Accumulation in the Water Cycle: Definition & Purpose Video

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  • 0:00 What Is the Water Cycle?
  • 0:41 Steps of the Water Cycle
  • 1:31 Accumulation
  • 1:56 Importance of Ecosystems
  • 3:05 Importance for Humans
  • 3:51 Lesson Summary
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Lesson Transcript
Instructor: Amanda Robb
In this lesson, we'll review the basic parts of the water cycle and then look at accumulation in detail. We'll go over why accumulation is important for both ecosystems and humans.

What Is the Water Cycle?

As you're studying and learning about the water cycle, you probably have a drink nearby. Cool, refreshing water is necessary for our brains to function. In fact, we are made of more than 50% water ourselves. Water is all around us, in precipitation like rain and snow; in bodies of water, like lakes and oceans; and in other living things, like trees and animals. Water moves between all living and non-living things in a process called the water cycle. Today, we'll look at one particular step called accumulation. But before we zoom in, let's get a general overview of the whole water cycle.

Steps of the Water Cycle

The water cycle starts from bodies of water on Earth, like lakes, streams, and oceans. As water is heated by the sun, it evaporates into the atmosphere. When it does, it collects in clouds, condenses, and eventually returns to Earth as precipitation. The precipitation runs off from mountains and other surfaces and accumulates in existing bodies of water and on land. Water is also stored as glaciers in colder areas of the earth, and in groundwater sources. Evaporation not only comes from bodies of water but also trees and plants. Trees and plants go through a process called transpiration, where water is sucked from the ground and evaporates through their leaves, returning water from the soil to the atmosphere. Now that we have the basics, let's look at the process of accumulation.


Accumulation is the process of water collecting in rivers, lakes, streams, oceans and other bodies of water. When water condenses and precipitates, it eventually runs off of surfaces and collects again in bodies of water. From there, the water evaporates, and the cycle begins again. Accumulation is important for a number of reasons, both in ecosystems and for humans.

Importance for Ecosystems

All living things are dependent on water. Plants make their own food and form the basis of most ecosystems. Plants use water, carbon dioxide, and sunlight to make food. Without water, both from precipitation and groundwater stores in the earth, they would be unable to make food, and thus animals that depend on plants for food would also die off.

Water stores that result from accumulation create aquatic ecosystems of their own. Rivers, lakes, and streams are home to many species of fish, which in turn support birds, mammals, and reptiles. Oceans cover nearly 70% of the globe and provide a home to tens of thousands of species of plants and animals. Ocean levels are kept constant through the cycle of evaporation and accumulation.

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