Salinity - Risk and Hazard - Tasmania
Tasmania
Where is there a dryland salinity risk or hazard and how was this determined?
The hazard assessment was based on field observation at the land system scale in the mid 1990s updated by expert opinion, questionnaire of Departmental and Landcare groups and limited ground truthing at a scale of 1:250 000 or greater. Groundwater data for Tasmania are extremely limited. As land system mapping units were used to portray areas within which dryland salinity hazard exists the areas depicted do not change between 2000 and 2050.
Land systems are areas of land with the same annual rainfall, geology, altitude, topography, soils and vegetation, defined by a unique six digit code.
In 1992, maps of those systems which contained private and freehold land were used as a basis for recording the extent of eight types of land degradation, including salinity.
The degradation was recorded by twenty Departmental officers, based on their collective detailed knowledge of local conditions, and published by Grice (1995). Grice defined levels of salinity as:
Nil no obvious visual signs.
Moderate plant and tree vigour reduced, no salt sensitive species, bare patches in pasture usually less than one square metre.
Severe extensive areas of bare ground and possibly salt crusts, trees dead or dying- only salt tolerant species present.
This report was used as the baseline for estimating the extent of salinity in 1992 (see table below).
| Land systems | % |
|---|---|
|
93 series (Quaternary sands and sandstones)
|
55% |
|
84 series (Tertiary mudstones)
|
25% |
|
88 series (Tertiary complexes)
|
5% |
Data collated by the Department's Salinity Officer, based on field work between 1995 and 2000 was used to identify new land systems not recorded as expressing salinity in 1992 and thence estimate the trend over eight years. Groundwater data for Tasmania are extremely limited.
How can dryland salinity risk change over time?
It is estimated that the area of salinity in agricultural land is as follows
| Year | Average area affected (ha) | Range of area affected (ha) |
|---|---|---|
| 1992 | 45 000 | 30 000 - 60 000 |
| 2000 | 53 500 | 6 200 - 71 200 |
| 2020* | 69 550 | 47 000 - 92 500 |
| 2050* | 93 625 | 63 350 - 106 800 |
* Assuming the present rate of increase in salinity, estimated to be 1.5%, is real and continues
It is likely that some of the increase is salinity recorded since 1992 is due to increased detection of land previously affected. Assuming about half is an actual increase, the average rate of increase between 1992 and 2000 was 1.5% per year.
Analysis of the 41 Land Systems identified in 1992 as containing areas of salinity has shown that the most frequently occurring are:
| 93 series (Quaternary sands and sandstones) | 55% |
| 84 series (Tertiary mudstones) | 25% |
| 88 series (Tertiary complexes) | 5% |
A further nine Land Systems were identified in the Tasmania Dryland Salinity Assessment 2000 report.
Further information
- Tasmania Dryland Salinity Assessment 2000 report
- Australian Dryland Salinity Assessment 2000 report
- National Technical Overview Report of the State-based dryland salinity assessments
- Australian Groundwater Flow Systems Report
- Tasmania Department of Primary Industries, Water and Environment
- National Dryland Salinity Program
- National Action Plan for Salinity and Water Quality
Tasmanian landsystems containing areas of salinity in 2000
Link to Map maker to make a map using this information.
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