Indicator description

Why is it indicative

What does the data show

Data

Acknowledgment

Indicator description

The area of land that is reported as having saline soils within the top metre, in regions of Australia of greater than 250 mm annual rainfall. This indicator covers areas affected by dryland (i.e. salinity caused by land use changes such as land clearance and/or dam and road construction etc) and irrigation salinity.

Why is it indicative

This indicator is a direct measure of the condition.

Care must be taken to partition changes between newly salinised land and land where previous salinisation has only recently been recognised. The distinction also needs to be made between primary (i.e. naturally occurring saline conditions e.g. salt lakes) and secondary types of salinity (i.e. human induced). There may be a significant time lag between the onset of salinity and the practices that cause it, and in some cases these practices may already have ceased. Similarly, the causes of salinisation may be spatially separated from the effects.

What does the data show

• Note the indicator used for the Tasmanian Salinity Audit was based on the estimated area in each Land System showing visual effects of salinity on vegetation and ground cover.
   
• On this basis, salinity affects 3% or 53,500 ha of Tasmania's agricultural land, particularly in the lower rainfall regions, below 750mm per year.
   
• This is an increase of 8,500 ha from the baseline 1992 data, which was estimated to be 45,000 ha. Assuming about half of this is an actual increase, it was estimated that the average rate of increase was 1.5% (675 ha) per year. At this rate Tasmania could have 93,600 ha of land affected by salinity by 2050.
   
• The majority of Tasmania's municipalities (i.e. 20 of the 29) contain land showing visual signs of salinity. The worst affected being Northern Midlands, Southern Midlands, Central Highlands and Dorset. These combined contain about 80% of the land thought to be affected by salt.
   
• Half of the 48 catchment areas in the State have had some surface water salinity testing. 19 of these contained water with levels above 0.8 dS/m (0.8 dS/m is the World Health Organisation highest preferred limit for drinking water). Twelve catchments contained water with levels above 1.5dS/m (adverse ecological effects are likely to occur in aquatic ecosystems if salinity rises above 1.5dS/m).
   

Data

The area of salt affected agricultural land in 2000 was estimated to be 53,500 ha or 3% of Tasmania's private land.

This is an increase of 8,500 ha from the baseline 1992 data, which was estimated to be 45,000 ha. Assuming half of this is an actual increase (with the other half assumed to be due to increased detection of land previously affected), it was estimated that the average rate of increase was 1.5% (675 ha) per year. The table below outlines the projections for the area of private land that maybe affected by salinity in the future.

Estimated area of salt affected agricultural land in Tasmania.

Year	Area (ha)
1992	45,000 (30,000-60,000)
2000	53,500 (35,600-71,300)
2020	69,550 (47,000-92,500)
2050	93,625 (63,350-106,800)

Source: Bastick and Walker 2000.

It is not possible to distinguish between the area of primary and secondary salinity. However, the majority of the 8,500 ha increase is likely to be secondary salinity. A small proportion could be new areas of primary salinity not reported before (Mike Walker pers. comm.).

The area of land containing salt by municipality and Tasmania's major water catchments are outlined in the tables below.

Area (hectares) of land showing visual signs of salinity by municipality in order of severity.

Surface water monitoring and salinity status in Tasmania's 48 planning and management catchments

Caption: Decisiemens/m (dS/m) is one standard unit of salinity. The Murray Darling Commission uses benchmarks for salinity based on electroconductivity. For example, 0.8 dS/m is the upper limit recommended for drinking water and for optimum irrigation.

Monitoring		Conductivity (dS/m)	Water catchment name	Total
Catchment with land systems containing salinity	No	-	Swan-Apsley, Little Swanport, Tasman, Clyde, Ouse, Upper Derwent, Montagu, Leven	8
	Yes	>0.8	Furneaux islands, Pitt Water -Coal, Jordan, King Island, Mersey, Rubicon, Brumby's - Lake, South Esk, North Esk, Tamar Estuary, Pipers, Little Forester, Great Forester - Brid, Boobyalla - Tomahawk	14
		<0.8	Forth - Wilmot, Meander, Lake - Macquarie, Ringarooma	4
Catchment with no land systems containing salinity	No	-	George, Scamander - Douglas, Port Davey, Wanderer - Giblin, Gordon - Franklin, Pieman, Nelson, Arthur, Welcome, Duck, Black - Detention, Inglis, Can, Emu, Blythe, Great Lake	16
	Yes	>0.8	Musselroe - Ansons, Lower Derwent, Huon, King - Henty	5
		<0.8	Prosser	1

Acknowledgment

Core Land Indicator L 5 (ANZECC 2000).