We use dams to impede or stop the flow of water along a river. Although this engineering structure gets commonly associated with the production of hydroelectric energy, we also use them for a variety of different purposes. When a river gets dammed, it creates an artificial lake behind it that can be used for drinking water, recreational purposes, and irrigation.
The first dams that humans created were considered gravity dams. They were made of masonry or concrete that could resist the water load because of their weight. The ancient Egyptians are thought to have built the first one, and it was called Sadd el-Kafara. That name translates to “Dam of the Pagans” in Arabic. Archaeologists believe that the structure was 37 feet tall and almost 350 feet wide at its crest. Over 100,000 tons of stone and gravel were used to build the structure, but it failed after a few years because of overflows.
Several advantages and disadvantages of dams are worth reviewing when we look at the immediate and long-term impacts of this technology.
List of the Advantages of Dams
1. Dams provide us with a source of clean energy.
Hydroelectricity is responsible for 19% of the world’s energy supply, offering over 3000 terawatts each year. We can produce power from dams because of the kinetic energy of the water movements as it causes turbines to spin. That’s what allows us to generate electricity that is clean and renewable. Once the dam gets entirely constructed, we no longer have a dependence on fossil fuels to be responsible for the energy we need to maintain a modern lifestyle.
The United States is one of the largest producers of hydroelectricity in the world today, even with the reduction of operational facilities. Americans generate over 103,000 megawatts of renewable electricity with this resource, with only Canada currently creating more power in this way.
2. Dams help us to retain our water supply.
When we take an opportunity to dam a river, then the water will pool to form a reservoir behind the structure. This outcome allows the population centers in that region to collect fresh water during periods of heavy precipitation for use during a dry spell or drought. We also use this engineering marvel to control floodwaters or to supply a fixed amount of fluid to the surrounding areas for agricultural irrigation.
That means a dam can provide a buffer to an entire region against extreme weather events or irregular precipitation patterns.
3. This technology provides us with critical recreational opportunities.
Dams can provide us with a wide range of economic, environmental, and social benefits. Numerous reservoirs around the United States offer opportunities to go camping, boating, and waterskiing. It gives regions that generally wouldn’t have water access a place to have a boat launch that supports commercial fishing activities. These destinations can be the perfect place to have a picnic, go hiking, and spend time with your family.
4. A well-constructed dam provides several flood-control benefits.
Dams help to prevent property loss while reducing the risk to human life from annual flooding events. These structures can impound the floodwaters into the reservoir behind the dam, allowing us to release them under control or to store it for future use. We can divert excessive precipitation toward municipalities for fresh drinking water, create more irrigation opportunities, and meet a variety of energy-related needs.
The Nile River is famous for its unpredictable annual flow throughout history. As climate change continues to progress, the patterns of El Nino and La Nina in the Pacific Ocean will continue to increase. That means we will have more cycles of excessive precipitation and drought, and dams can help us to regulate this issue.
5. Dams give us a way to irrigate croplands that may not receive enough moisture.
About 10% of the croplands in the United States are currently irrigated using water that is stored in reservoirs behind a dam. Tens of thousands of jobs are directly tied to crop production and other agricultural activities that happen because of this benefit. Our food distribution networks remain active and consistent because of this advantage, and it allows us to do more with our growing efforts than if we relied on seasonal precipitation patterns alone.
6. A dam can provide a stable system of navigation.
We can use dams on rivers to provide a stable system of inland water transportation. The navigable waterways of the United States, like those found on the Mississippi River, can be challenging for some boats to use because of varying water levels. Installing a system of locks with this technology creates a safe place for us to transport goods and a variety of additional benefits.
In some situations, dams can even provide enhanced environmental protection. This technology has the capability of delivering hazardous materials retention or reducing the influence of sedimentation on vulnerable rivers.
7. Reservoirs can serve as a source of drinking water.
Because the water stored behind a dam in a reservoir is fresh, we can use it as a source of drinking water for nearby towns and cities. It is not unusual for communities in the United States to obtain their entire supply from streams or rivers that are close. We can use large canals, pipes, and other methods of transportation to ensure that every home has access to safe and clean drinking water.
List of the Disadvantages of Dams
1. Dams can displace a significant number of people.
An estimated 500 million people have been displaced by dams in the last two centuries because of the reservoirs that form behind each structure. As the surrounding dry areas get flooded, we no longer have the option to use land that was previously accessible for a variety of purposes. That means local agricultural activities go through a disruption process, even though the eventual increase in available water supports more irrigation.
2. Reservoirs behind a dam can lead to higher greenhouse gas emissions.
When vegetation gets engulfed in water, then the plants will eventually die. When this outcome occurs, the dead organic material releases methane that ultimately makes its way into the atmosphere. The increase in the production of greenhouse gases is significant because methane is up to 20 times more potent as a reflector than carbon dioxide.
