Key Idea: Topic 4.2 explains why freshwater is unevenly distributed, how humans use it (by sector), what causes water scarcity and threatens water security, and how societies respond through management, cooperation, or conflict.
💧 Why freshwater feels scarce
- Only a small fraction of Earth’s water is accessible freshwater (most is ocean or frozen)
- Even where water exists, it may be remote, polluted, or expensive to access
- Shortage is shaped by climate, geography, population, wealth, pollution, climate change
Physical scarcity = not enough water exists. Economic scarcity = water exists but people can’t access/afford it.
🏭 Water use by sector (must memorise)
- Global pattern: Agriculture ~70%, Industry ~20%, Domestic ~10%
- LEDCs often have higher agricultural share (irrigation + less industry)
- MEDCs often have higher industrial + per-capita domestic use (higher living standards)
🛡️ Water security & water scarcity
- Water security = reliable access to enough safe water for people, ecosystems, and economies
- Water scarcity happens when demand exceeds supply (or supply is too polluted)
- Drivers: population growth, development, urbanisation, pollution, climate change
🧰 Management strategies (supply + demand)
Increase supply: Dams/reservoirs (storage, but ecological/social costs). Desalination (reliable, but expensive + energy-intensive). Groundwater extraction (short-term gain, depletion/subsidence risk). Water transfer schemes (costly, environmental impacts). Rainwater harvesting (local, low-tech).
Reduce demand: Drip irrigation (big efficiency gains). Leak reduction (huge losses in old networks). Water-efficient devices. Greywater recycling. Pricing + education.
High marks: give a mix of supply + demand, and add one drawback per strategy (cost, energy, ecosystems, equity).
⚔️ Conflict vs cooperation
- Conflict risk rises where rivers cross borders and upstream controls flow
- Competing users: agriculture vs industry vs domestic vs ecosystems
- Cooperation tools: treaties, joint basin management, tech sharing, virtual water trade
1) Define water security. 2) Physical vs economic scarcity. 3) Sector split (70/20/10). 4) Two supply + two demand strategies with one drawback each.