Dams hold danger of floods whenstrong earthquakes hit Himalayas

Prem Kumari Khanal piles corrugated sheets of tin in the destroyed village of Pokharidanda, near the

epicenter of April 25's massive earthquake, in the Gorkha District of Nepal, May 2, 2015. Photo: AP Photo/

Wally Santana

Earthquakes can create massive amounts of damage. The people of Nepal, a

nation of 27 million located in the Himalayan mountain range south of China,

know this all too well. Earlier this year, two massive earthquakes struck in the

Himalayas, killing more than 8,500 people.

The people of Nepal are still recovering. Scientists, meanwhile, are already

worrying about the next earthquakes that will strike the region. One growing

concern has to do with the dams in the Himalayas. More than 600 large dams

have been built or are in some stage of construction or planning in the

By Scientific American, adapted by Newsela staff on 09.10.15

Word Count 830

mountains. Scientists are worried that a large earthquake could cause some of

the dams in the Himalayas to burst. A burst dam would release a sudden flood

of water, posing a grave threat to local communities.

Nepal Quakes Caused Damage

The 2015 earthquakes that hit Nepal cracked or damaged several dams. The

next earthquake could be even stronger. According to a number of engineers

and scientists, many of the dams in the Himalayas are probably not strong

enough to withstand the worst earthquakes that could hit the region.

Burst dams would unleash huge quantities of water, which would rush down

through the mountains toward towns and cities. A collapse of Tehri Dam in the

central Himalayas, for instance, would set loose a wall of water about 650 feet

high. The water would hit two towns. The flooding would affect six additional

cities with a combined population of 2 million.

Earthquakes occur in the region because of the movement of layers of rock

miles below the surface. According to the theory of plate tectonics, different

pieces of the earth's crust ("plates") are in slow, steady motion. One plate below

Nepal, the Indian plate, is pushing under the Asian plate. It moves roughly 6 feet

per century, but it regularly gets stuck. This leads to a build-up of pressure.

When the pressure reaches a certain level, the plates become unstuck, causing

an earthquake. The Himalayas are located on a "fault line," an area where two

plates push against each other below the surface. Because of its location in the

Himalayas, Nepal experiences earthquakes.

"Great" Earthquake Seen As Likely

Laurent Bollinger is a seismologist, a scientist who studies earthquakes, at the

French Alternative Energies and Atomic Energy Commission. He has studied

the effects of the earthquakes that hit Nepal earlier this year. According to

Bollinger's research, the earthquakes destabilized the region, making a "great"

earthquake more likely to occur in the future. A "great" earthquake is any

earthquake that scores an 8.0 or higher on the Richter scale. The Richter scale

rates the strength of earthquakes from 0 to 10. The two earthquakes that hit

Nepal in April and May 2015 were measured as 7.8 and 7.3, respectively.

Other studies indicate that these earthquakes released only a fraction of the

pressure that has built up between the plates below the Himalayas. This

suggests that more earthquakes are likely in the coming years. Vinod K. Gaur is

a seismologist at the CSIR Fourth Paradigm Institute in India. He says that there

could be a 8.0 earthquake in the Himalayas in the near future. If there are no

earthquakes for 200 years, the pressure will keep increasing. When an

earthquake finally comes, it will be even more powerful.

Given the likelihood of more earthquakes in Nepal, the dams in the region have

to be specially reinforced. They must be able to withstand the strong ground

shaking of an extreme earthquake, says Martin Wieland of the International

Commission on Large Dams.

India, China Secretive About Dam Designs

Part of the trouble is that scientists are not always allowed to study the dams

freely to determine whether or not they are strong enough. Most of the dams in

the region supply power to India and China. Although every nation has its own

regulations, India and China are secretive about their dam designs. Outsiders

are rarely allowed to examine Indian and Chinese dams.

