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2001
Extent and impacts of dryland salinity
Rod Short
Cecilia McConnell
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Part of the Hydrology Commons, Natural Resources Management and Policy Commons, Soil Science Commons, and the Water Resource Management Commons
Recommended Citation Short, R, and McConnell, C. (2001), Extent and impacts of dryland salinity. Department of Primary Industries and Regional Development, Western Australia, Perth. Report 202.
This report is brought to you for free and open access by the Natural resources research at Research Library. It has been accepted for inclusion in Resource management technical reports by an authorized administrator of Research Library. For more information, please contact [email protected]. ISSN 0729-3135 January 2001
Extent and Impacts of Dryland Salinity
Rod Short and Cecilia McConnell
Resource Management Technical Report 202
Western Australian component of Theme 2 prepared for the National Land and Water Resources Audit EXTENT AND IMPACTS OF DRYLAND SALINITY
Author details:
Rod Short Catchment Hydrology Group Natural Resource Sciences Agriculture Western Australia Pinjarra WA 6208
Cecilia McConnell Catchment Hydrology Group Natural Resource Sciences Agriculture Western Australia South Perth WA 6151
Disclaimer
The contents of this report were based on the best available information at the time of publication. It is based in part on various assumptions and predictions. Conditions may change over time and conclusions should be interpreted in the light of the latest information available.
Chief Executive Officer, Department of Agriculture Western Australia 2001
2 EXTENT AND IMPACTS OF DRYLAND SALINITY
Contents Summary ...... 5 1.0 Introduction...... 9 2.0 Methodology ...... 10 2.1 Extent...... 10 2.1.1 Spatial units...... 10 2.1.2 Groundwater analysis...... 10 2.1.3 Risk analysis...... 12 2.1.4 Current extent...... 12 2.2 Impact resulting from the risk analysis...... 13 2.2.1 Infrastructure...... 13 2.2.2 Water resources...... 13 2.2.3 Biodiversity...... 14 2.2.4 Agriculture...... 14 3.0 Datasets used by the audit...... 15 3.1 Spatial units...... 15 3.2 Groundwater datasets...... 15 3.3 Data confidence...... 17 3.4 Constraints and issues raised from applying chosen methodology...... 19 4.0 Results...... 22 4.1 Extent of shallow groundwater ...... 22 4.1.1 Groundwater depth...... 22 4.1.2 Groundwater quality...... 22 4.1.3 Groundwater trend...... 24 4.1.4 Current extent based on wet and waterlogged soils ...... 24 4.1.5 Risk of shallow watertables ...... 24 4.2 Impacts of shallow groundwater...... 33 4.2.1 Biophysical impacts ...... 33 4.2.2 Economic impacts...... 45 5.0 Other datasets ...... 49 6.0 Future groundwater monitoring...... 50 7.0 Key outcomes...... 51 7.1 Extent...... 51 7.2 Impacts and implications...... 52 8.0 Recommendations...... 55 9.0 Acknowledgments...... 55 References ...... 56 Compact disk containing maps ...... Inside back cover
Appendices 1. Allocation of land use data and water balance calculations...... 58 2. Soil-landscape zone number, name, description and area (ha) ...... 61 3. Soil-landscape system details...... 64 4a. Zone area and allocated risk...... 70 4b. Percentage of each zone at risk of shallow groundwater...... 72 5. Risk allocated to systems...... 74
3 EXTENT AND IMPACTS OF DRYLAND SALINITY
6. AWRC basins and allocated risk as a percentage of basin area...... 76 7a. Length of highways and allocated risk...... 77 7b. Length of primary roads and allocated risk...... 79 7c. Length of secondary roads and allocated risk...... 81 7d. Length of minor roads and allocated risk...... 83 7e. Length of rail and allocated risk...... 85 8. Towns and allocated risk of shallow groundwater...... 86 9. Stream length and allocated risk of shallow watertable...... 87 10. Resource recovery catchment and allocated risk...... 88 11. Area of perennial vegetation at risk of shallow watertables...... 89 12. Important wetlands and allocated area at risk of shallow groundwater...... 91 13. Allocated risk of shallow watertables for agricultural land (ha)...... 93 14. Indicative estimates of the costs of salinity on and off-farm in Western Australia...... 95 List of figures 1. Soil-landscape mapping hierarchy...... 16 2. Soil-landscape zones for south-western Australia...... 18 3. Groundwater monitoring sites used for the NLWRA ...... 19 4. Confidence in data used for the NLWRA project...... 20 5. Groundwater depth for soil-landscape systems...... 22 6. Groundwater conductivity for soil-landscape systems...... 24 7. Groundwater trend for soil-landscape systems...... 26 8. Current extent of wet and waterlogged soils for soil-landscape systems...... 27 9. Risk of shallow groundwater for agricultural areas of Western Australia in year 2000 ...... 28 10. Predicted risk of shallow groundwater for agricultural areas in year 2020...... 29 11. Predicted risk of shallow groundwater for agricultural areas in year 2050...... 30 12. AWRC Basins in agricultural areas of Western Australia...... 32 13. Land use on Deep sands in Irwin River (271) and Arrowsmith Zone (224)...... 41 14. Comparison of difference in recharge between current and proposed future land use...... 44 List of tables A. Estimated current impacts of salinity...... 5 B. Use of Project 1A report and mapping products as a planning tool...... 7 1. The number and density of bores within zones...... 17 2. Allocated high risk of shallow watertables and potential for salinity for soil-landscape zones...... 21 3. Percentage of AWRC basins at high risk of shallow watertables...... 33 4. Road and rail at high risk of shallow watertables and potential salinity for 2000, 2020 and 2050... 34 5. Towns with shallow watertable by 2050...... 35 6. Risk of shallow watertables in systems occupied by surface water monitoring stations...... 36 7. Areas of Water Resource Recovery Catchments at high risk of shallow watertables...... 36 8. Percentage of soil-landscape zone occupied by perennial vegetation at high risk of shallow watertables...... 38 9. Average ratio of arachnid and vertebrate species for quadrants in non-saline, primary and secondary saline areas...... 38 10. Threatened ecosystems and risk of shallow watertables...... 39 11. Areas of Recovery Catchments at high risk of shallow watertables...... 39 12. Land use categories and equivalent Western Australian Land Use Codes (WASLUC)...... 41 13. Agricultural land at risk (ha)...... 43 14. Distribution of bores within zones...... 50 15. Use of Project 1A report and mapping products as a planning tool...... 54
4 EXTENT AND IMPACTS OF DRYLAND SALINITY
SUMMARY
The National Land and Water Resource Audit (NLWRA) identified Dryland Salinity (Theme 2) as one of seven major themes for an audit of the nation's land, water, vegetation and natural resources. Within this theme, Project 1 was developed to identify the Extent and Impact of Dryland Salinity nationally. This report details the results from work done in Western Australia (WA) to meet the Audit requirements.
The definition of dryland salinity was taken to be that salinity caused by shallow watertables which result from anthropogenic induced changes in a catchment in which the only water input is from natural precipitation (Nulsen and Evans 1998, unpublished). All analysis is based on groundwater depth and trend and the risk of shallow watertables is derived from these two attributes. As dryland salinity is caused by shallow watertables, the risk of salinity is inferred from the risk of shallow watertables. Not all shallow watertables will be saline.
Given the timeframe of the NLWRA, a requirement was that reporting of the extent and impacts be based on the best readily available data. The agreed data elements to be analysed for Project 1 nationally were groundwater levels and trends from bores and wells monitored over recent years. Future impacts were to be predicted for the years 2020 and 2050.
The Natural Resource Assessment Group (NRAG) of Agriculture WA has mapped the south-west of WA using a hierarchical landscape mapping system (Table B). The mapping process is based on geology and geomorphology. In WA most groundwater movement and process is controlled by the geology and regolith properties. Therefore, this system was seen as appropriate for attributing hydrologic properties. The maps were examined by members of the Catchment Hydrology Group to ensure that there were no major conflicts between the map units and the current understanding of groundwater processes.
The Catchment Hydrology Group had been progressively uploading over 5000 monitoring and research bore records to its AgBores database. This process was accelerated to provide a monitoring bore and time series database.
Groundwater hydrographs were analysed to determine depth to watertables and hydrograph trends within identified broad regional zones. Data elements analysed were groundwater levels from bores and wells monitored within each system. The average length of monitoring for each record was five years. Soil-landscape systems were then allocated a risk rating based on the frequency of depth and trends in available groundwater monitoring information. The resulting map is a spatial representation of both depth and trend at year 2000. Groundwater trends were assumed to continue at current rates to predict watertable depth and allocate a risk rating in 2020 and 2050.
The groundwater analysis was also used along with water balance information to identify risks to agriculture, infrastructure, biodiversity and surface water if current trends continued.
5 EXTENT AND IMPACTS OF DRYLAND SALINITY
The key results from the WA audit show that for the south-west region: • Groundwater trends are dominated by rising or stable trends. No systems have significant falling trends. • Approximately 16% of the region has the potential for salinity in 2000 due to shallow watertables. • 20% of the region has the potential for salinity in 2020 due to shallow watertables. • 33% of the region has the potential for salinity in 2050 due to shallow watertables. • Recharge modelling of current and future farming systems indicates that predicted changes in land use only sufficiently changed recharge in three zones to delay the onset of salinity. The reduction in recharge was not sufficient in any of these zones to reduce the eventual extent of salinity.
The datasets suggest that current and perceived future land uses will result in approximately one-third of the south-western agricultural areas being affected by shallow watertables and salinity. This will potentially affect about 30,000 km of road and rail networks and at least 27 major rural towns. Surface water resources in the south-west of the State are likely to become more saline. The impacts on biodiversity are only just starting to be appreciated, but it is estimated that at least 1500 plant species will be affected, with 450 subject to extinction. Salinisation is also likely to reduce fauna species by 30% in affected areas. It is estimated that around 6.5 million hectares of agricultural land will be subject to shallow watertables and salinity.
The annual costs of current impacts have been estimated in Table A. These are ‘best bet’ estimates and do not include any assessment of the costs and benefits of strategies designed to combat salinity.
Table A. Estimated current impacts of salinity. Annual cost* in year 2000 due to watertables/salinity Best bet Possible range Agricultural land – Opportunity cost of lost $80 $80-261 operating profit Rural towns – Annuity of a 50 year discounted $5 $2-16 present value Roads – Additional repair and maintenance $505 Not tested costs Railways – Additional repair and maintenance $11 Not tested costs Vegetation – Imputed cost of protection of 10% $63 $63-626 of affected areas * Values in millions of dollars.
It is important to recognise that the risk analyses and conclusions presented in this report provide only a statewide appreciation of the extent and impacts of dryland salinity. Groundwater trend analysis at the scale used will only provide an overview. Trends at local level (farm and paddock) can only be ascertained from individual bores whose location with respect to landscape position and hydro-geology is well known.
6 EXTENT AND IMPACTS OF DRYLAND SALINITY
The most important aspects of ongoing salinity investigation in Western Australia will include determining groundwater trends at catchment scale (1:10,000 to 1:25,000), and the impact that different management strategies will have on these trends.
Constraints related to audit methodology were identified. The issues of reporting scale, monitoring bore distribution and density, data quality and availability need to be considered when interpreting the results of this project. Methodologies and standards to improve the rigour of subsequent national, regional and local scale Audits need to be developed.
Future audits to determine the extent and impact of salinity will require improved datasets from those that were readily available within the given timeframe. The preferred approach based on remote sensing and groundwater data as outlined by Nulsen and Evans (1999) should be investigated.
Table B illustrates the hierarchical scale of mapping used in this study along with examples of how results can be used. The maps produced should only be used as a planning tool, with meaningful and defensible conclusions drawn, at the national, state and regional levels. More detailed work is required for reporting at the catchment and farm scale.
Recommendations include: • Continue to develop methodologies and standards for future audits. • Continue to develop a knowledge of groundwater processes in agricultural regions. • Improved data collection at a catchment scale (1:25,000). • Extension of the current groundwater monitoring networks to provide essential data on groundwater depth and trend. Monitoring various land management treatments should also continue. • Assess groundwater resources in agricultural areas. Improve the monitoring of both surface water and groundwater resources. • Completion of the Land Monitor project. • Estimates of costs associated with infrastructure repair, maintenance and replacement need to be improved.
7 EXTENT AND IMPACTS OF DRYLAND SALINITY
Table B. Use of Project 1A report and mapping products as a planning tool. SCALE USE USER EXAMPLE
REGIONS NATIONAL AND NATIONAL AND IDENTIFY AREAS STATE PLANNING STATE AT RISK OF GOVERNMENTS DRYLAND SALINITY
RESOURCE INDUSTRY GROUPS ALLOCATION
SPECIAL INTEREST ALLOCATE PROVINCES GROUPS RESOURCES TO IMPLEMENT SOLUTIONS
ZONES STATE , STATE AND LOCAL IDENTIFY REGIONAL AND GOVERNMENTS BROAD LOCAL PLANNING LANDSCAPES WHERE SALINITY MAY OCCUR
INDUSTRY GROUPS IDENTIFY RESEARCH NEEDS TO AMELIORATE EXTENT AND IMPACTS SYSTEMS SPECIAL INTEREST IDENTIFY NEW GROUPS INDUSTRIES
COMMUNITY
GROUPS
SUB- CATCHMENT LOCAL IDENTIFY THE PLANNING GOVERNMENTS CAPACITY TO SYSTEMS CHANGE
e.g. NEW OPPORTUNITY FOR INDUSTRY FARM PLANNING INDUSTRY GROUPS
SPECIAL INTEREST GROUPS SOIL PHASES COMMUNITY GROUPS
INDIVIDUALS
8 EXTENT AND IMPACTS OF DRYLAND SALINITY
1.0 INTRODUCTION
The National Land and Water Resource Audit (NLWRA) identified Dryland Salinity (Theme 2) as one of seven major themes for an Audit of the nation's land, water, vegetation and natural resources. Within this theme, Project 1 was developed to identify the Extent and Impact of Dryland Salinity nationally. This report details the results from work done in Western Australia (WA) to meet the audit requirements.
The national audit required a consistent analytical approach across States and Territories to provide an objective assessment of dryland salinity extent, severity, risks and impacts at the regional level. Knowing how big the problem is now and likely to be in the future, will enable National and State governments, industry and communities to make better informed decisions on policies and investment in management.
This project covered the south-west agricultural areas of WA, an area of 26.7 million hectares. The overall aim was: ‘To report on the extent and impact of dryland salinity in Western Australia and to provide a framework for future Audits.’
For the audit, the definition of dryland salinity was taken to be that salinity caused by shallow watertables which result from anthropogenic induced changes in a catchment in which the only water input is from natural precipitation (Nulsen and Evans 1999). All analysis is based on groundwater depth and trend and the risk of shallow watertables is derived from these two attributes. As dryland salinity is caused by shallow watertables, the risk of salinity is inferred from the risk of shallow watertables. Not all shallow watertables will be saline.
Given the timeframe of the NLWRA, a requirement was that reporting of the extent and impacts be based on the best readily available data. The agreed data elements to be analysed for Project 1 nationally were groundwater levels and trends from bores and wells monitored over recent years. Future impacts were to be predicted for the years 2020 and 2050.
To achieve the aim of reporting on the extent and impacts of dryland salinity, a further four objectives were developed. • Using existing datasets, identify appropriate spatial units for the south-west of WA in which to attribute groundwater data. • Identify and define areas at risk from dryland salinity (based on depth to groundwater) and include status and trend. • For each soil-landscape unit predict the current and future impacts of shallow watertables on infrastructure, water resources, biodiversity and agriculture. • Evaluate the effectiveness of current groundwater monitoring and identify the requirements for future audits.
These objectives logically set out the basis for the methodology whereby groundwater and spatial data were collated and analysed for this project.
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2.0 METHODOLOGY
The objectives identified above formed the basis of the working methodology for this project.
2.1 Extent 2.1.1 Spatial units
The Natural Resource Assessment Group (NRAG) of Agriculture WA has mapped the south-west areas of WA using a hierarchical landscape mapping system. The mapping process is based on geology and geomorphology. In WA most groundwater movement and process is controlled by the geology and regolith properties. Therefore, this system was seen as appropriate for attributing hydrologic properties. The maps were examined by members of the Catchment Hydrology Group (CHG), to ensure that there were no major conflicts between the map units and the current understanding of groundwater processes.
This mapping provided the spatial units to attribute groundwater depth and trend and also provided a basis for spatial analysis. The largest scale for which the mapping occurred ranged between 1:50,000 and 1:100,000. This represents a regional scale, and is not suitable for sufficient to extrapolating data to the catchment or farm level, ie to scales of 1:10,000 to 1:25,000.
2.1.2 Groundwater analysis
It was agreed nationally that the depth to the watertable would be used to indicate the likelihood of shallow watertables and the potential for salinity. To determine the ‘risk’ of shallow watertables, an analysis of available groundwater data were required.
The Agriculture WA Catchment Hydrology Group has over 5000 monitoring and research bores in its records. The group has been progressively uploading these to its AgBores database. This process was accelerated to complete the bore information and time series data database.
The custodian of the remaining groundwater data is the Water and Rivers Commission (WRC). A search was undertaken of WRC databases for any bore data with time series information greater than five years. Records from this search were included in this analysis.
Groundwater monitoring sites are established for a variety of reasons including the long-term monitoring of regional trends, assessment of the impacts of specific land management options and for catchment based monitoring. Many early sites were established near discharge sites, or at sites that have since become discharge sites. As a result, many sites may now only represent a small section of the landscape.
Groundwater data were filtered to remove sites that were specific for treatments such as tagasaste plots or lucerne trials. Data were also filtered to remove sites established on discharge areas where discharge sites were not representative of the particular unit.
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The groundwater data were allocated to the spatial units to allow analysis for each unit. This process was limited where the distribution of bores was significantly biased to one landscape position. Sites in some units were mainly located around discharge areas and/or there is only one groundwater record taken at the time when the bore was established. Where this occurred, the experience of the regional hydrologist was used to filter the datasets according to their understanding of groundwater processes. If the discharge areas were not representative of the land system as a whole, a greater significance was placed on those bores located away from discharge sites.
The spatial location of bores within a unit was highly variable. In some units the distribution was relatively even, whereas in others, the distribution was limited to a small section. Where a unit represented a large proportion of the study area and bores were not distributed evenly, the attributes of known bores were distributed across the entire system.
The scale of reporting necessarily required some generalisations to be made. Whilst systems are mapped at between 1:50,000 and 1:100,000 scale, there is still significant variation within a unit, particularly with respect to landforms.
Some units contain only minimal or unreliable bore information and there is insufficient knowledge to determine depth, trend or potential risk. If the unit occurred in areas either adjacent to systems with data and/or in similar hydrogeologic environments, the data was extrapolated. This was reflected in the confidence map (Figure 4).
The most frequently occurring depth and trend for each spatial unit that contained bores was determined. The frequency of occurrence for depth and trend was used in preference to using an average figure as the average would be influenced by extremes which may not be representative of the spatial unit.
Depth data were allocated to nationally agreed categories of: <2 m, 2-5 m, 5-10 m and >10 m. These data were used to undertake regional mapping of groundwater depths.
Given the complexity of analysing time series data, only simple linear trend analysis was used to determine trends. Bores were only considered to be rising or falling if the overall trend change was greater than 3 cm/year. Trend analysis was undertaken for hydrographs within each unit. This data was used to undertake regional mapping of groundwater trends.
Methodology was being developed through the NLWRA-initiated Implementation Project (Salt Scenarios 2020) to apply future rigour to time series hydrograph analysis. The methodology looked at fitting linear trends to segments of hydrographs to better describe groundwater trends. This approach is documented in Shao et al. (1999). This methodology was unavailable for practical application within the timeframe of this project. The resulting data provided regional scale depth and trend figures for each unit (see Figures 5 and 7).
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Groundwater quality was also examined. Data from bores in each system were analysed to produce groundwater quality in terms of conductivity (mS/m) as shown in Figure 6.
The data also yielded a bore distribution and location map (Figure 3). This was used to determine data confidence. The number of bores and the length of groundwater record available for each unit determined confidence.
