Q17 — Water Scarcity Index (Rws) and Solutions

Theoretical A Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license

Water is a common renewable resource on Earth; however, after its use, water loses some of its properties, such as purity, heat content, and potential energy. While they eventually will be restored, this happens on a geological timescale. Less than 1% of total water is available for human use — renewable freshwater resources (RFWR) — and even from this small fraction of water, only 10% is enough to fulfill the needs of humanity. While theoretically, there is more than enough water, many regions still experience a water crisis — a lack of accessible RFWR or an inability to utilize available RFWR.

World map colored by water scarcity index (Rws) value from 0.00 (white) to 1.00 (dark red), with the highest values concentrated in the western USA, the Middle East, South/Central Asia, and eastern China. Figure 1. The world map with Rws values.

$$R_{ws} = \frac{W - S}{Q} \quad (1)$$

$$A_w = \frac{Q}{C} \quad (2)$$

Equations: R_ws - water scarcity index, A_w - water crowding indicator, W - total annual water withdrawal by population, S - total water use from desalinated water, Q - RFWR, C - population size.

On your answer sheet, indicate “T” for true statements and “F” for false ones.

A. Higher human activity leads to shorter mean residence time of water molecules in reservoirs.

B. Low Rws indicates the absence of a water crisis

C. Correlation between Rws and 1/Aw is weaker in regions with poor water infrastructure.

D. Food import would be a better long-term solution for the water crisis in dry regions rather than water import.

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Question reproduced from IBO 2024, Theoretical Exam Part A, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)