flowing water to generate power for centuries. Today, hydroelectricity is used in many communities and nations around the world as a non-polluting, independent, and reliable source of energy. However, as useful as hydroelectricity has been for humanity to help meet our energy needs, it has both advantages and disadvantages.
The following are a number of advantages and disadvantages that should be considered prior to the development of a new hydroelectric project.
Advantages of hydroelectricity
Hydroelectricity is a proven technology and has a much longer track record of success than newer renewable energy technologies, such as wind and solar energy¹.
Consistent and renewable power
Unless drought conditions are present, hydroelectricity sources its energy from water, which is continually renewed through the water cycle².
Once hydroelectric facilities are constructed, the generation of electricity from flowing water is basically free, allowing the typical plant to cover its construction costs within 5-8 years¹.
Domestic energy resource
Unlike fossil fuels, which often need to be imported from foreign sources, hydroelectricity can be produced using local resources and the electricity can be used locally².
Available as needed
Extra water can be pumped into reservoirs and used to generate electricity during times of peak demand³.
In many areas, the constructed hydroelectric plant reservoirs can provide recreational opportunities such as swimming, boating, and fishing².
Disadvantages of hydroelectricity
To construct most hydroelectric facilities, a river must be dammed. A dam is required in order to harness the gravitational force of falling water that is needed to generate electricity³. The damming of rivers can cause many negative impacts to the local riparian (river) ecology and communities as the area upstream from the dam is flooded to create a reservoir¹.
Wildlife habitat can undergo flooding when hydroelectric plants are built, and can have dramatic impacts on a local ecosystem and the animals and plants that live there. Wildlife migrations may be dramatically altered, and there may be a loss of suitable habitat as well as a loss of important species¹. In many cases, fish may no longer be able to swim upstream when a dam has been constructed along their migration route to their spawning grounds, and fish may be injured or killed by hydroelectric power turbines. To aid fish passage, fish ladders or elevators have been added to many hydroelectric dams as well as the implementation of screens, racks and lights to reduce fish injuries and fatalities. It is also important to maintain a minimum spill flow beyond the turbines to assist with fish passage².
Impacts on water flow and quality
Because hydroelectric power plants and dams utilize the flow of water, this also alters the natural flow of rivers. Algal blooms can occur in reservoirs due a lack of dissolved oxygen levels that result in more stagnant water conditions. To address this issue, reservoir water can be aerated, and it is important to maintain a minimum flow of downstream water to preserve riparian habitats².
Impacted by drought
Because the generation of hydroelectricity is dependent upon river water flow, a regional drought that significantly reduces river water flow will negatively impact the ability of a facility to continue to produce electricity².
Hydroelectric plant construction requires large up-front investments, but such facilities should pay for themselves within 5-8 years once they have been generating electricity¹,³.
The flooding of ecosystems upstream from hydroelectric facilities also impacts human communities. Local cultures and historical sites may be damaged by flooding, and many local communities may be displaced and be forced to relocate. The world’s largest hydroelectric facility, China’s Three Gorges Dam, displaced more than 1.4 million people at the time it was constructed¹.
Water access issues
Building a hydroelectric facility may disrupt the water flow to communities that are downstream from the plant and reduce their access to water from the river³. This can lead to conflicts among those who share these water resources, but can be reduced through stakeholder participation throughout the project’s development. Available technology should also be implemented that aims to reduce the disruption in water supply to downstream communities as much as possible.
While hydroelectric power may be a valuable energy source now and in the future for many communities, it may not be the best energy source everywhere there is a river. Natural ecosystems must be preserved as much as possible, as well as local communities. Building a hydroelectric dam has many impacts that need to be considered before a project is developed.
Due to a changing climate, we are already seeing drought conditions in many regions across the globe, and the rivers that are flowing today may not reliably flow in the future. Therefore, hydroelectric power should only be considered an option when there is likely to be enough water flow to warrant its use within a drier global future. Global water resources are also likely to become greatly constrained as water becomes less plentiful to meet basic human needs, and hydroelectric power may not be the best source of renewable energy in these situations.