For hundreds of years dams have been used as a critical tool for local communities. They have provided people with control over a powerful resource that has provided a water source and power source, as well as a place for recreation and food supply. However, just recently the negative environmental impact of dams has started to become apparent. As the ecological impacts are becoming more researched and understood, many are realizing that the significant ecological impacts that dams have on the surrounding areas outweigh the benefits they may provide. Dams are a serious detriment to the ecosystem of the river and the surrounding environment, as well as water quality and air quality. Because of these drawbacks, the federal government should place restrictions on the construction of dams within the United States so that measures are taken to reduce the environmental impact of dams.
As of 1996, it was estimated that there are about 42,000 large dams containing nearly five times the volume of water contained in all rivers worldwide (Rosenberg). Furthermore, a study by the World Wildlife Foundation found that of the world's 227 largest rivers, more than 60% have been rerouted or fragmented by the creation of dams (WWF). One of the reasons dams are built is for water storage for use by local communities, especially when so that it be used for irrigation. Dam construction also helps control the flow of the river, avoiding situations such as floods and droughts that are occur naturally (Rosenberg). This also gives humans control over a limited research and allows them the freedom to decide where and how the river flows. Despite the many benefits of dams, possibly the most critical is that many dams provide a source of energy to communities. Dams are a great source of hydroelectric power, providing a green option for many communities (Rosenberg). Despite the benefits that dams provide, recently the environmental impact of dams has become a topic of discussion.
The construction of dams can have a serious and irreversible effect on the ecosystem of the river. First, the building of a dam disrupts the migration patterns of the species that inhabit it because it creates a barrier between upstream and downstream. This barrier keeps species from traveling along the river. Clearly, the barrier created by a dam also reduces the number of species that are able to survive in the riverbed, which can upset the entire local ecosystem. Second, a dam can disrupt the migration patterns of other species that travel across the river (McCully 2001).
Another way that dams impact the ecosystem of a river is that creating a reservoir impacts the water temperature of a riverbed. The creation of a much larger surface area usually causes the temperature of the reservoir to increase. This increase in water temperature may allow some species to survive better; however, they will not be natural to the local ecosystem and species that have become inherent to the area may not be able to survive. This increase can also impact the vegetation that is able to survive in the reservoir (McCully 2001).
While the creation of dams has an impact on the river's ecosystem, it can have a significant impact on the delicate ecosystem that surrounds a riverbed as well. The ecosystem that surrounds a river is one of the most diverse natural ecosystems, and the flooding of riverbeds destroy these ecosystems. Also, one of the reasons many dams are built is to manage water levels, especially to stop flooding. Although this may seem like an advantage, the lack of natural flooding can quickly upset the surrounding area. Much of the area is dependent on the natural flooding to survive, and the loss of this flooding can have a negative impact on local vegetation and growth, even threatening their survival. Furthermore, the creation of dams in forested areas often leads to a serious deforestation not only of the immediate riverbed, but for much of the surrounding area. Forest area is lost with the initial creation of the reservoir, but as new farming areas are created and access to remote locations becomes available trees are removed to build roads, houses, and farmland (McCully 2001).
Dams also affect both the sedimentation and the water quality of a riverbed. The creation of dams causes erosion down river because sediment is not being carried from up river. This is detrimental to the upper and lower riverbed and can also affect the water quality for both the reservoir and the river. The lack of water flow through the riverbed means it cannot perform its normal process of removing pollution from the water. Furthermore, over time sedimentation builds up behind the dam, causing it to shallow; this eventually causes its effectiveness as a power source to decrease (Rosenberg).
Dam construction can also cause an increase in the production of greenhouse gases which are detrimental to the environment. The normal process of greenhouse gas creation (such as CO2) and use by the natural ecosystem is disrupted. This can lead to the production and release of large amounts of greenhouse gases, which contributes to the risk of global warming (Rosenberg). Furthermore, the rotting of vegetation caused by the creation of reservoirs gives off a much higher amount of greenhouse gases than is released by natural bodies of water (World Commission).
Although dams offer many benefits to the surrounding communities, their construction cannot continue to be supported until restrictions are put into place to protect the surrounding environment. It is possible for dams to be constructed in a way that protects the fragile ecosystem of the river. A series of measures should be put into place to protect the environment while still offering benefits to the surrounding communities.
One restriction that must be put into place is a clause to protect the sensitive ecosystem of the river. The severe negative drawbacks that dams cause must be avoided whenever possible and reduced only when unavoidable. To achieve this, careful consideration should be given to site selection, including a thorough investigation into the ecosystem and the cycle of the river before a location is finalized so we fully understand how to work with the river and avoid its disruption (World Commission). The construction of the dam should also change to improve the flow from upriver to downriver which will help preserve the ecosystem’s balance. Finally, there should be a constant effort to maintain structures. This should include ongoing monitoring of the ecosystem of rivers that have been dammed as well as a review of the benefits of the dam. If the ecosystem of the area becomes strained or the dam is not providing clear advantages, it should be removed.
Second, a license or contract should be required for anyone attempting to create a dam. This contract would give the constructor full responsibility for the dam as well as the livelihood of the ecosystem for the time the dam is active. This would include proper removal when the dam is either ineffective or becoming a strain on the environment.
Furthermore, there should be a common set of guidelines and restrictions established by the federal government requiring that all dams are environmentally friendly yet effective and useful. Any group or company wishing to build a dam should agree to these guidelines and provide regular evidence that they are being followed (World Commission). Some states have already started similar programs for dam construction. Washington State’s Department of Ecology requires a permit for anyone attempting to build a dam within the state, as well as submission of plans for the dam’s construction to be reviewed by a professional engineer. The Department of Ecology also offers a set of guidelines regarding topics such as owner responsibilities, dam design and construction, operation and maintenance, and emergency plan information. Offering tools such as these to dam operators will improve the construction and maintenance of dams, which will help decrease the environmental impacts of these dams (Washington State).
Third, the government and private organizations should address dams that have already been built. We must take accountability for them and improve and optimize their effectiveness, as well as upgrade facilities. Unfortunately, it would be very costly to remove all existing dams considering both monetary cost and labor. However, a thorough investigation into existing dams should be started by each state. The most detrimental dams should have plans made to either improve or remove them within a short timeframe.
Work Cited
McCully, Patrick. Silenced Rivers: The Ecology and Politics of Large Dams. 2001. 28 Jan. 2009. <http://www.internationalrivers.org/en/node/1636>.
Rosenberg, David, McCully, Patrick., and Pringle, Catherine. Environmental Effects of Hydrological Alterations. International Rivers. 28 Jan. 2009.
The World Commission on Dams. Dams and Development: A New Framework for Decision-Making. 2001. 28 Jan. 2009.
Washington State Governor’s Office of Regulatory Assistance. Environmental Permit Handbook: Dam Construction Permit. 2008. 5 Feb. 2009.
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