2.1.3 Risk analysis
Risk of shallow watertable maps were constructed using groundwater depth and trend data. The risk categories applied were:
Risk Water level High: <2 m 2-5 m and rising Moderate: <2 m and falling 2-5 m and flat or falling 5-10 m and rising >10 m and rising Low: 5-10 m and flat or falling >10 m and flat No risk: >10 m and falling
Risk of shallow watertables in year 2000 was based on both trend and depth analyses. Predicted groundwater depths for the years 2020 and 2050 were determined by projecting trends at current rates of rise. An assumption is that land use and rainfall do not change.
Risk has been allocated to entire units based on the most frequently occurring depth and trend data for bores. Risk allocation is at a regional scale and not suitable for extrapolation to the catchment or farm scale. It is acknowledged that within each unit there will be variability that will change the risk at the local scale.
2.1.4 Current extent
To assist in the interpretation of the risk of shallow watertables in year 2000 the current extent of salinity was investigated.
Mapping by NRAG has identified wet and waterlogged soils across the agricultural areas of the State (Figure 8). A wet and waterlogged soil is defined as ‘soils seasonally wet within 80 cm of the surface for a major part of the year’ (Schoknecht 1999). This group of soils includes salt lake soils, saline wet soils, wet, semi-wet and tidal soils. Any soil that is wet for most of the year will be subject to evaporation and concentration of salts in the near-surface section. While not all soils in this group will be saline, it was considered a reasonable estimate of the current extent of salinity.
Within each unit, the percentage area of wet and waterlogged soils is known. The data was used to give an indication of what percentage of each unit could currently
12 EXTENT AND IMPACTS OF DRYLAND SALINITY be subject to salinity. This was mapped to show spatially the current extent, and is used to assist in the interpretation of the risk map generated for year 2000.
This data were collated as a GIS database enabling spatial analysis to be undertaken.
2.2 Impact resulting from the risk analysis
The groundwater analysis was used to identify risks to infrastructure, water resources, biodiversity and agricultural land if current groundwater trends continue. Areas at risk were calculated for each spatial unit. Areas were also calculated for the Australian Water Resources Council (AWRC) drainage basins.
Analysis was undertaken by attributing a level of risk to each soil-landscape system. The length of road, rail, and stream, the area of vegetation, agriculture, wetlands, recovery catchments, along with the number towns was calculated for each system. Within each risk category, total areas, lengths or numbers were then calculated. For example, the length of roads at high risk will equate to the total length of road contained within systems at high risk. Likewise, the total area of agricultural land at high risk has been calculated by summing the area of agricultural land in each system at high risk. The analysis is therefore broad and only suitable at a regional level.
2.2.1 Infrastructure
Infrastructure was considered to include road, rail and major towns. Most rail networks were constructed in the lowest parts of the landscape with the least gradient. Likewise many rural towns are located next to these rail networks. A study by Main Roads Western Australia also found that the length of main roads affected by salinity generally related to roads located in the lowest landscape positions. The mapping units adopted broadly reflect landscape position. Therefore the length of each road and rail type in each unit was determined. This risk rating of the unit was applied, and the length of road and rail in each risk category calculated.
These results were also compared to the outcomes of the Main Roads Report and similar work undertaken by the SS2020 project. The risk of loss of infrastructure for towns was allocated according to the system in which the town was located. Only major towns were considered.
2.2.2 Water resources
Water resources were considered in terms of stream length and surface water quality at stream monitoring sites. The length of stream line in each unit and risk category was calculated and comment made.
The Water and Rivers Commission (WRC 1999) provided water quality data for monitored streams. Monitoring sites were mapped and risk categories attributed. An assessment was made on monitoring sites with potable water (<500 mS/m).
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2.2.3 Biodiversity
The impact of shallow watertables and salinity on biodiversity is not easily illustrated. However, a number of datasets were examined to indicate the likely impacts on flora and fauna throughout the State. The datasets included areas of perennial vegetation defined as remnant vegetation (including forests and woodlands) and plantations (e.g. blue gum, pine and tagasaste). Perennial vegetation does not include herbaceous perennials such as lucerne. Other datasets included biodiversity and threatened ecosystems currently being studied by the Department of Conservation and Land Management (CALM), Natural Diversity Recovery Catchments and lists of wetlands (Environment Australia 1999).
Perennial vegetation was mapped initially from satellite data interpretation and later updated by interpretation of digital orthophotos. These data were analysed with risk data to determine how much vegetation was at risk in each landscape system and zone. Vegetation in systems with insufficient data was not considered.
Biodiversity is being investigated by CALM, which has been undertaking a biological survey in agricultural areas as part of the Salinity Action Plan (1996), now revised as the State Salinity Strategy (2000). The agricultural zones cover all, or significant parts of six of the eight biogeographic zones recognised in temperate south-western Australia (CALM 1999). Current outcomes of their work are reported. Similarly, Threatened Ecosystems (TEC), as defined by English and Blyth (1999), are also being examined by CALM. The risk to these was examined.
Natural Diversity Recovery Catchments are identified by the State Salinity Strategy (2000) as catchments with biological significance. Three catchments have been identified to date: Lakes Muir, Toolibin and Warden. Risk analysis to determine the area subject to shallow watertables was undertaken.
Environment Australia supplied a list of ‘Important wetlands’ (as defined by the Australian Nature Conservation Agency 1996). Wetlands were identified that could be subject to hydrologic change due to the development of shallow watertables.
2.2.4 Agriculture
Agricultural areas (19.7 million ha) were identified as those areas not occupied by perennial vegetation. Areas were allocated to systems and total area of risk calculated for each unit and timeframe. The current and future estimates of areas at risk were based on projections of current trends, assuming no changes in land use or rainfall.
The impact of changing land use was examined to determine if the potential area of shallow watertables could be reduced. Regional workshops were held to assess current land use and the most likely land use in 2020 after considering the capacity of each soil type for change, prediction of increased salinity, current research direction, extension programs, adoption and market factors. Land use for 2050 was not predicted as this was considered too distant for sensible comment. Water balances were determined from land use data and the likely impact of groundwater trends considered. The outcomes from the water balance analysis have been published as a technical report (McConnell 2000). The methodology is described in Appendix 1.
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3.0 DATASETS USED BY THE AUDIT
3.1 Spatial units
Agriculture WA’s Natural Resource Assessment Group (NRAG) has extensively mapped the land resources according to a hierarchical system based on Isbell (1996). This land system mapping was done to national guidelines (Australian Collaborative Land Evaluation Program) and was used to provide the spatial ‘units’ to allocate hydrological attributes such as depth to watertables, trends and to assign risk categories.
The hierarchical structure is shown in Figure 1. Analysis for this report was mainly carried out at the systems level and is reported to the Audit at the zone level. Region: Australia-wide units compiled by CSIRO Province: Units based on broad scale geology and regolith Zone: Units based on geomorphic and geological criteria System: Units based on landform patterns, soil parent material and soil associations
Land system mapping is available at 1:250,000 for agricultural areas. A hierarchical legend is used to describe soil-landscapes to account for different scales of information and the varying complexity of landscape. This allows for reporting at different scales using different levels of the mapping hierarchy. Minor land systems were grouped where appropriate.
Land system information is stored in a GIS environment to allow spatial interrogation. Common fields describing landform attributes are used within this database and the AgBores database to facilitate integration. The final land systems and zones used were defined in consultation with regional hydrologists with an understanding of broad conceptual models of groundwater systems and rainfall zones to ensure that boundaries reflect the hydrogeological processes occurring within each region.
Within the agricultural region of WA there are 30 zones (e.g. 245) with underlying systems (e.g. 226_Sc, 245_Es). Of the 308 systems in the Western region, 220 are greater than 10,000 ha in size and represent 98.7% of the region (B Nicholas pers. com.). Figure 2 shows the zone level map for south-west areas. (A full list of zone numbers, names and descriptions, and system details can be found in Appendices 2 and 3 respectively.)
3.2 Groundwater datasets
The AgBores database has been used in conjunction with soil-landscape system mapping to provide a spatial bore analysis. Figure 3 shows the bore distribution across the soil-landscape zones.
15 EXTENT AND IMPACTS OF DRYLAND SALINITY
Soil-landscape mapping hierarchy
2 25 255
255CfSKu 255Cf 255CfSK
Figure 1. Soil-landscape mapping hierarchy
There are 20 zones and 123 systems occupied by bores on the AgBores database. Zones with bores represent 90% of the study area. In a further two zones and 24 systems, data was extrapolated and has resulted in 95% of the study area being covered. Data were also allocated at a system level. The density of bores is shown in Table 1. The length and reliability of the record will determine confidence levels.
The scale of reporting necessarily required some generalisations. Whilst systems are mapped at between 1:50,000 and 1:100,000 scale, there is still significant variation within a system, particularly with respect to landforms. Local system variability can be significant. In the eastern wheatbelt, landforms such as valley floors are broad and dominate an entire system. However, in the coastal systems, topography becomes more dissected and confined, so that some systems cover areas from hilltops to valley floors. For example, this is evident in some of the coastal systems around Albany. This has made allocation of broad depth, trend and risk categories difficult.
Some systems contain only minimal or unreliable bore information and there is insufficient knowledge to determine depth, trend or potential risk. If the system occurred in areas either adjacent to systems with data and in similar hydrogeologic environments, the data was extrapolated. This is reflected in the confidence map (Figure 4). Areas with minimal data include the north-west of the agricultural area, the central eastern wheatbelt between Merredin and Lake Grace and the south coast around Ravensthorpe.
16 EXTENT AND IMPACTS OF DRYLAND SALINITY
Table 1. The number and density of bores within zones.
Zone Percentage of No. of Density agricultural areas bores (ha/bore) 212 1.5 8 50,108 213 1.0 141 1,912 221 1.2 35 9,326 222 2.5 52 13,056 224 2.1 16 34,759 225 1.0 40 6469 226 0.6 29 5,407 241 1.8 263 1,822 242 3.5 276 3,371 243 2.0 182 2,961 245 3.9 294 3,556 246 7.0 91 20479 247 0.6 100 1,467 253 4.5 761 1,591 254 5.7 590 2,576 255 4.5 77 15,509 257 11.1 908 3,262 258 19.6 164 31,829 259 13.9 727 5,090 271 2.8 26 28,322 Total 90.8 4,780
In some areas of the agricultural region, remnant vegetation is a major component of the system. Remnant vegetation dominates land use along the Darling Scarp (Zone 255, Western Darling Range) where the majority of water resource catchments are located. In Zone 255 in particular, this is important as groundwater depth, trend and risk have been allocated from systems that are not fully vegetated.
3.3 Data confidence
The confidence map (Figure 4) indicates the reliability of the data presented. Confidence ranges from low to very high and is based on the number of bores and the length of time series data. • Low confidence represents systems that contain no bores, but where data has been extrapolated from similar systems • Moderate confidence represents systems where there are some bores, but less than 50
17 EXTENT AND IMPACTS OF DRYLAND SALINITY
• High confidence where there are greater than 50 bores, but less than half of the bores have time series data longer than five years
Figure 2. Soil-landscape zones for south-western Australia.
• Very high confidence where there are greater than 50 bores and more than half of the data has time series greater than five years.
18 EXTENT AND IMPACTS OF DRYLAND SALINITY
Figure 3. Groundwater monitoring sites used for the NLWRA.
3.4 Constraints and issues raised from chosen methodology
The following constraints and issues were identified during the project: • Groundwater data is not evenly distributed through the State. Therefore while 90% of zones have some bore data, there are a significant ‘gaps’ in some areas, particularly the northern and central-eastern areas.
• Due to the lack of data, some systems have no allocated trend or risk. In some cases risk may have been allocated based on the experience of regional hydrologists.
19 EXTENT AND IMPACTS OF DRYLAND SALINITY
Figure 4. Confidence in data used for the NLWRA Project.
• For reporting at National, State or regional scale there can be poor data distribution both within and between catchments and regions. There may be bias in the data as some bores will have been sited for specific purposes such as looking at the response of certain treatments. However, getting the initial data quality controls done by Agriculture WA hydrologists with good local knowledge has reduced this bias. • The scale of reporting necessarily required some generalisations to be made. Whilst systems are mapped at between 1:50,000 and 1:100,000 scale, there is still significant variation within a unit, particularly with respect to landforms.
20 EXTENT AND IMPACTS OF DRYLAND SALINITY
• For existing bores on databases there can be some uncertainty regarding well construction. It may not be clear that recorded water levels represent the watertable level or piezometric surface. Bore construction details and drill logs are required to definitively assign the data to a watertable. • Analysis of trend data has an average length of record of 5.5 years, with a substantial skew to less than five years. Therefore some data may not represent long-term trends. • There can be temporal differences within the entire dataset. Length of record is a significant determinant of the reliability of calculated watertable elevation trends. In many areas there will be few records longer than ten years. Longer records become crucial as rainfall decreases and watertable accessions become increasingly episodic. • Current status of salinity has been based on areas mapped as wet and waterlogged, meaning the profile is saturated for longer than six months, (ie. it is not purely a winter waterlogging situation). This does not necessarily imply that the site is saline. However, due to high levels of salt stored in soil profiles, it is highly likely that if these are not presently saline, they are at risk of becoming so. • Estimates of hydrological risk for the years 2020 and 2050 have been based both on linear extrapolation of measured rates of rise and hydrological opinion where data are lacking. • Determining trends in hydrograph data depends on the frequency of observation. Automatically logged wells can show daily response. On a catchment and larger scale, annual response can generally be determined from four observations at three monthly intervals. This however would require between 10 and 20 years of data to verify a robust trend in some highly responsive catchments.
21 EXTENT AND IMPACTS OF DRYLAND SALINITY
4.0 RESULTS
4.1 Extent of shallow groundwater
4.1.1 Groundwater depth
Groundwater levels in bores were analysed and a depth allocated to each system. These were allocated to nationally agreed categories of: <2 m, 2-5 m, 5-10 m and >10 m. The depth to watertable map is shown in Figure 5.
Broad generalisations can be made. Most of the valley floor systems in the eastern wheatbelt are clearly mapped as <2 m. This reflects the naturally occurring salt lake chains through many systems, and some expansion of salinity in valley floors.
The eastern wheatbelt is covered by Zones 258 and 259 (Northern and Southern Zones of Ancient Drainage) and predominantly by the Australian Water Resource Council (AWRC), Avon Basin (Basin 615). In this region, depth to watertable is primarily related to topography and water levels are deepest in the highest parts of the landscape and are shallow in the lowest, such as valley floors.
This relationship is less obvious for the zones between the coast and the eastern wheatbelt. Landscapes within these zones are more dissected and cover a greater range of positions. Therefore the depth category is representative of the most frequently occurring depth according to the available data and/or local hydrological knowledge and experience.
The coastal zones are dominated by sedimentary formations and show wide variation in groundwater depth.
Regional mapping of groundwater depth is shown in Figure 5.
4.1.2 Groundwater quality
Groundwater electrical conductivity indicates water quality. The majority of the agricultural areas of WA have groundwater of moderate to saline quality (conductivity of 500 to 2500 mS/m). Water salinity increases in the broad wheatbelt valleys with conductivities up to 5000 mS/m. The most saline water is found in areas north of Esperance where groundwater conductivity has exceeded 5000 mS/m. In the Salmon Gums System (246Sg) it was estimated at 5500 mS/m and in the Scaddan System (246Sc) at 6000 mS/m.
22 EXTENT AND IMPACTS OF DRYLAND SALINITY
Figure 5. Groundwater depth for soil-landscape systems.
Some areas of the State, in particular the Northern Perth Basin (Arrowsmith Zone 224, Dandaragan 222 and Coastal 221) have potable water resources in regional groundwater aquifers (WRC 1995). This was noted in Zone 221 where groundwater quality is generally fresh. There is limited information regarding the superficial aquifers in this region. The WRC has only reported information relevant to salinity for the coastal corridor, west of the Brand Highway (Water Authority of Western Australia 1995). Further data are required from this region to assess salinity risk.
Fresh water was also recorded for the Scott River Plain System, (252Sr) and coastal areas between the Scott River and Albany. Regional mapping of groundwater quality is shown in Figure 6.
23 EXTENT AND IMPACTS OF DRYLAND SALINITY
4.1.3 Groundwater trend
Groundwater is dominated by rising or stable trends (Figure 7). No systems have significant falling trends. Rising trends occur over the majority of agricultural areas with only a few exceptions. Rates of rise are highly variable and have not been presented but range from less than 5 cm/year to greater than 50 cm/year.
Areas with ‘No trend’ have watertables that have reached the near surface, oscillate on a seasonal basis, or deeper watertables that show no trend. No trend was recorded for several zones — in particular 255 (Western Darling Zone) where the major land use is forest; some coastal systems; and for an area north-east of Esperance.
Where seasonal fluctuations occur in deeper systems and there is no long-term trend the area may have reached a local equilibrium.
Regional mapping of groundwater trends is shown in Figure 7.
4.1.4 Current extent based on wet and waterlogged soils
Wet and waterlogged soils have been mapped by NRAG. Within each system, the percentage area of wet and waterlogged soils is known. The data were used to give an indication of what percentage of each system could currently be subject to salinity (Figure 8 and accompanying map sheet titled ‘Current extent of wet and waterlogged soils for soil-landscape systems’).
The map based on wet and waterlogged soils shows that the major drainage lines have a high component of wet and waterlogged soils (>75%). This should be expected as they are naturally occurring major salt lake drainage lines. Large areas of the wheatbelt currently have about 10% wet soils, and are therefore potentially saline.
24 EXTENT AND IMPACTS OF DRYLAND SALINITY
Figure 6. Groundwater conductivity for soil-landscape systems.
4.1.5 Risk of shallow watertables
4.1.5.1. Risk for soil-landscape zones and systems
Risk of shallow watertables in years 2000, 2020 and 2050 are shown in Figures 9, 10 and 11, and in accompanying maps supplied in digital form. Figure 9 shows a spatial representation of both depth and trend of groundwater at year 2000 within broad regional systems. Trend data were then used to predict future watertable depths and to allocate a risk rating in 2020 and 2050. The future risk of shallow watertable is based on depth to groundwater. Predicted groundwater depths for the years 2020 and 2050 were determined by projecting trends at current rates of rise. An assumption is that land use and rainfall do not change.
25 EXTENT AND IMPACT OF DRYLAND SALINITY
Figure 7. Groundwater trend for soil-landscape systems.
Rainfall analysis by the Bureau of Meteorology, Western Australia, has shown that over much of the agricultural regions total winter rainfall (May-October) has decreased, while trends over the warmer months show a smaller increase. Annual totals have generally been declining between 5 and 30 mm per decade over the agricultural regions between Geraldton and Albany in the 1910 to 1997 period (Bureau of Meteorology 2000).
Rainfall analysis suggests that the gradient of the rising groundwater trend represents the minimum gradient expected based on rainfall alone and disregarding any change in land use. Should the average rainfall increase, the gradient might also increase and accelerate the impacts of salinity.
Risk has been allocated to entire systems based on the most frequently occurring depth and trend time series data for bores. In each system there will be variability that will change the risk at the local scale.
26 EXTENT AND IMPACT OF DRYLAND SALINITY
Figure 8. Current extent of wet and waterlogged soils for soil-landscape systems.
The current extent map gives some indication of the proportion of each system at risk in 2000. However there are no estimates of the actual extent predicted for 2020 and 2050 beyond the system scale.
In 2000 the risk is predominantly in the eastern wheatbelt valley floors and adjacent areas (Zones 258 and 259, the Northern and Southern Zones of Ancient Drainage respectively). Eastern sections of the northern wheatbelt also exhibit high risk.
There are some coastal areas at high risk around Bunbury and the southern system of Zone 252 (Donnybrook Sunkland) and within system 252Sr (Scott River). The latter has shallow watertables and is therefore categorised as high risk however groundwaters are relatively fresh (200 mS/m) in this region.
27 EXTENT AND IMPACT OF DRYLAND SALINITY
Figure 9. Risk of shallow groundwater for agricultural areas in year 2000.
