Rivers

Many rivers in our world start this way, including the second-longest river in the world, the Amazon River in South America. That is not the only way that rivers start. Some rivers start in lakes and underground springs. The place where a river begins is called its source.

From its source, a river winds downstream and drains the water from the area around it. The area a river drains is called a river basin. Rainwater, streams and other rivers drain into larger rivers.

The streams and rivers that flow into larger rivers are called tributaries. The largest river in the United States, the Mississippi River, has many tributaries. The Missouri River and the Ohio River are two large tributaries of the Mississippi.

Rivers not only drain water from the areas around them, they pick up loose soil, sand and plants and carry them downstream. At the mouth of a river, where it empties into a sea or a lake, the loose particles can build up. The build up is called a delta.

Some deltas are very large. The Nile River in eastern Africa is the longest river in the world and has a large delta. The Amazon River and Mississippi River also have large deltas.

River deltas make good farmland, as does the land along rivers, called flood plain. This land is called flood plain because it is low and easily flooded when a river overflows its banks. Floodwaters carry soil and other particles and leave them on the flood plain.

Floods can be good for the flood plain, but they also can be damaging. Many towns are built along rivers, too. When a river floods, it can damage homes and businesses in these towns. People have built levees and dams to prevent floodwaters from reaching their towns.

Levees are high banks built along rivers that keep them from overflowing. Dams are structures built on rivers that control the flow of water. The Mississippi and some of its tributaries use both levees and dams for flood control. Unfortunately, sometimes these do not work and damage occurs.

Dams also have other uses. On some fast-moving rivers, dams generate electricity. Dams also store water in big lakes called reservoirs. The water in reservoirs is used for drinking and irrigation.

Along with providing water for irrigation and drinking and making electricity, rivers help us in many other ways. For thousands of years, people have used rivers for travel and business.

Although rivers aren't used as much for travel anymore, they are still used to transport goods from state to state and country to country. Flat boats called barges transport goods up and down rivers.

Because people have used rivers for so many things, water pollution has become a problem. Water runoff from farms and cities has chemicals in it that make rivers dirty. The dirty water is not only bad for the fish and other river life, but it can make our drinking water dirty, too. Water treatment plants have been built to help protect our rivers and keep our drinking water safe.