The Risks of Dam Construction

For hundreds of years dams have been used one 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, the surrounding environment, water quality, and air quality. Because of these drawbacks, the federal government should ban the construction of dams within the United States unless measures are taken to reduce the risks of dam construction.

As of 1996, it was estimated that there are about 42,000 large dams worldwide containing nearly 10,000 km³, 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 it can be used for irrigation (Rosenberg). Dam construction also helps control the flow of the river, avoiding situations such as floods and droughts that are naturally occurring (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 species upstream and downstream. This barrier keeps species from traveling along the river, and also causes inbreeding among the species which can hurt its chance of survival (McCully 2001). 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 (McCully 2001). Second, a dam can disrupt the migration patterns of other species who used to travel across the river (McCully 2001). The building of dams also leads to the loss of aquatic biodiversity, including fisheries, floodplains, wetlands, and adjacent ecosystems (World Commission).

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 (McCully 2001). This increase can also impact the vegetation that is able to survive in the reservoir (McCully 2001).

While the creation of dams presumably 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 (McCully 2001). Furthermore, 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 surrounding area may be 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 (McCully 2001). 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 that it fails its normal process of removing both natural pollutants and outside sources of pollution from the water (Rosenberg). Furthermore, over time sedimentation builds up behind the dam, causing it to shallow; this eventually causes its effectiveness as a power source to decrease.

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 (such as CO2) creation 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 due to the creation of reservoirs gives off a much higher amount of greenhouse gases than is released by natural bodies of water (World Commission).

With every man-made construction there are both benefits and drawbacks. Though the construction of dams has provided humans with many resources, we are entering an age of environmental enlightenment. As the environment becomes more endangered we must consider how each of our actions impact our surroundings. Because of the many ecological drawbacks of dams we must cease construction and find other ways to benefit from our natural waterways.