Water consumption linked to economic development

Trends in Water Consumption – A‑Level Geography (Cambridge 9696)

Learning Objective

Explain how water consumption varies with economic development, describe the global water‑resource base and the human‑water‑cycle, and evaluate the physical and human factors that influence water supply and demand.

Key Concepts

• Domestic, industrial and agricultural water use
• Per‑capita water consumption (W_pc)
• Water‑use intensity (WUI)
• Stages of economic development (low, middle, high income)
• Physical water‑resource types and the human‑water‑cycle
• Physical and economic water‑scarcity
• Change‑over‑time (how water‑use patterns shift as economies develop)
• Systems (inputs, outputs, stores, transfers) – applied to the human‑water‑cycle

5.1 Global Water Resources

Cambridge expects candidates to know the four major natural water‑resource categories, their approximate share of the Earth’s fresh water, and the relevance of reservoirs.

• Rivers & streams – ≈ 0.3 % of fresh water; concentrated in humid, mountainous regions.
• Lakes & reservoirs – ≈ 0.01 % of fresh water; many lakes are natural, but the syllabus stresses that **reservoirs** (artificial lakes behind dams) are an important sub‑category, especially in water‑scarce regions.
• Groundwater – ≈ 30 % of fresh water; stored in aquifers and the most widely used source for irrigation and domestic supply.
• Ice & snow (glaciers, polar ice caps) – ≈ 68 % of fresh water; largely unavailable for direct use but vital for river flow in many basins.

5.1.2 Human‑Water‑Cycle & Modifications

The human‑water‑cycle is a **system**: water moves between stores (rivers, aquifers, reservoirs) via transfers (abstraction, conveyance) and produces outputs (use, disposal). Human activities modify each stage.

5.1.3 Trends in Water Consumption

Three‑Stage Development Model

1. Stage 1 – Low‑income economies
   • Economy dominated by rain‑fed agriculture.
   • Domestic per‑capita use < 50 m³ yr⁻¹.
   • Industrial water use negligible.
2. Stage 2 – Middle‑income economies
   • Rapid industrialisation and urbanisation.
   • Domestic per‑capita use rises sharply (≈ 150 m³ yr⁻¹).
   • Industrial water‑use intensity peaks.
3. Stage 3 – High‑income economies
   • Shift to service‑based economies.
   • Domestic per‑capita use plateaus or falls (≈ 200 m³ yr⁻¹).
   • Industrial water use declines, but total abstraction remains high because of high living standards.

Change‑over‑Time

As a country moves from Stage 1 → Stage 2 → Stage 3, the pattern of water use changes not only in magnitude but also in sectoral composition. The rise in per‑capita consumption during Stage 2 reflects increased domestic demand (appliances, indoor plumbing) and industrial expansion. In Stage 3, technological improvements, water‑saving policies and a shift toward less water‑intensive services cause the per‑capita curve to level off or decline, illustrating the syllabus’s “change over time” concept.

Quantitative Indicators

The water‑use intensity is calculated as:

$$WUI=\frac{W_{\text{total}}}{\text{GDP}}$$

where W_total is total annual water abstraction (m³) and GDP is gross domestic product (US$).

Water‑Stress & Water‑Scarcity

Two thresholds are used in the syllabus:

• Physical water‑scarcity: less than 1 000 m³ person⁻¹ yr⁻¹ of renewable water.
• Economic water‑scarcity: water is physically available but unaffordable or poorly managed.

In water‑scarce regions (e.g., the Middle East) the three‑stage curve is shifted left: even low‑income economies show relatively high domestic per‑capita use, and the Stage 3 plateau occurs at a lower absolute value because of limited supply. In water‑rich regions (e.g., Canada) the curve is broader and the plateau occurs at higher values.

5.2 Factors Influencing Water Resources

Physical Supply Drivers

Human Demand Drivers

Case Study Summaries (Illustrating the Three‑Stage Pattern)

• India (middle‑income): Industrial expansion has lifted total abstraction, yet domestic per‑capita use remains low (≈ 85 m³ yr⁻¹). Water‑stress is high in the north‑west because of limited renewable supply.
• China (transition to high‑income): Water‑use intensity fell from 0.015 to 0.009 m³ US$⁻¹ (2000‑2020) due to widespread adoption of water‑saving technologies and a shift from heavy industry to services.
• United Kingdom (high‑income): Domestic use stabilised at ≈ 150 m³ yr⁻¹; industrial abstraction declined sharply after de‑industrialisation, but total use stays high because of high living standards and extensive domestic demand.

Implications for Water Management

1. Target water‑saving technologies in sectors with high WUI (e.g., cooling‑water recycling in power generation).
2. Design progressive pricing structures that reflect scarcity and encourage efficient use.
3. Plan infrastructure (reservoirs, treatment plants, inter‑basin transfers) that matches projected demand as economies move through the three stages.
4. Integrate trans‑boundary cooperation and climate‑adaptation strategies to mitigate physical water‑scarcity.
5. Incorporate land‑use planning and cultural‑awareness programmes to address demand drivers beyond income and technology.

Key Points to Remember

• Water consumption rises sharply during industrialisation (Stage 2) and tends to level off or fall in service‑based economies (Stage 3).
• Water‑use intensity generally declines as income rises because of technological improvements and a shift away from water‑intensive industries.
• Physical water‑scarcity, climate, geology, land‑use change and trans‑boundary issues can modify the generic three‑stage pattern.
• Both supply (climate, geology, relief, water‑body size, trans‑boundary agreements, land‑use change) and demand (population, GDP, sectoral mix, seasonality, technology, policy, cultural factors) drivers must be evaluated when planning sustainable water management.
• Remember the syllabus terminology: *physical water‑scarcity* and *economic water‑scarcity*; and the systems concept of inputs, outputs, stores and transfers in the human‑water‑cycle.