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

Water security is having access to sufficient amounts of safe drinking water. Social, cultural, economic and political factors all affect the availability of freshwater and equitable access to it. For example, poorer households may have no piped supply, cultural values may shape how water is used, and governments decide who gets water and at what price.

Populations that grow, or economies that develop, must increase the supply of water or the efficiency with which it is used. Supply can be increased by:

• Dams and reservoirs: store water for dry periods; but evaporation losses, loss of habitat and displacement of people.
• Rainwater catchment systems: cheap and local; limited by rainfall.
• Desalination plants: provide water from seawater regardless of rainfall; high energy use and brine disposal.
• Enhancement of natural wetlands: store and filter water, and support biodiversity; slow, limited in volume.

Water scarcity refers to the limited availability of water to human societies. It can be tackled by conserving water.

• Domestic level: low-flow showerheads and dual-flush toilets, fixing leaks, reusing greywater, collecting rainwater, watering gardens at night.
• Industrial level (food production): drip irrigation and other efficient irrigation, scheduling irrigation by soil moisture, recycling water, growing drought-tolerant crops, reducing waste.

Mitigation strategies for scarcity include water pricing and metering, regulation and restrictions, public education, repairing leaking infrastructure, and the supply options above.

(HL) Freshwater use is a planetary boundary. Rising demand for limited freshwater increases water stress and the risk of abrupt and irreversible changes to the hydrological system, for example the drying of lakes or aquifers. Local and global governance is needed to keep use at sustainable levels: national and local laws, licensing and pricing, and international agreements on shared basins.

(HL) A water footprint measures the total volume of freshwater used to produce goods and services. It can serve as a measure of sustainable use by societies and inform decisions on water security, e.g. consumers choosing lower-footprint foods, or countries deciding what to grow or import. Global averages are around 15,000 litres per kg of beef, but only about 1,800 litres per kg of wheat.

(HL) Citizen science plays an increasing role in monitoring and managing water resources, e.g. volunteers recording river flow, rainfall or water quality, giving large datasets cheaply.

(HL) Water stress, like scarcity, measures limited supply, but it also takes into account water quality, environmental flows and accessibility. It is defined as a clean, accessible water supply of less than 1,700 m³ per person per year. The causes depend on the socioeconomic context: rapid population growth and irrigation in one country, poor infrastructure or pollution in another.

Water stress can arise from transboundary disputes when sources cross regional boundaries, as with the River Nile, shared by several countries. It can also be addressed at an industrial level (efficiency, recycling, treatment), but industrial freshwater production (e.g. desalination, large dams) has negative environmental impacts that can be minimised but not usually eliminated.

(HL) Inequitable access to drinkable water and sanitation harms human health (waterborne disease) and sustainable development: time spent collecting water, particularly by women and girls, reduces education and income, and illness reduces productivity.