

How does a lock work? 

A lot like an elevator—only slower! When a barge or other boat enters the lock, the gates close and the water level inside the lock is raised to the upstream level or lowered to the downstream level, depending on which way the boat is moving.

The locks are filled and emptied by gravity—no pumps are used. If the boat is going downstream, the water level in the lock is lowered by opening the downstream valves so the water can drain out. If the boat is moving upstream, the downstream valves are closed and the upstream valves are opened. This allows water from the upstream side to flow into the lock, filling the chamber to the upstream water level.

In about 45 minutes, when the water level inside the lock is equal to the level of the next reservoir, gates at the other end of the lock are opened and the boat can continue on its way.

You can see a little movie of how a lock works here.

Protecting Wildlife Habitats

TVA is in charge of 293,000 acres of public land and 11,000 miles of shoreline. It has set aside more than 181,000 acres of that land to preserve a home for wildlife and to protect and study animals, birds, and fish.

TVA has been working to protect wildlife for years. In 1976 TVA started the Natural Heritage Project. With help from the Nature Conservancy, TVA’s wildlife specialists make careful studies of the plants and animals that are at risk of becoming extinct. Then biologists create plans that will help protect wild areas.

Here are some other examples of how TVA wotks to benefit wildlife:

• Every year TVA studies the number and health of fish in the reservoirs during its spring sportfish survey.

• TVA helps count and protect bald eagles, America’s national symbol.

Aquatic life

“Aquatic life” means fish and other creatures that live in the water. TVA helps protect habitat for aquatic life in a number of ways.

TVA Natural Areas

TVA has set up a network of Natural Areas along the Tennessee River and its tributaries. They are designed to protect rare animals and plants and the natural communities where they live. By setting these areas aside, TVA is better able to limit activities that could put these animals and plants in danger. Some of the TVA Natural Areas are open to the public for hiking, wildlife observation, and nature appreciation