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Salinity - Monitoring - Tasmania

Tasmania

Monitoring now and in the future

Limitations of the assessment data

• In reviewing salinity assessment and management in Tasmania, Nulsen (1995) noted

"given that on a statewide basis salinity affects less than one percent of the agricultural land, it may not be appropriate to devote a large effort to obtain production from it. Resources might be better expended on catchment management to prevent further salinisation."

• This Audit has shown that, at the time Nulsen was reporting, the figure may possibly have been about two percent, or about three percent if remnant vegetation and private forestry is deducted from the total freehold area.
• This estimate is based almost entirely on collective visual assessments. When a number of individuals somewhat subjectively provide data in this way it is difficult to maintain consistency. The estimate must be treated with caution.
• Three indicators suggest that salinity may possibly be rising, namely

- the increase in the visual expression of salinity in agricultural land

- shallow bore water levels which are within the Audit benchmark of Risk

- isolated measurements of surface and ground water salinity levels above the WHO benchmark of Risk are triggers.

• Salinity emerges slowly, and the small annual changes which need to be measured to detect trends require systematic and continuous monitoring, which was not assured at the time of the Audit.

Future Monitoring Requirements

• There is no accurate, long-term trend data relating to the Salinity Audit indicators and there is limited understanding of the processes that are driving salinity. This is because work on salinity began comparatively recently and so there has been little emphasis on strategic salinity monitoring.
• In order to be able to establish a strategic approach to monitoring, a two pronged approach is needed. High priority activities to address particular issues need to be identified and key reference sites need to be established in which to monitor indicators of change in salinity across the State into the future.

High priority activities

• A rapid field check of the major Land Systems identified in the Audit as containing areas of salinity.

This is necessary to verify that the newly identified land systems do contain areas of salinity; to obtain a firmer estimate of the percentage of each land system actually affected; and to provide a more accurate estimate of the area affected and at risk across the State.

• A rapid survey of likely tributaries of rivers and streams in areas adjacent to critical Land Systems where there is limited or no current data on surface water salinity levels.

The audit has established that out of 48 catchments, only 25 have any salinity data. Of the 25 with any data, approximately 20 have indications of salinities above 800 EC. As the earliest indications of rising salinities is likely to be in the small tributaries of rivers and not in the main streams, snap shot recordings as being used on major sections of rivers may not be picking up elevated salinities.

• A rapid ground truthing of the Audit biodiversity data set and an initial assessment made of what aquatic ecosystems other than wetlands are at risk of changing salinity levels.

The main emphasis has been on wetlands and as yet no field assessment has been made of other aquatic ecosystems.

• A rapid survey of roads and infrastructure which could be at risk of salinity, especially those areas adjacent to known salinity and in critical land systems.

Roads have been considered because quantitative data was available. Regarding infrastructure, there is some evidence of salinity which has been driven by irrigation in urban areas which may ultimately impact on adjacent infrastructure and holdings..

• Establishing a systematic network of bores and piezometers for long-term monitoring of watertable trends.

Long term monitoring is needed in areas where there is rapid agricultural land use change, especially irrigation developments in high-risk land systems.

Currently there are only limited networks of bores and piezometers which can be used for long term monitoring. In almost all cases the locations are adjacent to existing salinity patches. To establish robust trend information key indicator bore networks need to be established which include areas where no obvious surface salinity is now visible but where there are water tables present below 2.0 m.

Key Reference Sites

1. Three Key Reference Sites should be established, covering possibly 100 square km, and based on critical regions and land systems as well as a representative set of natural ecosystems and agricultural land uses.
2. These selected sites need to be established because it would be prohibitively expensive to continually monitor all current and potentially saline areas.
3. These sites would combine the use of remote sensing by satellite, aerial surveys, salt storage assessment, hydrological analysis, as well as soil and vegetation surveys to measure selected change indicators for land management decisions.
4. In the absence of such monitoring, it will be impossible to say how extensive the problem of salinisation might become.
5. It will also be difficult to give credence either to any land management advice designed to prevent any increase at the local level, or to associated policy advice regarding natural resource management at the State level.

Application at the farm level

• The scale of the Audit results and the maps precludes using them at individual farm level for detailed decision making, other than as a risk assessment tool to identify potential areas requiring further detailed on farm investigation.

Application at the Catchment/Local Government/Regional level

• The results are most useful at this level, to assist in regional planning, priority setting for natural resource management, including the allocation of funds for on - ground preventative and / or remediation works.
• It must be stressed that maps based on land systems can only be used to indicate where further detailed investigations are needed, before final decisions are made.

Application at the State level

• The results and the maps will be essential in developing a State Salinity Management Strategy as well as policies in areas such as resource use, vegetation management, and infrastructure development.
• They should also find a use in the implementation of the State agricultural products marketing strategy, which emphasises Tasmania's reputation as environmentally responsible.

