4.2 Water access, use and securityIB Environmental Systems and Societies SL: Revision notes

Water security means having access to sufficient amounts of safe drinking water. Water scarcity is the limited availability of water to human societies: there is not enough to meet demand.

Access to fresh water is not shared equally. Social (gender roles, who collects water), cultural (traditions, beliefs about water), economic (income, cost of connection, infrastructure) and political (investment priorities, governance, treaties between countries) factors all affect availability and equitable access to water for human well-being.

Societies undergoing population growth or economic development need more water. They must either increase supply or use water more efficiently.

Ways to increase supply:

• Dams and reservoirs: store seasonal flow; may flood habitats and displace people.
• Rainwater catchment systems: collect rain from roofs or land; cheap, small volumes.
• Desalination plants: remove salt from seawater; reliable, but high energy use and brine disposal.
• Enhancement of natural wetlands: wetlands store and clean water and recharge groundwater.

Domestic conservation: low-flow showerheads, dual-flush toilets, fixing leaks, water butts, reusing grey water, shorter showers, metering and pricing.

Industrial conservation in food production: drip irrigation to the roots, scheduling with soil-moisture sensors, recycling wastewater, rainwater harvesting, mulching, drought-tolerant crop varieties and leak repair. Food production uses most of the world's fresh water, so savings here matter most.

Strategies to tackle scarcity can be grouped:

• Demand management: pricing and metering, restrictions, public campaigns (Cape Town reduced use sharply in 2017-18).
• Supply increase: dams, desalination, transfers, wetlands.
• Efficiency: fixing leaks, drip irrigation, recycling.
• Cooperation: agreements between countries sharing rivers.

To evaluate, weigh cost, energy use, environmental impact, who benefits and how quickly each works. Most real solutions combine several.