Hydraulic basin.
Hydraulic power.

Hydraulic power.

What Is Hydroelectric Energy?

Hydroelectric energy is the electrical energy produced in a hydroelectric power station from a stream of water. Usually, the energy sources come from a river.

What is hydroelectric energy?

According to the definition of hydroelectric energy, this consists of generating electricity from hydraulic energy.

Hydraulic power has been used since ancient times. it was used to grind flour and other tasks. At the end of the 19th century, the electric generator was developed and then it could be coupled to hydraulic systems. The demand for this technology increased considerably during the Industrial Revolution.

What types of hydroelectric energy are there?

There are different methods to take advantage of the water-energy to obtain hydroelectric energy. Next, we explain the main ones.

Conventional hydroelectric energy (hydroelectric dams)

Most of the energy of the hydropower facilities comes from the potential energy of the dammed water that drives a water turbine and a generator. The power extracted from the water depends on the volume and the difference in height. This difference in height is called the head. A large pipe delivers water from the reservoir to the turbine.

Pumped storage

This method produces electricity to supply the high peak demands by moving water between reservoirs at different elevations.

In times of low power demand, excess power generation capacity is used to pump water into the upper reservoir. The goal is to store water so that when demand increases, the water is released into the lower reservoir through a turbine that generates electricity again.

Pumped storage schemes currently provide the most commercially important means of large-scale grid energy storage. They also improve the daily capacity factor of the generation system. Pumped storage is not a source of energy, and it appears as a negative number on the charts.


Run-of-river hydroelectric stations are those with little or no reservoir capacity. Only water from the upstream is available for generation at that time, and any oversupply must go unused.

A constant supply of water from an existing lake or reservoir upstream is a significant advantage when choosing sites for the river flow.

What is the energy that comes from the tides? Tidal power

This type of renewable energy is a tidal power station. This type of energy makes use of the daily rise and fall of ocean water due to the tides. Such sources are highly predictable. If conditions allow the construction of reservoirs, they can also be dispatched to generate power during periods of high demand.

The less common types of hydroelectric schemes use the kinetic energy of water or undamped sources such as water wheels that are not reached.

Tidal energy is viable in a relatively small number of places around the world.

What is the potential of hydroelectric energy?

The technical potential for the growth of hydroelectric power around the world is,

  • 71% Europe

  • 75% North America

  • 79% South America

  • 95% Africa

  • 95% Middle East

  • 82% Asia Pacific.

It is believed that before 2050 25% of the remaining potential can be developed for different reasons:

  • The political realities of the new reservoirs in western countries.

  • Economic limitations in the third world and the lack of a transmission system in undeveloped areas.

Most of this development would take place in the Asia Pacific area.

On the other hand, some countries have this very advanced technology with little possibility of growth. For example, Switzerland 12% and Mexico 20%.

Hydroelectric plants

There are different types of exchanges but they all have the same basic principle. Take advantage of the power of moving water through a hydraulic turbine. Some of them use a dam to store water at a certain height.

The largest hydroelectric power station in the world is the Three Gorges Dam. Located in the Chinese province of Hubei.

Hydroelectric plants use the mechanical energy of the water stored by the intake that acts as a barrier. Water circulates through a pipe where potential energy is transformed into kinetic energy. The force of the water rotates the set of turbines, generators, and alternators located in the powerhouse. In the powerhouse, the electrical energy of alternating current is generated, which can be vertical or horizontal.

In this case, the energy extracted from the water depends on:

  • The flowing water.

  • The difference in height from which the water is drawn.

  • The type, height, and size of the turbines.

We will find hydroelectric plants in areas where there are water flows (rivers and lakes) and significant level differences.

Environmental impacts of hydroelectric power

Hydroelectric energy may be a good alternative to other energy sources such as fossil fuels and nuclear power. Nevertheless, there are several environmental impacts of hydroelectric energy.

  • Big extensions of land use.

  • Affects to the water quality.

  • Impacts into the wildlife.

  • Construction activities.

Land use

A hydroelectric project needs different sizes of the reservoir. The size depends on the size of the hydroelectric generators and the topography of the land. Hydroelectric plants in flat areas tend to require much more land than those in hilly areas or canyons. In hilly and canyons areas the reservoirs are deeper and can hold more volume of water on a smaller surface.

Flooding land for a hydroelectric reservoir has an extreme environmental impact: it destroys forests, wildlife habitat, agricultural land, and scenic lands. In many instances, entire communities have also had to be relocated to make way for reservoirs.

Water quality

The construction of dams and the stagnation of water can alter the quality of the water. The main risks are reduced oxygen in water, changes in temperature, stratification of sediments, and increased proliferation of diseases.

Wildlife impacts

Many species travel the river throughout their life cycle in one or both directions. In many places, the migration of fish (such as salmon) is an annual event, which is seriously hampered by prey. This migration is vitally important for maintaining populations of various species, and often represents rich economic resources for local populations.

In some cases, the reservoirs, in the long term, cause environmental problems due to the introduction of exotic species or not adapted to the habitat. Changes in water conditions can facilitate the colonization of alien species, creating pests.

Construction activities

Global warming emissions are produced during the installation and dismantling of hydroelectric power plants.

Construction activities cause alterations in the aquatic and terrestrial environment. In addition, and when construction is carried out near population settlements, noise pollution and other problems must be taken into account.


Published: May 17, 2018
Last review: August 24, 2020