River Ecosystems

Rivers and the Water Cycle

Written by Don Huie

Water on Earth is always moving and changing. There couldn't be life on Earth without water. One of the places where water collects on Earth is in rivers. Rivers contain freshwater, so they're different from oceans, which contain saltwater. Rivers are always moving water along, and they dump water into larger bodies of water. Rivers are an important part of the water cycle that moves water all around our planet.

All About Rivers

Rivers are large bodies of water that flow downhill. Although some rivers are narrow enough for people to walk across them, other rivers are very deep and quite wide. A small offshoot of a river might be called a stream, creek, or brook, and sometimes, streams will only flow during some parts of the year when there's more rain. Rivers start flowing at a specific point, and they flow downhill to the mouth of the river, which is where it ends and flows into a larger body of water, such as an ocean or a lake.

Water Cycle Basics

When rain or snow falls, it's called precipitation. Some of this water is absorbed down deep into the soil and rocks, and some water stays on the surface of the ground in rivers, lakes, and oceans. Water stored in bodies of water will slowly change from a liquid to a gas as it is warmed by the sun, which is called evaporation. As water evaporates, it becomes water vapor and moves up into the air. This water vapor forms clouds, which can then produce more precipitation that starts the water cycle over again.

People and Rivers

People need rivers for many reasons. Not only are rivers an important part of the water cycle, but they also make it possible for people to earn a living and survive. People in some areas depend on fresh river water for drinking, and there are even plants that grow in some rivers that filter out contaminants to help keep the water cleaner. People may use rivers to water their crops, to produce electricity, and for transportation. Rivers are also a popular place for fun activities like boating, fishing, and swimming.

River Ecosystems

River ecosystems provide homes for people, animals, and plants. Even people who don't live near the ocean are connected to these large bodies of water in some way, since rivers run everywhere and they all eventually connect to the ocean. Rivers include the river itself (which is called the riverbed); the riverbank, with its land, plants, and trees; and the floodplain, which spreads out farther than the riverbank. The floodplain may flood in the spring after a heavy snow melt and during the summer after heavy rain, and it's often a wetland habitat for plants and animals. River ecosystems are home to plants and animals that depend on each other for survival.

Fun River Facts

  • When streams meet and merge, they form a tributary. Eventually, many tributary streams will form a river.
  • Some rivers flow under Earth's surface. These are called subterranean rivers.
  • A delta is a flat area of land created when a river drops dirt it was carrying as it empties into the sea. Deltas are good areas for farming because the soil is rich with nutrients from the river.
  • Rivers can be different colors, including black, blue, red, green, and yellow, depending on what's in the water.
  • The Nile River is the longest river in the world, topping out at 4,132 miles.
  • The Amazon River is the second longest river in the world, coming in at 3,977 miles. The Amazon River is also the widest river in the world; it can reach almost 25 miles wide during the rainy season.
  • The Congo River is the deepest river in the world. It is 722 feet deep.

Rivers and the Water Cycle

The amount of water in rivers changes all the time: There may be less water during a drought or more water if there's a lot of rain. Freshwater bodies of water like lakes and rivers are very important in the water cycle because they help to collect water and move it to where it can evaporate more easily. Evaporation is an important part of the water cycle because it keeps the water moving to different parts of the world.

Additional Resources