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Difficulty: HardBridging Conflicting Premises

Five years ago, a government grant program helped farmers in the arid Oakhaven region install advanced drip-irrigation systems. These systems deliver water directly to plant roots, reducing the volume of water required per acre by over 40 percent compared to the previously used flood-irrigation methods. Today, even though over 90 percent of Oakhaven's farmers use drip-irrigation and there has been no shift toward more water-intensive crop varieties, the total volume of water drawn annually from the region's aquifers for agricultural use is 15 percent higher than it was five years ago.

Which one of the following, if true, most helps to resolve the apparent discrepancy described above?

  1. A
    The advanced drip-irrigation systems are highly effective at preventing surface evaporation, which was a major source of water loss in traditional flood-irrigation methods.
  2. B
    While the total volume of water drawn for agriculture increased, agriculture's percentage of the region's overall water consumption decreased due to a rapid expansion in industrial water needs.
  3. The reduction in water costs per acre achieved through the new drip-irrigation systems allowed many Oakhaven farmers to profitably cultivate large tracts of previously unplanted land.Answer
  4. D
    In neighboring agricultural regions that did not implement drip-irrigation systems, the total volume of water drawn for agricultural use increased by more than 30 percent over the same five-year period.
  5. E
    The government grant program was heavily oversubscribed, meaning that funds were exhausted quickly and 10 percent of the region's farmers had to continue using less efficient flood irrigation.

Answer

The correct answer states that the reduction in water costs allowed farmers to cultivate large tracts of previously unplanted land.
The correct answer directly resolves the discrepancy by addressing the mathematical relationship between per-acre usage (a rate) and total usage (an absolute volume). If the cost savings from the more efficient irrigation systems incentivized farmers to plant on significantly more acres of land, the total volume of water drawn would inevitably increase, successfully bridging the two conflicting premises.

Step-by-Step Solution

1
Analyze the stimulus to identify the two seemingly conflicting premises.
Premise 1: Per-acre water usage dropped by 40% for over 90% of farmers. Premise 2: Total agricultural water usage in the region increased by 15%.
Identifying the exact parameters of the paradox is necessary to find a bridging mechanism.
2
Determine the mathematical relationship between the variables presented.
Total water usage is calculated by multiplying the water used per acre (the rate) by the total number of acres cultivated (the multiplier).
Understanding how the variables interact reveals what information is missing from the stimulus.
3
Evaluate the options to find a mechanism that increases the total water usage despite the per-acre efficiency gain.
The correct option introduces a massive increase in the total number of acres cultivated.
An increase in total acreage perfectly reconciles a lower per-acre rate with a higher total volume.

Key Concept

Resolving a paradox by identifying a missing variable in a rate-versus-volume relationship (often related to the Jevons paradox in economics).
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Topics

Bridging Conflicting Premises

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