Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth

Water for a Healthy Country Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth Anthony Smith, Daniel Pollock and Don McFarlane

Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth Anthony Smith, Daniel Pollock and Don McFarlane

The Water for a Healthy Country National Research Flagship is a research partnership between CSIRO, state and federal governments, private and public industry and other research providers. The Flagship was established in 2003 as part of the CSIRO National Research Flagship Initiative. The work contained in this report is collaboration between CSIRO Land and Water, Water Corporation, and the Department of Environment Western Australia. Commonwealth of Australia 2005 All rights reserved. This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from the Commonwealth. Citation: Smith, A.; Pollock, D. and McFarlane, D. (2005), Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth, Client Report, CSIRO: Water for a Healthy Country National Research Flagship Canberra. DISCLAIMER You accept all risks and responsibility for losses, damages, costs and other consequences resulting directly or indirectly from using this report and any information or material available from it. To the maximum permitted by law, CSIRO excludes all liability to any person arising directly or indirectly from using this report and any information or material available from it. For further information contact: Ph: 02 6246 4565 Fax: 02 6246 4564 www.csiro.au Printed December 2005

Acknowledgements This project was funded jointly by the West Australian Water Corporation and CSIRO Land and Water and the Water for a Healthy Country Flagship. Datasets for the study were provided by Water Corporation (WC), Department of Environment (DoE), the Department for Planning and Infrastructure and the Department of Land Information. Special thanks are extended to the project Steering Group members: Olga Barron (CSIRO) Ron Colman (DoE) Phil Commander (DoE) Brad Fuller (DoE) Geoff Hughes (WC) Michael Loh (WC) Richard Silberstein (CSIRO) Bob Stokes (WC) Feedback on the work-in-progress was also obtained from Richard Lindsay (DoE), Cahit Yesertener (DoE) and Michael Martin (WC).

Executive Summary Introduction Installing more private garden bores in Perth is one way to ease the growing pressure on drinking water supplies. For this to happen, the cost of groundwater self supply must be affordable and there must be a secure and accessibility groundwater source that can be used without causing an unacceptable impact on existing users or on the environment. Future bore owners also want the current advantages of owning a bore the ability to water more than twice per week and being able to water larger garden areas due to the greater water pressures. Self supply by private bore-owners has increased since sprinkler bans were imposed in 1978-79. By 2001-02 there were an estimated 135,000 garden bores extracting in excess of 100 GL per annum from the Superficial Aquifer. Since February 2003, bore installation has been encouraged by the government offering a rebate to people in areas where bores are considered suitable according to the Perth Groundwater Atlas. Currently about 5,000 subsidies are being taken up each year. The interest in this study was to identify areas that have apparent low levels of self supply but with reasonable prospects for increasing self supply. Suburbs with high scheme water use were particularly of interest. It was also aimed to identify areas where continued installation of garden bores may not be viable if used in their current manner. The report presents a preliminary assessment of opportunity for additional self supply of groundwater from the Superficial Aquifer based on an analysis of ten-year trends in groundwater storage from 1995 to 2004. Results of this analysis are combined with information about existing groundwater and scheme water consumptions, and other relevant data themes such as superficial geology, depth to groundwater, seawater intrusion and groundwater isopotentials. The project study area encompassed from the Darling Scarp to the coastline and from Yanchep Beach to Secret Harbour south of Rockingham. Opportunity for additional self supply of groundwater was classified at the spatial scale of Water Corporation s billing suburbs, which closely match the names and extents of their corresponding suburbs within metropolitan Perth. Method and Results A total of 543 monitoring bores within the study area had water level data that were suitable for fitting meaningful linear regression models. After data treatments to minimise effects from sampling bias and data outliers, fitted slopes from these models were accepted as reasonable estimates of ten-year trends in freshwater thickness in the Superficial Aquifer. Freshwater thickness was considered to be a suitable surrogate for aquifer storage and was adjusted for seawater intrusion in coastal and estuarine areas. The results indicated that the ten-year trend in mean freshwater thickness beneath approximately 14% of the study area was stable; beneath approximately 41% was falling; and beneath approximately 45% could not be determined due to a lack of water level data. Areas with a rising trend were less than 1% of the study area. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth i

