Global water resources
The amount of water used on a global scale has increased rapidly in recent years. Increased demand is due to population growth and increased per capita consumption of water. The rate of increase in industrialised countries is the lowest; most of the increase is in the developing world, which has a much lower per capita water use at present: 70% of global water use is for agriculture, 22% for industry and 8% for domestic purposes. This division has a considerable regional variation: in Africa, India and Asia, agriculture is even more water-demanding, with Asia, for example, using 85% for agriculture. In Europe and the USA, industry uses a greater proportion: 55% and 49% respectively.
Water, however, is a resource in which 'used' is a relative term: some agricultural water and most industrial and domestic water is returned to rivers or groundwater after use, but usually with a change of quality. And, we have seen that rivers themselves have a residence time of only a few weeks, so the water in them is renewed on a very short timescale.
On a global scale, water is not scarce, but locally on a continental or national scale it often is, and with increasing demand is likely to be more so in the future.
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