A reservoir is a place where something (most often water) is collected and stored so it can be used later.

What is a reservoir? (Simple answer)

  • In everyday geography, a reservoir is usually a large (often artificial) lake formed behind a dam, used to store water for drinking, irrigation, industry, or electricity.
  • More generally, the word means any storage place for a fluid or resource, such as oil in an engine, ink in a pen, or even a “reservoir of infection” in biology.

If you picture a huge bowl holding water for a city or river system, you’re basically picturing a reservoir.

Main types of reservoirs (water)

  • Valley-dammed reservoir : A dam is built across a river valley, and the valley behind it fills with water.
  • Bank-side reservoir : Water is diverted from a nearby river into a specially dug, enclosed basin.
  • Service reservoir : Usually a covered tank or structure (on a hill or tower) that stores treated drinking water for distribution to homes.

These water reservoirs help with:

  • Reliable water supply for cities and farms
  • Hydroelectric power generation
  • Flood control by holding back excess water
  • Recreational uses like boating and fishing

Other uses of the word “reservoir”

The term is broader than lakes and dams:

  • In machines : A reservoir is a chamber that stores a liquid, like an oil reservoir in an engine or an ink reservoir in a fountain pen.
  • In biology/medicine : A “reservoir of infection” or “reservoir host” is an organism or environment that carries a pathogen without being harmed, and can pass it on.
  • In ecology and science : People talk about “carbon reservoirs” or “nutrient reservoirs” (places in Earth systems where those substances are stored).

Quick HTML table: common meanings

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<table>
  <thead>
    <tr>
      <th>Context</th>
      <th>What “reservoir” means</th>
      <th>Example</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Geography / engineering</td>
      <td>Large lake (usually artificial) used to store water.</td>
      <td>Lake behind a dam supplying a city.</td>
    </tr>
    <tr>
      <td>Urban water supply</td>
      <td>Service reservoir storing treated drinking water.</td>
      <td>Hilltop water tank feeding neighborhood pipes.</td>
    </tr>
    <tr>
      <td>Mechanical systems</td>
      <td>Container in a device where a liquid is stored.</td>
      <td>Oil reservoir in an engine; ink reservoir in a pen.</td>
    </tr>
    <tr>
      <td>Biology / medicine</td>
      <td>Host or environment that stores a pathogen.</td>
      <td>Animal species acting as a reservoir for a virus.</td>
    </tr>
    <tr>
      <td>Ecology / Earth systems</td>
      <td>Storage location for substances like water or carbon.</td>
      <td>Ocean as a reservoir in the water cycle.</td>
    </tr>
  </tbody>
</table>

TL;DR: A reservoir is any storage place , but most commonly it means a man-made lake behind a dam that stores water for human use.

Information gathered from public forums or data available on the internet and portrayed here.