Water scarcity occurs when the amount of water withdrawn from lakes, rivers or groundwater is so great that water supplies are no longer adequate to satisfy all human or ecosystem requirements, bringing about increased competition among potential demands.
Water scarcity has also been defined as a situation where water availability in a country or in a region is below 1000 m3 per person per year. However, many regions in the world experience much more severe scarcity, living with less than 500 m3 per person per year
Water scarcity is among the main problems to be faced by many societies and the World in the XXIst century. Water use has been growing at more than twice the rate of population increase in the last century, and, although there is no global water scarcity as such, an increasing number of regions are chronically short of water.
1,800 million people will be living in countries or regions with absolute water scarcity by 2025, and two-thirds of the world population could be under stress conditions.
Water scarcity causes enormous problems for populations and societies. The available water is not sufficient for the production of food and for alleviating hunger and poverty in some regions, where quite often the population growth is larger than the capability for sustainable use of the natural resources.
The lack of water does not allow industrial, urban and tourism development to proceed without restrictions on water uses and allocation policies for other user sectors, particularly agriculture.
In regions of water scarcity the water resources are probably already degraded, or subjected to processes of degradation in both quantity and quality, which adds to the shortage of water.
Health problems are commonly associated with scarcity, not only because the deterioration of the groundwater and surface waters favours water borne diseases, but also because poverty makes it difficult to develop proper water distribution and sewerage systems.
Water conflicts still arise in water stressed areas among local communities and between countries despite legal agreements, since sharing a very limited and essential resource is extremely difficult.
Poverty associated with water scarcity generates migratory fluxes of populations within countries or to other countries where people hope to have a better life, but where they may not be well received.
Water for nature has become a low or very low priority in water stressed zones. Preserving natural ecosystems is often considered a superfluous use of water compared with other uses that directly relate to healthy human life, such as domestic and urban uses, or that may lead to the alleviation of poverty and hunger, such as uses in industry, energy and food production. However, the understanding that natural ecosystems, namely the respective genetic resources, are useful for society is growing, and an effort to protect reserve areas is already developing, even in water scarce regions.
the publication ‘Coping with Water Scarcity: A strategic issue and priority for system-wide action’ [PDF format – 474 KB]
the 2nd UN World Water Development Report: ‘Water, a shared responsibility’
the United Nations Environment Network (UNEP Net) section on water scarcity
Source: UNESCO Water Portal, March 2007