Declining trends in aquifer storage were most evident in the northern coastal strip (especially near the Whitfords, Quinns and Neerabup borefields); central part of Gnangara Mound and in the region of the Gwelup and West Mirrabooka borefields. Storage appears to have been mostly stable around the East Mirrabooka borefield and in the Swan-Canning Estuary environs, including the southern-most part of Gnangara Mound, Cloverdale Mound and northern Jandakot Mound. The pattern of storage change in the central part of Jandakot Mound was less consistent and exhibited both falling and stable trends. Storage in the Serpentine Area has been mostly stable but there is a likelihood of seawater intrusion as a result of storage decline in the Safety Bay Mound and the Stakehill Mound. All billing suburbs with available data were classified as having high, moderate or low opportunities for additional self supply of groundwater. Areas with stable trends in aquifer storage, low density of domestic garden bores and predominantly sandy sediments were classified as having a high opportunity. Areas with either falling trends in aquifer storage, high densities of domestic garden bores, predominantly clay and silt sediments, or limestone with large depth to groundwater were classified as having a low opportunity. Areas with intermediate combinations of stable trends in aquifer storage, low to moderate densities of domestic garden bores and various proportions of clay, silt or limestone were classified as having a moderate opportunity. A high opportunity was evident in the northern part of Jandakot Mound, a small area on the southwest margin of Gnangara Mound, and in a two billing suburbs in the western part of the Cloverdale Area. This accounted for approximately 8% of the total area of billing suburbs. Low opportunities were apparent along the coastal margin of the study area due to a combination of declining trends in aquifer storage, the presence of limestone with large depth to groundwater, and the inherent risk of seawater intrusion. A mixture of low, moderate and unknown opportunities was evident within the central part of the study area around the Swan-Canning Estuary environs. The spatial pattern of opportunity in this area was mostly a reflection of the existing densities of garden bores, with those areas with a shallow sandy aquifer having high densities already. The opportunity for additional bores could not be determined in the eastern part of the Cloverdale Area and near the Canning River (east) due to the absence of water level data in these areas. Overall, a high relative opportunity for additional self supply was identified under approximately 8% of Water Corporation s billing suburbs, a moderate opportunity under approximately 30%, a low opportunity under approximately 51%, and an unknown opportunity under approximately 10% due to insufficient water level data. Conclusions The opportunity for additional self supply of groundwater from the Superficial Aquifer is highly variable across metropolitan Perth. Within the area of the Water Corporation s billing suburbs (51% of the above study area), the freshwater thickness beneath approximately 17% of the billing suburb area is stable; beneath approximately 35% is falling; and beneath approximately 48% cannot be determined due to a lack of water level data. A high relative opportunity for additional self supply was identified under approximately 8% of Water Corporation s billing suburbs, a moderate opportunity under approximately 30% and a low opportunity under approximately 51%. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth ii

