What is a Reservoir? - Definition, Formation & Characteristics

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  • 0:02 Definition of a Reservoir
  • 0:58 Types of Reservoirs
  • 2:49 Uses for Reservoirs
  • 3:36 Reservoir Problems
  • 4:20 Lesson Summary
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Lesson Transcript
Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson, we will review what a reservoir is and the different ways it can be formed. We'll also review characteristics reservoirs have in common, uses for reservoirs, and problems they can create.

Definition of a Reservoir

Go grab a drink of water. Or maybe you need to use the bathroom? Or do you need to take a shower before we get started studying? What do all these activities have in common? Water! Water is essential for our daily lives and today, we're going to look into reservoirs. This is how most of us get our water.

A reservoir is a man-made lake or large freshwater body of water. Many people think of a reservoir as a lake and might even use the words interchangeably. However, the key difference is that reservoirs are artificial and made by humans, while lakes are naturally occurring bodies of water. Reservoirs are great because they provide a supply of water for when naturally occurring bodies of water, like lakes or rivers, run dry. We'll talk more about what kinds of reservoirs there are, and what we use them for next.

Types of Reservoirs

There are three main types of reservoirs; valley-dammed reservoirs, bank-side reservoirs, and service reservoirs. Valley-dammed reservoirs are created in valleys between mountains. Usually, there is an existing lake or body of water. The mountain sides are used as the walls of the reservoir to hold the water. A dam, or artificial wall in the reservoir, is built at the narrowest point to hold in the water, as shown here.

Glen Canyon Dam

To create a valley-dammed reservoir, the river that will fill the reservoir must be diverted, so the ground can be cleared to lay a foundation for the dam. Next, a concrete lining is put in place, and dam construction can begin. It can take years to build a dam, but once it's done, the water pools in the valley, and a large source of water becomes available. You can see construction of a valley-dammed reservoir here:

valley-dammed reservoir construction

Bank-side reservoirs are reservoirs that are made by diverting water from local rivers or streams to an existing reservoir. Although this can be applied to many different geographical areas, unlike the valley-dammed reservoir, which requires a valley, diverting water from a river can create problems. The River Thames in London is one example of a bank-side reservoir.

Service reservoirs are entirely man made. They are usually stored in concrete basins above or below ground. You might be familiar with the large water towers in the countryside. This water tower is a service reservoir:

water tower

In some areas, people dig cisterns, or service reservoirs that are underground. Cisterns must be in a place of higher elevation to allow the water to flow where it needs to go, whereas water towers are already at a higher location than the surrounding land.

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