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
**Physical scarcity** = not enough water exists. **Economic scarcity** = water exists but people can’t access/afford it.
🏭 Water use by sector (must memorise)
🛡️ Water security & water scarcity
🧰 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
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.