FACTBOX - The how, where and cost of salinity
© 2000 Reuters Limited
November 10, 2000
SYDNEY - Salination is an ancient problem, having inflicted damage on the earth since the Babylonian and Roman Empires.
But its spread is growing alarmingly, posing a global threat to crops and to land use. Modern technology and development funding is helping to worsen the problem as damming and irrigation spreads. These are the main facts on salination, according to Australian scientists:
CAUSES:
-Salt deposited on land by millions of years of rainfall from the sea is collected in subterranean water tables.
-CLEARING of deep-rooted trees and native vegetation, which naturally draw off water, causes water tables and salt to rise.
-IRRIGATION of crops directly adds water to the table. -DAMMING stops natural runoff of salts, diverts water to irrigation and upsets the vegetation balance.
-AUSTRALIAN PROBLEM is worsened by ancient soil 60-200 million years old and untouched by glaciers; also further by inward-running rivers.
Australian scientists say saline groundwater is twice as salty as seawater; 150 millimetres of rain is leaking through the soil in Australian cropping areas compared with 5-10 mm with original vegetation, enough to raise the water table by one metre over time.
INCIDENCE:
-AUSTRALIA has about 2.5 million hectares, or around 15 million acres, of salinity affected land, about five percent of Australia's cultivated land, the National Dryland Salinity Programme (NDSP) says. It could rise to 12 million ha, or 22 percent, the government says. NDSP says up to 15 million ha of land could go saline in 50 years.
Southwest Western Australia is most severely affected, with salinity also a significant problem in the south of South Australia, in Victoria, New South Wales and Queensland, mainly in areas around the coastal strip.
AUSTRALIAN SALT-AFFECTED AREA 1996
Western Australia 1.80 mln ha South Australia 0.40 mln ha Victoria 0.12 mln ha New South Wales 0.12 mln ha Tasmania 0.02 mln ha Queensland 0.10 mln ha Northern Territory minor Total 2.476 mln ha
-The SUBCONTINENT has severe salinity. In INDIA, at least seven million acres, or about 1.13 million hectares, is affected, according to the Worldwatch Institute. PAKISTAN has at least four million acres, or around 0.65 million hectares affected. Damming at the mouths of the Ganges is worsening salinity in the Sundarbans of India and BANGLADESH.
-CHINA has about six million acres, or almost one million ha, affected by salinity, Worldwatch Institute says.
-Other affected areas are THAILAND, UZBEKISTAN, CALIFORNIA, and arid parts of SOUTH AMERICA and SOUTH AFRICA.
AUSTRALIAN COST:
Salinity in Australia costs A$270 million a year in lost agricultural production, infrastructure damage and environmental degredation, NDSP says. This includes about A$100 million damage to urban infrastructure, A$130 million lost agricultural production and A$40 million lost environmental assets.
SOLUTIONS:
-No quick fix, with up to 100 years of an integrated programme required to bring about rectification.
-Integrated programme would include: PLANTING TREES and deep-rooted vegetation; engineering projects and PUMPING OUT saline sludge (unsolved problem: where to put the sludge); resurrecting dried rivers by RELEASING DAMMED WATER into them; better CROP ROTATION to use deep-rooted crops such as lucern.
-Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) is conducting scientific work on new crops, crop rotation, on breeding PERENNIAL GRAIN CROPS to draw water off all year, and production of GENETICALLY MODIFIED CROPS which will draw off greater amounts of water.
Use of large pools of non-saline subterranean water reservoirs not seen as a solution because they are a non-renewable resource.
AUSTRALIA'S SALINITY PROGRAMME:
The Australian government announced on November 3 that the federal and state governments would spend a total A$1.4 billion over the next seven years. Consultations now in progress, expected start-up mid-2001.
Funds will pay for rehabilitation of waterways, re-vegetation and engineering work to combat salt intrusion into farmland. Compensation also will be offered to landowners affected by changes to land clearing and water rights.
Programme of works will be in about 20 catchment areas to address the problem in an integrated way. Details of action under consideration but will vary according to needs.