All in all there should be sufficient water on the Earth's surface to meet all domestic, agricultural or industrial uses. However this resource is very unequally distributed.
Pressures on Water Resources
The facts
The amount of water available on earth could, in theory, meet all human requirements, as the annual amount of water abstracted from the earth's surface only accounts for 2 % of the total amount of freshwater. However freshwater is extremely unequally distributed.
Geographically speaking, the greatest amount of freshwater - contained in the glaciers of the Polar Regions - is not available for human use. Moreover, some countries suffer from a chronic lack of water while others have abundant water resources.
The unequal distribution of water leads to local or regional shortages. Water stress occurs when those living in a particular region have less than 1,700 m3 of renewable water per capita per year (United Nations Development Programme).
The current situation is getting worse and worse, as pressure on water resources - i.e. ever increasing water abstraction - continues to grow around the world.
At present almost 700 million people in 43 countries find themselves below the water stress threshold. By 2025 this number could reach 3 billion people with increased shortages in China, in India and in Sub-Saharan Africa as highlighted in 2006 by the UNDP (United Nations Development Programme).
Causes of water stress
Several phenomena have led to the rise of water stress.
1 - Increased Urbanization and Increased Consumption
For the first time in the history of mankind the number of those living in towns and cities exceeds those living in the countryside. Within a generation two thirds of the world's population will live in towns or cities.
With regard to drinking water, this development increases the pressure on resources that are already in short supply.
As for sanitation, the effect of this increasing urbanization is a greater concentration of domestic and industrial pollution and a greater risk of run-off and flooding due to soil impermeabilisation.
For all of these reasons, it is highly possible that increased urbanization, if badly managed, will result in a water crisis.
2 - Wasting Resources
Water is very often wasted despite the fact that water resources are often scarce and fragile.
It is not uncommon for half the drinking water in the water supply system to be lost due to leakage, illegal connections to the water mains or a badly maintained water supply system.
In addition, agricultural irrigation - which accounts for 60% of water consumption - is often carried out with no thought given whatsoever to water conservation.
3 - Climate change
According to scientists, climate warming will lead to an increase in extreme climatic phenomena such as droughts and heatwaves, but also violent rainstorms and flooding, thereby increasing pressure on water resources in already arid areas.
4 - Lack of sanitation
The lack of a wastewater treatment system leads to rivers becoming polluted.
Such as in the Mediterranean region, where more than half the wastewater is released back into the environment untreated. Almost 60% of wastewater released back into the Caspian Sea has not been treated.
These figures are taken from a 2006 UNDP (United Nations Environment Programme) report on the impact of wastewater which also notes that "a rising tide of sewage is threatening the health and wealth of far too many of the world's seas and oceans."