Agriculture is by far the biggest user of water. The
DownloaD Graphic 2
expansion of hydropower generation and irrigated
Changes in global water use by sector
agriculture, now happening mostly in developing
km
3
countries, is vital for economic development and
3 200
assessment forecast
food production. But, the consequent changes in
2 800
Withdrawal
land and water use by agriculture, as well as for
Consumptive use
2 400
Returns and waste
urban and industrial growth, have major adverse im-
2 000
pacts on freshwater and coastal ecosystems. Agricul-
1 600
tural run-off containing nutrients and agrochemicals is
the main source of water pollutants in many coun-
1 200
tries. In addition to agricultural demands, pressures
800
on water resources are compounded by the physical
400
alteration and destruction of habitats by urban and 0
industrial development.
1900 1925 1950 1975 2000 2025
km
3
Increasing water withdrawals for irrigation increases
1 600
assessment forecast
the likelihood of salinity when there is inadequate
1 400 Withdrawal
drainage to carry the salt out of the soil. This is a
Consumptive use
1 200
threat to livelihoods and food security in dry areas,
Returns and waste
1 000
where most farm production is from irrigation and
800
farmers use whatever water is available, however
marginal, even on land with a high, saline water
600
table. In the long run, this renders the land unproduc-
400
tive. Salinity will increase unless the efficiency of 200
irrigation networks, in particular, is greatly improved.
0
1900 1925 1950 1975 2000 2025
Worldwide, some 20 per cent of irrigated land
km
3
(450 000 km
2
) is salt-affected, with
800
assessment forecast
2 500–5 000 km
2
lost from production every year 700
Withdrawal
as a result of salinity.
Consumptive use
600
Returns and waste
500
400
300
200
100
0
1900 1925 1950 1975 2000 2025
km
3
400
assessment forecast
350
Evaporation
300
250
200
l v
150
100
50
0
Salinity induced by irrigation in the Euphrates basin in Syria.
1900 1925 1950 1975 2000 2025
Credit: Mussaddak Janat, Atomic Energy Commission of Syria
Source: UNEP/GRID-Arenda 2002, based on Shiklomano and UNESCO 1999
Salinity induced by irrigation in
60 VITAL GEO GRAPH
the
I
Euphrates
CS
basin in Syria.
RESOURCE EFFICIENCY
Credit: Mussaddak Janat, Atomic
Energy Commission of Syria
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