The use of a dam in certain areas can also contribute to the loss of forests. When we lose a significant number of trees simultaneously, then there is a corresponding uptake of carbon dioxide that occurs because there are fewer photosynthesis processes happening each day.
3. This technology disrupts local ecosystems.
Dams create a flooding issue behind the structure as a way to form a reservoir. Not only does this disrupt human activities, but it also destroys the existing wildlife habitats that exist. This issue can disrupt entire ecosystems, which can have an adverse effect on a whole regional biome. Marine life that relies on an unobstructed flow of a river, such as migratory fish, can be adversely affected by the decision to dam the water.
4. Some river sediment is beneficial.
Dams can have a profound impact on the overall aquatic ecosystem of a region. The transformation upstream creates a lack of settlement that moves down the waterway to support the entire marine habitat. It can also cause changes in temperature, chemical composition, and shoreline stability. Many reservoirs also host invasive species, such as algae or snails, that undermine the natural communities of the plants and animals that lived on the river before.
The riverbeds that are downstream from a dam can erode by several yards within the first decade of operations. This damage can extend for hundreds of miles downstream afterward.
5. Dams create a flooding risk if they experience a failure.
We might use dams to provide us with a form of flood control, but the failure of this structure can have devastating consequences for downstream communities. The Vajont Dam Failed in 1963, only 4 years after its construction was finalized just outside of Venice, Italy. A landslide during the initial filling triggered a tsunami in the reservoir, causing over 50,000,000 cubic meters of floodwater that impacted nearby towns and villages. Some reports say that the wave was over 820 feet high.
Almost 2,000 people died in this disaster, and it was all because the dam was located in a geologically unstable area. When the Banqiao Reservoir Dam failed in 1975 in China, it caused an estimated 171,000 deaths.
6. Dams can have an adverse impact on the groundwater table.
When riverbeds experience deepening, then this problem creates a lower groundwater table along the river. That means it is more challenging for plant roots to reach what is required for survival. Homeowners in the vicinity must also dig deeper wells to draw water for their households. This issue can even change the mineral content and salts found in the fluid, creating damage to soil structures along the way.
7. The construction of a dam is a costly investment.
A large dam is defined as a structure that is higher than 15 meters. This definition means there are more than 57,000 structures around the world. Major dams are over 150 meters tall, and there are over 300 of these. China has the most, with over 23,000 operational facilities. The United States is in second, but far behind at 9,200. The cost of a large dam today can be over $20 billion, and it may take between 7 to 10 years to complete its construction. Those are resources that many communities could put to better use.
8. Dams can block water progression to different states, provinces, and countries.
When a dam gets built at or near a border between two states, provinces, or countries, then it might also block the progress of the water in one of those areas. That means the supply from the same river in the neighboring country is no longer under their direct control. This disadvantage can result in severe issues between neighbors, creating a constant source of conflict that can sometimes even lead to war.
9. It can make the water too shallow for navigation.
Dams try to avoid environmental impacts by releasing water downstream and creating marine life channels that allow for upstream movement. Although this approach is imperfect, the updates to this engineering process have had some benefits. What doesn’t get solved through this process is the depth of water that might be available downstream. The Colorado River is an excellent example of this issue because the waterway doesn’t make it to its outlet most years because of all the damming activity that occurs.
If the waters are too shallow to use in a river, then there is no way to use it for transportation benefits. This issue also changes the settlement profile so that marches and wetlands no longer receive the healthy supports from the river that they need.
10. Reservoirs can be challenging to maintain.
When drought is a significant issue for a community, then a reservoir that’s behind a dam can be a vital resource. Maintaining this new body of water comes with a set of its own challenges because evaporation can happen during dry times and result in an increase in environmental problems. There also tends to be a significant buildup of organic matter in the sediment with this disadvantage, resulting in potentially carcinogenic trihalomethanes when the water gets chlorinated for drinking purposes.
The Klamath River Has worked under the influence of four dams for almost 60 years. Those structures generate an average of 82 megawatts of power annually. That energy might be renewable, but it is not free of environmental consequences. These structures took a dynamic ecosystem and replaced it with a wretched impostor of itself. Even the dams’ owner decided that the cost of maintaining the structures it was no longer worth it, and so they are coming down.
The Reventazon Dam in Costa Rica tells a very different story. Engineers over the past 6 years have steadily corralled the river so that the facility can generate 305 megawatts of electricity annually. This project is the largest of its kind in Central America, and it almost guarantees that the country’s electrical grid will be nearly 100% renewable energy.
When we examine the advantages and disadvantages of dams, it is essential to remember that both perspectives make legitimate claims to be doing what is best for the environment. These structures might be coming down in the United States, but they are going up all over the rest of the world. That means this technology is going to be in the past for some populations, but it will also be the future for others.
Brandon Miller has a B.A. from the University of Texas at Austin. He is a seasoned writer who has written over one hundred articles, which have been read by over 500,000 people. If you have any comments or concerns about this blog post, then please contact the Green Garage team here.