Most areas at low risk are adjacent to the coast in the Northern Perth Basin (Zone 221) in coastal systems around Albany (242Bb Bremer, 242Kg King, 242Me Meerup and 254Wh Walpole Hills) and on the south-western edge of the Leeuwin Zone 251. Further inland, low risk areas include the Donnybrook Sunkland Zone (252), the Stirling Ranges (241St) and at Salmon Gums north of Esperance (246Sg). Low risk areas are related to deep watertables and/or watertables with no rising trend.
The remaining areas of the State have been classified as having moderate risk (excluding those areas with insufficient data). There will be local variability in the extent and impacts of shallow groundwater in these regions.
28 EXTENT AND IMPACT OF DRYLAND SALINITY
Figure 10. Predicted risk of shallow groundwater for agricultural areas in year 2020.
In total, approximately 16% of the south-west of WA has potential for salinity in 2000 due to shallow watertables. Of the area at risk, 81% is occupied by agricultural land and the remainder by perennial vegetation.
The changes in areas at risk in 2020 are reasonably subtle in the eastern wheatbelt (Zones 258 and 259) where high risk areas expand from the valley floors to secondary tributaries and lower slopes. Other soil-landscape systems and zones that move into a high risk category occur in the higher rainfall such as the Zone of Rejuvenated Drainage (Zone 275) and areas west and north-east of Esperance.
In total, approximately 20% of the south-west of WA has the potential for salinity in 2020 due to shallow watertables. Of the area at risk, 80% is occupied by agricultural land and the remainder by perennial vegetation.
29 EXTENT AND IMPACT OF DRYLAND SALINITY
Figure 11. Predicted risk of shallow groundwater for agricultural areas in year 2050.
In 2050 high risk has expanded in the eastern wheatbelt to include all valleys and lower slopes. In these zones (258 and 259) this will represent approximately 30% of the landscape.
High risk is also apparent in the majority of zones located east of the Darling Scarp (Zones 253, 254, 257, 258, 259 and 271). An exception is the vegetated Zone 255 (Western Darling Range) which has a moderate risk. Risk has also substantially increased in the region around Esperance and west of Albany.
Approximately 33% of the agricultural areas has potential for salinity in 2050 due to shallow watertables (Table 2). Of the area at risk, 73% is occupied by agricultural land.
Zones 223, 231, 232, 233, 261 and 271 had insufficient data to allocate risk. These zones represent less than 5% of the total area.
30 EXTENT AND IMPACT OF DRYLAND SALINITY
Table 2. Allocated high risk of shallow watertables and potential for salinity for soil-landscape zones.
Zone Zone Percentage Percentage Percentage of zone of 2000 2020 2050 allocated agricultural data areas 211 Coastal Dune 0 0 0 98 1.57 212 Bassendean 0 0 1 100 1.50 213 Pinjarra 1 1 1 99 1.01 221 Coastal Zone 0 0 0 70 1.22 222 Dandaragan Plateau 1 1 1 25 2.55 223* Victoria Plateau 0 2.55 224 Arrowsmith 0 0 0 2 2.09 225 Chapman 0 0 0 75 0.97 226 Lockier 0 0 0 36 0.59 231* Coastal Zone 0 0.14 232* Transitional Zone 0 0.17 233* Inland Zone 0 0.27 241 Stirling Range 0 0 1 85 1.80 242 Albany Sandplain 0 0 0 93 3.49 243 Jerramungup Plain 2 2 2 97 2.02 244 Ravensthorpe 0 0 0 100 1.23 245 Esperance Sandplain 0 1 3 77 3.92 246 Salmon Gums-Mallee 0 1 1 88 6.99 247 Boorokup Lakes 0 0 0 71 0.55 251 Leeuwin 0 0 0 73 0.37 252 Donnybrook Sunkland 0 0 0 85 1.75 253 Eastern Darling Range 0 1 4 95 4.54 254 Warren-Denmark Southland 0 0 2 74 5.70 255 Western Darling Range 0 0 0 85 4.48 257 Zone of Rejuvenated Drainage 1 2 4 67 11.11 258 Northern Zone of Ancient 5 5 6 90 19.58 Drainage 259 Southern Zone of Ancient 3 3 4 82 13.88 Drainage 261* Southern Cross 0 0.90 271 Irwin River 1 1 1 51 2.76 272* Greenough River 0 0.29 Totals 16% 20% 33%
Note: Risk is allocated as a percentage of the entire agricultural region of south-Western Australia. Full risk data can be found in Appendices 4 & 5.
4.1.5.2 Risk for Australian Water Resources Council drainage basins
Risk was also assigned to the Australian Water Resources Council drainage basins (Figure 12). Risk by percentage (based on area) in each basin is shown in Appendix 6 and the percentages at high risk of shallow watertables are shown in Table 3. Some boundaries extend beyond the agricultural areas and have not been assessed.
31 EXTENT AND IMPACT OF DRYLAND SALINITY
Figure 12. AWRC basins in agricultural areas of Western Australia.
The largest drainage basin, Avon (No. 615), covers most of the wheatbelt and currently has approximately 16% of its area at high risk. This increases to 18% by 2020 and 21% by 2050. This contrasts with the Blackwood Basin (609) where the area of high risk increases from 16% in 2000 to an estimated 45% by 2050.
32 EXTENT AND IMPACT OF DRYLAND SALINITY
Table 3. Percentage of AWRC basins at high risk of shallow watertables. (Based on total basin area and not just the area covered by system data)
AWRC Basin Percentage High risk Basin No. covered by system data 2000 2020 2050 602 Albany Coast 100 25 28 50 615 Avon River 71 16 18 21 609 Blackwood River 100 16 20 45 612 Collie River 99 7 7 9 603 Denmark Coast 99 7 7 71 608 Donnelly River 99 8 8 16 601 Esperance Coast 98 9 20 36 610 Preston River 99 8 8 12 605 Frankland River 100 3 3 58 701 Greenough River 73 6 6 7 613Harvey River 96252539 604 Kent River 99 6 6 72 617 Moore-Hill Rivers 100 15 17 28 702 Murchison River 3 0 0 0 614 Murray River 100 9 9 40 619 Ninghan 14 6 6 6 611 Busselton Coast 99 20 20 24 024 Salt Lake Basin 3 0 0 1 606 Shannon River 97 18 18 19 616 Swan Coastal 99 8 8 46 607 Warren River 100 7 7 25 618 Yarra-Yarra 23 9 9 9
4.2 Impacts of shallow groundwater
The groundwater analysis was used to identify risks to infrastructure, water resources, biodiversity and agricultural land, if current groundwater trends continue.
4.2.1 Biophysical Impacts
4.2.1.1 Infrastructure
Infrastructure was examined in terms of roads (highways, primary, secondary and minor roads), rail and major towns. The length (in kilometres) of each rail and road type was measured in each system, a risk allocated and then total lengths for each risk category determined. Total figures for each category are presented in Appendix 7. The total figures for the high risk category are shown in Table 4.
33 EXTENT AND IMPACT OF DRYLAND SALINITY
These values were compared with other studies. Main Roads Western Australia (McRobert et al. 1997) estimated that in 1997, 500 km of main roads were affected by salinity and that this was likely to double over the next 20 years.
A second study, by the SS2020 implementation project, was also reviewed. This project looked at the length of road networks affected by salinity in the 2.3 million hectares mapped by Land Monitor (an NHT and WA State Government project to map and monitor the extent of salinity through satellite imagery). Land Monitor found a total length of 3,333 km of road at risk from salinity. If the area is scaled up to cover the entire south-west (an area of 26.6 million hectares) the figures are comparable and of the same magnitude.
Table 4. Road and rail at high risk of shallow watertables and potential salinity for 2000, 2020 and 2050.
Infrastructure 2000 2020 2050 Total km in south-west Distance in km Highways 721 841 1,506 3,565 Primary roads 680 746 1,166 3,646 Secondary roads 1,196 1,427 2,326 6,158 Minor roads 11,552 13,852 22,936 67,522 Rail 1,359 1,488 2,182 5,695
Road types are designated according to the body controlling maintenance. National highways and primary roads are serviced by Main Roads Western Australia, secondary and minor roads are maintained by local government.
The risk of loss of infrastructure for towns was allocated according to the system in which the town was located. Many rural towns are located near or within close proximity to rail lines. Most rail lines are located in low parts of the landscape. It is therefore likely that a high proportion of rural towns will be subject to salinity.
Only major towns were considered. The full list of towns and allocated risk can be found in Appendix 8. Table 5 lists towns that are currently being investigated for groundwater and salinity issues as part of the Rural Towns Program funded by the WA State Salinity Strategy. These towns were all nominated as high risk by this Audit.
4.2.1.2 Water resources
The risk to water resources was considered in terms of the length of major streams (mapped at 1:250,000) in each system. Risk was attributed and total lengths in each risk category summed for each zone. The data showed the biggest increases in stream length likely to be affected by shallow watertables occurred for Zones 212, 241, 242, 252, 253 and 257. In all of these zones the stream length at high risk doubled between 2000 and 2050. (Full figures can be found in Appendix 9.)
The Water and Rivers Commission (WRC 1999) provided water quality data for monitored streams. Monitoring sites were mapped and risk values attributed. Monitoring sites which had non potable water resources (water quality >500 mS/m),
34 EXTENT AND IMPACT OF DRYLAND SALINITY were not considered. An assessment was made on those sites with potable water (<500 mS/m) as increasing salinity could degrade potential water resources.
Table 5. Towns with shallow watertable and therefore high risk by 2050.
Town Risk Rural Towns Program 2000 2020 2050 Harvey HHH Three Springs M M H Gnowangerup M M H Jerramungup H H H Cranbrook H H H * Boyup Brook H H H Darkan M H H Boddington M M H Walpole H H H Mt. Barker M M H Northam M M H Moora H H H * Katanning M M H * Brookton H H H * Carnamah H H H * Coorow H H H Calingiri M H H Wagin HHH * Williams H H H Beacon H H H * Kellerberrin H H H * Koorda H H H * Merredin H H H * Mukinbudin H H H * Narembeen H H H * Kondinin HHH Perenjori H H H * Western Australian State Salinity Strategy. H = High risk, M = Moderate risk. * denotes towns being investigated for groundwater and salinity under the Rural Towns Program.
While the majority of wheatbelt streams/rivers do not contain potable water, there are fresh waterways in high rainfall and coastal regions.
A total of 83 stream monitoring sites were identified of which 44 had potable water. Of these, 16 were located in systems with insufficient data to allocate risk. For the remaining 28, only four were in a high risk category in 2000. In 2050, eight were located within high risk systems (Table 6). The most significant of these waterways in the high risk category are the Denmark River (AWRC Basin 603), Preston River (611), Harvey River (613) and Ellen Brook 616). These basins were all larger than 500 km2.
The data show that shallow watertables are not always associated with salinity. The Preston River and Ellen Brook are examples where the allocated risk is high, i.e.
35 EXTENT AND IMPACT OF DRYLAND SALINITY these areas have shallow watertables in year 2000, but have high quality surface water.
Table 6. Risk of shallow watertables in systems occupied by surface water monitoring stations.
Risk Basin Station Name EC (mS/m) 2000 2020 2050 603 603136 Denmark River, Mt Lindesay 130 M M H 607 607220 Warren River, Barker Rd Crossing 170 M M M 608 608151 Donnelly River, Strickland 41 M M M 611 611004 Preston River, Preston Bridge 58 H H H 611 611111 Thomson Brook, Woodperry 56 M M M Homestead 612 612014 Bingham River, Palmer 55 M M M 612 612022 Brunswick River, Sandalwood 29 M M M 612 612006 Collie River, Mt Lennard 185 M M M 613 613052 Harvey River, Clifton Park 53 M M H 616 616189 Ellen Brook, Railway Parade 105 H H H Source: WRC (1999).
Water Resource Recovery Catchments are catchments specified for additional research and management to address salinity impacting on a water resource. The Collie, Helena, Kent and Warren catchments have been nominated. Currently the Warren is the only catchment with any areas falling into the high risk category. In the Warren this is a relatively small area (7%). All resource catchments except Collie have potential for extensive areas at risk of shallow watertables by 2050 (Table 7). Details can be found in Appendix 10.
The impact of shallow watertables and salinity on biodiversity is not easily illustrated. However, a number of datasets were examined to give an indication of the likely impacts on flora and fauna throughout the State. The datasets used include areas of perennial vegetation, lists of wetlands (Environment Australia 1999) and threatened ecosystems and biodiversity work currently being undertaken by the Department of Conservation and Land Management (CALM).
Table 7. Areas of Water Resource Recovery Catchments at high risk of shallow watertables.
Area at risk (ha) Catchment Area (ha) % coverage of 2000 2020 2050 catchment Collie 278,550 0 0 3 0 431 0 100 Helena 147,780 0 0 0 0 122,535 83 83 Kent 240,517 0 0 0 0 144,025 60 61 Warren 413,293 29,110 7 29,110 7 108,213 26 72
36 EXTENT AND IMPACT OF DRYLAND SALINITY
4.2.1.3 Biodiversity 4.2.1.3.1 Impacts on perennial vegetation
Perennial vegetation was mapped initially from satellite data interpretation and later updated by interpretation of digital orthophotos. These data were analysed with the risk data to determine how much vegetation was at risk in each landscape system and zone. Totals are presented in Table 8. Vegetation in systems with insufficient data was not accounted for. Total figures in Appendix 11 show that in 2000, nearly 600,000 hectares of perennial vegetation was potentially at risk and that by 2050 this would increase to over 1.8 million hectares. There were no compiled data to indicate the likely impact on particular species. Perennial vegetation includes both remnant and planted vegetation.
4.2.1.3.2 Impact on flora and fauna
CALM has been undertaking a biological survey of the agricultural areas as part of the Salinity Action Plan (1996), now revised as the State Salinity Strategy (2000). The agricultural zones cover all, or significant parts of, six of the eight biogeographic zones recognised in temperate south-western Australia, (CALM 1999). The current outcomes summarised from the CALM report for flora include: • An estimated vascular plant flora of some 4000 species of which over 60% are endemic to the agricultural area. • 850 of these species are found only in fresh or naturally saline lowlands directly threatened by rising groundwater and salinity. • Of the 4000 species, 1500 occur low in the landscape, in riverine valleys, freshwater or primary saline lands. Of these taxa, 450 are endemic to the agricultural zone and are in danger of extinction as a consequence of rising saline groundwaters. • Areas affected by secondary salinisation show major declines in vascular plant biodiversity. • Fauna studies have found a significant decline in the biodiversity of terrestrial animals. Quadrants in areas affected by secondary salinity averaged 30% fewer species than non-salinised quadrants (Table 9).
A 50% reduction in the number of waterbirds using wheatbelt wetlands due to the saline-induced death of shrubs and trees was reported. Species richness also declines with salinity.
Threatened Ecosystems (TEC), as defined by English and Blyth (1999), are also being examined by CALM. The work to date has identified 14 occurrences of TECs in the south-western region (Table 10). Not all systems where TECs have been identified, have sufficient data to determine risk. For some systems, (e.g. 257Bv) shallow groundwater may be an imminent threat to these communities. Factors other than shallow groundwater and salinity may be impacting some TECs.
37 EXTENT AND IMPACT OF DRYLAND SALINITY
Table 8. Percentage of soil-landscape zone occupied by perennial vegetation, at risk of shallow watertables.
Zone High risk
2000 2020 2050
211 2 2 2 212 0 0 50 213 8 8 8 221 0 0 0 222 7 7 7 226 0 0 2 241 2 2 7 242 0 2 3 243 28 31 31 245 6 9 15 246 0 1 1 247 16 16 16 251 0 0 2 252 7 7 21 253 2 3 37 254 0 0 18 255 0 0 0 257 1 1 3 258 1 1 1 259 3 3 4 271 4 4 4
Table 9. Average ratio of arachnid and vertebrate species for quadrants in non-saline, primary and secondary saline areas.
Quadrant status Average ratio of species per quadrant (standard deviation in brackets) Non-saline 2.3 (1.3) 2.8 (0.8) Primary salinity 1.0 (0.8) 1.0 (0.2) Secondary salinity 1.3 (0.7) 1.9 (1.0) Source: CALM (1999)
38 EXTENT AND IMPACT OF DRYLAND SALINITY
Table 10. Threatened ecosystems and risk of shallow watertables.
System TEC Number of 2000 2020 2050 occurrences 221Ea VU 1 221Ga CR 1 L L L 224Ir PD 1 M M H 241St CR 1 L L L 257Bv EN 1 H H H 257Wg LR 1 258Kb CR 1 H H H 259Co CR 1 M M M 259Sh CR 1 M M H 271Ko VU 1 271Mw VU 2 271Ng PD 1 H H H CR = Critically endangered, EN = Endangered, VU = Vulnerable, PD = Presumed destroyed, LR = Low risk L = Low risk, M = Moderate risk, H = High risk Source: CALM (Hamilton-Brown pers. comm.) 4.2.1.3.3 Natural Diversity Recovery Catchments
Natural Diversity Recovery Catchments are catchments identified by the State Salinity Strategy (2000) as catchments with biological significance. Three catchments have been identified to date: Lakes Muir, Toolibin and Warden. Regional risk analysis has shown that Lake Muir has the worst prognosis with approximately 58% of the catchment area currently impacted by shallow watertables, increasing to 83% by 2050 (Table 11).
Table 11. Areas of Recovery Catchments at high risk of shallow watertables.
Catchment Area Area at risk (ha) 2000 2020 2050 Lake Muir 59,700 34,458 58% 34,458 58% 49,824 83% Lake Toolibin 48,661 9,058 19% 9,058 19% 9,058 19% Lake Warden 191,442 0 0% 0 0% 95,106 50% 4.3.1.3.4 Impact on wetlands
Environment Australia supplied a list of Important wetlands (as defined by the Australian Nature Conservation Agency, 1996). Wetlands were identified that could be subject to hydrologic change due to the development of shallow watertables. Of the 54 wetlands located within the agricultural areas of Western Australia, 47 were fully or partially located in systems that could be allocated a risk category. The final analysis used 35 wetlands with data that covered more than 75% of the wetlands total area.
39 EXTENT AND IMPACT OF DRYLAND SALINITY
The full details for these wetlands are shown in Appendix 12. The wetlands at high risk vary in size from less than one hectare to thousands of hectares.
Both Lakes Muir and Toolbin were allocated high risk. The surrounding catchments have been nominated as Recovery Catchments in WA (Salinity Action Plan 1996). While many wetlands currently have or will have a high watertable, their dynamics are likely to be impacted by increasing inundation and salinity. CALM (1999) documented that the death of many trees and shrubs in wheatbelt wetlands due to salinity has caused a 50% decrease in the number of water bird species using those wetlands. The data show that there are many important wetlands at high risk which are currently not receiving a similar level of investigation and management as the Recovery Catchments.
4.2.1.4 Agriculture
Agricultural areas were identified as those areas not occupied by perennial vegetation. Areas were allocated to systems and total area of risk for each zone determined. Areas at high risk are shown in Table 12 (a full dataset can be found in Appendix 13). The data show that shallow watertables currently underlie 3.5 million hectares of agricultural land. These areas have the potential to be saline. It is predicted that this area in WA could expand to 6.5 million hectares by 2050. This figure is similar to those proposed by Ferdowsian et al. (1996) who estimated the potential extent of salinity in cleared land as 6.1 million hectares.
The current and future estimates of areas at risk were based on projections of current trends, assuming no changes in land use or rainfall. The impact of changing land use was examined to determine if the potential area in 2050 could be reduced.
Regional workshops were held to assess current land use and the most likely land use in 2020 after considering of the capacity of each soil type for change, prediction of increased salinity, current research direction, extension programs, adoption and market factors. Land use for 2050 was not predicted as this was considered too far in the future for sensible comment. The outcomes from the water balance analysis have been published as a technical report (McConnell 2000). The methodology is described in Appendix 1.
The major land use groups used are shown in Table 12. These were broad groups that represented land uses of a similar type and water use, e.g. annual crop broadly represented wheat, barley, oats, lupins, grain legumes etc.
Land use data were collated at soil-landscape zone level. Water balances were calculated for each land use and recharge determined. These were used to compare the percentage difference in recharge between current and proposed land use.
