Hydropower, which is energy harnessed from the power of falling water, has been used around the world for thousands of years.1 The first hydroelectric power plant in the United States went online in 1882, and within a few decades hydroelectric power made up approximately 40% of U.S. electricity.2 Hydropower now constitutes only 10% of U.S. electricity production, and nearly 20% of electricity generated around the world.3 In the realm of renewable energy, hydroelectricity is dominant – it is responsible for more than 90% of all energy produced from renewable sources in the United States.4
How Hydroelectricity Works
The mechanics of hydroelectric power production are not too different from those of coal-fired power plants. Both use a source of energy—water in the case of hydropower or coal for traditional energy production—to run an electricity-generating turbine. In the case of coal, steam moves the turbine that powers the generator, while falling water is used for hydroelectric plants.5 Dams must be built in order to create a source of falling water, and thus hydropower. Because gravity plays an important role in the process, dams are located at points where a river drops in elevation. Engineers can control the amount of water that flows through the dam, thereby altering the rate of electricity production.6
Advantages of Hydroelectricity
One of the primary advantages of hydroelectric power is its reliance on a renewable resource—water.8 Hydroelectricity requires no fuel to run other than water, which is naturally recycled and replenished through rainfall. As a result, the viability of hydroelectricity is not subject to variations in fuel cost, production and availability.9 The constant supply of water not only solves the fuel problem, it also allows for flexibility and control in levels of electricity production. Whereas solar and wind energy generators are at the mercy of fluctuations in their natural power sources—cloudy or calm days, respectively—hydroelectric plants have a steady flow of water that can even be adjusted in order to provide more power at peak times.10
Another benefit provided by the simple power source is smooth operation. Once they come online, hydroelectric power plants can be mostly automated and require very little attention or maintenance. Indeed, they have proven to be quite long-lasting, with some functioning well past the 50-year mark.11 Hydroelectric power is also the cheapest method of electricity production, largely because of the reasons described above. Hydroelectric plants require minimal resources after their initial construction and none at all to acquire and process energy, which means that they are incredibly efficient to operate.12
Disadvantages of Hydroelectricity
Hydroelectric power is not perfect. If it was a perfect energy source, there would be no need to debate so many different alternative energy sources! One of the key drawbacks to this type of energy production is that hydroelectric plants only work in specific locations. They must be built on a river, of course, and the site must provide a suitable drop in elevation to run the generator.14 While the costs of operation are minimal, as discussed above, initial construction costs certainly are not. Building a new plant can often be extremely expensive, especially if there is not already an existing dam in place.15 In addition to building the dam, electric generators and transmission lines must also be built.16
Hydroelectric plants tend to run smoothly, but they are not immune to failure. Floods in particular can cause serious problems for a dam, as they can exert much more pressure on the dam than it is intended to withstand. One of the largest failures in history occurred in 1975 at China’s Banqiao Dam. Although the dam was built for extreme levels of flooding, a typhoon in August created flood levels higher than engineers had ever anticipated and caused the dam to collapse. 26,000 people died from the flooding itself, while tens of thousands more died as a result of disease and water contamination in the aftermath of the flood.17 Finally, while hydroelectric power plants do not use fossil fuels, they still produce emissions. This is not due to the electricity generation itself. Rather, the construction of a plant causes flooding in the nearby area, which often kills many plants and trees and leads to the release of methane as they decompose.18 This also leads to loss of biodiversity, another major threat to our environment.
Controversy Surrounding Hydroelectricity
Constructing a new hydroelectric plant is not as simple as finding a good location and starting to build. In recent decades, scientists and environmentalists have been paying close attention to the impacts of hydroelectric power plants on their surrounding environment. One of the most critical issues is the safety of local fish populations. In the Northwestern States, dams have prevented thousands of salmon from traveling upstream to spawn and have also blocked their passage on the way back down.19 John Seebach, director of the Hydropower Reform Initiative, acknowledged the difficulty of the issue: “Hydropower does have pretty significant and serious impacts on rivers… It also provides some pretty significant benefits in terms of power production. So it’s a tricky balance to get those benefits while trying to minimize those impacts.”20
In response to the concerns over disrupting fish populations, the hydroelectric power industry developed ways to protect the passage of fish without interrupting the operation of their generators. Workers at Rocky Reach Dam in Washington, for example, recently completed a nearly $300 million project that included the creation of a “mile-long safe passage tunnel” that will keep the route traversable for the millions of fish that pass through annually.21 Beyond such alterations, there is pressure from advocacy groups and the government for industry leaders to find new ways of minimizing their environmental impact. The Department of Energy recently encouraged “low-head, low-power” facilities—which are smaller units that would be able to produce significant amounts of electricity with a reduced level of environmental impact. 22
In developing nations, the enormous potential of hydroelectric power is being weighed against the potential environmental impacts of new hydroelectric installations. There has been heated debate around new dams in Brazil, Chile, and Laos, among other countries, as environmentalists and downstream residents voice their concerns over the potential consequences—both known and unknown. 23
Hydroelectricity’s Future
There are signs that hydroelectric power will play a growing role in the coming years. The National Hydropower Association aims to double the amount of hydroelectric power generated in the U.S. over the next 15 years, a process made easier by increasing concern over climate change and by the fact that only a small fraction of the nation’s 82,600 dams currently have hydroelectric generators.24 New hydroelectric facilities began running in unprecedented numbers in both 2008 and 2009, suggesting that if the current environmental concerns can be addressed quickly and efficiently, hydroelectric power will have a very bright future.25 Of further interest, wave power from our oceans is an emerging renewable energy source, and has less of an impact on fish and human populations than hydroelectricity.26 We will have to watch and see where the power of water can take us.
