Matt Ackroyd
ENG308J
Assignment #5
Dams: Good or Bad?
In the past 50 to 60 years, dams have been popping up everywhere. There are many reasons for installing a dam on a river. It may be a large hydroelectric dam that’s 600 feet high or just a small, 10 foot earth fill dam to hold back some extra water. But for every dam come a lot of different effects and impacts on the environment and the economy. Some of these effects are very beneficial, like hydroelectric power generation, but there are also the negative impacts on the river’s flow and wildlife as well as the effects on the surrounding environment. And it is the job of the engineers to account for all these effects and impacts before starting such a project. But for the already existing dams, what is to be done about those that aren’t very beneficial and have many negative impacts? This is an up and coming concern for engineers as many dams’ life spans are continuing to come closer to an end. So are dams good or bad? Do their benefits for humans outweigh their negative effects on the land its natural way of life?
Well as mentioned before, dams have many reasons to be built and have many uses. The main reason for dams is their ability to create and store a very large fresh water supply (ICOLD). Damming a river, no matter what the size, creates a larger, constant supply of water that can be used for irrigation for farming, drinking water for people in cities nearby, improved in-land navigation, and the recreational uses of a large lake-like body of water. Almost all of the dams in the Western United States are built and used for these reasons. This area of the country is fairly dry but is also very flat and useful for agriculture. And the water for these activities has to come from somewhere. It’s estimated that by the year 2025, 67% of water used for agriculture will come from means of some sort of irrigation (Boutraa). So to help aid in the irrigation, reservoirs are creating by building a dam. Dams also aid in another problem of nature, flooding.
Flooding is the major national disaster in the world, taking about 200 lives a year in the U.S. (http://floodsafety.org/national/life/statistics.htm). One way to prevent a flooding disaster from occurring in areas where it is common, a dam can be erected to help hold some of the excess runoff water back that produced during a heavy rain, resulting in lower water levels of main rivers and streams. In 1941, the U.S Army Corps of Engineers (USACE) built the Blackwater Dam in Webster, New Hampshire. It is part of a series of five flood control dams that were constructed in response to a flooding disaster in the Merrimack River Basin (http://www.nae.usace.army.mil/recreati/bwd/bwdfc.htm). It protects a large, populated area spanning from three cities in New Hampshire to three cities of Massachusetts and is estimated by the USACE to have prevented over $15 million in flood damages since its construction. And it only cost $1.32 to build. As for the effects the dam has on the flow of the river, it flows naturally through the dam and only when a flood is evident does the Corps close the flood gates to hold back the water (http://www.nae.usace.army.mil/recreati/bwd/bwdfc.htm). The reservoir has also created a diverse habitat for various types of animals, including the bald eagle and a couple species of trout. Unfortunately this particular dam doesn’t contribute to another important advantage a dam could have, which is the production of hydro electricity.
Figure 1: The Blackwater Dam in Webster, New Hampshire
The reason hydroelectric power is important is because it’s considered a clean energy resource because it essentially is produced by the simple falling of water due to gravity, which has no negative impact on the environment. The United States’ many hydroelectric dams produce a massive amount of electricity. The well known, 736.4 foot height Hoover Dam in Nevada produced a net average annual power generation of 4.2 billion kilowatt-hours between 1999 and 2008. This is in combination with the Bureau of Reclamation’s 57 other dams, which combine to produce an estimated 42 billion kilowatt-hours a year (http://www.usbr.gov/power/edu/pamphlet.pdf). A kilowatt-hour is the amount of energy used that is equivalent to 1000 watts in one hour. To put it in perspective, 42 billion kilowatt hours can power a city of 14 million people for a year. This type of power generation is reproducible and can be accessed anytime with the push of a couple buttons on a control panel. This is very advantageous in the event of some kind of major power loss, where a large quantity of electricity is needed quickly. And according to the Bureau of Reclamation, hydroelectric power plants are generally inexpensive to maintain, last for a long while compared to other types of power plants, and do not require of any other type of natural resource to keep this electricity production flowing. Engineers are searching for more ways to access and use hydroelectric power, especially in states like Ohio, who got about 87% percent of their power from coal in 2002, just because coal is so abundant in the area, compared to Washington, who got 90% of their electricity from hydropower (http://www.usbr.gov/power/edu/pamphlet.pdf). Low head dams, which are small dams with a water drop of less than 65 feet, are a considerable option because they produce a large amount of power compared to their size and costs to build. But one of the reasons dams, big and small, aren’t being built everywhere possible is there major effects on the natural environments.
*Adding negative effects and discussion of the option of dam removal, and a conclusion*
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