5 Facts You Should Know about Hydropower

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Hydropower is one of the most established and the biggest source of renewable energy in the world. Often, we think of hydropower as simple: water flows, turbines spin, and electricity is generated. But behind the scenes, there's a lot more to this intricate system than simple diagrams, and hydropower impacts people in a variety of ways.

Here are five key facts about hydropower that highlight its role, potential and some pitfalls as we look toward a sustainable future.

1. Hydropower dates back to ancient times

Long before electricity was discovered, humans harnessed the power of flowing water for mechanical work. The ancient Greeks used water wheels for grinding wheat into flour as early as the 4000 BCE. Similar technologies spread across civilizations, from Roman aqueducts to Chinese water wheels, demonstrating humanity's long-standing recognition of water's potential as an energy source.

In 1882, the world's first hydroelectric power plant began operating on the Fox River in Appleton, Wisconsin. Shortly after, hydro plants emerged in water -rich regions, establishing hydropower as a serious energy source. This period of rapid development saw the rise of iconic facilities like the Hoover Dam, which, beyond providing energy, became essential for water management and irrigation and even a recreational hot spot!

After World War II, hydroelectric power expanded, particularly in developing nations, due to its capacity for clean energy and economic benefits. This trend of hydropower reliance, however, was gradually replaced by fossil fuels and nuclear energy as the main source of electricity and energy in general.

2. Modern Hydropower Plants Can Achieve Remarkable Efficiency

Unlike other power generation methods that can struggle to convert the energy they collect into electricity, hydroelectric plants can achieve efficiency rates of up to 90% when converting the mechanical energy of flowing water into electrical energy. This efficiency rate far surpasses that of fossil fuel plants, which typically operate at 30-40% efficiency.

The high efficiency of hydroelectric power plants is largely attributed to their direct use of kinetic energy from water flow, which eliminates the energy losses associated with fuel combustion in fossil fuel power plants. In this system, water released from a reservoir flows through a penstock (a large group of pipes), driving a turbine connected to a generator. As a result, all of the water that flows through the penstock can drive the turbine into producing kinetic energy that can be converted into usable electricity.

3. Hydropower's Role In Energy Storage

One important thing that hydroelectric power plants have been doing in addition to generating electricity is storing them. Through pumped storage hydropower (PSH), the plant can act as a giant rechargeable battery.

During times of high demand, the stored water from the upper reservoir is released back into the lower reservoir, which will pass through the turbines and generate electricity. While demands are low, excess power from the grid can be used to pump water from the lower reservoir to the upper one.

Unlike other storage technologies such as lithium-ion batteries, which are constrained by capacity and shorter lifespans, PSH can store vast amounts of energy for extended periods and provide rapid response during peak demand times, a flexibility that makes it indispensable as more intermittent renewables like wind and solar are added to the energy mix. As a result of this dependability, PSH is the world's overwhelmingly largest form of grid energy storage, accounting for 90% of the global storage capacity.

4. Negative Impacts Extend Beyond Fish

One of the most well known impacts associated with dam construction is the impact to aquatic ecosystems, especially for spawning fish like sturgeons and salmon which find their migratory routes blocked by the dams. However, the negative impacts of larger scale hydropower projects, both environmental and social, goes beyond just the fish.

A direct impact of large impoundment facilities, hydropower that uses dam and reservoir systems, is that entire communities are often forced to relocate as a result.

To construct the Three Gorges Dam in China, an estimated 1.2 million people had to abandon their homes and their land when hundreds of towns were submerged under the Yangtze River. These relocations disrupt the social fabric of affected communities and often lead to economic hardship, especially in regions in the Global South. Displaced individuals may struggle to adapt to new environments or find equivalent sources of income.

Dams also prevent the natural flow of sediment, which is essential for maintaining downstream ecosystems and agricultural lands. Without this sediment, riverbanks and deltas can erode, and soil fertility can decline, affecting local agriculture and biodiversity.

When forests, vegetation, and organic matter are flooded by reservoir creation, they decompose anaerobically (without oxygen), producing methane and carbon dioxide. The gasses are eventually released into the atmosphere, either from the reservoir surface or through dam turbines. Climate change also exacerbates the risks associated with dams, as more extreme weather events and glacial melt raise the likelihood of flooding and dam failure.

5. The Future of Hydropower Lies Beyond Large Dams

America hasn't constructed any large dam projects in decades as a result of the environmental and social impact of such projects, which has become more palpable as a result of increasing research.

The future of hydropower is increasingly moving beyond the construction of large dams. Newer hydropower technology and systems aim to maintain the natural flow of rivers and avoid large reservoirs. This significantly reduces environmental impact and makes hydropower projects more adaptable to local environments and communities.

New hydropower technologies, like underground plants and gravitational vortex systems, offer a way to harness water's energy while reducing environmental impact. These systems operate within excavated caverns, using high-altitude water channeled through tunnels to drive turbines deep below the surface. This setup minimizes land disruption, preserves surface ecosystems, and enables efficient energy generation and storage.

Meanwhile, gravitational vortex systems provide energy from low-head water flows by creating a whirlpool in a small basin, spinning a turbine at the vortex's center. This approach is particularly eco-friendly, allowing for energy production in smaller rivers and streams without extensive construction, reducing environmental disturbance, and offering a sustainable solution for decentralized power generation.

Hybrid hydropower systems are also gaining traction, where hydropower reservoirs are paired with floating solar panels to create multi-source energy plants. This approach allows for efficient land use and provides a dual energy output that enhances reliability, particularly during dry seasons when water levels may be lower. Additionally, floating solar arrays help reduce evaporation in reservoirs, preserving water resources and improving long-term sustainability.

To learn more about hydropower, and other renewable energy such as solar, geothermal and wind, please read our more in depth EXPLAINERS.

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Plus if hydropower has got you fired you up please sign the Our Power, Our Planet Renewable Energy Petition HERE. Join us in urging governments across the world to prioritize the tripling of renewable energy from sources like solar, wind, geothermal, hydroelectric, and tidal by 2030.

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