40 EXTENT AND IMPACT OF DRYLAND SALINITY
Table 12. Land use categories and equivalent Western Australian Land Use Codes (WASLUC).
Land use description WASLUC Code Crop - annual 8118 Crop - irrigated 8118 Crop - summer E.g. 811930 Pasture - annual 81162 Pasture - perennial 81165 Pasture - irrigated annual 81162 Pasture - irrigated perennial 81165 Trees - remnant vegetation 911 Trees - commercial 831 Trees – non-commercial 92# Trees - alleys Fodder - alleys Fodder - perennial shrub (non-saline) Fodder - perennial saline Horticulture (vines, trees etc) 8169 Fallow Lakes - free water Urban Rural 8119 # Forest areas – non-commercial
The data have shown that predicted land use change will have a variable impact on recharge, and is not guaranteed to reduce recharge. Despite our knowledge of the need to adopt land uses that reduce recharge in order to control salinity, the most realistic land uses predicted for 2020 might actually increase recharge in some cases. For example, in Zone 271 (Irwin River), the predicted land use resulted in increases to recharge by 17% while in Zone 224 (Arrowsmith) a reduction of 43% was predicted.
Figure 13 shows that only minor increases in perennials (herbaceous or woody) are predicted for Zone 271. Increased area of fallow is also predicted on the Deep sands. This soil is likely to have the highest volumes of recharge. Current land use (primarily poor annual pastures) has resulted in soil loss due to wind erosion and has increased recharge. It was predicted that conditions would decline given current land management. A combination of high recharge soils and lack of vegetative cover is contributing to the increases in recharge for the water balance in 2020.
In contrast, Zone 224 shows increases in the area of perennials in all major soil groups, particularly in the form of perennial pastures. On the Deep sands more commercial and non-commercial woody perennials are anticipated. As most contributions to recharge were found to occur on the sandy soils, this increase in perennials resulted in the greatest overall reduction in modelled amounts of recharge for any of the zones.
41 EXTENT AND IMPACT OF DRYLAND SALINITY
Landuse allocation for Deep sands in the Irwin River Zone (271) 12 Year 2000 - current 10 Year 2020 - future
8
6
4
2
Estimated % of deep sands 0 Crop - annual Pasture - Trees - Trees - non Fallow annual remnant commercial vegetation
Landuse allocation for Deep sands in the Arrowsmith Zone (224) 25 Year 2000 - current 20 Year 2020 - future
15
10
5 Estimated % of deep sands. deep % of Estimated 0 Crop - Pasture - Pasture - Trees - Trees - non Fodder - annual annual perennial remnant commercial perennial vegetation shrub (non saline)
Figure 13. Land use on Deep sands in Irwin River (271) and Arrowsmith Zone (224).
The results in Figure 13 indicate that predicted land use sufficiently reduced recharge to delay the onset of salinity in only three zones (224, 246 and 247). The reduction in recharge was not sufficient in any of these zones to reduce the eventual extent of salinity.
42 EXTENT AND IMPACT OF DRYLAND SALINITY
Table 13. Agricultural land at risk.
Zone High risk (ha) Percentage Percentage of south- of zone allocated west agricultural areas 2000 2020 2050 data 211 11,929 11,929 11,929 98 1.57 212 0 0 187,368 100 1.50 213 212,779 212,779 212,779 99 1.01 221 0 0 0 70 1.22 222 125,802 125,802 125,802 25 2.55 223 0 0 0 0 2.55 224 0 0 9,763 2 2.09 225 0 0 0 75 0.97 226 32,641 32,641 54,421 36 0.59 231* 0 0.14 232* 0 0.17 233* 0 0.27 241 26,411 31,567 260,333 85 1.80 242 0 60,315 100,834 93 3.49 243 314,228 353,385 353,385 97 2.02 244 0 0 0 100 1.23 245 65,140 246,571 603,961 77 3.92 246 0 7,110 7,110 88 6.99 247 16,640 16,640 16,640 71 0.55 251 0 0 1,867 73 0.37 252 22,372 22,372 33,235 85 1.75 253 73,928 151,182 636,056 95 4.54 254 0 0 247,118 74 5.70 255 0 0 0 85 4.48 257 359,996 618,532 974,259 67 11.11 258 1,321,296 1,321,296 1,361,028 90 19.58 259 635,446 635,446 958,088 82 13.88 261* 0 0.90 271 334,127 334,127 334,127 51 2.76 272* 0 0.29 Total area 3,552,735 4,181,694 6,490,103 % of cleared 18 21 33 agricultural land
* Insufficient data.
43 EXTENT AND IMPACT OF DRYLAND SALINITY
% change in recharge for predicted future landuse
272
259
257
254
252
247
245
243 Zone
241
232
226
224
222
213
211
-50 -40 -30 -20 -10 0 10 20 30 % change in recharge
Figure 14. Comparison of the difference in recharge between current and proposed future land use.
44 EXTENT AND IMPACT OF DRYLAND SALINITY
4.2.2 Economic impacts
As part of the audit, a broad economic analysis was undertaken after identifying the impacts of shallow groundwater on infrastructure, biodiversity and agriculture. The indicative estimates of the costs of salinity on and off-farm in Western Australia were prepared by Allan Herbert, Economics Group, Agriculture Western Australia.
Details and comments on the methodologies used and range testing appear in Appendix 14. Results were obtained for three impact topics (infrastructure, biodiversity and agriculture) for three time periods – years 2000, 2020 and 2050. No attempt was made to quantify water resources in dollar terms or to cost solutions to the problem in a benefit:cost context.
4.2.2.1 Infrastructure
A draft consultant’s report (Dames and Moore – URS, June 2000) on the cost of salinity for the town of Merredin provided the base assumptions for both whole towns and individual components of infrastructure costs. The town was ‘zoned’ according to land use (e.g. residential, commercial, industrial, vacant land, recreation, civic buildings, roads, railways, etc) and individual repair/maintenance costs attached to each – according to when watertables reached within 1.5 and 0.5 m of the surface. Current and predicted watertable profiles were applied across the townsite such that repair and maintenance costs and asset write-offs were progressively brought into a cost flow budget at designated times.
(a) Rural towns
The total cost of salinity for Merredin (high risk category) was used to scale off all other towns in zones with a high or medium risk – based on respective populations. Changes in town risk profiles between year 2000, 2020, and 2050 allowed calculation of the extra costs over the 20 and 50 year periods. Medium risk towns were assumed to attract 25% of the costs of high risk towns – after scaling for population. • Current year The present value of costs for 60 affected towns under the year 2000 risk profile was estimated as near $68M. This is today’s value of the sum of all future expected costs of repair and maintenance and asset write-off over a 50 year period. • After 20 years The present value of costs for each of the years 2000 and 2020 risk profiles were converted to an annuity as an estimate of what each town would need to spend each year to combat rising watertables/salinity. The difference in annual cost flows provides an estimate of the extra costs with progression of the salinity problem. Over the first 20 year period, the total additional cost is $0.8M. This is a relatively small increment reflecting the relatively small increase in risk for the first 20 year period. The implication is that timing of implementation of major control works is not critical. Dealing with the current problem is important but there is time to properly plan control strategies to address the more major increases in
45 EXTENT AND IMPACT OF DRYLAND SALINITY
salinity risk in the following 30 years. (This is a sweeping generalisation and not necessarily the case for individual towns.) • After 50 years The present value of costs for year 2050 risk profile was also converted to an annuity for comparison with the year 2000 profile. There is greatly increased impact on rural towns in the 20 to 50 year period and the total additional cost (i.e. over and above the current impact) is estimated at $22.5M. This is a large increase over the $0.8M estimated for the first 20 years and reflects the greatly increased risk in the 30 years after year 2020. Control strategies designed for the year 2020 situation will be inadequate and need to have increased capacity to address the increasing watertable rises in the subsequent period – notwithstanding that earlier intervention might slow the process. (b) Roads An approximate annual cost of repair per kilometre was calculated for each type of road and risk profile. Comparison of normal maintenance cost with the increased cost gave an estimate of the extra costs due to watertables/salinity. Length of road affected at the three time periods was used to frame a series of cost flows over the 20 and 50 year periods of analysis. Costs for road repair and maintenance within towns are already captured in the total rural towns costs above. • Current year The annual cost in year 2000 of extra repairs due to watertables/salinity is estimated as $505M. That is, annual road expenditure is $505M more than it would be if no roads were affected. This appears to be an excessively large number and is probably caused by the difficulty in discerning between ‘normal’ costs and costs associated with watertable impacts – and the large difference in estimated repair costs between the two situations. • After 20 years Rising watertables will increase the lengths of roads affected with a total extra repair cost of $91M. This is today’s value of the sum of all future extra costs of repair and maintenance over a 20 year period. • After 50 years Today’s value of the sum of all future extra costs of repair and maintenance over a 50 year period is estimated at around $288M. The large increase over the $91M for the first 20 year period is not only because an additional 30 years of costs has been brought to account. There is also greatly increased lengths of roads affected in this latter period. (c) Railways An approximate annual cost of repair per kilometre was calculated for railways and for each risk profile. Comparison of normal maintenance cost with the increased cost gave an estimate of the extra costs due to watertables/salinity. Lengths of railway affected at the three time periods was used to frame a series of cost flows over the 20 and 50 year periods of analysis.
46 EXTENT AND IMPACT OF DRYLAND SALINITY
• Current year The annual cost in year 2000 of extra repairs due to watertables/salinity is estimated as $11M. That is, annual railway expenditure is $11M more than it would be if railways were not affected. As for roads, this appears to be an excessively large number and is probably caused by the difficulty in discerning between ‘normal’ costs and costs associated with watertable impacts – and the large difference in estimated repair costs between the two situations. • After 20 years Rising watertables will increase the lengths of railway affected with a total extra repair cost of near $2M. This is today’s value of the sum of all future extra costs of repair and maintenance over a 20 year period. • After 50 years Today’s value of the sum of all future extra costs of repair and maintenance over a 50 year period is estimated at around $7M. Both the 20 and 50 year additional costs are relatively small compared to other infrastructure components. While the assumed repair/maintenance cost differences need more detailed investigation, it also reflects the low density of railway lines in rural areas compared with roads.
4.2.2.2 Biodiversity of vegetation
A ‘protection’ cost based on the capital and operating costs of a pumping strategy was allocated as a proxy value to a hectare of vegetation. While the capital costs were held constant, differential operating costs were applied for each risk profile. Conversion to an annuity provided an estimate of the annual cost of protection and allowed a series of cost flows to be constructed. The present values of these cost flows then provided a basis for estimating the $ impact of increasingly affected areas.
All vegetation in the same risk category was therefore valued equally – ‘medium risk’ value was $126/ha/yr and ‘high risk’ value was $209/ha/yr. There was no consideration of differential biodiversity, habitat, or rare/endangered species values. The same pumping strategy proxy value was used throughout regardless of landform, geological structure, soil types, etc.
The following results are based on 10% of the affected areas being protected. • Current year The annual cost of protection of 10% of the year 2000 affected areas is estimated as $63M. • After 20 years If 10% of the increased areas affected in year 2020 are protected, the annual cost is estimated as $64M. • After 50 years
47 EXTENT AND IMPACT OF DRYLAND SALINITY
If 10% of the increased areas affected in year 2050 are protected, the annual cost is estimated as $78M. The total sum (present value, 7%) of the extra costs of protection over the 50 years is estimated as $15M.
4.2.2.3 Agriculture
An annual ‘operating profit’ was assigned to each hectare of farmed land. The values differed between zones but were assumed to be an average across all hectares within zones. High and medium risk land was scaled off against an unaffected land operating profit. The annual operating profits chosen for each zone were derived from farm business client data bases prepared recently by a bank and private consultants.
The 2000, 2020, and 2050 predictions for salinity impacts were then used to calculate total operating profit for each zone. Year 2000 without salinity was used as a base case for comparison to calculate the additional costs of salinity in subsequent years in terms of ‘lost’ operating profit. • Current year
The opportunity cost of lost operating profit in year 2000 due to watertables/salinity is estimated as $80M. That is, if all the currently affected land was still able to produce normal income, farmers would have an extra $80M operating profit available to spend elsewhere in year 2000. • After 20 years
To year 2020, rising watertables/salinity will cause progressive losses in operating profit each year. The sum (present value, 7%) of these extra losses (i.e. over and above the current impact) is estimated at around $19M.
• After 50 years
Until 2050, rising watertables/salinity will cause progressive losses in operating profit each year. The sum (present value, 7%) of these extra losses (i.e. over and above the current impact) is estimated at around $120M. This is significantly more than the $19M estimated after 20 years and reflects greatly increased area of land achieving the medium and high risk categories in the subsequent 30 years.
These estimates cover the major costs of rising watertables/salinity for rural towns, roads, railways, vegetation and agricultural land.
Other likely cost items not captured in the analyses would include water resources, lakes, wetlands, telecommunications (minor) and pipelines (minor).
All other components are at least partially captured. The vegetation component includes forests (native or commercial) and parts of wetlands and streams — although many people will justifiably argue they might have higher/lower/different asset values than a protection cost.
48 EXTENT AND IMPACT OF DRYLAND SALINITY
5.0 OTHER DATASETS
Nulsen and Evans (1998 unpublished) described a preferred approach for evaluating the extent of dryland salinity that would provide a situation statement and an on- going performance indicator. The detailed situation statement was based on LANDSAT TM analysis. They noted however that such analysis was only feasible in selected areas over a three year period and that WA was currently processing five scenes (each 34,225 km2) per year under State and NHT funds. Trained personnel limitations restrict additional analysis to a further five scenes per year. Thus, the three years of the audit could cover some 500,000 km2 of States other than WA. The LANDSAT TM output will contain errors of omission and commission. However, it will indicate the location and extent of current salinity on a small catchment basis (1,000 to 10,000 ha) upwards. Accuracy at farm and paddock level will be contingent on the level of local ground-truthing.
They further noted that:
“While the areal extent of salinity is of interest, it provides no insight into the state of catchments and risk of further salinisation. Salinisation will only occur if watertables continue to rise. Conversely, salinity will only be reduced if watertable elevations are reduced. Even in catchments where the watertable is currently well below the critical depth for surface salinity development, a rising watertable indicates the potential for salinisation and the need to take preventative action.”
Land Monitor (an NHT and WA Government project to map and monitor the extent of salinity through satellite imagery), has the most extensive LANDSAT TM dataset from which current and predicted extent of salinity has been mapped. However, this does not provide full coverage of the agricultural areas. This mapping currently represents a snapshot of low productivity land. Low productivity land could be due to inherent or anthropogenic causes, natural resource characteristics (primary or secondary salinity, waterlogging, soil acidity, trace element deficiency etc.) or due to management factors (weed burden, lack of fertiliser, wind erosion etc.).
Accuracy of this mapping is largely dependent on ground-truthing. This is particularly important in sedimentary basins where salinity processes are less well understood and make classification procedures difficult. Land Monitor is yet to provide satisfactory interpretation of satellite imagery for salinity mapping in the Perth Basin.
Land Monitor provided draft prediction data for comparison with the outcomes of this project. The data covered a small area around Dumbleyung and Mt Barker. An initial evaluation showed that the two datasets were very similar, and at a regional scale, almost identical. The major differences occurred at scales larger than the reporting scale of the Audit, i.e. Land Monitor was able to map localised change. The prediction produced by Land Monitor is based in part on the understanding of groundwater processes by Agriculture WA hydrologists. Hence, it is not surprising that the two datasets are similar.
The final predictions from the Land Monitor work suggested that at equilibrium, 31% of the area is expected to be at risk from salinity (Evans 2000). This figure is in the same range as shown by Ferdowsian et al. (1996) and the outcomes of this project.
49 EXTENT AND IMPACT OF DRYLAND SALINITY
6.0 FUTURE GROUNDWATER MONITORING
Both Agriculture WA and WRC carry out groundwater monitoring programs. In general terms, Agriculture WA’s Catchment Hydrology Group maintains groundwater datasets in agricultural areas on its AgBores database. These data are primarily used for salinity research. The WRC does some monitoring but is primarily concerned with potable/industrial groundwater resources. This arrangement is ongoing.
More than 5,000 bores were interrogated for use in the audit. After removing those with limited data, 4,780 bores are now available on the AgBores database for future monitoring.
Agriculture WA has begun a census to determine those that should remain as priorities for long-term monitoring. An initial analysis has identified more than 1400 bores that should receive priority to provide long-term groundwater trend data. Table 14 shows the distribution of these bores within zones used for analysis in this audit along with those bores nominated as high priority long-term sites for Agriculture WA. Two zones (241 and 243) still require further analysis to determine which sites will provide the most representative long-term data.
Table 14. Distribution of bores within zones.
Zone Bores used in Bores identified as NLWRA long-term sites 212 8 8 213 141 64 221 35 36 222 52 9 224 16 16 225 40 40 226 29 29 241 263 na 242 276 116 243 182 na 245 294 113 246 91 43 247 100 8 253 761 268 254 590 248 255 77 56 257 908 109 258 164 82 259 727 188 271 26 5 Total 4780 1438 na = no long-term bores have been identified for these areas
50 EXTENT AND IMPACT OF DRYLAND SALINITY
Analysis has shown that bores identified as long-term sites do not occupy all the systems analysed in this project. Some bore sites were not considered suitable.
The findings in this report are based at a regional scale (1:100,000 to 1:250,000). Should future assessment be undertaken at a larger scale (e.g. farm scale, 1:10,000), improved geo-referencing of bore locations will also be necessary. It is recommended that GPS-based referencing of bore locations become standard procedure during site establishment.
This assessment has identified systems and zones lacking data. These areas have been used to prioritise sites for drilling programs initiated by Agriculture WA during 2000. These programs are designed to fill some of the gaps in current monitoring networks.
Systems identified at high risk due to shallow watertables in the future and which do not currently have sites suitable for long-term monitoring will be given priority in future drilling programs. This work will provide improved data for future audits. 7.0 KEY OUTCOMES
The key results from the WA audit show that for the south-west region: • Groundwater trends are dominated by rising or stable trends. No systems have significant falling trends. • Approximately 16% of the region has the potential for salinity in 2000 due to shallow watertables. • 20% of the region has the potential for salinity in 2020 due to shallow watertables. • 33% of the region has the potential for salinity in 2050 due to shallow watertables. • Recharge modelling of current and future farming systems indicates that predicted changes in land use only sufficiently changed recharge in three zones to delay the onset of salinity. The reduction in recharge was not sufficient in any of these zones to reduce the eventual extent of salinity.
The outputs from the project include maps, tables and graphs. All time series groundwater data have been collated and evaluated to determine appropriateness for future reporting on dryland salinity status and trends. These data form part of Agriculture WA’s Agbores database which is regularly updated and used for ongoing analysis. 7.1 Extent
The issues of reporting scale, monitoring bore distribution and density, data quality and availability, need to be considered when interpreting the results of this project.
It is important to recognise that the risk analyses and conclusions presented provide only a statewide appreciation of the extent and impacts of dryland salinity. Groundwater trend analysis at the scales used will only provide an overview and is intended to enable national and State governments, industry and communities to make better informed decisions on policies and investments in management. Trends
51 EXTENT AND IMPACT OF DRYLAND SALINITY at local level (farm and paddock) can only be determined from individual bores whose location with respect to landscape position and hydrogeology is well known.
Ongoing mapping of ‘salinity’ at farm and catchment scale is being undertaken by the Land Monitor project. This is mapping areas of low productivity, most of which have been attributed to salinity. When complete, this should provide a current estimate of the extent of salinity at a catchment scale (1:10,000 to 1:25,000). Determining groundwater trends for catchments, and the impacts that different management strategies will have on these trends will be of greater importance for the long-term management of salinity.
The data published by this project are intended to be used at regional scale and should not be applied at local level (1:25,000 to 1:10,000). A regional scale cannot recognise local variability and various assumptions must therefore be made. Within the context of the regional scale these assumptions are reasonable, however there is a temptation to relate the outcomes to the local scale. Any results or conclusions drawn will be clearly out of context.
