MEASURING WATER USE IN A GREEN ECONOMY - UNEP

example, the Food and Agriculture Organization
of the UN (FAO) uses a type of water accounting
approach to calculate the world’s national water
balances. The method consists of a set of rules
and guidelines (FAO/BRGM (1996)), in which
renewable water resources are determined
on the basis of the hydrological cycle and
represent the long-term average annual flow
of rivers, surface waters and groundwater,
and non-renewable water resources are
groundwater bodies (i.e. deep aquifers) that
have a negligible rate of recharge on the human
time-scale. It is from here that we understand
the regional aspects of global water availability.
Below are some of the most common phrases
and the way in which they are more specifically
defined in the water-resource literature.
Water availability varies around the world
and depends on both precipitation and
evapotranspiration. It is given as a percentage
of global runoff, usually by region. Latin
America is the most water-rich region with
about one third of the world’s run-off, and the
Middle East and North Africa the least with only
1 per cent of global runoff.
Water consumption, or water abstraction, is
usually described in terms of annual water
withdrawal as the gross amount of water
extracted from all sources, either permanently
or temporarily, for a given use. Some may be
returned to the original source, the rest may
be consumed in the use. Consumptive use
refers to water that is made unavailable for
reuse in the same basin or irrecoverable, for
example through seepage to a saline sink,
evapotranspiration or contamination (Gleick,
1996; 2003). Most agricultural water use is
consumptive, being bound up in plants or
consumed by evapotranspiration, whereas
water abstracted for electricity generation is
nearly all returned to a water body. In Europe,
total abstraction is 288 km 3 per year. Of this, 44
per cent is for energy production, 24 per cent
for agriculture, 21 per cent for public water
supply and 11 per cent for industry. However
regional differences are very pronounced: for
example, in the south the largest extraction is
for agriculture which can be as high as 80 per
cent (for irrigation).
Water withdrawal usually describes the
amount of water used per person. This varies
considerably around the world, from 20 m 3 per
year in Uganda to 5 000 m 3 in Turkmenistan;
the average is 630 m 3 per person per year from
surface and groundwater sources.
Water scarcity can be described as a physical
or a social measure; it is a measure of the
relationship between the use of water and its
availability. For clarity, the physical term will be
used in this report to denote a lack of enough
water (i.e. quantity) and/or access to safe water
(i.e. quality).
Water shortage is an absolute lack of water,
where the available amount does not meet
defined minimum per capita requirements for
water use. In some cases it is measured as the
number of people that have to share each unit
of water resource (Falkenmark et al., 2007).
Global and regional trends in water shortages
show that in 2005 2.3 billion people lived under
chronic water shortage conditions (Kummu et
al., 2011).
Water stress describes the consequences
of water scarcity on ecosystems and human
populations. It can be related to a decline in
quality or to the level of conflicts.
Water exploitation index (WEI) is a relatively
straightforward indicator of the pressure or
stress on freshwater resources. It is calculated
annually as the ratio of total freshwater
abstraction to the total renewable resource. In
Europe it is given as a national index; a value
above 20 per cent implies that water resources
are under stress and values above 40 per cent
indicate severe water stress and unsustainable
use of water resources (Raskin et al., 1997;
EEA, 2009). Despite its limitations, the WEI
shows a broad correlation between river basins
with a high WEI value and detrimental impacts.
2.3.3 Water as an economic resource
There is also a need to move beyond physical
indicators to those linked with efficiency,
conversion of water as a resource into goods
and services, and ultimately measures of
monetary value. There are two key concepts:
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