Dam+Removal+Pros+and+Cons

by: Matt Plomp

Dams are used around the world for numerous purposes, including flood prevention, irrigation, hydroelectric power, water supply, and more. However, in recent years, the scientific community has become more aware of environmental issues and hazards represented by the presence of dams on river systems worldwide. The dramatic decrease in fish diversity upstream of dams and the buildup of sediment and heavy metals are but a few of the impacts of dams. However, the removal of dams can be hazardous as well, as improper deconstruction of dams can unleash pollution to the rest of the river, and dramatically change the river's structure.

Dam Removal: Dams were originally built before understanding of their impacts on rivers were widely known. While beneficial to humans, dams cause stress on a river system, stopping the flow of sediment and nutrients downstream and negatively impacting fish species that spawn in upstream areas. The nutrients contained within this sediment gets caught behind the dam and downstream areas can suffer increased erosion from the lack of sediment already held by the water. Areas downstream of dams generally have differing temperatures from the rest of the river depending on the size of the dam. For instance, a dam that forms a reservoir or lake behind it still must let some water pass through the dam. The water that passes through is the water from the bottom of that reservoir and is colder than the rest of the river. The deconstruction of dams, while not perfect, can aid in the restoration of a river's natural state, including biodiversity and fertility of nearby soils. "The most important positive outcome of dam removal is the reconnection of river reaches so that they can operate as an integrated system, which is the basis of a river with restored physical integrity."

Dam Retention: One of the major factors against dam removal is the cost. Consumers Power, an electric company in West Michigan, has cited the cost of the removal of one dam at close to $100 million. Other considerations need to be made, including those who live nearby the dam. Those who live along a reservoir will suddenly find themselves without lakefront property upon the removal of a dam, and those downstream may be displaced by the increase in water flow. This can make the decision to remove a dam an unpopular one for those in political power.

Dams that provide hydroelectric power, when removed, leave a void in the electrical budget, leaving to a potential need to increase power generated by dirtier methods such as coal or natural gas. The possibility of nuclear power filling that void and the built up heavy metals in the sediment behind a dam can lead to public safety issues.

Sources: http://www.heinzctr.org/publications/PDF/Frontmatter_dams.pdf http://www.hydroreform.org/news/2007/06/06/the-cost-of-removing-dams-on-michigans-muskegon-au-sable-and-manistee-rivers http://en.wikipedia.org/wiki/Dam