Water Resource Management

Water is essential for human survival, agriculture, industry, and ecosystem health. Yet global water resources are unevenly distributed, increasingly stressed by population growth, economic development, and climate change. For AQA A-Level Geography, understanding the concepts of water stress and scarcity, the role of virtual water, and the controversies surrounding large-scale management interventions is essential for constructing evaluative arguments.

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Water Stress and Scarcity

Definitions

• Water stress occurs when the demand for water exceeds the available supply during a certain period, or when poor quality restricts its use. The Falkenmark indicator defines water stress as below 1,700 m³ of renewable freshwater per person per year.
• Water scarcity is more severe: below 1,000 m³ per person per year (Falkenmark, 1989).
• Absolute scarcity: Below 500 m³ per person per year.

Global Picture

• Approximately 2.3 billion people live in water-stressed countries (UN-Water, 2023).
• By 2025, an estimated 1.8 billion people will face absolute water scarcity.
• Water stress is concentrated in the Middle East and North Africa (MENA), South Asia, and parts of sub-Saharan Africa, but is increasingly affecting southern Europe, the western United States, and northern China.

Causes of Water Stress

Factor	Mechanism
Population growth	Increasing demand for domestic, agricultural, and industrial water
Economic development	Industrialisation and rising living standards increase per capita water use
Climate change	Altered precipitation patterns; increased evaporation; glacial retreat reduces dry-season flows
Pollution	Contamination of surface and groundwater reduces usable supply
Over-abstraction	Extraction of groundwater faster than recharge depletes aquifers (e.g. Ogallala Aquifer, USA)
Inefficient irrigation	Flood irrigation wastes 40–60% of water through evaporation and seepage

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Virtual Water and Water Footprint

Virtual Water

Virtual water (Allan, 1993) is the volume of water embedded in the production of goods and services. It is "virtual" because the water is not physically present in the final product but was consumed during its production.

Examples of Virtual Water Content

Product	Virtual Water (litres)
1 kg of beef	~15,400
1 kg of wheat	~1,800
1 kg of rice	~2,500
1 cup of coffee	~140
1 cotton T-shirt	~2,700
1 kg of chocolate	~17,000

Water Footprint

The water footprint of a nation, individual, or product includes:

• Green water footprint: Rainwater consumed (mainly in agriculture).
• Blue water footprint: Surface and groundwater consumed (irrigation, industry, domestic use).
• Grey water footprint: Volume of freshwater needed to dilute pollutants to acceptable standards.

Global Virtual Water Trade

• Water-scarce countries often import water-intensive products (especially food) rather than growing them domestically — this is known as virtual water trade.
• The global virtual water trade is estimated at approximately 2,320 km³/yr (Hoekstra and Mekonnen, 2012).
• Major virtual water exporters include the USA, Brazil, Argentina, and Australia (agricultural exporters with relatively abundant water).
• Major virtual water importers include Japan, the UK, Germany, and many MENA countries.

Exam Application: Virtual water trade can alleviate local water scarcity but may exacerbate environmental degradation in exporting countries (e.g. depletion of the Ogallala Aquifer to irrigate US grain exports).

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Large Dam Controversies

Three Gorges Dam, China

The Three Gorges Dam on the Yangtze River is the world's largest hydroelectric project.

Key Statistics:

• Completed: 2006 (fully operational 2012).
• Height: 185 m; length: 2,335 m.
• Reservoir length: ~660 km.
• Installed capacity: 22,500 MW — the world's largest power station by capacity.
• Cost: Estimated at $31–37 billion.

Benefits:

• Generates approximately 100 TWh/yr of clean electricity, displacing coal-fired power.
• Flood control: designed to manage the Yangtze's devastating floods (the 1931 flood killed an estimated 145,000–4 million people).
• Improved navigation on the upper Yangtze.

Costs and Controversies: