“Hydropower is the forgotten giant of clean electricity, and it needs to be put squarely back on the energy and climate agenda if countries are serious about meeting their net zero goals.”
Dr Fatih Birol
IEA Executive Director 
Hydropower is a form of renewable energy that has been a key player in providing sustainable alternatives to fossil fuels. Running water has long been a source of power, for example, in Southern Europe and China, water wheels have been used to mill grain for more than 2,000 years .
Modern hydropower uses flowing water to turn turbines and generate electricity. This can be done using large dams, constructed to contain water and create reservoirs, used to generate power on demand. Power can also be generated using smaller run-of-river systems, relying on the natural water flow of rivers. Hydropower is currently one of the largest sources of renewable energy globally, accounting for roughly 16% of total electricity production. It is currently responsible for the generation of more electricity than all other forms of renewable energy generation combined. This is expected to continue long into the 2030’s .
Read on for the 6 main reasons why hydropower is a vital part of the global energy transition towards net zero.
Hydropower creates clean energy
Hydropower’s clean energy is one of the clearest advantages to its use. This method of power generation produces near-zero emissions. The energy source is fuelled by water and does not pollute the air, leading to a reduction in carbon emissions . It is also entirely renewable as the water is not consumed, but constantly returned in the form of precipitation .
Hydropower is low cost
The costs associated are among the most competitive of the renewable energy industry. This form of renewable electricity has levelised cost of electricity values that are one of the lowest of all energy technologies . It is an affordable alternative to other sources of energy which provides low-cost electricity and high durability compared to other sources of energy. Construction costs can even be mitigated by using pre-existing structures such as bridges, tunnels and dams .
This economic energy source exploits domestic water resources, thereby achieving price stability, by avoiding market fluctuations . It is also primarily a domestic source of energy, allowing countries to produce their own energy with little reliance on international fuel sources .
Hydropower is reliable
Another key advantage is that it is a highly reliable source of energy. Unlike solar and wind power, which can be intermittent and dependent on weather conditions, water flows are consistent and predictable, making them a valuable source of baseload power. This allows hydropower to have a stabilising effect on the power grid by pumping additional capacity into the grid when electricity demand exceeds the availability of solar and wind resources . An example of this stabilising effect is the 2021 heat wave in California when hydropower (which normally accounts for 16% of the state’s electrical capacity) generated up to one third of the electricity required in the evening when solar resources were no longer useful .
Hydropower is flexible
Conventional hydropower facilities can quickly go from zero power to maximum output . This ability to generate power to the grid immediately provides essential backup power during major electricity outages or disruptions . Water can be stored in reservoirs to allow adjustment of power generation to meet consumption needs – leaving scope for the expansion of other renewable energy sources .
Hydropower provides support for other sources of power
Hydropower is an important component of power systems worldwide. It can enable a higher penetration of variable renewables such as solar and wind by providing balancing and flexibility services. Power generated can also be used in combination with other energy sources. Some sites offer the possibility of developing hybrid projects (e.g. wind/hydro or photovoltaic/hydro), opening the possibility of deploying even more renewable capacity . Although wind and solar are expected to outgrow hydrogen, it will play an integral role in the renewable energy industry. Primarily, it will act as a back-up power source to balance out variations in the power generated from other sources. For many countries, the use of hydropower reduces external energy dependence as it is an abundant resource .
Beyond power generation
In addition to being a low-carbon renewable electricity source, the advantages are not limited to power generation. Facilities can provide water services such as flood control, irrigation control, water distribution and wastewater control . Hydropower can also be used to mitigate the problems caused by the effects of climate change on ice retreat. Areas which face these issues often experience diminishing water resources and changes in run-off which could be offset by the storage capacity of hydropower facilities .
The water storage areas involved in the production of hydropower can also offer recreational opportunities such as fishing, swimming and boating. Many hydropower installations are required to provide some public access to the reservoir to allow the public to take advantage of these opportunities .
Challenges facing hydropower
Despite the many advantages of using hydropower, there are also some potential drawbacks to these technologies. One concern is that large-scale projects can have significant environmental impacts. These include the displacement of communities and the disruption of natural river ecosystems. Other challenges include:
- The need to ensure sustainability and climate resilience.
- Ageing facilities and related investment requirements.
- The need to adapt operation and maintenance to modern power system requirements.
- Outdated market structures and business models that do not recognise the full range of services provided.
As challenging as the present situation is, it also presents opportunities to modernise hydropower plants and equip them with the means to continue providing critical services to power systems globally.
Hydropower’s long-standing position as a source of energy should not be seen as a sign that it is outdated. It continues to be a valuable power source with a unique position as a balancing force to be used alongside other technologies. Its many advantages and continual growth make it a key part of the future of energy production and part of the global movement away from traditional fossil fuel sources which will be integral to achieving net zero targets in the coming years.
If you would like to find out more about hydropower you can study our accredited course, as part of the Sustainable Energy Consultant Expert Certificate or the overall Master in Renewable Energy Award.
 https://www.enelgreenpower.com/learning-hub/renewable-energies/hydroelectric-energy/advantages https://www.renewableenergyworld.com/baseload/how-hydropower-can-support-a-stable-low-carbon-grid-and-healthy-rivers/#gref
 https://www.mdpi.com/2073-4441/14/16/2563 https://www.repsol.com/en/energy-and-the-future/future-of-the-world/hydropower/index.cshtml