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Global water supplies are not evenly distributed. Some places have a water surplus, whereas others have a water deficit.

Global water supply

Different countries have different amounts of water. Generally speaking:

• Countries along the Equator have enough water. Warm, moist air rises here, which causes high levels of rainfall.
• Countries to the north of the Equator (at a latitude of approximately 30°) have physical water scarcity. This is when there isn't enough rainfall. Cooler drier air falls here and so it is arid.
• Countries to the south of the Equator (at a latitude of approximately 30°) experience some water scarcity. This is less severe than in the north because countries in the south tend to span greater latitudes, eg Australia has both desert and rainforest and so water can be transferred.
• Countries with the highest latitudes (those that are furthest away from the Equator) have enough rainfall to provide plenty of fresh water. Exceptions to this rule exist in countries with high population densities, eg the UK, or countries where poverty causes economic water scarcity, eg Nigeria.