A significant proportion of billing suburbs have inadequate water level records to assess ten-year trends in aquifer storage. Some of these suburbs have a low opportunity for additional self supply because of other limiting factors, such as the likelihood of poor bore yields. Overall, the opportunity for additional self supply of groundwater was not assessed in 36 out of 240 billing suburbs (equivalent to 10% by area) due to a lack of monitoring bores and water level data in these areas. Assuming a continuation of the climate of the past ten years, it is expected that additional self supply of groundwater from the Superficial Aquifer will further reduce aquifer storage under parts of Perth. This will increase the general risks of seawater intrusion, loss of urban wetlands and the need for some existing bores to be deepened. Areas with high existing bore ownership (indicating more reliance on self supply) and falling aquifer storage could place future stresses on scheme water supplies if the groundwater supplies from the Superficial Aquifer in these areas were jeopardised. This could occur due to seawater intrusion or groundwater contamination, the need to lower garden bore intake screens in response to falling levels, or the need to protect important wetlands or groundwater dependent ecosystems. Deep superficial bores and bores located closest to the coast may be at risk from seawater intrusion if superficial groundwater levels continue to fall in these areas (e.g., Rockingham-Warnbro area and the northern coastal strip between Whitfords and Yanchep). The results obtained in this study are based on several uncomplicated assumptions that provide only a preliminary assessment of the opportunity for additional self supply. The presented classification of data into Low, Moderate and High Opportunity categories neglects potential influences of spatial variability within billing suburbs; differences in housing density and building type; groundwater aesthetic quality; potential impacts of additional bores on groundwater dependent ecosystems; risks from groundwater contamination; and regulatory and social factors that influence groundwater use. The spatial pattern of ten-year change in aquifer storage is poorly correlated to the billing suburb boundaries, which makes the task of objectively overlaying the water level data with other spatial datasets (that are compiled based on suburb areas) difficult. A better method could be developed using more-advanced geostatistical methods than utilised in this study. Judgements about the environmental impact, significance and acceptability of changes in aquifer storage are subjective and should be made based on a framework of agreed values. A rigorous examination of the significance of groundwater level trends and their management implications was beyond the scope of this study; however, it appears that the information required to take this next step may be lacking. Recommendations Suburbs that are identified as having high opportunity for additional self supply should be further investigated at the local scale to verify the results of this study, and to determine the factors that control existing groundwater use in these areas. Assuming that current levels of self supply are expressions of current demand, identifying these controls would provide information for designing incentives to increase demand. Local scale investigations should also be conducted in areas with falling groundwater levels to determine whether these falls are likely to pose a significant risk to groundwater dependent ecosystems, licensed and unlicensed abstraction or seawater intrusion. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth iii

The numbers of garden bores within in each Perth suburb need to be re-estimated. In particular, the apparent discrepancy between 2003 and 1995 estimates of garden bores in the Jandakot and Rockingham-Warnbro areas needs to be resolved. If possible, garden bores locations should be compiled as a point dataset so that the distribution of garden bores can be determined independently of the suburb boundaries. A dedicated groundwater observation network should be established to monitor seawater intrusion in susceptible coastal areas, including monitoring the depth of the seawaterfreshwater interface at a number of strategic locations. Particular areas that should be targeted for monitoring are the Rockingham-Warnbro area where there is increasing groundwater demand due to new housing developments and easy access to groundwater; and in the northern coastal strip between Whitfords and Yanchep where groundwater extraction for public supply has increased significantly during the past five years. Large spatial gaps in the Superficial Aquifer monitoring network prevent the assessment of groundwater storage levels beneath approximately half of metropolitan Perth. Lindsay (2004) recommended the drilling of an additional twenty-eight monitoring bores into the Superficial Aquifer between Coogee-Armadale and Marmion-West Swan. This assessment of monitoring requirements should be revisited and extended to include areas further north and south (e.g., from Secret Harbour to Yanchep). The monitoring should target areas with existing high densities of garden bores to assess the impacts on aquifer storage in these areas. A comprehensive overlay analysis using GIS tools is recommended to achieve a more objective classification and assessment of opportunity for additional self supply from the Superficial Aquifer. This requires the development of a broadly-agreed set of criteria for classifying groundwater supply opportunities and risks based upon multiple factors (e.g., groundwater condition, access, cost, availability, demand, etc). An adequate set of criteria does not exist at present. The criteria develop in this study are preliminary and require development and refinement through broader input from State Government, private stakeholders and research and development organisations. An explicit set of values-based criteria against which to assess the significance of groundwater level change beneath different areas of metropolitan Perth also is needed. For example, the impact of a one-metre fall in the watertable may be judged as either acceptable or unacceptable dependent upon the local context and associated values. It has not been possible in this study to classify and map the hazard and acceptability of change in aquifer storage because the criteria on which to base an assessment are lacking. The geodatabase and datasets produced for this project are useful resources that should be updated regularly to allow storage trends in the Superficial Aquifer to be analysed on an ongoing basis. The methodology developed for this study is semi-automated and suitable for regularly producing updated maps of freshwater thickness and trend. It is recommended that a custodian for the database be identified, and that a protocol be put in place for producing annual assessments of the status and trend in superficial groundwater levels and aquifer storage beneath metropolitan Perth. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth iv

