Less than one percent of the water on Earth is in lakes, rivers, wetlands, and shallow aquifers that are available for human use. The annual replenishment of these systems constitutes the renewable water supply; humans consume approximately 10 percent of this supply annually. Yet only 15 percent of people worldwide live in relative water abundance.
Citation: World Resources Institute - PAGE, 2000. Data are for 1995. For a complete description and full source listing please refer to EarthTrends. A map of projected annual renewable water supply per person by river basin for the year 2025 is also available from EarthTrends.
WRI has estimated that 41 percent of the world's population, or 2.3 billion people, live in river basins under 'water stress,' meaning that per capita water supply is less than 1,700 m³/year (Revenga, 2000). Water scarcity is partly due to the uneven geographic distribution of water, as determined by the Earth's climate system. It is also a result of regional variations in population size. Maps, such as the one above, can provide an initial quantitative assessment of water availability, but they do not highlight the additional social and economic facets of limited water resources. For example:
*In the Middle East and North Africa, small amounts of annual rainfall create a physical water scarcity. As a result, the region is largely dependent upon unsustainable groundwater abstractions.
*In the United States, the destruction of wetlands and continued strains on rivers caused by pollution and excessive use (for example, The Colorado River) limit the ability of these ecosystems to provide other important goods and services.
*In sub-Saharan Africa, a high degree of precipitation variability coupled with a severe lack of necessary infrastructure have led to extreme water scarcity in many places (despite an indication of per capita water abundance on the above map).
Water scarcity, whether due to physical, social, or infrastructural reasons, poses significant challenges. The 1.1 billion people without safe drinking water and 2.6 billion people who lack sanitation are particularly at risk for poor health. Globally, nearly 6000 children under the age of five die every day from diarrhoea-related diseases (UNICEF/WHO). Water scarcity issues also have relevance for food production, business, and livelihoods; globally, 70 percent of all water withdrawals are for agricultural purposes and 20 percent are for industrial purposes (see graph above).
As glacial retreat, habitat destruction, deforestation, and other aspects of anthropogenic climate change continue to alter the hydrologic cycle, water resources become increasingly vulnerable and unpredictable. Uncertain or depleted water supplies will be particularly relevant for competing interests between urban and rural communities, and in the allocation of transboundary water resources (for example, Lake Chad; see below). With water use expected to increase with population growth--demand may double by 2050 (SIWI)--steps must be taken to improve the way water is managed.
Lake Chad, 1972 (left) and 2001 (right)
Above images are from the United Nations Environment Programme's One Planet Many People: Atlas of Our Changing Environment.
Last week, representatives from the business, policy, and civil society communities convened in Stockholm for World Water Week. The conference explored technological changes to increase water-use efficiency and agricultural intensity, scaling-up of infrastructure, and adoption of sustainable water management practices. Representatives advocated for the strengthening of public and private partnerships and the sharing of both responsibility for water management and its economic and social benefits. Although the use of water resources often presents difficult choices, with water, there is no alternative.
RELATED LINKS
Watersheds of the World: A Special Collection of River Basin Data
EarthTrends Water Resources and Freshwater Ecosystems Indicators
Dirty Water: Pollution Problems Persist
Giving Nature Its Share: Reserving Water For Ecosystems
Vital Water Graphics
The United Nations Environment Programme/GRID-Arendal has produced a fantastic collection of maps, charts, and graphs related to water resources and management.
AQUASTAT
A global information system of water and agriculture developed by the Land and Water Development Division of the Food and Agricultural Organization of the United Nations.
GEMStat: Global Water Quality Data and Statistics
The United Nations Global Environment Monitoring System (GEMS) Water Programme's GEMStat is designed to share surface and ground water quality data sets collected from over 1,400 stations for over 100 parameters.
Stockholm International Water Institute (SIWI)
A policy institute that contributes to international efforts to find solutions to the world's escalating water crisis.
International Water Management Institute (IWMI)
A non-profit scientific organization funded by the Consultative Group on International Agricultural Research (CGIAR). IWMI's research agenda is organized around four priority themes covering key issues relating to land, water, livelihoods, health and environment.
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