Scientists who have been able to study dams in the region have sometimes

found cause for concern. Probe International is a Canadian environmental

research organization. It studied China's Three Gorges Dam. It found that the

designers had not considered worst-case scenarios when designing the dam's

earthquake resistance.

Scientists Seek Safer Construction

If the Indian and Chinese governments have not put in place the proper

reinforcements, hundreds of dams could be in danger of bursting when the next

big earthquake hits the Himalayas. If that happens during a rainy season, when

the dams are full, the burst dams could create massive damage.

A handful of scientists have taken the lead in arguing for safer dam

construction. They have only had limited success, though. For now, all they can

do is call attention to the problem.

Scientists hope that, with the help of public pressure, dams in the Himalayas will

be reinforced to withstand great earthquakes. Otherwise, the next great

earthquake in the area may result in a man-made tsunami.

Quiz

1 All of the following are reasons why another earthquake is likely to happen in the

Himalayas EXCEPT:

(A) The Himalayas are over a fault line.

(B) Often when there is a lot of flooding, there are also earthquakes.

(C) Once there is an earthquake, it makes it more likely for another one

because the area becomes unstable.

(D) The scientists have discovered that the last earthquake only

released a small percentage of the pressure from below the Earth's

crust.

2 According to the article, what is the MOST likely reason why the scientists might be

frustrated?

(A) because they do not have a lot of power to convince countries to

build stronger dams

(B) because the earthquakes in Nepal will probably continue

(C) because a tsunami in the Himalayas could cause a lot of damage

and cost lives

(D) because other countries do not build dams as strong as the ones

that Indian and China built

3 Read the following sentence from the introduction [paragraphs 1-2].

A burst dam would release a sudden flood of water, posing a

grave threat to local communities.

Using the word "grave" in the above sentence adds all the following tones to the

sentence EXCEPT:

(A) formal

(B) sarcastic

(C) serious

(D) pessimistic

4 Read the following selection from the article.

Laurent Bollinger is a seismologist, a scientist who studies

earthquakes, at the French Alternative Energies and Atomic

Energy Commission. He has studied the effects of the

earthquakes that hit Nepal earlier this year. According to

Bollinger's research, the earthquakes destabilized the region,

making a "great" earthquake more likely to occur in the future.

What phrase below is the BEST definition for the word "destabilized"?

(A) to bring peace

(B) to upset people

(C) to keep the status quo

(D) to cause unrest

Answer Key

1 All of the following are reasons why another earthquake is likely to happen in the

Himalayas EXCEPT:

(A) The Himalayas are over a fault line.

(B) Often when there is a lot of flooding, there are also

earthquakes.

(C) Once there is an earthquake, it makes it more likely for another one

because the area becomes unstable.

(D) The scientists have discovered that the last earthquake only

released a small percentage of the pressure from below the Earth's

crust.

2 According to the article, what is the MOST likely reason why the scientists might be

frustrated?

(A) because they do not have a lot of power to convince countries

to build stronger dams

(B) because the earthquakes in Nepal will probably continue

(C) because a tsunami in the Himalayas could cause a lot of damage

and cost lives

(D) because other countries do not build dams as strong as the ones

that Indian and China built

3 Read the following sentence from the introduction [paragraphs 1-2].

A burst dam would release a sudden flood of water, posing a

grave threat to local communities.

Using the word "grave" in the above sentence adds all the following tones to the

sentence EXCEPT:

(A) formal

(B) sarcastic

(C) serious

(D) pessimistic

4 Read the following selection from the article.

Laurent Bollinger is a seismologist, a scientist who studies

earthquakes, at the French Alternative Energies and Atomic

Energy Commission. He has studied the effects of the

earthquakes that hit Nepal earlier this year. According to

Bollinger's research, the earthquakes destabilized the region,

making a "great" earthquake more likely to occur in the future.

What phrase below is the BEST definition for the word "destabilized"?

(A) to bring peace

(B) to upset people

(C) to keep the status quo

(D) to cause unrest