Tuesday, February 15, 2011

The Negative Side of Hydroelectricity...

Let's look at the disadvantages of hydropower. Despite the fact that the United States and other countries gain a large percent of electricity from hydropower, there are a few disadvantages of hydropower.

1. Hydropower dams disrupt the natural flow of rivers. This will alter the river and riverside habitat. Whenever I read about a hydroelectric plant being developed, my mind is drawn back to the 1972 movie "Deliverance".

It was in this movie that the three men wanted to canoe a river in North Georgia before the engineers began construction of a dam for hydroelectricity.

In reality the river in the movie is the Chattooga River and the dam formed Lake Tugalo. Arising high in the North Carolina Appalachians, the Chattooga River travels a rugged 50 miles before ending in Lake Tugalo?s still waters.

For much of its journey, the Chattooga forms the state line between South Carolina and Georgia.

On May 10, 1974, Congress designated the Chattooga be protected as a National Wild and Scenic River. The protection was awarded because of the river?s outstanding scenery and recreation, and its wildlife, geologic, and cultural values. The river is famous with white water thrill seekers, and is well known among trout anglers.

Chattooga River

Even though the Chattooga Rive and Lake Tugalo are still mighty impressive, it did, never the less, alter the ecology of that region.

2. Impedes the natural flow of sediments. Rivers naturally erode, carry, and deposit sediment. These processes are what shape the river, form meanders, pools, and riffles.

The river deposits its sediment load in the impoundment when the flow velocity slows and the particles settle out. Over time, sediment can fill in the impoundment.

Eventually, the impoundment may become so shallow that the sediment must be removed by dredging or other means. The river downstream of the dam is ?starved? for sediment because the sediment naturally flowing in the river has been trapped behind the dam.

The water flowing through the outlet of the dam may be relatively clear, and carry little sediment.A third of the disadvantages of hydropower is...

3. Scour holes. Water flowing over a dam can cause scour holes to form immediately below the dam. Scour holes may undercut the foundation of the dam threatening the integrity of the structure. In addition, the currents in scour holes present a hazard to swimmers. For more information, click here.

4. Obstacles to fish migration. Here is another of the disadvantages of hydropower. According to the Water Resource Management practicum:

"Building a dam on a river has major implications for the biota found in the river system. Because fish and other biota cannot move past a dam, the dam effectively splits the river into separate ecological zones: the river above the dam and the river below the dam.

Fish passages may be added to a dam to help fish move up and downstream, but they are not always effective. Although the free movement of fish can sustain a healthy fishery, a dam may be a barrier to the movement of unwanted invasive species.

Water tends to warm more in an impoundment than in a free-flowing river, which may affect the types of fish found upstream, in, and downstream of the impoundment. Impounded and free-flowing river systems provide habitat for amphibians, reptiles, birds and mammals.

hydropower dam

5. Catastrophic Failure. If dam breaks it would be a disaster and would kill many people. One classic example in American history is the Johnstown Flood. According to Wikipedia:

"The Johnstown Flood disaster (or Great Flood of 1889 as it became known locally) occurred on May 31, 1889.

It was the result of the failure of the South Fork Dam situated 14 miles (23 km) upstream of the town of Johnstown, Pennsylvania, USA, made worse by several days of extremely heavy rainfall.

The dam's failure unleashed a torrent of 20 million tons of water (18.1 million cubic meters/ 4.8 billion gallons). The flood killed over 2,200 people and produced US$17 million of damage."

Johnstown Flood

A dam catastrophe waiting to happen is being reported in China with the Three Rivers Gorge.

View the original article here

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