Question

Letter to the editor: If the water level in the Searle River Delta continues to drop, the rising sea level will make the water saltier and less suitable for drinking. Currently, 40 percent of the water from upstream tributaries is diverted to neighboring areas. To keep the delta’s water level from dropping any further, we should end all current diversions from the upstream tributaries. Neighboring water utilities are likely to see higher costs and diminished water supplies, but these costs are necessary to preserve the delta.

Which of the following would, if true, indicate a serious potential weakness of the suggested plan of action?

Option A
Option B
Option C
Option D
Option E

(This question is from Official Guide. Therefore, because of copyrights, the complete question cannot be copied here. The question can be accessed at GMAT Club)

Solution

The Story

Letter to the editor: If the water level in the Searle River Delta continues to drop, the rising sea level will make the water saltier and less suitable for drinking.

We’re presented with a conditional in the first statement. It is not given yet whether the water level in the delta will continue to drop. However, if it continues to drop, the water will become saltier and less suitable for drinking through the rising sea level.

Currently, 40 percent of the water from upstream tributaries is diverted to neighboring areas.

“Upstream tributaries” indicates these are water bodies that feed into the delta. However, 40% of the water from these tributaries does not reach the delta and is diverted to neighboring areas.  

To keep the delta’s water level from dropping any further, we should end all current diversions from the upstream tributaries.

 To prevent the water level in the delta from dropping further, the author suggests that they should end all ‘current diversions’ from the upstream tributaries (This would include the 40% water that is diverted to neighboring areas).

Neighboring water utilities are likely to see higher costs and diminished water supplies, but these costs are necessary to preserve the delta. 

While the neighboring areas will likely experience higher costs for water, and diminished water supplies, these costs are necessary to preserve the delta. (So if the delta water becomes saltier and less suitable from drinking,the delta is not preserved.)

Gist: If the water levels in the delta continue to drop, the water will become saltier and less drinkable. In order to prevent the level from dropping further (goal), we should end all diversions from the upstream tributaries (plan) which include diversions to neighboring areas. While there will likely be inconveniences caused, these steps are necessary to preserve the delta.

The Gap

“To keep the delta’s water level from dropping any further, we should end all current diversions from the upstream tributaries.” The author assumes that if all current diversions are not ended, the delta’s water level will continue dropping.

The Goal

Anything that attacks the assumption we have discussed above will get the job done. There could be other assumptions and other ways to weaken the suggestion as well.

The Evaluation

(A) IncorrectThe letter states that if the water level continues to drop the water will become saltier AND less suitable for drinking. While drinkability is one concern, there very well might be other issues related to saltier water in the delta. So, even if certain equipment helps the water to become drinkable, the delta might still not be preserved. For example, what if the delta water is used for irrigation and if the water gets saltier? the delta water would no longer be usable for irrigation. And the delta might still not be considered preserved.

(B) Incorrect.  Do we care whether water level is only one factor i.e. that there are other factors that affect salinity in the delta? Does that indicate that we should not end diversions from the upstream tributaries? As long as the water level is a significant reason for salinity in the delta, the plan still makes sense. This option does not indicate any weakness in the suggested plan.

Let’s consider an example. Say a doctor suggests to a patient that she should stop consuming fatty foods to control her rising cholesterol level. Does it make sense for the patient to refute the suggestion by saying that since consuming fatty foods is only one factor that affects cholesterol levels, she need not stop consuming such foods?

(C) Incorrect. How water levels of the upstream tributaries are controlled is entirely irrelevant to the issue at hand.

(D) Incorrect. If, as the option suggests, the diversion of water into the neighboring areas led to an increase in the population in the areas, ending diversions might lead to a decrease in the population. Ending diversions would, at least,  inconvenience the people and have a cost implication for them. However, there is no relationship between population fluctuations and the water level of the delta.

(E) Correct. The drop in the water level was mainly due to a drought. The drought has now ended. So, perhaps the water levels in the delta will start to rise again, or at least the levels will likely not continue to drop. We now question the need to implement the suggested plan to achieve the desired goal of increasing the delta water level in the first place.

This solution was created by Anish Passi and Chiranjeev Singh.

If you have any doubts regarding any part of this solution, please feel free to ask in the comments section.

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