Table of Contents Executive Summary... i 1. Introduction... 1 1.1. Objectives... 2 1.2. Study Area... 2 1.3. Period Chosen for Analysing Water Level Trends... 2 2. Project Geodatabase... 4 3. Groundwater Monitoring Bores... 4 4. Methods... 4 4.1. Linear Regression of Water Level Trends... 4 4.2. Seawater Intrusion Effects... 5 5. Results... 6 5.1. Ten-year Trends in Groundwater Levels (1995 to 2004)... 6 5.1.1. Comparison with Previous Results... 7 5.2. Ten-year Trends in Freshwater Thickness (1995 to 2004)... 8 6. Analysis and Discussion... 13 6.1. Groundwater Availability... 14 6.2. Spatially Interpolated Trend in Aquifer Storage... 14 6.3. Opportunity for Additional Self Supply... 18 6.3.1. Classification... 18 6.3.2. Discussion... 19 7. Conclusions... 27 8. Recommendations... 28 APPENDIX A : Description of the Superficial Aquifer Geodatabase...A-1 APPENDIX B : Summary of Monitoring Bores...B-1 APPENDIX C : Method for Fitting Linear Trends...C-1 C.1. Removal of Outliers...C-1 C.2. Aggregation of Data to Mean Annual Water Levels...C-3 C.3. Linear Regression...C-3 C.4. Statistical Tests...C-4 APPENDIX D : Methodology for Estimating Seawater Intrusion Effects...D-1 D.1. Change in Mean Freshwater Thickness...D-1 D.2. Regional Mapping of the Seawater-Freshwater interface...d-2 References... 5 Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth v

Tables Table 6-1: Summary by study area of interpolated trend in freshwater thickness (P-value < 0.05) masked at two-kilometre radii from each data value...15 Table 6-2: Summary by billing-suburb of interpolated trend in freshwater thickness (P-value < 0.05) masked at two-kilometre radii from each data value...15 Table 6-3: Relative opportunity for additional self supply...19 Table 6-4: Proportion of billing suburbs with high, moderate and low opportunities for additional self supply of groundwater...20 Appendix Tables Appendix Table A-1: Geodatabase data dictionary... A-2 Appendix Table C-1: Slopes with P-value < 0.025; linear regression of 1995-2004 water levels...c-5 Figures Figure 1-1: Study area...3 Figure 4-1: Schematic of seawater intrusion effects on freshwater thickness...5 Figure 5-1: Trends in mean groundwater levels for the period 1995 to 2004; P-value < 0.025...9 Figure 5-2: Trends in mean groundwater levels for the period 1995 to 2004; P-value < 0.05...10 Figure 5-3: Trends in mean groundwater levels for the period 1995 to 2004; P-value < 0.1...11 Figure 5-4: Trends in mean freshwater thickness for the period 1995 to 2004 overlayed on the hydrostatic approximation of seawater intrusion; P-value < 0.05...12 Figure 6-1: Opportunity for additional self supply of groundwater...13 Figure 6-2: Trend in Superficial Aquifer storage overlayed on the estimated extent of seawater intrusion...16 Figure 6-3: Interpolated (TIN) trend in freshwater thickness (P-value < 0.05) with the result masked at two-kilometre radii from each data value...17 Figure 6-4: Trend in Superficial Aquifer storage overlayed on garden bore density 2003-04...21 Figure 6-5: Trend in Superficial Aquifer storage overlayed on per capita scheme water consumption 2003-04...22 Figure 6-6: Trend in Superficial Aquifer storage overlayed on superficial geology...23 Figure 6-7: Trend in Superficial Aquifer storage overlayed on depth to groundwater (May 2003)...24 Figure 6-8: Trend in Superficial Aquifer storage overlayed on groundwater isopotentials (May 2003)...25 Figure 6-9: Relative opportunity for additional self supply of groundwater...26 Appendix Figures Appendix Figure C-1: Examples of verified outliers: water level data (symbols); fitted 4 th order polynomial (blue line); outlier bounds at three standard deviations from the fitted polynomial (green lines)...c-2 Appendix Figure C-2: Example linear regression models: water level data with outliers removed (black symbol); aggregated mean annual water levels (blue symbols); linear regression (blue line)...c-3 Appendix Figure C-3: Bubble plot from linear regression of 1995-2004 water level trends...c-5 Appendix Figure C-4: Histogram of slope with P-value < 0.025 from linear regression of 1995-2004 water level trends...c-6 Appendix Figure C-5: Histogram of slope (all sites) from linear regression of 1995-2004 water level trends...c-7 Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth vi

