What Is Hydropower?

Hydropower is essential as we transition toward a Net Zero future. As the largest renewable energy source worldwide, and the third largest energy source overall after coal and natural gas, hydropower has a crucial role to play. According to the International Hydropower Association, “no country has come close to achieving 100% renewables without hydropower in the energy mix.” But what exactly is hydropower, and how can it help to accelerate momentum toward renewable energy sources? 

How Hydropower Works 

As the name suggests, hydropower uses water to generate power. In nature, moving water - such as in streams and rivers - flows downhill. Before water moves downhill, it has potential energy, which can also be artificially recreated using dams. Hydropower harnesses this potential energy, causing the turbine blades to rotate, converting this potential energy into kinetic energy. The turbines are connected to generators, which transform the kinetic energy into electrical energy.  

Over the last 50 years, the use of hydropower has stopped over 100 billion tonnes of carbon dioxide from entering the atmosphere. In Iceland, where almost 100% of energy is from renewable sources, approximately three quarters of electricity generation is from hydropower. In comparison, 6.3% of the U.S.’ electricity is generated from hydropower. 

Benefits of Hydropower 

There are many benefits of hydropower, including being efficient (with modern hydropower plants converting more than 90% of potential energy into electricity), providing a fossil-free option, and having a quick response to emergency energy demands. However, there are some less-known facts about hydropower that have wider implications for us. 

Cost-effective 

Hydropower currently provides most of the electricity for 800 million people in developing economies, as well as offering a more economically viable opportunity to improve electricity access in countries where there is evident economic inequity. It is the most efficient way to generate electricity (converting as much as 90% of potential energy into electricity), is considered to have the lowest cost of all energy sources globally, with U.S. states including Idaho, Washington, and Oregon, receiving most of their electricity from hydropower. 

Flood control 

It can help to bolster flood defences, by controlling water levels along waterways. With the consequences of climate change and flooding reiterated by the recent events in Pakistan, hydropower may help to combat the increasing occurrence of flooding. 

Combatting food insecurity 

Almost 10% of the global population suffers from hunger. Despite the United Nations’ Sustainability Development Goals (SDGs), we are currently not on track to reaching Zero Hunger by 2030, with 50 million people across 45 countries at risk of famine. Hydropower can assist in combatting food insecurity, with water-containing reservoirs being used in irrigation systems to provide a water source on an as-needed basis. 

Clean water 

Universal clean water and sanitation is another fight that we are currently losing, and we must quadruple our efforts to meet the SDG target by 2030. Similarly to combatting food insecurity, stored water in reservoirs used for hydropower can also be used as a source of clean water and sanitation. 

Obstacles to Overcome 

Unfortunately, hydropower is not perfect. As with most green transitions for a Net Zero future, there is the initial financial cost. There is also the risk of flooding, which is only likely to increase given the implications of climate change. As a renewable energy source, hydropower is often considered better than burning fossil fuels in respect to pollution and climate change. However, from a triple planetary lens (of climate change, pollution, and biodiversity), hydropower is still damaging to the environment. 

Environmental impact 

Hydropower plants still create greenhouse gases, including carbon dioxide and methane, when vegetation in the water decomposes. While many act as carbon sinks (absorbing more carbon dioxide, through vegetation undergoing photosynthesis, than they produce), some hydropower plants produce more greenhouse gases than they are able to absorb. 

Furthermore, hydropower plants require a large amount of land and can affect biodiversity. In larger-scale hydropower plants, the amount of land required can cause ethnic group displacement. Furthermore human-made dams particularly affect downstream biodiversity, altering fish migration and population sizes (with hydropower being one of the main culprits for reducing freshwater species’ populations by 84%), changing how the water flows and trapping flood-protecting sediments. 

Drought 

With increasing global temperatures, there is a greater chance of rain through increased cloud formation and air moisture. However, global warming is also associated with drought, due to quicker evaporation of water. During periods of drought, water levels are lower in hydropower plants’ reservoirs. Consequently, there is less available potential energy to be converted to electricity. This is reiterated by 61% of hydropower plants worldwide predicted to be at high risk of drought (as well as flooding) by 2050. 

The effects of drought are already evident in Brazil, where up to two-thirds of energy comes from hydropower. Brazil has experienced severe droughts over the last decade, causing both hydropower energy provision and the Brazilian public to suffer with higher energy costs. 

Similar issues have also been presented around the world. China is the largest hydropower producer worldwide. However, they have been affected by severe droughts in 2022, with AP News and TIME reporting that hydropower energy generation has been halved in the Sichuan province (which normally produces 80% of electricity). Furthermore, in the U.S., there is concern of drought affecting hydropower across several regions in particular, including Montana, Nevada, Texas, Arizona, California, Arkansas, and Oklahoma. 

The Future for Hydropower 

Hydropower plays a key role in the future of renewable energy. However, given the obstacles currently present, it cannot be the only renewable that we rely on. We must promote hydropower use to help transition from fossil fuel reliance, and to improve electricity access worldwide. However, we must remain aware of its limitations, and utilise other renewables where possible to help overcome these.  

Sustainable hydropower, which focusses on the principles of the mitigation hierarchy (to take a stepwise approach to maintain biodiversity in the order of avoid, minimise, mitigate, and compensate) can reduce biodiversity loss, and promote a triple planetary lens perspective. The challenges posed by drought and flooding are likely to continue. Therefore, further dedicated research and innovation to create climate-resilient, cost-effective, and universal hydropower is essential if we are to transition to a green future.