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Difficulty: Very hardResolving Paradoxes and Discrepancies

In an arid agricultural basin, the regional water board subsidized advanced drip-irrigation technology for 80 percent of commercial farms, cutting the volume of water required per crop growing cycle by 35 percent. Surprisingly, over the three years following the widespread adoption of this technology, overall agricultural groundwater extraction from the basin's primary aquifer rose by nearly 20 percent, even though total cultivated land area remained unchanged and seasonal precipitation matched historic averages. Which of the following, if true, most helps to resolve the apparent paradox described above?

  1. A
    The price of electricity required to operate deep groundwater pumps in the agricultural basin increased significantly during the three-year period.
  2. The drip-irrigation systems enabled farmers in the basin to replace single-season crops with multi-harvest perennial crops and execute double-cropping cycles on the same acreage throughout the year.Answer
  3. C
    Traditional flood-irrigation methods previously used in the region lost up to 40 percent of applied water to surface evaporation before it could reach crop roots.
  4. D
    Substantial population growth in neighboring urban municipalities caused municipal domestic water consumption from the same aquifer to rise by 15 percent over the same timeframe.
  5. E
    The government subsidy covered only 60 percent of the initial equipment installation costs, requiring participating farm owners to fund the remaining portion out of pocket.

Answer

The apparent paradox is resolved by the option explaining that drip-irrigation enabled year-round double-cropping and perennial crop cultivation on the same acreage, raising total annual water consumption despite improved per-cycle efficiency.
The correct answer resolves the discrepancy by introducing a new factor: land use intensity. While each individual crop cycle requires 35 percent less water thanks to drip technology, the ability to farm year-round with double-cropping means farms are running multiple additional growing cycles each year. The cumulative water required for multiple annual harvests exceeds the savings gained per individual harvest, thereby explaining why total annual agricultural groundwater extraction rose.

Step-by-Step Solution

1
Identify the two conflicting facts presented in the passage.
Fact 1: Drip-irrigation reduces water needed per crop growing cycle by 35% across 80% of farms (with acreage and rainfall held constant). Fact 2: Total agricultural groundwater extraction increased by nearly 20%.
Resolving a paradox requires understanding both facts that appear mutually exclusive.
2
Formulate a hypothesis for how per-cycle water reduction can coexist with an overall increase in total annual water use.
An increase in total annual volume can occur if the total frequency of growing cycles per year increases or if crop selection changes drastically to offset the per-cycle savings.
Efficiency is measured per crop cycle, whereas total consumption depends on the overall annual intensity of land use.
3
Evaluate the options to find the scenario that reconciles both facts without contradicting either.
The option describing year-round double-cropping demonstrates that farmers utilized the efficiency gains to plant multiple harvests per year on the same land, driving up total annual water extraction.
This provides a direct causal mechanism for increased total volume while maintaining the premise of per-cycle efficiency.

Key Concept

Reconciling per-unit efficiency gains with aggregate consumption increases (Jevons paradox / Rebound effect)
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Resolving Paradoxes and Discrepancies

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