One option to improve the reporting of the extent of salinity may be to start at a larger scale (e.g. 1:10,000) and then work up to a regional context (1:250,000). This process would require significantly more data, resources and time than was available for this project. Lack of data at local (farm and catchment) scale clearly limited the outcomes of the SS2020 project.
Table 14 illustrates the hierarchical scale of mapping used in this study, with examples of how results can be used. The maps produced should only be used as a planning tool, with meaningful and defensible conclusions drawn, at national, State and regional levels. More detailed work is required to assess the data at catchment and farm scale. 7.2 Impacts and implications
Future audits assessing the impact of groundwater and salinity on infrastructure, biodiversity, water resources and agriculture should consider implications and issues raised by this study that might limit or restrict any future assessment of impacts.
Infrastructure • Approximately 20% of all road and rail networks are currently affected. This could increase to 40% by 2050. Twenty-seven of the larger rural towns were identified as having a current or potential risk. • Datasets for infrastructure need to be well maintained. • To fully value the costs to infrastructure, improved dollar values of infrastructure are required.
Biodiversity • Of the land classified as perennial vegetation (excluding herbaceous perennials), 600,000 ha are affected, increasing to 1.8 million ha by 2050. This may result in the extinction of up to 450 plant species and a significant reduction in fauna
52 EXTENT AND IMPACT OF DRYLAND SALINITY
species. The main areas of State Forest, which broadly cover the Western Darling Scarp Zone (255) from Perth to Albany, are not at risk. • Datasets relating to biodiversity are still largely being developed in WA. • These datasets need to be established and long-term sites identified to allow for ongoing assessment. • Attributing costs is virtually impossible as there few, if any, precedents for determining the cost of extinction species or the cost of replacing entire ecosystems.
Water resources • In WA a high proportion of surface water resources are saline. • The impact on significant groundwater resources within the Perth Basin and in other regions has not been assessed by this audit. • Future monitoring should consider assessing these groundwater resources and will require improved datasets. • A standard methodology for valuing water resources should be developed.
Agriculture • About 13% of cleared agricultural land is affected by shallow watertables increasing to about 33% by 2050. These areas occur predominantly inland with the most significant changes occurring in the 400 to 800 mm rainfall zone. There is limited groundwater information in some areas such as the Northern Perth Basin (Northern Agricultural Region). • The assessment of predicted land use change does not indicate any significant reduction in recharge. The future extent of salinity is unlikely to change. • Annual reporting is difficult due to the size of WA. • Improved satellite interpretation, or extending the process used by WA in this Audit to a catchment level may provide a better estimates for future Audits. • Improved groundwater monitoring systems in agricultural areas will be critical for establishing better estimates of local and regional groundwater trends, depths and qualities. This would improve the estimates of areas at risk, and improve the estimates of management impacts leading to, and changes or delays in the eventual extent of salinity.
Monitoring a range of data is critical to enable ongoing investigations. Future investigations should include: • Identification of groundwater processes and trends in areas currently lacking data • Risk assessment at a larger scale more applicable to land management • Assessment of risk to water resources • Assessment of the impacts of changing land use management.
53 EXTENT AND IMPACT OF DRYLAND SALINITY
Table 15. Use of Project 1A report and mapping products as a planning tool. SCALE USE USER EXAMPLE
REGIONS NATIONAL AND NATIONAL AND IDENTIFY AREAS STATE PLANNING STATE AT RISK OF GOVERNMENTS DRYLAND SALINITY
RESOURCE ALLOCATION INDUSTRY GROUPS
SPECIAL ALLOCATE INTEREST RESOURCES TO GROUPS IMPLEMENT PROVINCES SOLUTIONS
ZONES STATE, STATE AND IDENTIFY REGIONAL AND LOCAL BROAD LOCAL PLANNING GOVERNMENT LANDSCAPES WHERE SALINITY MAY OCCUR
INDUSTRY IDENTIFY SYSTEMS RESEARCH GROUPS NEEDS TO AMELIORATE EXTENT AND IMPACTS
SPECIAL INTEREST IDENTIFY NEW GROUPS INDUSTRIES
COMMUNITY GROUPS
SUB- CATCHMENT LOCAL IDENTIFY THE PLANNING GOVERNMENT CAPACITY TO SYSTEMS CHANGE
e.g. NEW SOIL FARM PLANNING INDUSTRY OPPORTUNITY PHASES GROUPS FOR INDUSTRY SPECIAL INTEREST GROUPS
COMMUNITY GROUPS
INDIVIDUALS
54 EXTENT AND IMPACT OF DRYLAND SALINITY
8.0 RECOMMENDATIONS • Develop methodologies and standards to improve the rigour of subsequent national, regional and local scale audits. Future audits to determine the extent and impact of salinity will require improved datasets from those that were readily available within the given timeframe. The preferred approach based on remote sensing and groundwater data as outlined by Nulsen and Evans (1999) should be investigated. • Continue to improve satellite and other remote sensing interpretations and increase their availability. By using these datasets along with extending the process used by WA in this audit to a catchment level will provide better estimates during future audits. • Continue to investigate and build a knowledge of groundwater processes in agricultural regions. • Improve groundwater monitoring systems and networks in agricultural areas. Extend current groundwater monitoring networks to provide essential data on groundwater depth and trend. Monitor the impacts of land management treatments on the water balance. • Assess groundwater resources in agricultural areas and improve the monitoring of both surface water and groundwater resources.
9.0 ACKNOWLEDGMENTS
The input and assistance of the following people is gratefully acknowledged:
• Dr Bob Nulsen In particular, for input, comment and support from the project’s conception through to the final products.
• Brendan Nicholas, Noel Schoknecht and other members of NRAG for providing the spatial framework and for assistance during the land use workshops.
• Regional members of the Catchment Hydrology Group who provided expert hydrology advice.
• Ned Stephenson of SRIG for input into the methodology for the GIS data analysis and map production.
• Allan Herbert and his colleagues for tackling the issues surrounding an economic analysis.
• Other colleagues within Agriculture WA and other WA government agencies for discussions and comment throughout the project.
• The Water and Rivers Commission, Department of Conservation and Land Management and Environment Australia for supplying data for the impact assessment.
55 EXTENT AND IMPACT OF DRYLAND SALINITY
REFERENCES Argent R.M. (1999). AgET Water Balance Calculator, Version 2.0 Technical Reference. Agriculture WA. Argent, R.M. (2000). Catcher. A Catchment rainfall, runoff and recharge calculator. User Manual, Agriculture WA. Bureau of Meteorology, WA. (2000). Some comments of Aspects of Rainfall Trends and Variability in the South-West of Western Australia. Internal Report. CALM (1999). CALM Biodiversity Survey of the Agricultural Zone. September 1999 Status Report. Dames and Moore – URS (2000). The economics of predicted rising groundwater and salinity in Merredin townsite – Draft Report. Economic Impact Study for Rural Towns Program. DNRE (1997). Know Your Catchments, Victoria 1997: An assessment of catchment condition using interim indicators. Department of Natural Resources and Environment, Victorian Catchment and Land Protection Council and Environment Protection Authority. English, V. and Blyth, J. (1999). Development and application of procedures to identify and conserve threatened ecological communities in the South West Botanical Province of Western Australia. Pacific Conservation Biology 5:124-38. Evans, R. (2000). Land Monitor salinity risk prediction. Dumbleyung and Mt Barker regions. CSIRO CMIS Task Report No. 2000/45. Ferdowsian, R., George, R., Lewis, F., McFarlane, D., Short, R. and Speed, R. (1996). The extent of dryland salinity in Western Australia. In Proc. 4th National Workshop on the Productive Use and Rehabilitation of Saline Lands, Albany, March 1996, pp. 88-89. George, R., Clarke, C., Hatton, T., Reggiani, P., Herbert, A., Ruprecht, J., Bowman, S. and Keighery, G. (1999). The effect of recharge management on the extent of dryland salinity, flood risk and biodiversity in Western Australia. Preliminary computer modelling, assessment and financial analysis. WA Salinity Council. Isbell, R.F. (1996). The Australian Soil Classification. Australian Soil and Land Survey Handbook, Volume 4. CSIRO Publishing, Collingwood, Victoria. WASLUC (1988). Western Australian Standard Land Use Codes. A standard system for identifying and coding land use activities. Western Australian Land Information System, WALIS Secretariat, Midland. McConnell, C. (2000). Predicted land use changes in the agricultural areas of WA and the resulting impact on the extent of dryland salinity. Resource Management Technical Report No. 201. Agriculture WA. McRobert, J., Foley, G., Shayan, A. (1997). An investigation of the Impact of waterlogging and salinity on the road asset in WA. Main Roads Western Australia, CR 6033, October 1997.
56 EXTENT AND IMPACT OF DRYLAND SALINITY
Nulsen B. (1998). Groundwater trends in the agricultural area of Western Australia. Resource Management Technical Report No 173. Natural Resource Management Services, Agriculture WA. Nulsen, B. and Evans, R. (1999). Dryland Salinity. National Land and Water Resources Audit. http://www.nlwra.gov.au/full/30_themes_and_projects/50_scoping_projects/04_ methods_papers/21_Nulsen/Dryland_Salinity.html Shao, Q., Campbell, N.A., Ferdowsian, R. and O’Connell, D. (1999). Analysing trends in groundwater levels. CSIRO CMIS Technical Report CMIS 99/37. Schoknecht, N. (1999). Soil Groups of Western Australia. A guide to the main soils of Western Australia, Edition 2. Resource Management Technical Report No. 193. Short, R. (2000). A Conceptual Hydrogeological Model For The Lake Warden Recovery Catchment Esperance, WA. Resource Management Technical Report No. 200. WAWA (1995). Jurien Groundwater Area Management Plan. Water Resources Division, Water Resources Planning and Allocation Branch, Water Authority of Western Australia. Report No. WG202. WRC (1999). Status and Trends of Stream Salinity in South Western Australia. Unpublished, Water and Rivers Commission.
57 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 1. ALLOCATION OF LAND USE DATA AND WATER BALANCE CALCULATIONS
Land use data were required to determine current and future land use and its impact on salinity. Data were acquired for the agricultural areas through a series of workshops held throughout regional WA. The participants were mainly from Agriculture WA and of varied background (economists, agronomists, local farm business consultants, hydrologists etc).
Current and future agricultural land uses were attributed at a zone level and a water balance comparison carried out.
The percentage of each major soil group is known at both a system and zone level. Land use was allocated against major soil types for each zone. Data was collected for current land use (2000) and for 2020. Due to both the purpose and scale of the project, land use was then allocated at the zone level. Land use in 2020 was allocated based on the perceived capacity or potential for change for each soil type and a range of likely scenarios (economic, environmental etc.) for the next 20 years.
Land use data were available in some formats prior to the workshops. However, no data were available for estimates of current and future land use based on ‘likely’ on- ground land use as opposed to ‘desirable’ land use. Data were therefore collected for soil groups within zones for both current and predicted future land use.
Current and future land use was allocated as a percentage of each soil type within each zone. The major soil groups (referred to as supergroups) are known for each zone and have been allocated by percentage to each zone. Supergroups are defined by texture or permeability profile, coarse fragments and water regime. Soil groups (which combine to form supergroups) are defined by calcareous layer, colour, depth of horizons, pH and structure (Schoknecht 1999). In most zones approximately 80% of the zone area is defined by five to six supergroups.
Land use was allocated to each supergroup in each zone. Broad categories, e.g. annual crop, annual pasture, perennial pasture, fodder crops (generally tagasaste), trees etc were adopted to standardise data. Categories were made for rural lifestyle and urban land use, as these were perceived as significant in some zones. These categories have been aligned with standard classifications (WASLUC). Land uses were generally allocated at minimum amounts of 5 or 10%, to a maximum of 100% of soil group area.
Future land use data was collected for 2020 but not specifically for 2050. This was seen as too far in the future for sensible prediction. Predictions for 2020 were subjective, but based on a wide range of experience and background of those participating in the workshops. Consideration was given to the capacity for change in each soil type, predictions for increased salinity, current research direction, extension programs, adoption factors and market factors. The aim was to increase overall water use where it was realistically possible. Land use was recorded as the most likely land use ‘on-ground’ as opposed to the ‘desirable’ land use and documented for each zone.
58 EXTENT AND IMPACT OF DRYLAND SALINITY
Perennial vegetation (remnant and planted) has been measured through satellite and photo interpretation by the Spatial Resource Information Group of Agriculture WA. Each region was made aware of these data, and a figure allocated to remnant vegetation with the understanding it would be scaled to represent actual data. The remaining areas were allocated land uses proportionally. The proportions were considered correct and modified according to the area of remnant vegetation.
Land use change may alter recharge. The data were analysed to determine relative amounts of recharge should land use change between 2000 and 2020. Two water balance programs developed by Agriculture WA were used, AgET and Catcher.
The relative difference in recharge was used to provide an assessment of the impact on salinity. Previous modelling carried out for the WA State Salinity Council (George et al. 1999) suggested that without immediate radical change, new agricultural systems will only delay salinity development. The work suggested that if a recharge reduction of 25% is achievable, a delay in the onset of salinity of 10-20 years might be expected, and a 50% reduction might deliver a delay of 50 to 60 years. This effectively delays the watertable rise from 2000 to 2020 or 2050 dependent on the suggested change.
The magnitude of the change in recharge was used in conjunction with this work to provide a broad assessment of the likely impact of land use change to salinity.
Water balance calculations
The impact of different land use will impact on watertables if it changes the amount of recharge significantly. To determine the significance of the proposed land use changes the data were used to run two water balance models. These models allowed relative amounts of recharge to be calculated.
AgET is a simple water balance calculator. It was developed to assist farmers and their advisers to understand how differing climates, plants, soils and rotations influence components of the water balance. The model uses ‘average’ climate, and ‘representative’ soil and plant information obtained within the WA agricultural areas.
To operate AgET, the user selects a site, soil unit, plant or farming system of interest, and then runs the model using current and alternative farming systems (land use) that may be suited to that environment. The output shows the magnitude of the components of the water balance, i.e. the amount of recharge, runoff, evapotranspiration etc. These calculations can be made for a range of annual or perennial plants used within farming systems.
AgET contains a soil file with general soil attribute data applicable across the State. However, soil groups vary significantly between zones. To improve the accuracy of the model, new soils files were compiled for each zone.
Crop data include Plants/ Crop Name, Crop Type Indicator, 12-monthly crop factor values, minimum, effective (recommended), and maximum rooting depth and a data quality code. Data for crop factors and crop rooting depths are not widely available across the State, and are of variable quality. The default values that are used by the
59 EXTENT AND IMPACT OF DRYLAND SALINITY program were established from a variety of sources (AgET Technical Reference, Argent 1999) and were used in the calculations.
Model calibration was achieved using data from the Catchment Hydrology Group, Agriculture WA. The group has summarised groundwater trends across the State (Nulsen 1998). Soil and crop files were manipulated to produce recharge estimates consistent with measured rates of rise. Where these data were not available, it was assumed that 10% of rainfall would become recharge.
Water balances for each land use/soil supergroup/zone were calculated and stored for use in Catcher (Argent 2000).
Catcher is a ‘back of the envelope’ calculator for analysing catchment water balances - how much rain falls, how much water evaporates (E/T) and is used by crops, how much runs off (Runoff), and how much percolates into the subsoil (Deep flow). It uses monthly point-value estimates of E/T, Runoff and Deep flow from the AgET program, adds them up for a given catchment, and allows users to see how much effect different crop plantings in different areas of a catchment might have on the catchment water balance.
The program was used to allow the proportions of each land use to be recognised in the water balance, i.e. AgET determines the individual water balance for each land use, Catcher determines the overall water balance for each super group, given a range of nominated land uses. Recharge was then summed for each zone based on the proportion of each supergroup in that zone.
Whilst the approach is approximate, the exact figures for recharge are not required. Instead, the relative differences have been used to indicate the impact of land use change on watertable levels.
CONSTRAINTS • Land use data have been acquired through agency experience, rather than ABS statistics, and may have some element of subjectivity. This is particularly so for land use allocation in 2020. • Recharge estimation for land use analysis was based on broad characteristics. Some zones cover substantial areas of the State and show significant variability of soils and climate. Average conditions have been assumed. • Limited economic data of the value of natural resource assets will restrict a financial assessment of the impact of salinity.
60 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 2. SOIL-LANDSCAPE ZONE NUMBER, NAME, DESCRIPTION AND AREA (HA). Zone Name Description Area (ha) 211 Coastal Dune Zone Coastal sand dunes and calcarenite. Late Pleistocene to Recent. (Quindalup and Spearwood dune 418,370 systems.) Calcareous and siliceous sands and calcarenite. 212 Bassendean Mid-Pleistocene Bassendean sand. Fixed dunes inland from coastal dune zone. Non-calcareous sands, 400,850 podsolised soils with low-lying wet areas. 213 Pinjarra Alluvial deposits (early Pleistocene to Recent) between the Bassendean Dunes Zone and the Darling Scarp, 269,570 colluvial and shelf deposits adjacent to the Darling Scarp. Clayey to sandy alluvial soils with wet areas. 221 Coastal Coastal dunes with alluvial plains (alluvium from the Greenough, Chapman and Irwin Rivers). Low hills of 326,390 Pleistocene Tamala Limestone. 222 Dandaragan Plateau Gently undulating plateau with areas of sandplain and some laterite. On Cretaceous sediments. Broad u- 678,890 shaped valleys 80-150 m deep, smaller v-shaped east of the Gingin Scarp in the south. Soils are formed in colluvium and weathered rock. 223 Victoria Plateau Gently undulating sandplain on Silurian sandstone and Proterozoic granulite with laterite exposed at 679,520 dissected margins. 224 Arrowsmith Dissected lateritic sandplain on Cretaceous and Jurassic sediments. Bounded by the Dandaragan Scarp to 556,140 the east and in the south, the Gingin Scarp to the west. Soils formed in colluvium and weathered in-situ rock. 225 Chapman Mesas of Triassic and Jurassic sediments on undulating Proterozoic granulite and migmatite with numerous 258,760 dolerite dykes. Soils formed in in-situ weathered rock, and lateritic colluvium on the sedimentary rocks (mesas). 226 Lockier Valleys of the Irwin, Lockier and Arrowsmith Rivers. Alluvial valley plains underlain by Proterozoic granulites, 156,800 Permian and Jurassic sediments. Outliers of Victoria Plateau Zone occur within the zone. Clayey to silty soils. 231 Coastal Zone Coastal dunes, calcareous in places. Undulating sandplain on limestone (Pleistocene calcarenite). 37,900 232 Transitional Zone Undulating sandplain on Silurian and Devonian sediments of the Gascoyne Sub-Basin (Carnarvon Basin), 45,070 some Cretaceous sediments. Moderately dissected in places with laterite remnants. 233 Inland Zone Gently undulating sandplain with some dunes, on Silurian sandstone. 73,200
61 EXTENT AND IMPACT OF DRYLAND SALINITY
Zone Name Description Area (ha) 241 Stirling Range Steep mountains of the Stirling Ranges (Proterozoic metasediments) and undulating rises on Archaean 479,240 granitic rocks in the Upper Pallinup catchment. 242 Albany Sandplain Gently undulating plain dissected by a number of short rivers flowing south. Eocene marine sediments 930,260 overlying Proterozoic granitic and metamorphic rocks. Soils are sandy duplex soils, often alkaline and sodic, with some sands and gravels. 243 Jerramungup Plain Level to gently undulating plain dissected by a number of short rivers flowing south. On Eocene marine 538,870 sediments overlying Proterozoic granitic and metamorphic rocks. Soils are alkaline sandy duplex soils with some clays, sands and gravels. 244 Ravensthorpe Rolling low hills on greenstone (mafic and ultramafic). Moderately dissected with south-flowing rivers. Red 327,880 fine-textured soils. 245 Esperance Sandplain Level to gently undulating plain dissected by a number of short rivers flowing south. Formed on Eocene 1,045,600 marine sediments overlying Proterozoic granitic and metamorphic rocks. Soils are grey fine sandy duplex soils and fine sands. 246 Salmon Gums-Mallee evel to gently undulating plain, with Tertiary sediments over Proterozoic granites. Salt lakes, scattered or in 1,863,620 swarms are a common feature. Drainage lines become indistinct to the north. 247 Boorokup Lakes Poorly drained flats with lake systems on Eocene sedimentary deposits. Sandy duplex soils. 146,650 251 Leeuwin Leeuwin Block (tectonic geology), moderately dissected lateritic plateau on granite. Colluvial soils in valleys. 98,700 On the western margin the granite is overlain by Tamala Limestone and there are some coastal dunes. 252 Donnybrook Sunkland Moderately dissected lateritic plateau on Perth Basin sedimentary rocks. Soils are formed in lateritic 465,390 colluvium, weathered in-situ sedimentary rocks and alluvium (poorly drained sandy alluvial plain in the south). 253 Eastern Darling Moderately to strongly dissected lateritic plateau on granite with eastward-flowing streams in broad shallow 1,211,000 Range valleys, some surficial Eocene sediments. Soils are formed in laterite colluvium or weathered in-situ granite. 254 Warren-Denmark Rises in a series of broad benches from the Southern Ocean north to the Blackwood Valley. Deeply 1,519,570 Southland weathered granite and gneiss overlain by Tertiary and Quaternary sediments in the south. Swampy in places. 255 Western Darling Moderately dissected lateritic plateau on granite with deeply incised valleys, includes the Darling Scarp on the 1,194,200 Range western margin. Soils are formed in laterite, lateritic colluvium and weathered in-situ granite and gneiss. 257 Zone of Rejuvenated Erosional surface of gently undulating rises to low hills. Continuous stream channels that flow in most years. 2,962,020 Drainage Colluvial processes are active. Soils formed in colluvium or in-situ weathered rock.
