G40: Water Resources
Global patterns of water surplus and deficit, factors affecting consumption and availability, strategies to increase supply, and sustainable water futures with a case study of Lesotho.
🌍 Global Water Distribution
Key Fact: 97.5% of Earth's water is saltwater. Of the 2.5% that is freshwater, 70% is locked in ice and glaciers. Only 0.3% of all water on Earth is accessible freshwater in rivers, lakes, and aquifers.
Water stress = when a country's water consumption exceeds 20% of its available renewable water supply.
Water scarcity = when consumption exceeds 60% of available supply.
The UN predicts that by 2025, 1.8 billion people will live in countries with absolute water scarcity.
Surplus and Deficit Patterns
Water surplus areas have more rainfall than they need; deficit areas have less rainfall than they need.
| Water Surplus Areas | Water Deficit Areas |
|---|---|
| Canada (high rainfall, low population) | Middle East (low rainfall, high population) |
| Scandinavia | North Africa |
| Northern Russia | Central Asia (Aral Sea region) |
| Tropical rainforest regions (Amazon, Congo) | Australia (interior) |
| Ireland, Scotland, Wales | Southern Spain, Italy, Greece |
Key Point: Water surplus and deficit are not just about rainfall - they depend on the balance between water supply (from precipitation, rivers, aquifers) and water demand (from population, agriculture, industry). Canada has a surplus because its high rainfall combines with low population density. The Middle East has a deficit because very low rainfall combines with high population and water-intensive agriculture.
🚿 Factors Affecting Water Consumption
| Factor | Explanation | Example |
|---|---|---|
| Climate | Hot, dry climates increase water demand for irrigation and cooling | Saudi Arabia uses desalination to meet demand in its arid climate |
| Population density | More people = more water for domestic use, sanitation, and food production | South East England has water stress due to high population and low rainfall |
| Wealth | Richer populations consume more water (swimming pools, gardens, appliances) | USA uses 5,700 litres per person per day (including industrial/food); Mali uses 1,200 litres |
| Industrial development | Manufacturing and energy production require large water volumes | It takes 150 litres of water to make 1 kg of steel; 10 litres for 1 sheet of paper |
| Agriculture | Agriculture accounts for 70% of global freshwater withdrawals | 1 kg of beef requires 15,000 litres of water (including feed production) |
| Technology | Water-efficient technology can reduce consumption | Israel uses drip irrigation to reduce agricultural water use by 50% |
Example: Virtual Water
Virtual water (or embedded water) is the water used to produce goods. A cup of coffee requires 140 litres of water to produce (growing, processing, shipping). A cotton t-shirt requires 2,700 litres. When countries import these goods, they are effectively importing water. This means water-poor countries can preserve their own water by importing water-intensive products.
🔍 Factors Affecting Water Availability
Physical Factors
- Precipitation: Areas with high, reliable rainfall have greater water availability. Monsoon regions get heavy rain but in a short season, creating seasonal shortages
- Geology: Permeable rocks (chalk, limestone) store water in aquifers; impermeable rocks (clay, granite) cause surface runoff. Porous aquifers can store vast quantities of freshwater
- Seasonality: Some regions have distinct wet and dry seasons (e.g. the Sahel), creating periods of water scarcity even if annual rainfall is adequate
- Climate change: Changing rainfall patterns, shrinking glaciers, and more frequent droughts are reducing water availability in many regions
Human Factors
- Over-extraction: Pumping groundwater faster than it is recharged causes falling water tables. The Ogallala Aquifer in the USA has dropped by over 30 metres in some areas since the 1950s
- Pollution: Industrial waste, agricultural runoff, and inadequate sanitation contaminate water sources. The Ganges River receives 1.3 billion litres of domestic waste daily
- Deforestation: Removing trees reduces transpiration and rainfall, and increases surface runoff, reducing water infiltration into aquifers
- Population growth: More people increase demand and can outpace the development of water infrastructure
🏗️ Strategies to Increase Water Supply
1. Dams and Reservoirs
Definition: A dam blocks a river to create a reservoir (artificial lake) that stores water for use during dry periods. It also generates hydroelectric power and controls flooding.
| Advantages | Disadvantages |
|---|---|
| Reliable water supply year-round for irrigation and domestic use | Expensive to build (large dams cost billions) |
| Hydroelectric power (clean, renewable energy) | Flooding of valleys displaces communities (Three Gorges Dam displaced 1.3 million) |
| Flood control downstream | Sediment trapped behind dam reduces soil fertility downstream |
| Creates recreational opportunities (tourism, fishing) | Disrupts fish migration (e.g. salmon) |
| Can support multiple uses simultaneously | Risk of dam failure (Banqiao Dam failure, China 1975, killed 171,000) |
2. Water Transfer Schemes
Definition: Water transfer schemes move water from areas of surplus to areas of deficit through pipelines, canals, and aqueducts.
Example: China's South-North Water Transfer Project
This is the largest water transfer project in the world, moving water from the humid Yangtze River basin in the south to the dry north (including Beijing). The project has three routes (east, central, and western) spanning over 1,400 km. By 2020, the eastern and central routes were operational, transferring over 7 billion cubic metres of water annually. Cost: over $79 billion. Benefits: supplying water to 300 million people in water-scarce northern China. Problems: environmental damage; displaced communities; the western route remains unbuilt due to technical challenges at high altitude.
