Queensland
The area estimated to be affected by dryland salinity in Queensland is 48 000 ha. This area does not include all land with groundwater levels within 2 m of the surface. Affected land is distributed throughout the eastern part of the State with only minor occurrences in western Queensland.
The Condamine-Balonne and Border Rivers catchments are the only catchments in the State where sufficient data exist to determine, on a catchment-wide basis and with a moderate level of accuracy, the area with groundwater levels within 2 m of the surface (some 17 500 ha).
Although little data are available on which to base future water level trends over most of the State, a salinity hazard map indicating land potentially at risk of developing salinity has been produced. There is a wide distribution of land with a high salinity hazard (Table 12). Known areas of distribution are in the Murray Darling, the Burnett and Fitzroy regions.
The hazard map was produced by collating available datasets for geology, Atlas of Australian Soils, elevation, land use change and potential excess rainfall. It reflects potential dryland salinity areas related to the extent of land use change. There are no State-wide data which capture salt storage in the weathered landscape zone. This factor must be taken into consideration in tropical areas where most of the salt has been flushed from the system. The index-overlay approach used to derive areas affected by dryland salinity provides an estimate of `equilibrium' or `worst-case' scenarios with the assumption of no change in land use or management. As a result a significant overestimation of areas at risk is likely to have been made. It should not be directly compared with 2050 predictions using the groundwater trend approach.
Table 12.Estimates of areas (ha) potentially affected by dryland salinity under current land use.
|
Catchment region |
2050 |
|
Fitzroy |
732 421 |
|
Murray-Darling |
628 393 |
|
Gulf |
546 412 |
|
Burdekin |
476 886 |
|
North Coastal |
206 534 |
|
Burnett |
180 837 |
|
South-east Coastal |
179 970 |
|
Central Coast |
90 101 |
|
Curtis |
87 399 |
|
Western |
2 687 |
|
Total |
3 131 639 |
Figure 7. Dryland salinity hazard in Queensland 2050
Estimates of projected dryland salinity hazard in 2050 were based on a map overlay analysis using attributes that drive salinisation such as geology, landscape features, regolith depth and type, land use and climate. Groundwater data for assessing salinity risk in Queensland are extremely limited. Groundwater trend analysis was possible only in Condamine-Balonne and Border Rivers catchments of the Murray Darling Basin. The estimate of area affected (48 000 ha) by dryland salinity was based on field observation in the early 1990s, and workshop-based consultations. Information has been prepared at a scale of 1:2 500 000.
Findings
Although Queensland has an extensive groundwater monitoring network for management of groundwater extraction, the network was not designed for monitoring the shallower groundwater systems that are associated with dryland salinity processes. Hence there are very limited groundwater condition and trend monitoring data to assess and predict dryland salinity processes and impacts.
Table 13.Key assets located in the areas of dryland salinity hazard in Queensland. [INSERT]
- A total of 3.1 million hectares are considered to have a high salinity hazard; and 2.6 million hectares are in agricultural lands.
- Where groundwater trend modelling was undertaken in the Condamine-Balonne and Border Rivers areas, 373 000 ha are predicted to have groundwater levels within 2 m of the surface by 2050.
- Only a very small length of roads has been specifically identified as having deteriorated as a direct result of salinity but approximately 12 000 km of roads are in the areas of high hazard.
- An increase in salinity in streams has been noted in parts of the Condamine, Lockyer Creek, the lower Mary, the South Burnett, Three Moon Creek and some tributaries of the Fitzroy.
- The Ramsar-listed wetlands in Queensland are predominantly tidal and it is expected that coastal-related processes will dominate the future health of these systems.
- No costing of the effect of salinity has been undertaken. Most outbreaks are small, localised and are not considered of serious economic consequence to agricultural land at this stage.
- Impacts on wetlands and riparian zones have not been assessed.
Key issues
- Current monitoring networks do not provide a suitable framework for assessment of dryland salinity and its impacts in Queensland. There is an urgent need to establish a State-wide monitoring network of groundwater, surface water, key land use and biodiversity parameters to better inform managers of the trends and implications of dryland salinity.
- It is vital that preventive and protective action is taken in maintaining water balance for those areas where salt stores would be mobilised with the clearing of native vegetation.
- Work is required to develop and then implement farming systems that deliver sustainability and production outcomes, particularly taking into account long-term risks of watertable rise in salinity.
- The index-overlay approach generated a `salinity hazard' map for Queensland. However, the approach does not provide an assessment of trends in dryland salinity. Based on our understanding of salinity processes and groundwater flow systems, the method does provide a sound basis for prioritisation of salinity research and development activities.
- The lack of available data limits the capacity to provide a State-wide salinity risk assessment that would underpin at fine scales regional and property planning processes for vegetation management. Nevertheless, for selected catchments in the Murray Darling Basin where 1:25 000 scale data are available, this is possible and of priority.
Government response
This assessment has resulted in the first State-wide hazard assessment of dryland salinity in Queensland. It has identified a significant long-term risk associated with dryland salinity in Queensland and will assist in setting priorities for investigations, assessments and development of management responses on dryland salinity.
Several natural resource management initiatives have recently been implemented within Queensland and contain specific actions to minimise the future risk of dryland salinity. The Queensland Government has enacted the Vegetation Management Act 1999 (Qld) to provide controls over the clearing of remnant vegetation on freehold land to complement the Land Act 1994 (Qld) that covers leasehold land. The provisions of the Act include the preparation of regional vegetation management plans and the assessment of applications for the clearing of remnant vegetation. The accompanying policy and assessment code provides for the protection of vegetation in areas susceptible to salinisation. The Water Act 2000 (Qld) includes provisions for the preparation of property-level plans and district water use plans to address land and water management issues associated with irrigation water use including salinisation and rising groundwater levels.
Salinity outbreaks are generally localised and technical assistance is provided through government in planning control options on an individual or group basis. Numerous dryland salinity projects have been implemented with the support of Landcare and integrated catchment management groups throughout Queensland (e.g. the Balfes Creek catchment in North Queensland was a focus catchment for dryland salinity research under the National Dryland Salinity Program).
A review of the information needs for assessing and monitoring of dryland salinity has been completed in conjunction with this Audit. The review includes a work plan that will significantly increase the knowledge base on salinity and provide the technical support to underpin government policy initiatives in land and water management, and vegetation clearing. Work is being undertaken to refine salinity risk assessment in Queensland in key regions utilising the groundwater flow system approach as the framework. Implementation of the salinity work plan will be considered as part of Queensland's response to the Commonwealth's National Action Plan for Salinity and Water Quality.
Table of Contents for the Australian Dryland Salinity Assessment 2000
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