62 EXTENT AND IMPACT OF DRYLAND SALINITY
Zone Name Description Area (ha) 258 Northern Zone of An ancient peneplain with low relief. There is no connected drainage, salt lake chains occur as remnants of 5,220,050 Ancient Drainage ancient drainage systems which now only function in very wet years. Lateritic uplands dominated by yellow sandplain. 259 Southern Zone of An ancient peneplain with low relief. There is no connected drainage, salt lake chains occur as remnants of 3,700,660 Ancient Drainage ancient drainage systems which now only function in very wet years. Lateritic uplands dominated by grey sandy gravel plain. 261 Southern Cross Rises and low hills on Archaean greenstones, with broad valleys often containing salt lake chains. Soils are 240,470 usually red, loamy to clayey and calcareous. 271 Irwin River The Irwin and Lockier River catchments within the Yilgarn Craton. Archaean granites, gneisses, 736,360 metasediments and basic igneous rocks. 272 Greenough River The Greenough and Murchison River catchments within the Yilgarn Craton. Archaean granites, gneisses, 77,980 metasediments and basic igneous rocks.
63 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 3. SOIL-LANDSCAPE SYSTEM DETAILS
Zone System Name Area (ha) Zone System Name Area (ha) 211 211Qu Quindalup South 117,540 222 222Cp Capitella 135,010 211 211Sp Spearwood 273,910 222 222Da Dandaragan 117,520 211 211Va Vasse 19,070 222 222Er Eradu 18,680 212 212Bs Bassendean 387,340 222 222La Launer 86,780 212 212Mo Moore River 12,880 222 222Mb Mogumber 25,490 213 213Ab Abba 41,900 222 222Mm Moochamulla 1,470 213 213Fo Forrestfield 26,120 222 222Mr Mooladara Hill 20,730 213 213Jd Jindong 5,410 222 222Ot Otorowiri 20,620 213 213Pj Pinjarra 153,550 222 222Re Reagan 5,210 213 213Ya Yanga 39,320 222 222Rw Rowes 37,420 221 221Al Allanooka 2,960 222 222Sd Saline Drainage 500 221 221Cy Correy 38,610 223 223Bd Badgedong 7,700 221 221Ea Eatha 12,680 223 223Bi Binnu 281,560 221 221En Eneabba Plain 36,710 223 223Bn Bindoo 4,210 221 221Ga Greenough Alluvium 20,300 223 223Ca Casuarina 73,230 221 221In Indoon 3,210 223 223Da Dartmoor 126,790 221 221Qu Quindalup Central 37,320 223 223Er Eradu 135,620 221 221Sw Swamp 520 223 223Ge Greenough 9,980 221 221Ta Tamala 168,420 223 223Mj Munja 5,870 222 222Ag Agaton 290 223 223Og Ogilvie 20,710 222 222Ca Casuarina 4,030 223 223Sd Saline Drainage 13,840 222 222Cb Coonambidgee 2,160 224 224Al Allanooka 2,850 222 222Co Coalara 202,890 224 224Bh Boothendara 65,280
64 EXTENT AND IMPACT OF DRYLAND SALINITY
Zone System Name Area (ha) Zone System Name Area (ha) 224 224Ca Casuarina 7,790 226 226Mb Mount Budd 13,940 224 224Ir Irwin 10,830 226 226Mg Mullingarra 8,730 224 224Ma Mount Adams 84,190 226 226Mo Moresby 250 224 224Mh Mount Horner 131,050 226 226Ms Mount Scratch 9,250 224 224Mj Munja 22,320 226 226Ne Nebru 22,800 224 224Ms Mount Lesueur 4,710 226 226Nt Nangetty 25,940 224 224Ny Nylagarda 13,520 226 226Pi Pindar 890 224 224Ye Yerramullah 213,140 226 226Sd Saline Drainage 7,230 225 225Aj Ajana 28,530 226 226Yn Yandanooka 19,230 225 225Bi Binnu 15,830 231 231Ge Greenough 1,320 225 225Ca Casuarina 8,450 231 231Qu Quindalup North 5,100 225 225Da Dartmoor 4,820 231 231Sw Swamp 4,890 225 225Du Durawarra 9,020 231 231Ta Tamala 26,590 225 225Ge Greenough 640 232 232Ba Balline 38,520 225 225Mh Mount Horner 1,620 232 232Ch Christmas Hill 4,050 225 225Mo Moresby 28,190 232 232Mr Murchison 990 225 225No Northampton 98,210 232 232Wi Wittecarra 1,510 225 225Su Sugarloaf 60,080 233 233Bi Binnu 27,980 225 225Wo Wollya 2,210 233 233Mr Murchison 7,500 225 225Ya Yallabatharra 1,150 233 233Ur Urina 19,490 226 226Bi Binnu 240 233 233Wo Wollya 4,310 226 226Cs Coalseam 3,220 233 233Ya Yallabatharra 13,910 226 226Da Dartmoor 18,320 241 241Dd Dedatup 24,820 226 226Dd Dudewa 15,110 241 241Hd Hydenup 14,830 226 226Er Eradu 10,420 241 241Jf Jaffa 24,560 226 226Ir Irwin 1220 241 241Kb Kokarinup 9,620 65 EXTENT AND IMPACT OF DRYLAND SALINITY
Zone System Name Area (ha) Zone System Name Area (ha) 241 241Mb Mabinup 5,960 244 244Wh Whoogarup 48,970 241 241St Stirling 116,590 245 245Co Condingup 28,000 241 241Tm Toompup 46,210 245 245Es Esperance 401,160 241 241Up Upper Pallinup 236,630 245 245Go Gore 70,390 242 242Bb Bremer 14,630 245 245Je Jerdacorradup 4,610 242 242Ch Chillinup 202,470 245 245Mu Munglinup 214,050 242 242Hp Hillup 213,050 245 245Mv Merivale 52,680 242 242Jo Jonacoonack 84,860 245 245Ne Ney 35,640 242 242Kg King 135,280 245 245Th Thomas River 21,270 242 242Lp Lower Pallinup 29,250 245 245To Toore.g.ullup 87,510 242 242Me Meerup 46,840 245 245Yo Young 130,290 242 242Mm Mount Manypeaks 28,080 246 246Bu Buraminya 228,030 242 242Pr Porongurup Range 39,320 246 246Ha Halbert 703,010 242 242Re Redmond 83,240 246 246Jn Johnston 184,020 242 242Tb Torbay 4,960 246 246Sc Scaddan 542,840 242 242Uk Upper Kalgan 48,140 246 246Sg Salmon Gums 174,790 243 243Fz Fitzgerald 140,140 246 246Wm Wittenoom 30,930 243 243Jm Jerramungup 128,060 247 247Gd Gordon Flats 42,730 243 243Lg Lower Gairdner 46,220 247 247Nt North Stirlings Basin 63,870 243 243Mp Middle Pallinup 78,500 247 247Uc Unicup 40,060 243 243Su Suzetta 16,650 251 251Co Cowaramup Uplands 50,540 243 243Ug Upper Gairdner 74,230 251 251Gr Gracetown Ridge 16,610 243 243Ya Yarmarlup 55,070 251 251Gy Glenarty 3,700 244 244Ky Kybulup 28,610 251 251Kp Kilcarnup Dunes 10,390 244 244Od Oldfield 181,720 251 251Mt Metricup Scarp 1,790 244 244Ra Ravensthorpe 68,580 251 251Wv Willyabrup Valleys 15,670 66 EXTENT AND IMPACT OF DRYLAND SALINITY
Zone System Name Area (ha) Zone System Name Area (ha) 252 252Bp Blackwood Plateau 195,090 254 254Kd Kentdale 70,030 252 252Br Blackwood River 10,050 254 254Ke Kent 227,630 252 252Dx D'Entrecasteaux Dunes 25,820 254 254Mp Manjimup Plateau 233,170 252 252Gv Goodwood Valleys 26,940 254 254Nf Northcliffe 82,250 252 252Mc McLeod 7,070 254 254Nk Nullakai Dunes 64,140 252 252Np Nillup Plain 79,130 254 254Pi Pingerup 22,310 252 252Sr Scott River Plain 52,650 254 254Pp Perup Plateau 120,000 252 252Th Treeton Hills 47,300 254 254Pv Pimelia Valleys 196,600 252 252Ws Whicher Scarp 20,790 254 254Rh Roe Hills 82,070 253 253Bn Bindoon 22,190 254 254Wh Walpole Hills 106,900 253 253Bo Boscabel 77,980 254 254Wv Wilgarup Valleys 24,560 253 253Bv Boyup Brook Valleys 94,310 254 254Ya Yaraleena 23,840 253 253Cc Clackline 203,330 255 255Cf Coalfields 24,690 253 253Dk Darkan 92,470 255 255Co Cooke 11,970 253 253Eu Eulin Uplands 130,980 255 255Dp Darling Plateau 823,430 253 253Ga Gabbla 11,340 255 255Lv Lowden Valleys 191,720 253 253Mu Marradong Upland 140,150 255 255Mv Murray Valleys 135,760 253 253Nn Nooning 1,570 257 257Af Avon Flats 23,660 253 253Qd Quindanning 112,740 257 257Ag Agaton 97,780 253 253Ug Udamong 71,710 257 257Ar Arthur River 25,270 253 253Wa Wannamal 3,030 257 257Bb Balgerbine 87,540 253 253Wn Wundowie 226,200 257 257Be Beaufort 31,190 253 253Yh Yarawindah 22,910 257 257Bg Burabidge Hill 125,620 254 254Br Broke 73,300 257 257Bv Berkshire Valley 48,840 254 254Ca Caldyanup 69,270 257 257Ca Carrolup 282,480 254 254Fh Frankland Hills 113,650 257 257Cw Coorow 85,770 67 EXTENT AND IMPACT OF DRYLAND SALINITY
Zone System Name Area (ha) Zone System Name Area (ha) 257 257De Dellyanine 223,190 258 258Ho Hope North 68,590 257 257Dy Dryandra 249,880 258 258Ht Hunt 23,780 257 257Er Eradu 2,050 258 258Jb Jilbadji 5,540 257 257Fa Farrar 174,380 258 258Ka Karlgarin North 122,260 257 257Gh Greenhills 177,810 258 258Kb Kellerberrin 669,720 257 257Go Goomalling 104,990 258 258Ky Kwolyin 1,009,580 257 257Gt Glentrome 63,310 258 258Md Meranda 8,530 257 257Ih Inering Hill 95,020 258 258Mw Morawa 1,190 257 257Jc Jelcobine 244,450 258 258Ng Noolagabbi 6,870 257 257Jp Jingalup 45,860 258 258Ns Nesheeb North 59,280 257 257Mb Morbinning 270,350 258 258Pk Poeneke 7,130 257 257No Norring 27,550 258 258Rd Rockdale 33,190 257 257Pb Pumphreys Bridge 46,910 258 258Sd Saline Drainage 41,670 257 257Ps Phillips Sandplain 43,700 258 258Ta Tandegin 936,270 257 257Sd Saline Drainage 12,050 258 258Ud Upsan Downs 204,080 257 257Wb Whimbin 244,940 258 258Wa Wallambin 344,510 257 257Wg Wongan Hills 60,380 258 258Wd Wadderin 46,580 257 257Wh Winchester 16,280 258 258Wy Walyerming 157,310 257 257Wk West Kokeby 50,750 259 259As Alderside 23,390 258 258Ba Baladjie 96,400 259 259Bg Burngup 147,280 258 258Bd Ballidu 265,250 259 259Cb Coblinine 208,640 258 258Be Beacon 172,410 259 259Co Corrigin 197,460 258 258Bn Bendering 203,820 259 259Dn Dunns Rock 50,450 258 258Br Bonnie Rock 681,880 259 259Do Dongolocking 145,980 258 258Dw Dalwallinu 20,080 259 259Dt Datatine 109,030 258 258Go Goodhill 21,720 259 259Ek East Katanning 108,400 68 EXTENT AND IMPACT OF DRYLAND SALINITY
Zone System Name Area (ha) Zone System Name Area (ha) 259 259Ho Hope South 82,790 271 271Co Cookes 12,140 259 259Hy Hyden 108,570 271 271Dg Dalgooka 16,410 259 259Ka Karlgarin South 192,640 271 271Er Eradu 6,050 259 259Ke Kweda 114,430 271 271Fe Fegan 17,600 259 259Ki Kondinin 187,640 271 271Gn Granada 115,340 259 259Kk Kukerin 328,590 271 271In Indar 26,850 259 259La Lagan 259,780 271 271Ko Koolanooka 17,520 259 259Ln Lillian 332,960 271 271Mn Mount Nunn 9,820 259 259Ns Nesheeb South 66,230 271 271Mw Morawa 35,620 259 259Nw Newdegate 591,520 271 271Ng Noolagabbi 117,740 259 259Ny Nyabing 112,420 271 271Pe Peterwangy 97,440 259 259Pg Pingrup 104,860 271 271Pi Pindar 181,600 259 259Sh Sharpe 132,990 271 271Sd Saline Drainage 56,450 259 259Tn Tieline 59,350 271 271Th Thindindawah 3,840 259 259Yg Yealering 35,260 271 271Wa Warreno 14,090 261 261Bd Buladagie 19,560 272 272Da Dartmoor 1,780 261 261Gi Ghooli 67,820 272 272In Indar 1,720 261 261Gr Greenmount 109,500 272 272Mu Mullewa 34,250 261 261Gt Garratt 19,250 272 272Na Nangerwalla 31,290 261 261Ld Lake Deborah 9,030 272 272Th Thindindawah 8,930 261 261Pe Perilya 15,210 271 271Bo Bowgarder 7,860
69 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 4a. ZONE AREA AND ALLOCATED RISK Area at risk in 2000 (ha) Area at risk in 2020 (ha) Area at risk in 2050 (ha) Zone Area (ha) % Coverage Low Medium High Low Medium High Low Medium High 211 418,370 0 391,450 19,070 0 391,450 19,070 0 391,450 19,070 98 212 400,860 0 400,220 0 0 400,220 0 0 12,880 387,340 100 213 269,570 26,120 5,410 234,770 26,120 5,410 234,770 26,120 5,410 234,770 99 221 326,400 188,720 38,610 0 188,720 38,610 0 188,720 38,610 0 70 222 678,890 0 0 172,430 0 0 172,430 0 0 172,430 25 223 679,5100000000000 224 556,140 0 10,830 0 0 10,83000010,8302 225 258,750 96,720 98,210 0 96,720 98,210 0 88,270 106,660 0 75 226 156,790 0 23,840 33,170 0 23,840 33,170 0 0 57,010 36 23137,9000000000000 23245,0700000000000 23373,1900000000000 241 479,220 116,590 257,420 34,440 116,590 251,460 40,400 116,590 0 291,860 85 242 930,260 196,750 671,080 0 196,750 671,080 0 196,750 539,700 131,380 93 243 538,870 0 55,070 467,150 0 0 522,220 0 0 522,220 97 244 327,880 48,970 278,910 0 48,970 278,910 0 48,970 278,910 0 100 245 1,045,600 0 678,850 130,290 0 464,800 344,340 0 28,000 781,140 77 246 1,863,620 174,790 1,473,880 0 174,790 1,245,850 228,030 174,790 1,245,850 228,030 88 247 146,660 0 0 103,930 0 0 103,930 0 0 103,930 71
70 EXTENT AND IMPACT OF DRYLAND SALINITY
Zone Area (ha) Area at risk in 2000 (ha) Area at risk in 2020 (ha) Area at risk in 2050 (ha) % Coverage 251 98,700 68,000 3,700 0 52,330 19,370 0 0 68,000 3,700 73 252 465,380 263,180 79,130 52,650 263,180 79,130 52,650 0 263,180 131,780 85 253 121,1020 0 1,055,560 97,340 0 963,090 189,810 0 71,710 1,081,190 95 254 1,519,580 106,900 946,990 73,300 106,900 946,990 73,300 0 536,670 590,520 74 255 1,194,190 0 1,015,150 0 0 1,015,150 0 0 1,015,150 0 85 257 2,962,000 0 1,594,330 391,820 0 1,323,980 662,170 0 908,670 1,077,480 67 258 5,220,020 0 3,234,740 1,458,120 0 3,234,740 1,458,120 0 3,192,940 1,499,920 90 259 3,700,660 0 2,319,430 722,290 0 2,319,430 722,290 0 1,935,900 1,105,820 82 261 240,4700000000000 271 736,370 0 0 372,200 0 0 372,200 0 0 372,200 51 27277,9700000000000
Total 26,659,910
71 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 4b. PERCENTAGE OF EACH ZONE AT RISK OF SHALLOW GROUNDWATER Percentage at risk in 2000 Percentage at risk in 2020 Percentage at risk in 2050 Zone % Coverage Low Medium High Low Medium High Low Medium High 21109450945094598 21201000010000397100 213 10 2 87 10 2 87 10 2 87 99 221 58 12 0 58 12 0 58 12 0 70 222 0 0 25 0 0 25 0 0 25 25 2230000000000 2240200200022 225 37 38 0 37 38 0 34 41 0 75 226 0 15 21 0 15 21 0 0 36 36 2310000000000 2320000000000 2330000000000 241 24 54 7 24 52 8 24 0 61 85 242 21 72 0 21 72 0 21 58 14 93 243 0 10 87 0 0 97 0 0 97 97 244 15 85 0 15 85 0 15 85 0 100 245 0 65 12 0 44 33 0 3 75 77 2469790 967129671288 247 0 0 71 0 0 71 0 0 71 71 251 69 4 0 53 20 0 0 69 4 73
72 EXTENT AND IMPACT OF DRYLAND SALINITY
Percentage at risk in 2000 Percentage at risk in 2020 Percentage at risk in 2050 Zone % Coverage Low Medium High Low Medium High Low Medium High 252 57 17 11 57 17 11 0 57 28 85 253 0 87 8 0 80 16 0 6 89 95 254 7 62 5 7 62 5 0 35 39 74 25508500850085085 257 0 54 13 0 45 22 0 31 36 67 258 0 62 28 0 62 28 0 61 29 90 259 0 63 20 0 63 20 0 52 30 82 2610 000000000 271 0 0 51 0 0 51 0 0 51 51 2720 000000000
73 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 5. RISK ALLOCATED TO SYSTEMS (High risk = H, Medium risk = M, Low risk = L) Risk System 226Nt H H H 244Od M M M 2000 2020 2050 226Sd H H H 244Ra M M M 211Qu M M M 241Dd H H H 244Wh L L L 211Sp M M M 241Hd M M H 245Co M M M 211Va H H H 241Kb H H H 245Es M M H 212Bs M M H 241Mb M H H 245Mu M H H 212Mo M M M 241St L L L 245Ne M M H 213Ab H H H 241Up M M H 245Yo H H H 213Fo L L L 242Bb L L L 246Bu M H H 213Jd M M M 242Ch M M M 246Ha M M M 213Pj H H H 242Hp M M M 246Sc M M M 213Ya H H H 242Jo M M M 246Sg L L L 221Cy M M M 242Kg L L L 247Nt H H H 221Ga L L L 242Me L L L 247Uc H H H 221Ta L L L 242Pr M M M 251Co L L M 222Cp H H H 242Re M M H 251Gy M M H 222Rw H H H 242Uk M M H 251Mt L L M 224Ir M M H 243Fz H H H 251Wv L M M 225Ca L L M 243Jm H H H 252Bp L L M 225Mo L L L 243Lg H H H 252Np M M H 225No M M M 243Mp H H H 252Sr H H H 225Su L L L 243Ug H H H 252Th L L M 226Dd M M H 243Ya M H H 252Ws L L M 226Mg M M H 244Ky M M M 253Bo M M H
74 EXTENT AND IMPACT OF DRYLAND SALINITY 258Ta M M M Risk 257Ca M M H 258Ud M M M System 2000 2020 2050 257De M M M 258Wa H H H 253Bv H H H 257Dy M M M 258Wy M M M 253Cc M M H 257Fa M M M 259Cb H H H 253Dk M H H 257Go H H H 259Co M M M 253Eu M M H 257Gt M M H 259Do M M M 253Mu M M H 257Ih H H H 259Dt M M M 253Qd M M H 257Jp M M H 259Ek M M H 253Ug M M M 257Mb M H H 259Ho M M H 253Wa H H H 257No H H H 259Hy M M M 253Wn M M H 257Pb H H H 259Ka M M M 254Br H H H 257Sd H H H 259Ke M M M 254Fh M M H 257Wb M M M 259Ki H H H 254Kd M M H 257Wh M M M 259Kk M M M 254Ke M M H 258Ba H H H 259La H H H 254Mp M M M 258Be H H H 259Ns H H H 254Pv M M M 258Bn M M M 259Nw M M M 254Rh M M H 258Br M M M 259Ny M M M 254Wh L L M 258Dw M M H 259Sh M M H 254Ya M M H 258Go M M H 259Tn M M H 255Dp M M M 258Ho H H H 259Yg M M M 255Lv M M M 258Jb H H H 271Dg H H H 257Af M M H 258Kb H H H 271Ng H H H 257Ar H H H 258Ky M M M 271Pi H H H 257Be H H H 258Ns H H H 271Sd H H H 257Bv H H H 258Sd H H H