3. Desalination
Definition: Desalination removes salt from seawater or brackish water to produce freshwater. The two main methods are thermal distillation (boiling) and reverse osmosis (pressure-filtering through membranes).
- Saudi Arabia is the world's largest desalination producer, meeting 60% of its water needs this way
- The UK's first desalination plant opened in Beckton, East London, in 2010 (Thames Water)
- Desalination is energy-intensive: it requires 3-4 kWh per cubic metre of freshwater produced
- Brine waste is highly concentrated saltwater that damages marine ecosystems when discharged
🏔️ Case Study: Lesotho Water Transfer Scheme
Background: Lesotho is a small, mountainous, landlocked country entirely surrounded by South Africa. It has abundant water (surplus) due to high rainfall in the Maloti Mountains. South Africa, particularly the industrial heartland of Gauteng (Johannesburg and Pretoria), has a water deficit.
The Lesotho Highlands Water Project (LHWP)
The LHWP is one of Africa's largest infrastructure projects. It transfers water from the Senqu (Orange) River in Lesotho to South Africa's Vaal River system via a series of dams, tunnels, and pumping stations.
- Phase 1A (completed 1998): Katse Dam (185m high - Africa's second-tallest dam) and 82 km transfer tunnel
- Phase 1B (completed 2003): Mohale Dam and 32 km tunnel connecting to Katse reservoir
- Phase 2 (under construction): Polihali Dam, expected to increase transfer capacity by 50%
- Total cost: Over $8 billion for all phases
- Water transferred: Approximately 780 million cubic metres per year to South Africa
| Advantages for Lesotho | Disadvantages for Lesotho |
|---|---|
| Revenue from water sales (approximately $50 million/year) | Villages flooded by reservoirs; approximately 30,000 people displaced |
| Hydroelectric power from Muela Dam (Lesotho now self-sufficient in electricity) | Lost farmland and grazing land in reservoir areas |
| Improved roads and infrastructure built for construction | Compensation payments were often inadequate or delayed |
| New jobs during construction (3,000+ workers) | Health problems from construction (respiratory diseases from tunnel dust) |
| Development of tourism around dams | River flow reduced downstream, affecting ecosystems and communities |
| Advantages for South Africa | Disadvantages for South Africa |
|---|---|
| Reliable water supply for 6 million+ people in Gauteng | High cost - water is expensive compared to local sources |
| Supports industrial and economic development in the region | Dependence on another country for a critical resource |
| Reduces pressure on existing water sources | Does not address the underlying issue of unsustainable water consumption |
💧 Sustainable Water Futures
Key Concept: Sustainable water management means using water in ways that meet current needs without compromising future availability. This requires reducing demand, improving efficiency, and protecting water quality.
Water Conservation Strategies
- Drip irrigation: Delivers water directly to plant roots, reducing evaporation. Saves up to 70% compared to flood irrigation. Israel uses drip irrigation on 75% of irrigated land
- Greywater recycling: Reusing water from sinks, showers, and washing machines for irrigation and toilet flushing. Can reduce household water use by 30-50%
- Rainwater harvesting: Collecting rainwater from roofs for domestic and agricultural use. Simple systems cost $50-200 in LICs
- Water metering: Households with meters use 15-20% less water. The UK has about 60% metering
- Leak reduction: UK water companies lose approximately 3 billion litres/day through leaks. Thames Water alone loses 600 million litres/day
- Efficient appliances: Low-flow showers save 40-60% water; dual-flush toilets save 50% compared to single flush
Example: Singapore's Water Strategy (Four National Taps)
Singapore, with no natural water sources, developed a sustainable strategy: (1) Local catchment water (collecting rainwater from two-thirds of land area); (2) Imported water from Malaysia; (3) NEWater (recycling treated wastewater to drinking standard - meets 40% of demand); (4) Desalination (meets 30% of demand). By 2060, Singapore aims for NEWater to meet 55% and desalination 30% of demand, reducing dependence on imports.
❓ Practice Questions
Q1: Explain why some areas of the world have water surplus while others have water deficit.
Q2: Describe three factors that affect water consumption in different countries.
Q3: Using the Lesotho Highlands Water Project, evaluate the advantages and disadvantages of water transfer schemes.
Q4: Explain why desalination is not a sustainable solution to water scarcity for most countries.
Q5: "Water conservation is more effective than increasing supply." How far do you agree?
Q6: Describe three sustainable strategies for managing water resources.
✅ Answers
- Water surplus occurs where rainfall exceeds demand (e.g. Canada, Scandinavia - high rainfall, low population density). Water deficit occurs where demand exceeds supply (e.g. Middle East - low rainfall, high population and agricultural demand). The balance depends on physical factors (precipitation, geology, seasonality) and human factors (population density, wealth, industrialisation, agriculture). Some regions have seasonal surplus and deficit (monsoon areas).
