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# Building the Glenn Canyon dam on the Colorado river caused

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Senior Manager
Joined: 23 May 2006
Posts: 324

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02 Aug 2008, 11:03
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Building the Glenn Canyon dam on the Colorado river caused unforeseen
environmental effects. One of these is that, by preventing annual
floods, the dam prevents the river from stirring up sediments
collected on the river bottom and depositing them high on the banks of
the river. The deposited sediments are needed to create and maintain
sandbars, which form natural habitats for native fish. By releasing
water from the dam annually, we will flood the river and thus recreate
the sandbars normally found below the dam."
Which of the following must be true if the prediction of the land
management specialist above is also to prove true?

1. There are no other effects of the dam which will prevent the native
fish of the river from using the new sandbars below the dam.
2. The flood caused by massively releasing water from the dam will be
like a natural flood in every major respect.
3. The size of a sandbar on a river always stays the same or increases
after a flood.
4. Any other dams upriver from the Glen Canyon dam must also release
enough water to cause a flood in order for the flood from the Glen
Canyon dam to be successful.
5. The dam does not prevent the flow of sediments from upriver needed
to replenish the sediments that inevitably wash downstream over time.
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Joined: 17 Jun 2008
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02 Aug 2008, 11:25
x97agarwal wrote:
Building the Glenn Canyon dam on the Colorado river caused unforeseen
environmental effects. One of these is that, by preventing annual
floods, the dam prevents the river from stirring up sediments
collected on the river bottom and depositing them high on the banks of
the river. The deposited sediments are needed to create and maintain
sandbars, which form natural habitats for native fish. By releasing
water from the dam annually, we will flood the river and thus recreate
the sandbars normally found below the dam."
Which of the following must be true if the prediction of the land
management specialist above is also to prove true?

1. There are no other effects of the dam which will prevent the native fish of the river from using the new sandbars below the dam. -> this must be true in order to work out the solution provided in the argument as well as prediction to b true IMO (1)
2. The flood caused by massively releasing water from the dam will be like a natural flood in every major respect. -> this is OOS since we are not concerned with quality of flood here
3. The size of a sandbar on a river always stays the same or increases after a flood. -> irrelevant how does size of sandbars affect native fish ?
4. Any other dams upriver from the Glen Canyon dam must also release enough water to cause a flood in order for the flood from the Glen Canyon dam to be successful. -> this is irrelevant
5. The dam does not prevent the flow of sediments from upriver needed to replenish the sediments that inevitably wash downstream over time. -> weakens the argument

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Senior Manager
Joined: 23 May 2006
Posts: 324

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02 Aug 2008, 12:01
spriya wrote:
x97agarwal wrote:
Building the Glenn Canyon dam on the Colorado river caused unforeseen
environmental effects. One of these is that, by preventing annual
floods, the dam prevents the river from stirring up sediments
collected on the river bottom and depositing them high on the banks of
the river. The deposited sediments are needed to create and maintain
sandbars, which form natural habitats for native fish. By releasing
water from the dam annually, we will flood the river and thus recreate
the sandbars normally found below the dam."
Which of the following must be true if the prediction of the land
management specialist above is also to prove true?

1. There are no other effects of the dam which will prevent the native fish of the river from using the new sandbars below the dam. -> this must be true in order to work out the solution provided in the argument as well as prediction to b true IMO (1)
2. The flood caused by massively releasing water from the dam will be like a natural flood in every major respect. -> this is OOS since we are not concerned with quality of flood here
3. The size of a sandbar on a river always stays the same or increases after a flood. -> irrelevant how does size of sandbars affect native fish ?
4. Any other dams upriver from the Glen Canyon dam must also release enough water to cause a flood in order for the flood from the Glen Canyon dam to be successful. -> this is irrelevant
5. The dam does not prevent the flow of sediments from upriver needed to replenish the sediments that inevitably wash downstream over time. -> weakens the argument

OA is not A
Director
Joined: 25 Oct 2006
Posts: 635

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02 Aug 2008, 12:33
IMO B.

1. There are no other effects of the dam which will prevent the native
fish of the river from using the new sandbars below the dam.
--this could be an assumption but can’t be inferred
2. The flood caused by massively releasing water from the dam will be
like a natural flood in every major respect.
--if water from dam can help recreate the sand bars, flood will also be same as natural flood
3. The size of a sandbar on a river always stays the same or increases
after a flood.
-- size of sandbar is not in discussion
4. Any other dams upriver from the Glen Canyon dam must also release
enough water to cause a flood in order for the flood from the Glen
Canyon dam to be successful.
--Other dams are not concerned
5. The dam does not prevent the flow of sediments from upriver needed
to replenish the sediments that inevitably wash downstream over time.
-- May be true but no information from passage.
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Manager
Joined: 28 Aug 2006
Posts: 142

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02 Aug 2008, 12:38
IMO - B
VP
Joined: 17 Jun 2008
Posts: 1382

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02 Aug 2008, 20:34
priyankur_saha@ml.com wrote:
IMO B.

1. There are no other effects of the dam which will prevent the native
fish of the river from using the new sandbars below the dam.
--this could be an assumption but can’t be inferred
2. The flood caused by massively releasing water from the dam will be
like a natural flood in every major respect.
--if water from dam can help recreate the sand bars, flood will also be same as natural flood
3. The size of a sandbar on a river always stays the same or increases
after a flood.
-- size of sandbar is not in discussion
4. Any other dams upriver from the Glen Canyon dam must also release
enough water to cause a flood in order for the flood from the Glen
Canyon dam to be successful.
--Other dams are not concerned
5. The dam does not prevent the flow of sediments from upriver needed
to replenish the sediments that inevitably wash downstream over time.
-- May be true but no information from passage.

Yes true here the question is if X is true then Y must be true and we are looking for Y.I took the question vice versa and started looking for cause(X) instead of effect (Y)
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Its Now Or Never

Manager
Joined: 31 Jul 2006
Posts: 235

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04 Aug 2008, 01:55
My answer is B too. What's the OA?
Senior Manager
Joined: 06 Apr 2008
Posts: 435

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04 Aug 2008, 02:23
IMO C)
Senior Manager
Joined: 14 Mar 2007
Posts: 297
Location: Hungary

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04 Aug 2008, 06:34
I got B as well.

Retired Moderator
Joined: 18 Jul 2008
Posts: 970

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04 Aug 2008, 11:13
Is this an inference question, or assumption question?

I believe it is an assumption question.

priyankur_saha@ml.com wrote:
IMO B.

1. There are no other effects of the dam which will prevent the native
fish of the river from using the new sandbars below the dam.
--this could be an assumption but can’t be inferred
2. The flood caused by massively releasing water from the dam will be
like a natural flood in every major respect.
--if water from dam can help recreate the sand bars, flood will also be same as natural flood
3. The size of a sandbar on a river always stays the same or increases
after a flood.
-- size of sandbar is not in discussion
4. Any other dams upriver from the Glen Canyon dam must also release
enough water to cause a flood in order for the flood from the Glen
Canyon dam to be successful.
--Other dams are not concerned
5. The dam does not prevent the flow of sediments from upriver needed
to replenish the sediments that inevitably wash downstream over time.
-- May be true but no information from passage.
Re: CR: land Management   [#permalink] 04 Aug 2008, 11:13
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