75 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 6. AWRC BASINS AND ALLOCATED RISK AS A PERCENTAGE OF BASIN AREA 2000 2020 2050 AWRC Name % Coverage Basin Low Moderate High Low Moderate High Low Moderate High
602 Albany Coast 100 16 52 25 16 48 28 16 27 50 615 Avon River 71 0 42 16 0 40 18 0 36 21 609 Blackwood River 100 7 73 16 7 69 20 0 51 45 612Collie River99085708570829 603 Denmark Coast 99 19 65 7 19 65 7 12 8 71 608 Donnelly River 99 3 77 8 3 77 8 0 73 16 601 Esperance Coast 98 2 69 9 2 59 20 2 42 36 610 Preston River 99 7 76 8 7 76 8 1 78 12 605 Frankland River 100 5 73 3 5 73 3 1 23 58 701 Greenough River 73 10 6 6 1066957 613 Harvey River 96 2 65 25 2 65 25 2 51 39 604Kent River99766676660772 617 Moore-Hill Rivers 100 2 30 15 2 29 17 2 18 28 702Murchison River3000000000 614 Murray River 100 1 83 9 1 83 9 1 52 40 619Ninghan14096096096 611 Busselton Coast 99 49 17 20 45 21 20 0 62 24 24Salt Lake Basin3020020021 606Shannon River9715261815261803919 616 Swan Coastal 99 1 69 8 1 69 8 1 32 46 607 Warren River 100 0 62 7 0 62 7 0 45 25 618Yarra-Yarra23079079069
76 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 7a. LENGTH OF HIGHWAYS AND ALLOCATED RISK 2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High
211 0.0 35.9 4.6 0.0 35.9 4.6 0.0 35.9 4.6 212 0.0 106.9 0.0 0.0 106.9 0.0 0.0 3.6 103.3 213 65.0 0.0 222.5 65.0 0.0 222.5 65.0 0.0 222.5 221 105.1 24.1 0.0 105.1 24.1 0.0 105.1 24.1 0.0 222 0.0 0.0 13.3 0.0 0.0 13.3 0.0 0.0 13.3 223 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 224 0.0 5.2 0.0 0.0 5.2 0.0 0.0 0.0 5.2 225 7.0 46.8 0.0 7.0 46.8 0.0 7.0 46.8 0.0 241 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 242 68.7 97.3 0.0 68.7 54.3 43.0 63.8 59.1 43.0 243 0.0 18.5 132.2 0.0 0.0 150.7 0.0 0.0 150.7 244 0.0 61.1 0.0 0.0 61.1 0.0 0.0 61.1 0.0 245 0.0 148.2 23.8 0.0 96.6 75.5 0.0 0.0 172.0 246 38.9 71.6 0.0 38.9 71.6 0.0 38.9 71.6 0.0 247 0.0 0.0 45.1 0.0 0.0 45.1 0.0 0.0 45.1 251 28.9 7.2 0.0 25.1 11.0 0.0 0.0 28.9 7.2 252 35.1 0.0 0.3 35.1 0.0 0.3 0.0 35.1 0.3 253 0.0 208.9 0.0 0.0 208.9 0.0 0.0 22.8 186.0 254 53.7 314.8 54.7 53.7 314.8 54.7 0.0 256.8 166.4
77 EXTENT AND IMPACT OF DRYLAND SALINITY
2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High 255 0.0 189.8 0.0 0.0 189.8 0.0 0.0 189.8 0.0 257 0.0 383.6 108.4 0.0 376.6 115.4 0.0 223.6 268.4 258 0.0 116.0 110.8 0.0 116.0 110.8 0.0 114.3 112.6 259 0.0 0.0 5.2 0.0 0.0 5.2 0.0 0.0 5.2 261 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 271 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Total 402.5 1,835.8 721.0 398.7 1,719.4 841.2 280.0 1,173.4 1,505.9
78 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 7b. LENGTH OF PRIMARY ROADS AND ALLOCATED RISK (KM) 2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High 211 0.0 286.3 13.3 0.0 286.3 13.3 0.0 286.3 13.3 212 0.0 41.4 0.0 0.0 41.4 0.0 0.0 0.8 40.7 213 2.4 0.0 14.7 2.4 0.0 14.7 2.4 0.0 14.7 221 13.0 0.0 0.0 13.0 0.0 0.0 13.0 0.0 0.0 223 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 224 0.0 7.9 0.0 0.0 7.9 0.0 0.0 0.0 7.9 225 7.3 0.0 0.0 7.3 0.0 0.0 7.3 0.0 0.0 226 0.0 14.1 2.7 0.0 14.1 2.7 0.0 0.0 16.8 241 24.6 136.4 0.9 24.6 136.4 0.9 24.6 0.0 137.3 242 23.3 32.9 0.0 23.3 21.6 11.3 10.2 24.3 21.7 243 0.0 0.0 30.0 0.0 0.0 30.0 0.0 0.0 30.0 244 0.0 28.0 0.0 0.0 28.0 0.0 0.0 28.0 0.0 247 0.0 0.0 9.9 0.0 0.0 9.9 0.0 0.0 9.9 253 0.0 80.4 31.1 0.0 65.1 46.5 0.0 0.0 111.6 254 0.0 9.9 0.0 0.0 9.9 0.0 0.0 0.0 9.9 255 0.0 150.6 0.0 0.0 150.6 0.0 0.0 150.6 0.0 257 0.0 296.4 95.0 0.0 256.7 134.7 0.0 183.4 208.0 258 0.0 397.5 198.9 0.0 397.5 198.9 0.0 397.5 198.9 259 0.0 615.5 198.5 0.0 615.5 198.5 0.0 553.5 260.5 261 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
79 EXTENT AND IMPACT OF DRYLAND SALINITY
2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High 271 0.0 0.0 85.1 0.0 0.0 85.1 0.0 0.0 85.1 272 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Total 70.6 2,097.2 680.1 70.6 2,030.8 746.4 57.5 1,624.3 1,166.1
80 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 7c. LENGTH OF SECONDARY ROADS AND ALLOCATED RISK
2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High 211 0.0 66.5 6.3 0.0 66.5 6.3 0.0 66.5 6.3 212 0.0 84.6 0.0 0.0 84.6 0.0 0.0 3.4 81.2 213 12.1 0.0 109.3 12.1 0.0 109.3 12.1 0.0 109.3 221 71.4 2.7 0.0 71.4 2.7 0.0 71.4 2.7 0.0 222 0.0 0.0 21.3 0.0 0.0 21.3 0.0 0.0 21.3 223 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 224 0.0 1.8 0.0 0.0 1.8 0.0 0.0 0.0 1.8 225 22.3 57.4 0.0 22.3 57.4 0.0 22.3 57.4 0.0 226 0.0 18.6 21.9 0.0 18.6 21.9 0.0 0.0 40.5 231 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 233 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 241 9.8 67.9 20.4 9.8 62.9 25.5 9.8 0.0 88.3 242 103.4 39.3 0.0 103.4 39.3 0.0 86.4 53.7 2.6 243 0.0 0.0 21.9 0.0 0.0 21.9 0.0 0.0 21.9 244 0.0 19.7 0.0 0.0 19.7 0.0 0.0 19.7 0.0 245 0.0 106.9 0.0 0.0 99.1 7.8 0.0 10.9 96.0 247 0.0 0.0 27.1 0.0 0.0 27.1 0.0 0.0 27.1 251 75.6 2.5 0.0 53.6 24.5 0.0 0.0 75.6 2.5 252 47.7 63.1 0.0 47.7 63.1 0.0 0.0 47.7 63.1 253 0.0 371.2 46.0 0.0 295.5 121.7 0.0 20.5 396.7 254 8.4 339.3 43.5 8.4 339.3 43.5 0.0 201.6 189.6 255 0.0 226.3 0.0 0.0 226.3 0.0 0.0 226.3 0.0
81 EXTENT AND IMPACT OF DRYLAND SALINITY
2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High 257 0.0 533.6 192.0 0.0 391.4 334.2 0.0 276.1 449.5 258 0.0 887.7 440.8 0.0 887.7 440.8 0.0 887.7 440.8 259 0.0 321.2 164.1 0.0 321.2 164.1 0.0 279.9 205.4 261 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 271 0.0 0.0 82.0 0.0 0.0 82.0 0.0 0.0 82.0 272 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Total 350.7 3,210.3 1,196.5 328.7 3,001.6 1,427.2 202.0 2,229.6 2,325.9
82 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 7d. LENGTH OF MINOR ROADS AND ALLOCATED RISK (KM) 2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High 211 0.0 1,571.4 88.3 0.0 1,571.4 88.3 0.0 1,571.4 88.3 212 0.0 1,318.2 0.0 0.0 1,318.2 0.0 0.0 24.2 1,293.9 213 161.8 49.0 1,433.0 161.8 49.0 1,433.0 161.8 49.0 1,433.0 221 241.4 29.1 0.0 241.4 29.1 0.0 241.4 29.1 0.0 222 0.0 0.0 366.0 0.0 0.0 366.0 0.0 0.0 366.0 223 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 224 0.0 21.9 0.0 0.0 21.9 0.0 0.0 0.0 21.9 225 248.9 330.3 0.0 248.9 330.3 0.0 240.2 339.0 0.0 226 0.0 77.0 58.5 0.0 77.0 58.5 0.0 0.0 135.5 231 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 232 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 233 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 241 148.5 646.0 62.9 148.5 641.4 67.5 148.5 0.0 708.9 242 653.1 1,158.1 0.0 653.1 842.1 315.9 530.5 818.2 462.5 243 0.0 127.0 671.6 0.0 0.0 798.6 0.0 0.0 798.6 244 19.5 277.0 0.0 19.5 277.0 0.0 19.5 277.0 0.0 245 0.0 1,426.1 160.0 0.0 971.9 614.3 0.0 71.1 1,515.1 246 400.5 1,618.0 0.0 400.5 1,577.9 40.1 400.5 1,577.9 40.1 247 0.0 0.0 198.2 0.0 0.0 198.2 0.0 0.0 198.2 251 453.4 13.4 0.0 348.8 118.0 0.0 0.0 453.4 13.4 252 860.1 100.4 113.7 860.1 100.4 113.7 0.0 860.1 214.2 253 0.0 2,468.9 309.6 0.0 2,228.7 549.8 0.0 117.9 2,660.6 254 528.6 3,573.2 192.4 528.6 3,573.2 192.4 0.0 2,842.9 1,451.3 83 EXTENT AND IMPACT OF DRYLAND SALINITY
2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High 255 0.0 2,968.0 0.0 0.0 2,968.0 0.0 0.0 2,968.0 0.0 257 0.0 5,517.3 1,193.5 0.0 4,599.8 2,111.0 0.0 3,081.7 3,629.1 258 0.0 9,811.9 4,078.8 0.0 9,811.9 4,078.8 0.0 9,660.0 4,230.7 259 0.0 6,201.2 1,697.1 0.0 6,201.2 1,697.1 0.0 5,152.0 2,746.3 261 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 271 0.0 0.0 928.4 0.0 0.0 928.4 0.0 0.0 928.4 272 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Total 3,715.7 39,303.5 11,552.2 3,611.2 37,308.4 13,651.8 1,742.4 29,892.9 22,936.1
84 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 7e. LENGTH OF RAIL AND ALLOCATED RISK 2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High 211 0.0 80.3 5.2 0.0 80.3 5.2 0.0 80.3 5.2 212 0.0 74.0 0.0 0.0 74.0 0.0 0.0 0.0 74.0 213 30.6 0.0 249.7 30.6 0.0 249.7 30.6 0.0 249.7 221 92.3 0.0 0.0 92.3 0.0 0.0 92.3 0.0 0.0 222 0.0 0.0 12.4 0.0 0.0 12.4 0.0 0.0 12.4 224 0.0 18.0 0.0 0.0 18.0 0.0 0.0 0.0 18.0 225 39.5 56.5 0.0 39.5 56.5 0.0 39.5 56.5 0.0 226 0.0 10.0 1.5 0.0 10.0 1.5 0.0 0.0 11.6 241 2.0 67.4 0.0 2.0 67.4 0.0 2.0 0.0 67.4 242 18.3 43.6 0.0 18.3 25.9 17.7 18.3 16.1 27.5 244 0.0 24.6 0.0 0.0 24.6 0.0 0.0 24.6 0.0 245 0.0 43.1 0.0 0.0 35.2 7.9 0.0 0.0 43.1 246 37.2 72.9 0.0 37.2 72.9 0.0 37.2 72.9 0.0 247 0.0 0.0 21.9 0.0 0.0 21.9 0.0 0.0 21.9 252 25.5 0.0 0.0 25.5 0.0 0.0 0.0 25.5 0.0 253 0.0 155.3 47.8 0.0 125.8 77.2 0.0 0.9 202.1 254 21.7 132.0 32.8 21.7 132.0 32.8 0.0 100.6 85.9 255 0.0 266.6 0.0 0.0 266.6 0.0 0.0 266.6 0.0 257 0.0 620.4 261.8 0.0 546.6 335.6 0.0 328.1 554.2 258 0.0 877.9 448.7 0.0 877.9 448.7 0.0 867.5 459.0 259 0.0 386.5 181.3 0.0 386.5 181.3 0.0 313.9 253.8 271 0.0 0.0 96.0 0.0 0.0 96.0 0.0 0.0 96.0 Total 267.1 2,929.0 1,359.1 267.1 2,800.2 1,487.9 219.9 2,153.4 2,181.9
85 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 8. TOWNS AND ALLOCATED RISK OF SHALLOW GROUNDWATER Risk Risk Risk Name Name Name 2000 2020 2050 2000 2020 2050 2000 2020 2050 Albany L L L Forrestfield M M M Perenjori H H H Augusta L L M Gnowangerup M M H Pingelly M M M Beacon H H H Greenbushes M M M Pinjarra M M H Bencubbin M M M Harvey H H H Quairading M M M Boddington M M H HydenMMM Ravensthorpe M M M Boyup Brook H H H Jerramungup H H H Rockingham M M M Bremer Bay L L L Katanning M M H Tammin M M M Bridgetown M M M Kellerberrin H H H Three Springs M M H Brookton H H H KojonupMMM Trayning M M M Bruce Rock M M M Kondinin H H H Wagin H H H Bunbury H H H Koorda H H H Walpole H H H Busselton M M M KulinMMM Westonia M M M Calingiri M H H Lake Grace M M M Wickepin M M M Carnamah H H H Manjimup M M M Williams H H H Coorow H H H Margaret River L M M Wyalkatchem M M M Corrigin M M M Merredin H H H Cranbrook H H H Moora H H H Cunderdin M M M Mt. Barker M M H Darkan M H H Mukinbudin H H H Denmark L L M Narembeen H H H Dongara L L L Narrogin M M M Donnybrook M M M Northam M M H Dowerin M M M Northampton M M M Dumbleyung M M M Pemberton M M M 86 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 9. STREAM LENGTH AND ALLOCATED RISK OF SHALLOW WATERTABLE 2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High 211 0.0 47.3 14.0 0.0 47.3 14.0 0.0 47.3 14.0 212 0.0 116.5 0.0 0.0 116.5 0.0 0.0 53.0 63.4 213 12.4 10.6 242.2 12.4 10.6 242.2 12.4 10.6 242.2 221 31.9 0.0 0.0 31.9 0.0 0.0 31.9 0.0 0.0 222 0.0 0.0 25.5 0.0 0.0 25.5 0.0 0.0 25.5 223 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 224 0.0 62.7 0.0 0.0 62.7 0.0 0.0 0.0 62.7 225 27.0 0.0 0.0 27.0 0.0 0.0 27.0 0.0 0.0 226 0.0 0.0 14.4 0.0 0.0 14.4 0.0 0.0 14.4 241 13.2 77.5 32.6 13.2 77.5 32.6 13.2 0.0 110.1 242 108.4 275.2 0.0 108.4 266.1 9.1 108.4 213.0 62.2 243 0.0 69.1 259.0 0.0 0.0 328.2 0.0 0.0 328.2 244 25.0 182.7 0.0 25.0 182.7 0.0 25.0 182.7 0.0 245 0.0 28.6 304.2 0.0 17.1 315.6 0.0 0.0 332.7 246 0.8 67.7 0.0 0.8 67.7 0.0 0.8 67.7 0.0 247 0.0 0.0 0.7 0.0 0.0 0.7 0.0 0.0 0.7 251 20.1 0.6 0.0 0.6 20.1 0.0 0.0 20.1 0.6 252 74.7 10.8 14.1 74.7 10.8 14.1 0.0 74.7 25.0 253 0.0 377.4 124.3 0.0 301.9 199.8 0.0 11.2 490.5 254 143.9 596.8 50.1 143.9 596.8 50.1 0.0 399.9 391.0 255 0.0 505.6 0.0 0.0 505.6 0.0 0.0 505.6 0.0 257 0.0 479.7 363.1 0.0 464.1 378.7 0.0 233.5 609.3 258 0.0 0.0 0.2 0.0 0.0 0.2 0.0 0.0 0.2
87 EXTENT AND IMPACT OF DRYLAND SALINITY
2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High 259 0.0 21.3 29.5 0.0 21.3 29.5 0.0 21.3 29.5 271 0.0 0.0 47.4 0.0 0.0 47.4 0.0 0.0 47.4 272 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Total 457.3 2,930.2 1,521.3 437.8 2,768.9 1,702.1 218.6 1,840.6 2,849.6
APPENDIX 10. RESOURCE RECOVERY CATCHMENT AND ALLOCATED RISK Area (ha) at risk % Catchment Area (ha) 2000 2020 2050 Coverage Low Medium High Low Medium High Low Medium High Collie 278,550 0 288,068 0 0 288,065 3 0 287,637 431 100 Helena 147,780 0 122,535 0 0 122,535000122,535 83 Kent 240,517 3,120 144,025 0 3,120 144,025 0 374 2,746 144,025 61 Warren 413,293 21 266,591 29,110 21 266,591 29,110 0 187,509 108,213 72 Percentage Percentage Percentage Catchment Area (ha) % Coverage Low Medium High Low Medium High Low Medium High Collie 0 100 0 0 100 0 0 100 0 100 Helena 08300830008383 Kent 16001600016061 Warren 0 65 7 0 65 7 0 45 26 72
88 EXTENT AND IMPACT OF DRYLAND SALINITY APPENDIX 11. AREA OF PERENNIAL VEGETATION AT RISK OF SHALLOW WATERTABLES 2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High 211 0 219,363 6,388 0 219,363 6,388 0 219,363 6,388 212 0 203,286 0 0 203,286 0 0 3,521 199,765 213 5,202 621 21,769 5,202 621 21,769 5,202 621 21,769 221 49,960 13,752 0 49,960 13,752 0 49,960 13,752 0 222 0 0 46,644 0 0 46,644 0 0 46,644 223000000000 224 0 1,040 0 0 1,040 0 0 0 1,040 225 13,152 9,149 0 13,152 9,149 0 12,296 10,005 0 226 0 2,081 523 0 2,081 523 0 0 2,604 231000000000 232000000000 233000000000 241 0 23,471 8,019 0 22,648 8,842 0 0 31,490 242 97,603 241,715 0 97,603 218,845 22,870 83,350 225,492 30,476 243 0 15,918 152,939 0 0 168,857 0 0 168,857 244 27,333 118,456 0 27,333 118,456 0 27,333 118,456 0 245 0 94,468 64,825 0 61,819 97,474 0 3,602 155,691 246 24,863 138,875 0 24,863 128,602 10,273 24,863 128,602 10,273 247 0 0 23,396 0 0 23,396 0 0 23,396 251 28,183 1,818 0 20,187 9,814 0 0 28,183 1,818 252 229,796 68,299 30,274 229,796 68,299 30,274 0 229,796 98,573 253 0 441,449 23,394 0 426,205 38,638 0 19,672 445,171 254 84,932 676,153 0 84,932 676,153 0 0 491,189 269,896
89 EXTENT AND IMPACT OF DRYLAND SALINITY
2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High 255 0 827,812 0 0 827,812 0 0 827,812 0 257 0 203,000 31,778 0 191,220 43,558 0 131,748 103,030 258 0 302,855 60,545 0 302,855 60,545 0 300,788 62,612 259 0 364,243 94,326 0 364,243 94,326 0 303,608 154,961 261000000000 271 0 0 30,396 0 0 30,396 0 0 30,396 272000000000
90 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 12. IMPORTANT WETLANDS AND ALLOCATED AREA AT RISK OF SHALLOW GROUNDWATER Area at risk (ha) % Total area Wetland Zone wetlands (ha) 2000 2020 2020 covered
Low Medium High Low Medium High Low Medium High Becher Point Wetlands 211 0.12 0.00 0.12 0.00 0.00 0.12 0.00 0.00 0.12 0.00 100.00 Booragoon Swamp 211 29.58 0.00 29.58 0.00 0.00 29.58 0.00 0.00 28.31 1.27 100.00 Gibbs Road Swamp 211 5,829.90 0.00 5,049.83 0.00 0.00 5,049.83 0.00 0.00 30.44 5,019.39 86.62 Karakin Lakes 211 621.62 0.00 621.62 0.00 0.00 621.62 0.00 0.00 616.60 5.02 100.00 Lake McLarty 211 263.48 0.00 152.25 54.31 0.00 152.25 54.31 0.00 151.65 54.92 78.40 Lake Thetis 211 1.21 0.00 1.21 0.00 0.00 1.21 0.00 0.00 1.21 0.00 100.00 Peel-Harvey Estuary 211 3,235.38 0.00 948.52 2,229.43 0.00 948.52 2,229.43 0.00 23.51 3,154.45 98.23 Rottnest Island Lakes 211 137.28 0.00 137.28 0.00 0.00 137.28 0.00 0.00 137.28 0.00 100.00 Spectacles Swamp 211 164.43 0.00 46.66 117.78 0.00 46.66 117.78 0.00 6.27 158.16 100.00 Vasse-Wonnerup 211 1,980.96 0.00 78.94 1,897.28 0.00 78.94 1,897.28 0.00 78.94 1,897.28 99.76 Wetland Barraghup Swamp 212 18.76 0.00 18.76 0.00 0.00 18.76 0.00 0.00 0.00 18.76 100.00 Benger Swamp 212 1,086.15 0.00 1.84 1,084.31 0.00 1.84 1,084.31 0.00 0.00 1,086.15 100.00 Forrestdale Lake 212 0.12 0.00 0.12 0.00 0.00 0.12 0.00 0.00 0.00 0.12 100.00 Guraga Lake 212 364.80 0.00 364.80 0.00 0.00 364.80 0.00 0.00 0.00 364.80 100.00 Perth Airport 212 192.12 0.00 181.67 10.45 0.00 181.67 10.45 0.00 0.00 192.12 100.00 Woodland Swamps Chandala Swamp 213 435.59 0.00 0.00 433.03 0.00 0.00 433.03 0.00 0.00 433.03 99.41 Ellen Brook Swamps 213 19.92 0.00 0.00 19.92 0.00 0.00 19.92 0.00 0.00 19.92 100.00 Wannamal Lake 222 915.64 0.00 0.00 915.01 0.00 0.00 915.01 0.00 0.00 915.01 99.93