- Factor 1: Wealth - richer populations consume more water for swimming pools, gardens, and appliances. The USA uses 5,700 litres/person/day compared to Mali's 1,200 litres. Factor 2: Agriculture - farming accounts for 70% of global water withdrawals; irrigation-intensive countries use much more water. Factor 3: Climate - hot, dry climates increase demand for irrigation and cooling, while cooler, wetter climates need less.
- Advantages: Lesotho gains $50 million/year in revenue and hydroelectric power; South Africa receives reliable water for 6 million+ people in Gauteng; infrastructure improvements. Disadvantages: 30,000 people displaced; lost farmland; inadequate compensation; health problems from construction; reduced river flow downstream. Overall, the project benefits both countries economically but the social and environmental costs for Lesotho's local communities are significant.
- Desalination is energy-intensive (3-4 kWh per cubic metre), making it expensive and carbon-intensive unless powered by renewables. The brine waste produced is highly concentrated salt that damages marine ecosystems. It is only viable for wealthy coastal countries - Saudi Arabia can afford it, but many water-scarce LICs cannot. It does not address the root causes of water scarcity (overconsumption, poor management). It should be part of a strategy alongside conservation and efficiency improvements.
- Water conservation is more sustainable long-term because it reduces demand rather than creating new supply. Strategies like drip irrigation (saves 70%), greywater recycling (saves 30-50%), and metering (saves 15-20%) are cheaper and have fewer environmental impacts than dams or desalination. However, conservation alone may be insufficient in areas of absolute scarcity (e.g. Middle East) where supply must also increase. The most effective approach combines both: reducing demand through conservation while developing sustainable new supplies (e.g. Singapore's Four National Taps approach).
- Strategy 1: Drip irrigation delivers water directly to plant roots, reducing evaporation by up to 70% compared to flood irrigation. Strategy 2: Greywater recycling reuses water from sinks and showers for irrigation and toilet flushing, reducing household consumption by 30-50%. Strategy 3: Rainwater harvesting collects rainwater from roofs for domestic and agricultural use, providing an affordable, low-technology solution particularly suitable for LICs.
🎯 Exam Tips
- Know the Lesotho case study in detail - specific dams (Katse, Mohale), figures, and impacts
- For water surplus/deficit questions, consider both physical and human factors
- Use the term "water stress" correctly (consumption exceeding 20% of supply)
- Always evaluate strategies - consider economic, social, AND environmental impacts
- Remember that 70% of global freshwater is used for agriculture
- Higher mark questions: argue for combining supply increase and demand reduction strategies
- Singapore's Four National Taps is a useful case study for sustainable water management
📝 Exam Technique
Geography Exam Tips — Water Resources:
1. For Water Resources questions, always name specific case studies with factual detail
2. Use geographical terminology precisely (e.g. specific processes, not vague descriptions)
3. Consider social, economic and environmental perspectives in your evaluations
4. Support your points about Water Resources with data, statistics or named examples
5. For 'assess' or 'evaluate' questions, reach a clear judgement supported by evidence
1. For Water Resources questions, always name specific case studies with factual detail
2. Use geographical terminology precisely (e.g. specific processes, not vague descriptions)
3. Consider social, economic and environmental perspectives in your evaluations
4. Support your points about Water Resources with data, statistics or named examples
5. For 'assess' or 'evaluate' questions, reach a clear judgement supported by evidence
⚠️ Common Errors
Watch Out!
Students often write vague answers without specific geographical evidence. Wrong: Writing generalised statements like 'it causes problems' Correct: Using specific data and named examples, e.g. 'the 2010 Haiti earthquake killed over 200,000 people due to poor building quality'
Students often confuse causes and effects. Wrong: Mixing up what caused the event with what resulted from it Correct: Clearly separate causes (why it happened) from effects (what happened as a result)
Students often describe rather than evaluate. Wrong: Listing strategies without assessing their effectiveness Correct: Weighing up strengths and weaknesses of each approach and reaching a supported judgement
✍️ Model Answer
Full-Mark Response
6 marks: Explain the key factors affecting water resources.
Water Resources involves multiple interconnected factors that geographers must understand. The key concepts include the processes that create and change water resources, the impacts on both people and environment, and the strategies used to manage associated challenges. For a comprehensive answer, specific case study evidence should be used throughout, with named examples and data to support each point. Geographical terminology should be used precisely, and the interrelationship between physical and human factors should be demonstrated. Top-level responses evaluate the relative importance of different factors and consider how the situation varies between locations.
Mark scheme: 2 marks for identifying key factors, 2 marks for explaining processes with detail, 2 marks for using specific evidence
📊 AO Deep Dive
Assessment Objective Analysis
AO1 requires knowledge of the key facts and processes related to water resources. AO2 demands understanding of how and why these processes operate, and their implications. AO3 asks you to analyse, evaluate and make judgements — this is where grade 9 answers stand out by weighing up competing perspectives and reaching supported conclusions. AO4 may involve interpreting maps, graphs or data related to this topic. To move from grade 5 to grade 9: use precise geographical terminology, support every point with specific case study evidence, and always evaluate rather than just describe.
📝 Exam Questions by Topic
🎬 Video Resources
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