Water scarcity is the limited availability of water to human societies. In IB ESS subtopic 4.2, this is core content for both SL and HL and should not be confused with water that exists but is unsafe or inaccessible.
Water scarcity occurs when the usable water supply is insufficient to meet demand. Supply may fall because of low precipitation, drought, climate change, groundwater depletion, pollution or reduced river flow. Demand may rise because of population growth, economic development, irrigation, industry and increasingly water-intensive lifestyles.
Scarcity is therefore produced by interactions between environmental and societal factors:
| Factor | How it increases water scarcity |
|---|---|
| Climate and drought | Reduce precipitation, river discharge and reservoir storage |
| Population growth | Increases domestic, agricultural and industrial demand |
| Agriculture | Irrigation removes large quantities of surface water and groundwater |
| Pollution | Reduces the quantity of water that is safe and usable |
| Weak infrastructure or governance | Prevents available water from reaching communities efficiently or equitably |
Three related terms must be distinguished:
| Concept | IB ESS meaning |
|---|---|
| Water scarcity | Limited availability of water to human societies |
| Water security | Access to sufficient amounts of safe drinking water |
| Water stress | An HL concept considering scarcity, water quality, environmental flows and accessibility; it occurs below of clean, accessible water per person per year |