Environmental Engineering Reference
In-Depth Information
Table 5.1
Degradation facts and figures
Salinity impacts
Remnant vegetation and wetlands
• 2 million ha of remnants and replanted perennial vegetation damaged or at risk from
rising watertables and increasing salinity
• Remnant native vegetation and fauna threatened
• Riparian vegetation, critical to stream bank stability and wetland areas, is damaged
and under increasing threat
• In WA, 80% of the length of rivers and streams are degraded by salinity, half the water
bird species have disappeared from the many wetlands that were once fresh or
brackish, 450 plant species are threatened with extinction.
Land
• About 2.5 million ha affected; could increase to more than 12 million ha
• Estimated capital value of land lost to dryland salinity exceeds $700 million.
Water quality
• Increasing salt concentrations in most streams and rivers
• Salinity levels in the Murrumbidgee River are increasing at rates of 0.8-15% per
annum
• Stream salinity in the Murray River exceeds World Health Organization guidelines
for about 10% of the year.
Road, bridges and urban infrastructure
• At risk or damaged. For example, the National Dryland Salinity Program estimated
that high watertables in south-western NSW affect about 34% of state roads and 21%
of national highways, amounting to damage costs of about $8 million per year.
Soil acidification
• Already occurs on more than 90 million ha; of these, production could be seriously
affected on 33 million ha.
Wind erosion
• A major problem throughout the margins of the Australian cereal cropping zone and
large areas of the southern rangelands
• The loss of the most valuable topsoil is largely irreversible. It reduces the nutrient
levels of the soil and its ability to retain moisture for plant growth
• An estimated 2.6 million ha of cropland in Victoria, (2.5% of the Murray-Darling
Basin) is potentially subject to wind erosion.
Water-induced erosion
•
Estimated to affect 1 million ha of cropland in Victoria, most within the Murray-
Darling Basin
•
Affects 4.8 million ha (about 0.5%) of grazing land, most within the Murray-Darling
Basin
•
15 million ha of cultivation land in NSW and 16.3 million ha of grazing land (14%
and 15% respectively) are subject to water and wind erosion.