Plates PLATE 1: Topography...I PLATE 2: Superficial Aquifer flow areas...ii PLATE 3: Water Corporation production bores (not all of these bores are commissioned)...iii PLATE 4: Main drain network and surface catchments... IV Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth vii

1. Introduction Installing more private garden bores in Perth is one way to ease the growing pressure on drinking water supplies. With about half of all scheme water currently being used outside the house, installing a garden bore can greatly reduce household consumption of scheme water and utilise water that is fit-for-purpose rather than high quality drinking water. Currently, about 5,000 subsidies ($300 rebate) for garden bore installations are being taken up each year. This is on top of about 135,000 bores that were already installed in Perth in 2001-02 (Kern, unpublished). In 2005/06 there may therefore be between 150,000 and 155,000 bores in metropolitan Perth. Garden bores are estimated to water almost a third of all gardens (some bores are shared between neighbours) and extract between 100 and 120 GL per annum from the Superficial Aquifer, with an average use of approximately 800 KL per annum per bore. Some of the water extracted by garden bores is recycled stormwater derived from roof and road runoff that is directed into the Superficial Aquifer via infiltration basins and domestic soak wells. In drained areas with high watertables, bores may be using water that would otherwise be drained into the Swan-Canning Estuary or ocean, contributing additional nutrients to these systems. Nevertheless, a bore is not suitable for everyone and the capacity of the Superficial Aquifer to accommodate more bores may be insufficient in some areas. The potential for self supply of groundwater within metropolitan Perth differs between suburbs because the feasibility and cost of installing garden bores varies. The cost of groundwater self supply must be affordable compared to the cost of scheme water supply to make groundwater an attractive alternative for garden use; though some bore-owners are prepared to pay the extra cost for a more reliable and flexible water supply 1. At the same time, there must be a secure and accessibility groundwater source that can be allocated to self supply without unacceptable impact on existing uses or the environment. The Superficial Aquifer allows Perth to have a much greener environment and cheaply and effectively recycles stormwater. If supplies from this aquifer were to fail in some areas due to seawater intrusion, contamination or low groundwater levels, increased demand would fall on the scheme water supplies. Even if the additional scheme water were available, the size of supply pipes may be inadequate to accommodate the increased demands. Thus, monitoring the status and trend of groundwater storage in the Superficial Aquifer is important for both bore owners and non-owners. Offering subsidies for people to install private bores is the most cost effective method for the government to balance scheme supplies with demand (McFarlane, 2005). Nevertheless, the savings will only be realised if use of the Superficial Aquifer is sustainable in the long term. This report presents a preliminary assessment of the opportunity for additional self supply from the Superficial Aquifer beneath metropolitan Perth. Potential groundwater sources were identified based on mapping of contemporary trends in aquifer storage. Current levels of groundwater self supply (existing demand) were estimated based on domestic garden bore densities within Perth suburbs. Per capita consumption of scheme water was also examined to identify areas with low groundwater use and high scheme water use. The study did not consider water quality, aesthetic characteristics of groundwater, regulatory or social factors that influence groundwater use. 1 Under the current water restrictions, bore owners can use their bore between 6 pm and 9 am on any day of the week compared with scheme water users who can only water on two specified days of the week. The pressure that comes from bores also allows larger areas to be watered at any one time compared with the pressure supplied from scheme supplies. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 1

