Global patterns of water

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

Exploring the issues linked to distribution and access to water in different parts of the world

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, dry air falls here and so it is very arid.
  • Countries to the south of the Equator (at a latitude of approximately 30°) also experience some water scarcity. It is less severe than in the north because there is less land in the southern hemisphere.
  • 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.
Northern Africa and central Asia are areas with water scarcity.

Reasons for increasing water consumption

Water consumption has been rising globally over time. There are two main reasons for this.

Rising population

Everyone needs water in order to survive. Water makes up at least 60% of a person's bodyweight and it is needed for all bodily functions. People also use water for hygiene, cooking and cleaning. The population of the world is increasing, but there is only a fixed amount of fresh water available for people to use.

Economic development

As countries develop, their water use increases. People in wealthier nations have water delivered into their homes via pipeline. Modern appliances, such as dishwashers and washing machines, use a lot of water. Commercial agriculture, industry and tourism in high income countries (HICs) consume vast quantities of water too . The water footprint of HICs is much higher than low income countries (LICs). As more countries develop, the demands on water will increase.

Water footprint

A water footprint is defined as the total volume of freshwater consumed and polluted for the production of the goods and services used by the consumer. It is calculated by adding the direct water use by people and their indirect water use.

Case study: drought in California

California is a coastal state in western USA. It has deserts inland to the east, but there is usually plenty of rainfall to provide water along the coast.

California is on the west coast of the USA.

California has experienced drought since 2011. Irrigated crops use a lot of the freshwater supplies in the region. Rising temperatures, falling rainfall levels and a growing population are also contributing to the problem.

The drought has lowered groundwater levels. This can cause lots of problems, such as:

  • Subsidence - this is a fall in the level of the land, which damages properties.
  • Sea water intrusion - this is when sea water flows in to groundwater spaces known as aquifers. People cannot drink sea water as it is salty.
  • Wildfires - vegetation becomes very dry and intense heat, such as lightning strikes, can set it alight easily.
  • Ecosystem damage.

There are no official rules in California that stop property owners from pumping more water out of the ground. Groundwater limits are now being considered, but these couldn't be enforced until 2020. Until then, people are being encouraged to use less water.