91 EXTENT AND IMPACT OF DRYLAND SALINITY
Area at risk (ha) % Total area Wetland Zone wetlands (ha) 2000 2020 2020 covered
Low Medium High Low Medium High Low Medium High Fitzgerald Inlet 242 1,127.81 32.26 1,095.54 0.00 32.26 1,095.54 0.00 32.26 1,095.54 0.00 100.00 Lake Pleasant View 242 436.47 0.00 436.47 0.00 0.00 436.47 0.00 0.00 1.24 435.23 100.00 Yellilup Yate Swamp 242 756.36 74.20 670.60 11.57 74.20 670.60 11.57 74.20 670.60 11.57 100.00 Balicup Lake 247 1,005.63 0.00 0.00 1,005.63 0.00 0.00 1,005.63 0.00 0.00 1,005.63 100.00 Byenup Lagoon 247 10,339.18 0.00 729.65 9,601.77 0.00 729.65 9,601.77 0.00 444.02 9,887.41 99.92 Lake Muir 247 3,990.78 0.00 0.00 3,990.78 0.00 0.00 3,990.78 0.00 0.00 3,990.78 100.00 Gingilup-Jasper 252 2,765.02 0.00 0.00 2,171.30 0.00 0.00 2,171.30 0.00 0.00 2,171.30 78.53 Wetland Avon River Valley 253 0.12 0.00 0.12 0.00 0.00 0.12 0.00 0.00 0.00 0.12 100.00 Chittering-Needonga 253 225.64 0.00 198.42 0.00 0.00 198.42 0.00 0.00 0.00 198.42 87.94 Lakes Doggerup Creek 254 16,042.02 0.00 0.00 15,061.81 0.00 0.00 15,061.81 0.00 0.00 15,061.81 93.89 Owingup Swamp 254 905.97 0.00 0.00 905.97 0.00 0.00 905.97 0.00 0.00 905.97 100.00 Toolibin Lake 257 1,251.04 0.00 0.00 1,251.04 0.00 0.00 1,251.04 0.00 0.00 1,251.04 100.00 Yorkrakine Rock Pools 258 156.70 0.00 156.70 0.00 0.00 156.70 0.00 0.00 156.70 0.00 100.00 Coyrecup Lake 259 0.12 0.00 0.00 0.12 0.00 0.00 0.12 0.00 0.00 0.12 100.00 Dumbleyung Lake 259 5,591.42 0.00 92.73 5,498.69 0.00 92.73 5,498.69 0.00 74.89 5,516.54 100.00 Lake Grace 259 29,443.79 0.00 8.99 25,198.53 0.00 8.99 25,198.53 0.00 8.99 25,198.53 85.61 Yealering Lakes 259 1,059.44 0.00 0.88 1,058.56 0.00 0.88 1,058.56 0.00 0.88 1,058.56 100.00
92 EXTENT AND IMPACT OF DRYLAND SALINITY
APPENDIX 13. ALLOCATED RISK OF SHALLOW WATERTABLES FOR AGRICULTURAL LAND (HA) 2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High 211 0 165,639 11,929 0 165,639 11,929 0 165,639 11,929 212 0 196,712 0 0 196,712 0 0 9,344 187,368 213 20,881 4,769 212,779 20,881 4,769 212,779 20,881 4,769 212,779 221 138,481 24,844 0 138,481 24,844 0 138,481 24,844 0 222 0 0 125,802 0 0 125,802 0 0 125,802 22300 000 0000 224 0 9,763 0 0 9,763 0 0 0 9,763 225 83,598 89,042 0 83,598 89,042 0 76,006 96,634 0 226 0 21,780 32,641 0 21,780 32,641 0 0 54,421 23100 000 0000 23200 000 0000 23300 000 0000 241 0 233,922 26,411 0 228,766 31,567 0 0 260,333 242 102,262 389,604 0 102,262 329,289 60,315 77,196 313,836 100,834 243 0 39,157 314,228 0 0 353,385 0 0 353,385 244 20,326 138,066 0 20,326 138,066 0 20,326 138,066 0 245 0 562,634 65,140 0 381,203 246,571 0 23,813 603,961 246 105,999 566,680 0 105,999 559,570 7,110 105,999 559,570 7,110 247 0 0 16,640 0 0 16,640 0 0 16,640 251 39,291 1,867 0 31,848 9,310 0 0 39,291 1,867 252 33,387 10,863 22,372 33,387 10,863 22,372 0 33,387 33,235 253 0 614,201 73,928 0 536,947 151,182 0 52,073 636,056
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2000 2020 2050 Zone Low Moderate High Low Moderate High Low Moderate High 254 21,859 343,514 0 21,859 343,514 0 0 118,255 247,118 255 0 187,370 0 0 187,370 0 0 187,370 0 257 0 1,391,183 359,996 0 1,132,647 618,532 0 776,920 974,259 258 0 2,876,240 1,321,296 0 2,876,240 1,321,296 0 2,836,508 1,361,028 259 0 1,971,831 635,446 0 1,971,831 635,446 0 1,649,189 958,088 26100 000 0000 271 0 0 334,127 0 0 334,127 0 0 334,127 27200 000 0000 Total 566,084 9,839,681 3,552,735 558,641 9,218,165 4,181,694 438,889 7,029,508 6,490,103
94 EXTENT AND IMPACTS OF DRYLAND SALINITY
APPENDIX 14. INDICATIVE ESTIMATES OF THE COSTS OF SALINITY ON AND OFF-FARM IN WESTERN AUSTRALIA
By Allan Herbert, Economics Group, Agriculture Western Australia. June 2000 BACKGROUND
Theme 2 Project 1 of the National Land and Water Resource Audit (NLWRA) has two main outcomes for reporting: • The extent of dryland salinity • The impact of dryland salinity
Hydrologists Rod Short and Cecilia McConnell (both Agriculture Western Australia) supervised the major part of the project. Spatial distributions of areas at low, medium, and high risk of being affected by rising watertables were produced for the south western agricultural areas of the State for each of three time periods – years 2000, 2020 and 2050. Actual areas at risk were calculated for a series of hydrological datasets and applied to each of 29 zones. From this work, estimates of impact were supplied for the following: • Agricultural land – area affected • Rural towns – by name • Roads – four types by length affected • Railways – length affected • Vegetation – area affected • Streams – length affected • Water – risk to quality for rivers
This information was used to provide an “estimate of the broad economic implications”. Cost estimates were made of what a high risk category would mean for each of the topic areas with the medium risk category scaled off against it – generally half the impact. The attached papers (Sections A-E) describe the methodology used for each and the results obtained for the first five impact topics. No attempt was made to quantify streams or water quality in $ terms. CLARIFICATION
The analysis of broad economic implications was done with limited resources and consequently many assumptions have been made as outlined in the attached section notes. The exercise was seen as a quick ‘first pass’ look at the possible magnitude of the problem hence minimum consultation has occurred in checking many dependent variables. The process would be improved if more time was available to source appropriate material.
95 EXTENT AND IMPACTS OF DRYLAND SALINITY
It was moreover seen as a threshhold project – “Let’s have a look at possible methodologies and some rough calculations and perhaps revisit it later if necessary”. It is understood that all States are going through a similar process and there is a possibility of sorting through the methods used to determine a standard approach – and even some standard unit costs. This would then place all States on a similar footing in terms of quantifying the $ impacts of dryland salinity.
Given the uncertainty in many of the assumptions, and indeed in the broad scale of the base risk profile data, there seemed little point in doing elaborate sensitivity/range testing. WHAT IS THE QUESTION?
It was understood that the task was to quantify the costs of rising watertables and salinity. That is – “what are the range of costs likely to be incurred if watertables continue to rise at the assessed rate without intervention?” The numbers generated are seen to be the upper bounds of “costs saved” if some magical wand could be waved over the problem to make it go away. Hence all analysis concentrated on this perspective.
This is a different question to “what is the cost of amelioration measures relative to the benefits likely to be obtained?” Analysis of this question is a much more complicated process and would require response functions to adequately address it. But it is a more relevant approach. The costs of salinity are meaningless without some assessment of the costs of the strategies to combat it and the benefits obtained from those strategies – either in production terms, retrieving land or infrastructure which otherwise would be lost, or in avoiding future costs. COSTS OF SALINITY
Agricultural land An annual ‘operating profit’ was assigned to each hectare of farmed land. The values differed between zones but were assumed to be an average across all hectares within zones. High and medium risk land was scaled off against an unaffected land operating profit.
The year 2000, 2020, and 2050 predictions for salinity impacts were then used to calculate total operating profit for each zone. Year 2000 without salinity was used as a base case for comparison to calculate the additional costs of salinity in subsequent years in terms of ‘lost’ operating profit. • Current year The opportunity cost of lost operating profit in year 2000 due to watertables/salinity is estimated as $80M. That is, if all the currently affected land was still able to produce normal income, farmers would have an extra $80M operating profit available to spend elsewhere in year 2000. • After 20 years
96 EXTENT AND IMPACTS OF DRYLAND SALINITY
Up to year 2020, rising watertables/salinity will cause progressive losses in operating profit each year. The sum (present value, 7%) of these extra losses (i.e over and above the current impact) are estimated at around $19M. • After 50 years Up to year 2050, rising watertables/salinity will cause progressive losses in operating profit each year. The sum (present value, 7%) of these extra losses (i.e over and above the current impact) are estimated at around $120M. Rural towns A draft consultant’s report on the cost of salinity for the town of Merredin (high risk category) was used to scale off all other towns in zones with a high or medium risk – based on respective town populations. Changes in town risk profiles between year 2000, year 2020, and year 2050 allowed calculation of the extra costs over the 20 and 50 year periods. Medium risk towns were assumed to attract 25% of the costs (compared to high risk towns) – after scaling for population. • Current year The present value of costs for 60 affected towns under the year 2000 risk profile was estimated as near $68M. This is today’s value of the sum of all future expected costs of repair and maintenance over a 50 year period. • After 20 years The present value of costs for each of the years 2000 and 2020 risk profiles were converted to an annuity as an estimate of what each town would need to spend each year to combat rising watertables/salinity. The difference in annual cost flows provides an estimate of the extra costs with progression of the salinity problem. Over the first 20 year period, the total additional cost is $0.8M. • After 50 years The present value of costs for year 2050 risk profile was also converted to an annuity for comparison with the year 2000 profile. There is greatly increased impact on rural towns in the 20 to 50 year period and the total additional cost (i.e. over and above the current impact) is estimated at $22.5M. Roads An approximate annual cost of repair per kilometre was calculated for each type of road and risk profile. Comparison of normal maintenance cost with the increased cost gave an estimate of the extra costs due to watertables/salinity. Lengths of road affected at the three time periods was used to frame a series of cost flows over the 20 and 50 year periods of analysis. • Current year The annual cost in year 2000 of extra repairs due to watertables/salinity is estimated as $505M. That is, annual road expenditure is $505M more than it would be if no roads were affected. • After 20 years Rising watertables will increase the lengths of roads affected with a total extra repair cost of $91M. This is today’s value of the sum of all future extra costs of repair and maintenance over a 20 year period.
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• After 50 years Today’s value of the sum of all future extra costs of repair and maintenance over a 50 year period is estimated at around $288M.
Railways
An approximate annual cost of repair per kilometre was calculated for railways and for each risk profile. Comparison of normal maintenance cost with the increased cost gave an estimate of the extra costs due to watertables/salinity. Lengths of railway affected at the three time periods was used to frame a series of cost flows over the 20 and 50 year periods of analysis. • Current year The annual cost in year 2000 of extra repairs due to watertables/salinity is estimated as $11M. That is, annual railway expenditure is $11M more than it would be if railways were not affected. • After 20 years Rising watertables will increase the lengths of railway affected with a total extra repair cost of near $2M. This is today’s value of the sum of all future extra costs of repair and maintenance over a 20 year period. • After 50 years Today’s value of the sum of all future extra costs of repair and maintenance over a 50 year period is estimated at around $7M.
Vegetation
A ‘protection’ cost based on a pumping Strategy was allocated as a proxy value to a hectare of vegetation. While the capital costs were held constant, differential operating costs were applied for each risk profile. Conversion to an annuity provided an estimate of the annual cost of protection and allowed a series of cost flows to be constructed. The present values of these cost flows then provided a basis for estimating the $ impact of increasingly affected areas of vegetation.
The following results are based on 10% of the affected areas being protected. • Current year The annual cost of protection of 10% of the year 2000 affected areas is estimated as $63M. • After 20 years If 10% of the increased areas affected in year 2020 are protected, the annual cost is estimated as $64M. • After 50 years If 10% of the increased areas affected in year 2050 are protected, the annual cost is estimated as $78M. The total sum (present value, 7%) of the extra costs of protection over the 50 years is estimated as $15M.
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SUMMARY OF CURRENT ANNUAL COSTS DUE TO WATERTABLES/SALINITY
The above summaries and section documents provide the detail behind the ‘best bet’ values summarised below. The values shown in the table below are estimates of the additional costs incurred in year 2000 due to currently affected land/infrastructure.
Annual cost in year 2000 due to watertables/salinity Best bet Possible range Agricultural land – Opportunity cost of lost operating $80M $80—$261M profit Rural towns – Annuity of a 50 year discounted present $5M $2—$16M value Roads – Additional repair and maintenance costs $505M Not tested Railways – Additional repair and maintenance costs $11M Not tested Vegetation – Imputed cost of protection of 10% of $63M $63—626M affected areas
SUMMARY OF EXTRA COSTS OF WATERTABLES/SALINITY AFTER 20 AND 50 YEARS
The summaries above and the section documents provide the detail behind the ‘best bet’ values summarised below. In each case, the base case for comparison is the current (year 2000) affected area/infrastructure.
After 20 years (to 2020) After 50 years (to 2050) Best bet Possible range Best bet Possible range Agricultural land – Total $18.6M $19—84M $120.3M $120—351M present value of extra lost operating profit Rural towns – Total $0.8M $0.2—2.9M $22.5M $13—38M present value of extra repair costs Roads – Total present $90.8M Not tested $288.4M Not tested value of extra repair costs Railways – Total present $1.6M Not tested $6.6M Not tested value of extra repair costs Vegetation – Total present -$0.8M ($0.08M) – $14.6M $14.6—145.7M value of extra protection (10% of ($8.2M) (10% of costs affected affected vegetation) vegetation)
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