World Water: Resources, Usage and the Role of Man-Made Reservoirs

Revised May 2019

This review is concerned with the global availability and usage of fresh water and the role of man-made reservoirs in providing storage of this essential human resource. Man-made reservoirs play a particularly important role where natural precipitation is erratic or seasonal because they store water during wet periods to make it available during dry periods.

The review was first produced in 2005 with the title World Water Storage in Man-Made Reservoirs. This updated version utilises a) more recent data on population, water resources and reservoir storage where available and b) current evidence on global warming and climate change which may affect our perception of future water resources and storage needs.

Sources of information, all of which are in the public domain, include the Food and Agriculture Organisation of the United Nations (FAO), the United States Census Bureau, the International Commission on Large Dams (ICOLD) and the Intergovernmental Panel for Climate Change (IPCC).

Man-made reservoirs are important because of their role in providing fresh water for irrigation (food supply) and also for domestic and industrial consumption. The dams associated with these reservoirs also make a significant contribution to energy supplies.

The benefits attributable to dams and reservoirs, most of which have been built since 1950, are considerable and stored water in reservoirs has improved the quality of life worldwide. These benefits can be classified under three main headings: -

In many areas of the world the life span of reservoirs is determined by the rate of sedimentation which gradually reduces storage capacity and eventually destroys the ability to provide water and power. Many major reservoirs are approaching this stage in their life.

This ROCK reviews the world stock of reservoirs, considers the problem of sedimentation and possible measures to minimise the impact of sedimentation. But first, the contribution of reservoirs is put into context by considering overall water resources and water usage. Future demand for storage is considered in the light of the increasing world population and the need to provide extra water for domestic, industrial and agricultural purposes. Finally, the possible effects of global warming and climate change are considered with a view to establishing, in very general terms, regions where the provision of storage may become less or more important.

Copies of this report are available from the Foundation, price 15.00, less 20% to FWR members.

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