Key Terms

📖 Key Terms

Water security

Having reliable access to sufficient, safe water to maintain health, livelihoods and economic development. Defined by the UN as access to at least 50-100 litres per person per day of clean water within 1 km of home. Currently around 2 billion people lack it.

Physical water scarcity

When insufficient water exists in an area to meet demand, due to low rainfall, high evaporation or limited river and groundwater sources. Affects North Africa, the Middle East and parts of Central Asia. Approximately 1.2 billion people affected globally.

Economic water scarcity

When water physically exists but people cannot access it due to poverty, lack of infrastructure (pipes, wells, treatment plants) or weak governance. Affects large parts of sub-Saharan Africa and South Asia. More people are affected by economic than physical scarcity globally.

Virtual water

The water embedded in the production of goods and traded invisibly when those goods are exported. 1 kg of beef contains approximately 15,000 litres of virtual water. Countries that import food and goods are effectively importing the water used to produce them.

Over-abstraction

Withdrawing water from rivers, lakes or groundwater faster than it is replenished by rainfall and the water cycle. The Aral Sea was destroyed by over-abstraction from its feeder rivers for irrigation. Groundwater over-abstraction is also occurring in major aquifers in India, the US and the Middle East.

Eutrophication

The process by which excessive nutrients (typically nitrates and phosphates from agricultural fertilisers) enter a water body, triggering massive algal bloom growth. When the algae die and decompose, bacteria consume oxygen, creating "dead zones" with no oxygen and no aquatic life.

Appropriate technology

Technology that is matched to the skills, resources and conditions of the community using it — typically low-cost, community-managed and locally maintainable. Fog catchers, sand dams and rainwater harvesting are examples. Contrasts with high-tech engineering that requires specialist expertise and large capital investment.

Water transfer

Moving water from an area of surplus to an area of deficit through pipelines, tunnels or aqueducts. The Three Gorges Dam supports the South-North Water Diversion Project in China, transferring water from the water-rich south to the dry north. Transfer schemes are expensive and can have negative environmental and social impacts at the source.

Desalination

The process of removing salt from seawater to produce fresh water, primarily through reverse osmosis. Widely used in Saudi Arabia, UAE and Israel. Produces clean water regardless of rainfall but requires 3-10 kWh of electricity per cubic metre — making it expensive and carbon-intensive unless powered by renewables.