Areservoir is a reservoir of water that forms artificially. Typically, the mouth of a valley is closed through a dam or a dike, storing water from a river or a stream . With these waters, nearby populations can be supplied, produce electricity or irrigate land.

For example: "Concern in the south: they denounce that the waters of the Arizturi reservoir have high levels of pollution", "In the morning we will visit the reservoir and in the afternoon we will try to reach the top of the mountain", "Construction from the dam it will demand a millionaire investment, but it will generate great benefits to the inhabitants of this region .

It is known as a multi-use reservoir to which it is intended for several purposes, such as the generation of electric energy, sport fishing and recreational activities.

When we talk about a reservoir, it is important to know that it has a series of elements or characteristics that define it, among which the following stand out: the regularized flow, which is what you can withdraw during the year; the firm flow, which is the maximum that can be taken from it in a critical period due to droughts; the curve called flooded surface-dimension and the volume-volume curve.

In the same way, when referring to a reservoir it is also essential to take into account the level of water it has. In this sense, it should be noted that there are various types of levels, among which it is worth highlighting those set out below:
  • Minimum minimum level, is the minimum that construction can have.
  • Minimum operational level, which is the one below which the reservoir and the rest of the structures it has cannot function properly.
  • Maximum operational level, which indicates that when the water reaches it, it is necessary to start pouring it.
  • Normal maximum level. When this goal is reached, it is none other than taking care of the millimeter what is the safety of the reservoir.

Numerous are the reservoirs that exist throughout the entire world geography. However, among the most important are these:
  • Kariba Lake, located on the border between Zimbabwe and Zambia.
  • Bratsk Reservoir in Russia.
  • Lake Volta, in Ghana.
  • Guri reservoir in Venezuela.
  • Krasnoyarskoye reservoir in Russia.
  • Lake-reservoir of Tharthar, in Iraq.

It is important to note that the construction of a reservoir can generate irreversible ecological effects. Problems of erosion, earthworks, alterations in the course of the river or stream and changes in soils, flora and fauna are some of the consequences.

Beyond that the notion of reservoir is associated with a water tank built by man, the truth is that reservoirs that are created by natural actions can be found. In this regard, hillside collapses, ice accumulation in very cold regions or dams built by beavers can be mentioned . These reservoirs often escape human control and do not allow water use management.