What is being monitored

Tasmania

Responsibility

The Department of Primary Industry, Water and Environment (DPIWE) has primary responsibility for management and monitoring of dryland salinity. Mineral Resources Tasmania (MRT) is the custodian for the state's groundwater database.

Mapping of land salinisation

Mapping of dryland salinity has been undertaken on a 1:250 000 scale for land systems (areas with consistent patterns of annual rainfall, geology and topography). The first survey, completed in 1992, involved 20 Department of Primary Industry officers who were issued with 1:100 000 land systems maps of private and freehold land depicted on a topographic base and asked to delineate those areas in which they had seen visual symptoms of salinity. As part of the NLWRA Dryland Salinity theme, this assessment was updated based on field work by DPIWE's Salinity Officer (Bastick and Walker, 2000).

Groundwater monitoring

MRT are the custodians for Tasmania's groundwater database. About 4 340 bores in the database have location coordinates and, of these, 2 930 contain records for 'depth to water struck'. Most of these bores were drilled for mineral exploration and they do not represent a structured sampling of the hydrogeology of Tasmania. Consequently, some areas known to contain salinity are under-represented, such as the Central Highlands LGA. Salinity measurements are available for only 444 of the 4 340 MRT bores, including 70 drilled in 1999 to estimate the potential of ground water for irrigation in five districts known to contain salinity. The only trend data are from a series of around 50 bores monitored by DPIWE mainly in the Cressy Longford area and the Coal River Valley irrigation schemes (Bastick and Walker, 2000).

The spatial distribution of these DPIWE bores is summarised in Table C.4. Figure C.4 shows the spread of bores with respect to local (light grey), intermediate (mid grey) and regional (dark grey) groundwater flow systems.

Table C-4: Distribution of Groundwater Monitoring Bores in Groundwater Flow Systems in Tasmania

Basin Number	Basin Name	Region Name	km² per monitoring Bore - Local GFS	km² per monitoring Bore - Intermediate GFS	km² per monitoring Bore - Regional GFS	km² per monitoring Bore - Entire Basin
319	PIPER-RINGAROOMA RIVERS	BASS STRAIT	49	44	-	95
302	EAST COAST	TASMAN	80	9	-	82
318	TAMAR RIVER	BASS STRAIT	10	2	46	35
317	RUBICON RIVER	BASS STRAIT	-	21	-	72
316	MERSEY RIVER	BASS STRAIT	88	36	88	71
304	DERWENT RIVER	TASMAN	159	146	-	154
303	COAL RIVER	TASMAN	7	4	-	4
306	HUON RIVER	GORDON	-	31	-	333
314	SMITHTON-BURNIE COAST	BASS STRAIT	20	6	439	118

Figure C-4: Tasmanian Monitoring Bore Network

Surface water monitoring

Tasmania's stream monitoring network is sparse. Twenty-five of the 48 catchment areas in the State have had some surface water salinity testing which, in some cases, consists of just one sample. In 1994, 12 permanent record sites were installed by DPIWE to monitor flow and salinity.

Mapping of land cover/land use

Tree clearing/re-afforestation is assessed on a five-yearly basis by DPIWE. Land use mapping for the entire state will be undertaken at scales ranging from 1:25 000 to 1:100 000 as part of the Bureau of Rural Sciences' land use mapping program.

Modeling of current impacts

No assessment of the economic, social and biodiversity impacts of salinity was made prior to the NLWRA Extent and Impacts of Dryland Salinity project in which mapped salinity was intersected with infrastructure, endangered species and agriculture to estimate impacts (Bastick and Walker, 2000).

Future Extent

Similarly, no modeling of future salinity extent was undertaken before the NLWRA Extent and Impacts of Dryland Salinity project in which the trends observed between the 1992 and 2000 salinity surveys were extrapolated to estimate future extent (Bastick and Walker, 2000).

What type of monitoring is needed for Australia?

If we are to make informed decisions about how to prioritise our investment in salinity, and how to assess the effectiveness of investments, we need to be equipped with sufficient, good quality data that enable us to answer some fundamental questions at the catchment scale.

• How effective have management activities been?
• What is the likely future extent/severity/impact of salinity?
• What is the contribution to improving groundwater level of any salinity management investment?
• What investments are likely to deliver the most effective changes to water balance and over what time frame?
• How are systems-such as in-stream water quality, wetlands and soils-responding to improvements in groundwater level?
• What are the minimum components for an effective Australia-wide dryland salinity assessment and monitoring program?

We need:

• an analytical framework based on our understanding of hydrogeological processes controlling salinity, including timescales and spatial extents;
• evaluation methods and appropriate data (including indirect and surrogate indicators) that allow continuing evaluation of land management responses; the methods must enable the linking of biophysical, social and economic dimensions;
• consistent design and standards for data collection; and
• a capability to collect and manage data, and to produce information and assessments from this data.

Link to national overview of: Why monitor dryland salinity?

Further information

• Dryland Salinity Evaluation and Monitoring Report
• 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 the Map Maker to make a map using this information.

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