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Water - Global Patterns

Water resources – Supply and Demand.

Key Words
Water quality
  - Quality can be measured in terms of the chemical, physical, and biological content of water. The most common standards used to assess water quality relate to health of ecosystems, safety of human contact and drinking water.
Water security - The reliable availability of an acceptable quantity and quality of water for health, livelihoods and production.
Water stress  - Water stress occurs when the demand for water exceeds the available amount during a certain period or when poor quality restricts its use.
Water surplus - This exists where water supply is greater than demand.
Water insecurity -When water availability is not enough to ensure the population of an area enjoys good health, livelihood and earnings. This can be caused by water insufficiency or poor water quality

Water is an essential resource for human survival, but its distribution and availability vary within countries and across the planet.  Only 2.5% of the water on the Earth is freshwater, the rest is found in the oceans.  Unfortunately, a lot of the freshwater is “locked up” in ice caps and glaciers so is unavailable for human use.  This poses problems for people as freshwater is a scarce resource.

Location of worlds water

The second issue with water availability is that it is in continuous movement across the globe.  It moves in a cycle called the hydrological cycle. Global freshwater supplies are affected by three major factors;
1. Geology – This affects where water is stored and the location of aquifers and groundwater
2. Climate – influences the availability of rainfall, snowfall and rates of evaporation.  Climate can vary over time, with wetter and drier periods, hotter and colder periods.  This can affect water availability.
3. Rivers – which move or transfer water across river basins


Water surplus (security) and deficit (insecurity):

Across the planet, the amount of water varies from place to place and from time to time. There are 2 basic situations for any place on Earth with reference to water availability;
1. Water surplus exists where supply exceeds demand.  These are known as WATER SURPLUS areas.  These are located in temperate and tropical wet areas with high rainfall and lower populations.  Areas include the Amazon Basin, large parts of North America and Western Europe.  Over 60% of the world’s freshwater is found in just 10 countries.  These areas are known to have SECURITY in their water sources.


Freshwater in various countries

2. Water deficit exists where demand is greater than supply.  These are known as WATER DEFICIT areas and can be in deficit because of either low precipitation or high evaporation rates.  They might also be in deficit because of high populations. Areas.  These areas are INSECURE in the provision of water for their populations. Both of these situations can be seen on the map below; 

Water scarcity map


Physical water scarcity is where countries do not have enough water due to climatic reasons and other physical reasons, such as Northern Mali in the Sahara Desert. This is most common in arid and semi-arid areas where rainfall is low and river flow fluctuates. As seen on the map, this includes North Africa, the Middle East, and North-Central Asia.  Similar issues face the Southwest of the United States, Northern Mexico, and Southern Australia.
Economic water scarcity is where a country has water, but does not have the economic means to access it or make it safe to drink, as is the case in parts of Afghanistan.

Water Conflict
In regions with scarce water conflict is possible. If countries have water resources that are shared (such as Lake Chad which is surrounded by 4 countries) then disputes can arise over water use.  Similarly, rivers often start in one country and flow into another. The River Nile is a good example, with Sudan being upstream of Egypt.  If Sudan trap or use lots of the water this could result in conflict with Egypt.  Conflict can also arise within countries.  The UK has shortages of water in the South East and surpluses in the West: should water be transferred between these areas?

Where do our water supplies come from?
• Rivers and Lakes – these are naturally occurring sources of water but they are not always located next to large populations.  Water often needs to be moved via pipeline and canal to where it is needed.  Rivers and lakes are also prone to pollution, which then limits freshwater availability.
• Aquifers – These are naturally occurring stores of water found under the ground.  Water soaks down through soils and rocks via the pores spaces in them to collect under ground.  People then extract the water by drilling boreholes or wells through the rock and brought up using buckets, pumps or pressure.  This source of water is also known as ground water.

Aquifer
• Reservoirs - Humans can create artificial lakes by buildings big concrete walls known as dams across rivers to prevent them flowing.  We can then treat the water and consume it.  Kielder water in Northumberland is a good example of this.

NEXT TOPIC - Water - Reasons for rising consumption

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