Hydroelectric Dams Pros and Cons: Everything You Need to Know

Anyone who lived through a coastal hurricane or major flood will testify to the mighty power of flowing water. The devastation of the aftermath tells the tale of crushing force and unstoppable movement. Utilizing this dynamism to human advantage is a practice as old as ancient Greece, where water wheels powered the grain milling process. Since then, humankind developed all kinds of ways to harness energy from water pressure. Damming rivers is one such method, for better and for worse.

Hydroelectric Dams Pros

USACE Center Hill Dam


The electricity generated by dams is in little danger of long-term dissipation. This ongoing availability is a huge factor when weighing the hydroelectric dams pros and cons. Turbine blades, located inside the dam structure, spin as water surges through the embankment. Connected to generators, the blades produce electricity for local and regional power grids. So, as long as rain falls and rivers flow, hydropower is a feasible and usable energy supply, and a promising presence far into the future.

As if that is not compelling enough, scientists believe that hydroelectricity has only contributed to a fraction of its potential. This means hydroelectric dams can possibly replace some fossil fuel percentage of total energy production.


Petroleum and coal, economically important as they were, contribute to a destabilized troposphere and global warming. Serving as an alternative to fossil fuels counts heavily in favor when evaluating hydroelectric dams pros and cons. Since no fuel is burned there is no air pollution. By logical extension, no greenhouse gasses disperse thereby aggravating climate change.

The dams also provide ancillary environmental benefits. For one thing, they control flooding during heavy rains. They also afford irrigation during times of drought. All in all, hydroelectric facilities provide needed resources and protection to vulnerable ecosystems while brining relief to the atmosphere.


The water levels and consequent pressure of rivers and streams is variable over time. Dams offset that irregularity with constancy. By gathering water in reservoirs, they store hydropower for later use in the event of extended dry conditions. In this way, the reservoir acts like a battery—charging the generators when there is no accessible current.

This matter of storage gives (at least at present) hydropower an advantage over solar and wind sources, which are still awaiting greater repository capacity. It also makes this form of electricity more reliable since it has its own back-up system. Another positive in the array of hydroelectric dams pros and cons.


Few worries attend to the safety and soundness of hydropower generation. Any malfunction possible will not match in danger or magnitude an accident at a nuclear production facility. Moreover, there are neither toxic substances to leak nor poisonous emissions to escape. These alone count as assets in the hydroelectric dams pros and cons.

In addition, engineers protect the dam structures themselves with the installation of spillways. Ramp-like passages in design and function, spillways respond to floods by redirecting overflow from the turbines and generators to the waterway ahead of the dam.

Hydroelectric Dams Cons

Adam Beck Complex

Disadvantages that Come with Building

There are about 57,000 large dams in the world. Many are nearly 500 feet tall and the size of four-story commercial buildings. Constructing them is no mean feat and estimates determine that at least 80 million people were displaced since the first dam project. Within the pantheon of hydroelectric dams pros and cons, such a statistic should give one pause.

The building of these levees not only expels human settlements, but also removes many species habitats—both fish and wildlife—during the creation process. One study conducted by the University of East Anglia determined that a plethora of species was flooded out when a dam was built in the Amazonia region of Brazil in the 1980s.

Huge Cost

Not only does the erection of gargantuan dams affect the ecology, they affect the pocketbook as well. Hydroelectric plants receive funding from private sources and from supra-national organizations like the World Bank. Yet they also depend heavily on government dollars, i.e. taxpayer dollars. For example, the U.S. Department of Energy made a sizable, multi-billion dollar commitment to hydropower in 2014.

Worldwide, aspirations for hydropower will call for over three-trillion dollars of investment. The money has to come from somewhere. This is a minus when it comes to hydroelectric dams pros and cons.

May Cause Droughts

Wait? What about the reservoirs? They ensure against the possibility of drought, right? Yes and no. Droughts afflict landscapes for varying durations. However, some droughts hang on…and on. A 16-year long drought in the Nevada-Arizona region, for instance, sunk Lake Mead to its lowest level in history.

Lake Mead is a reservoir formed with the establishment of the Hoover Dam. It is the largest reservoir in the United States and is augmented by melting snow from the Colorado River. In 2016, the Voice of America reported that Lake Mead dropped to only 37 percent of its total capacity.

The Use of Reservoirs

Back to reservoirs, those batteries that stored power for the generators. Careful consideration is applicable to the other needs that reservoirs address. Humans require water for life, for one thing. We use water to clean our clothes, our cars, our homes and our bodies. Although water is a renewable resource, it is not infinite, especially all the time.

As recent drought events in California remind us, farmers need a lot of water to grow food and irrigate soil. The competition for this seemingly inexhaustible element makes water a little more precious. In the enthusiasm to build more dams, planners should bear in mind the ubiquitous needs for water.

The Bottom Line

As with many advances in energy production and natural resources, hydropower—so promising and efficient—produces side effects that are problematic. Recognizing this, policy makers do well to include hydroelectric dams in a larger regime of renewable energy incorporation. With no carbon emissions or chemical ingredients, this form of power is attractive. The initial expense to economy and ecology makes it less so.

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