The amount of precipitation falling on land is almost 110 000 km3 per year. Almost two-thirds of this amount evaporates from the ground or transpires from vegetation (forest, rangeland, cropland). The remaining 40 000 km3 per year is converted to surface runoff (feeding rivers and lakes) and groundwater (feeding aquifers). These are called renewable freshwater resources. Part of this water is being removed from these rivers or aquifers by installing infrastructure. This removal of water is called water withdrawal. Most of the withdrawn water is returned to the environment some period of time later, after it has been used. The quality of the returned water may be less than the quality when it was originally removed.
In the spirit of transparency, and since much depends on definition and methodology, AQUASTAT provides the following documents to clarify its water withdrawal and wastewater statistics:
In AQUASTAT, three types of water withdrawal are distinguished: agricultural, municipal (including domestic), and industrial water withdrawal. A fourth type of anthropogenic water use is the water that evaporates from artificial lakes or reservoirs associated with dams. Information on evaporation from artificial lakes will be available in the AQUASTAT database in the near future.
At global level, the withdrawal ratios are 70 percent agricultural, 11 percent municipal and 19 percent industrial. These numbers, however, are biased strongly by the few countries which have very high water withdrawals. Averaging the ratios of each individual country, we find that "for any given country" these ratios are 59, 23 and 18 percent respectively.
The ratios also vary much between regions, going from 91, 7 and 2 percent for agricultural, municipal and industrial water withdrawal respectively in South Asia to 8, 16 and 77 percent respectively in Western Europe. For more details about water withdrawal by region, please see this table.
Examples of organizations/initiatives that consistently use AQUASTAT water resources and withdrawal data are the following:
For Africa, Asia, Latin America and the Caribbean, AQUASTAT obtains water withdrawal values from ministries or other governmental agencies at a country level, although some data gaps are filled from UN Data. For Europe and for Northern America, Japan, Australia and New Zealand, Eurostat and OECD are valuable sources of information, and also used to fill data gaps. Links to these organizations are provided below:
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