Geography Reference
In-Depth Information
of sustainability in developing world. Even in the developed world increasing prob-
lems are emerging to threaten urban water supplies. One is that global warming
is predicted to reduce the rainfall in some areas, or will lead to major downpours,
so existing reservoirs may not be able to cope and fulfil future demand. Unless
more local systems are developed and per capita water use can be reduced, future
investments will be required in large storage sites, especially in sites nearer existing
cities, to reduce transport costs. However, the creation of such sites is likely to run
into opposition from farmers and environmentalists in the areas affected. Second,
many systems are less efficient that they appear, given high levels of leakage due to
aging and poorly maintained pipelines. For example, there was an average loss of
approximately 25 % of the water carried between reservoirs to households in south-
ern England in 2012 (WT
2012
). This means that one way of obtaining significant
urban water consumption savings, without the huge costs of new reservoir capac-
ity, is by improving the efficiency of the existing water delivery system. Third, it
is clear that there are huge variations in the per capita consumption of water. The
Green Index research described above showed that Amsterdam consumed the least
water in the cities surveyed in the developed countries, at 146 L per person day,
compared to 262 L in New York, and 300 L in Yokohama, the leading consumers
in the American and Asian centres respectively. This evidence helps to provide the
background to questioning why people in different cities have such different con-
sumption levels and about how such cultural variations in water use can be reduced.
More specifically, many new policies are being introduced to reduce current water
use levels, such as by: installing household water meters to encourage conservation
among cost-conscious consumers; using low-flush toilets, and more effective show-
er-heads and taps which reduce per capita water use. Indeed, increasing numbers of
urban jurisdictions now make such water-saving devices mandatory in new build-
ings, or provide subsidies for consumers who install such devices. Another grow-
ing trend which needs wider adoption has been the development of two different
water systems in houses. One is for drinking water; the other uses recycled or 'grey'
water. This is derived from water previously used for washing, or from rain water
collected in separate systems, which is then re-used to flush human waste away, or
to water lawns, for it does not make sense to use expensively filtered drinking water
to flush toilets. A return to the greater use of water barrels to store rainwater for
use on gardens also reduces the use of household water for this purpose. However,
despite the growing use of these conservation measures, many cities in the world
are still facing a long-term water shortage. Although local artesian sources have
long been exploited, it is recognized that many have been over-used and are not
being replenished, so the long-term ability to extract more water from such sources
is limited in many regions. A big problem in many countries is the increasing com-
petition for declining water supplies from rivers, aquifers and reservoirs between
agricultural usage and city needs. There seems little doubt that many cities need to
find new water supplies, and to reduce water use, while it is very possible that deci-
sions have to be made to phase out crops in some agricultural areas that need large
amounts of water. These problems mean that some coastal cities have turned to the
sea as a source of water by using desalination plants to take the salt out of seawater
