ABSTRACT
At the start of the twenty-first century, the average world citizen had a water footprint of 1,385 m3/yr (Hoekstra and Mekonnen, 2012a). We found, however, big differences between and within countries. The average consumer in the United States had a water footprint of 2,842 m3/yr, whereas the average citizens in China and India had water footprints of 1,071 and 1,089 m3/yr, respectively. The global average of 1,385 m3/yr has brought us where we are now: overexploitation of blue water resources in roughly half of the world’s river basins and pollution beyond assimilation capacity in at least two-thirds of the river basins in the world (see Chapter 9). We can try to shift the burden to some extent from overexploited to not-yet overexploited river basins to find better regional balances between water consumption and water availability and between water pollution and waste assimilation capacity. In this way we may be able to better accommodate our current global water footprint. It is hard to imagine, however, that an increase of the current global water footprint can work out sustainably. According to the medium population scenario of the United Nations, the world population is expected to increase from 6.1 billion in the year 2000 to 9.3 billion in 2050 and 10.1 billion by the end of this century (UN, 2011). This means that, if we want to make sure that the water footprint of humanity as a whole will not increase over the coming century, the average water footprint per capita will have to decrease from 1,385 m3 in 2000 to 910 m3 in 2050 and 835 m3 in 2100. If we assume an equal water footprint share for all global citizens, the challenge for countries like China and India is to reduce the current water footprint per capita level by about 22.5 per cent over the coming century. For a country like the USA, it means a reduction of the average water footprint per capita by about 70 per cent. Improved technologies alone will not be sufficient to reach this goal.
