Commentary
About the data
Definitons
Data Sources
Freshwater may well be the oil of the late 20th century—an essential and increasingly scarce resource. For water, the concept of availability transcends physical quantities alone. Other important dimensions are quality, accessibility, and reliability of supply.
Although abundant globally, natural freshwater resources are unevenly distributed. Because of the central role of water in the functioning of economic, ecological, and social systems, its scarcity raises concerns for long-term development prospects in some regions.
Where water is not only scarce but also shared by more than one region or state, competition for limited supplies is a likely source of conflict, particularly in the Middle East. Uneven distribution makes it important to identify "hot spots" where pressures on water supply are likely to be greatest, as captured by annual freshwater withdrawals as a percentage of total water resources. In Saudi Arabia, the United Arab Emirates, and Yemen, for example, withdrawals exceed 100 percent, indicating a reliance on sources other than rivers and groundwater.
With expanding populations needing more water for human consumption and agricultural, industrial, and commercial uses, it is important to know which sector places the greatest strain on freshwater resources. As the indicators show, in most countries agriculture consumes the lion’s share (60–80 percent in most countries and as much as 90 percent in some).
Access to reliable sources of freshwater depends to a large extent on the ability to treat water and transport it to consumers. In industrial countries water from natural sources is treated to render it pollutant-free and brought to consumers through piped networks. In developing countries such infrastructure may be lacking or poorly maintained. As a result, many people in the world still depend on water supplies that are unreliable in both quantity and quality.
The data on freshwater resources hide what can be significant variations in total renewable water resources from one year to the next. They also fail to distinguish between seasonal and geographic variations in water availability within a country. Data for small countries and countries in arid and semiarid zones are less reliable than those for larger countries and countries with higher rainfall. The data on freshwater resources are based on estimates of runoff into rivers and recharge of groundwater. These estimates are based on different sources and refer to different years, so the data on freshwater resources should be used with caution when comparing countries. Caution is also necessary in comparisons using the data on annual freshwater withdrawal, which are subject to variation in collection and estimation methods.
While information on access to safe water is widely used, it is extremely subjective, and such terms as "adequate amount" and "safe" may have very different meanings in different countries despite official World Health Organization (WHO) definitions (see the definitions for table 2.12). Even in industrial countries treated water may not always be safe to drink. While access to safe water is equated with connection to a public supply system, this does not take account of variation in the quality and cost (broadly defined) of the service once connected. Thus comparisons across countries must be made cautiously. Changes over time within countries may be a result of definitional or measurement changes.
Definitions
• Freshwater resources refer to both internal renewable resources and, where noted, river flows from other countries. Internal renewable water resources include flow of rivers and groundwater from rainfall in the country.
• Annual freshwater withdrawals refer to total water withdrawal, not counting evaporation losses from storage basins. Withdrawals also include water from desalination plants in countries where that source is a significant part of all water withdrawal. Withdrawal data are for single years between 1980 and 1995. Withdrawals can exceed 100 percent of renewable supplies when extractions from nonrenewable aquifers or desalination plants are considerable or if there is significant water reuse. Withdrawals for agriculture and industry are the share of total withdrawal for agriculture (irrigation and livestock production) and the share for direct industrial use, including withdrawals for cooling thermoelectric plants. Withdrawals for domestic uses include drinking water, municipal use or supply, and use for public services, commercial establishments, and homes. For most countries sectoral withdrawal data are estimated for 1987–95.
• Access to safe water refers to the percentage of people with reasonable access to an adequate amount of safe drinking water in a dwelling or located within a convenient distance from the user’s dwelling (see About the data).
Data are compiled by the World Resources Institute from various sources and published in World Resources. The Département Hydrogéologie in Orléans, France, compiles data on water resources and withdrawal from published documents, including national, United Nations, and professional literature. The Institute of Geography at the National Academy of Sciences in Moscow also compiles global water data on the basis of published work and, where necessary, estimates water resources and consumption from models that use other data, such as area under irrigation, livestock populations, and precipitation.