Vital GEO Graphics

Agriculture is by far the biggest user of water. The expansion of hydropower generation and irrigated agriculture, now happening mostly in developing countries, is vital for economic development and food production. But, the consequent changes in land and water use by agriculture, as well as for urban and industrial growth, have major adverse im- pacts on freshwater and coastal ecosystems. Agricul- tural run-off containing nutrients and agrochemicals is the main source of water pollutants in many coun- tries. In addition to agricultural demands, pressures on water resources are compounded by the physical alteration and destruction of habitats by urban and industrial development. Increasing water withdrawals for irrigation increases the likelihood of salinity when there is inadequate drainage to carry the salt out of the soil. This is a threat to livelihoods and food security in dry areas, where most farm production is from irrigation and farmers use whatever water is available, however marginal, even on land with a high, saline water table. In the long run, this renders the land unproduc- tive. Salinity will increase unless the efficiency of irrigation networks, in particular, is greatly improved. Worldwide, some 20 per cent of irrigated land (450 000 km 2 ) is salt-affected, with 2 500–5 000 km 2 lost from production every year as a result of salinity.

D ownload G raphic 2

Changes in global water use by sector

3 200 km 3

assessment

forecast

Withdrawal Consumptive use Returns and waste

2 800

2 400

2 000

1 600

1 200

800

400

0

1900

1925

1950

1975

2000 2025

1 600 km 3

assessment

forecast

Withdrawal Consumptive use Returns and waste

1 400

1 200

1 000

800

600

400

200

0

1900

1925

1950

1975

2000

2025

km 3

800

assessment

forecast

Withdrawal Consumptive use Returns and waste

700

600

500

400

300

200

100

0

1900

1925

1950

1975

2000

2025

km 3

400

assessment

forecast

Evaporation

350

300

250

200

150

100

50

0

Salinity induced by irrigation in the Euphrates basin in Syria. Credit: Mussaddak Janat, Atomic Energy Commission of Syria

1900

1925

1950

1975

2000

2025

Source: UNEP/GRID-Arendal

2002, based on Shiklomanov and UNESCO 1999

60 V I TAL GEO GRAPH I CS

Salinity induced by irrigation in the Euphrates basin in Syria. Credit: Mussaddak Janat, Atomic Energy Commission of Syria