1.1. Objectives Specific objectives of the study were to: Build a Superficial Aquifer geodatabase as a tool for analysing and understanding changes in aquifer storage during recent years; Develop and apply a simple and robust methodology for estimating trends in aquifer water levels and storage, taking into account seawater intrusion effects in coastal areas; Classify and map trends in aquifer storage and their statistical significance; Identify and map groundwater availability based on trends in aquifer storage; Assess the opportunity for additional self supply; and Identify areas where additional bores may cause a problem, or where existing use of groundwater may need to be more efficient to maintain the resource under a drying climate. 1.2. Study Area The project study area (Figure 1-1) extends from the Darling Scarp to the coastline and from Yanchep Beach to Secret Harbour south of Rockingham. It incorporates the groundwater flow areas: Gnangara Mound (South), Swan Helena Area, Cloverdale Area, Jandakot Mound, Armadale Area, Byford Area, Safety Bay Mound, Stakehill Mound and Serpentine Area (PLATE 2). For the purposes of this report, the study area is referred to as metropolitan Perth. 1.3. Period Chosen for Analysing Water Level Trends Groundwater levels in the Superficial Aquifer beneath metropolitan Perth have been measured in various monitoring bores since the early 1920s; however, the main network of superficial monitoring bores was not established until the early 1970s (Lindsay, 2004). Using the available long-term records, Lindsay (2004) and Yesertener (2005) examined twenty to thirty-year trends in superficial groundwater levels across metropolitan Perth with a focus on the Gnangara Mound. The number of groundwater level records and monitoring locations that could be analysed in these studies was limited, to some extent, by the lack of monitoring bores with continuous, long-term measurements. Over the years, groundwater level trends have varied upward and downward. The aim in this study was to establish a contemporary picture of superficial water level trends and current storage in the Superficial Aquifer across as many locations as possible; with the expectation that spatial patterns in groundwater level change would be apparent. The tenyear period from 1995 to 2004 was chosen for the following reasons: Ten years is a practical period for contemplating recent change and current status; Perth s rainfall has decreased significantly since the early 1970s and again during the past eight to ten years; Water Corporation has adopted the climate and stream flow regime of the past eight years (1997 to 2004) as a basis for long-term (2005-2050) water source development planning. Groundwater level trends during the past ten years are relevant to this planning outlook; and There were enough monitoring bore locations with ten-year records to provide a reasonable spatial impression of water level change across the monitored parts of the Superficial Aquifer. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 2

Figure 1-1: Study area Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 3

2. Project Geodatabase All data obtained for the study were incorporated into a project geodatabase that is accessible using Microsoft Access and ArcGIS software applications. The geodatabase is described briefly in APPENDIX A and a listing of all datasets stored in the geodatabase is presented in Appendix Table A-1. Results from all analyses performed in the study were also stored in the geodatabase. 3. Groundwater Monitoring Bores A summary of the Superficial Aquifer groundwater monitoring bores used in this study is presented in APPENDIX B. All monitoring bore sites and associated groundwater level data were acquired from the Department of Environment s WIN and GRAMPS databases (APPENDIX A). 4. Methods 4.1. Linear Regression of Water Level Trends Ten-year mean water level trends in the Superficial Aquifer monitoring bores were estimated by the following procedure: Outlier analysis to identify, verify and remove outlier water level records; Data aggregation to remove seasonal effects and sampling bias; Linear regression of mean annual water levels to estimate mean water level trends; and Statistical analyses of the significance of the linear regression models. The methodologies used to conduct these analyses are introduced below and described in detail in APPENDIX C. Data outliers can have an unwanted effect on simple linear regression models, particularly when the regression is based on a limited number of data. These data are visually obvious and can be identified using statistical tests, such as the z-score test applied in this study. It was convenient to use a statistical approach that could be computer coded to process the large amount of available water level data. Visual checks were performed to verify manually all potential outliers identified from the z-score test. Example hydrographs depicting verified outliers are presented in Appendix Figure C-1. Seasonal effects and sampling bias also have unwanted consequences for linear regression models. Sampling bias was common in the data and occurred at various time scales; for example, when many water level measurements were taken during particular days, months or years but few measurements were taken during others days, months or years. To minimise this bias, water level data from each groundwater monitoring bore were sequentially aggregated and averaged at daily, monthly, half-yearly (semester) and yearly time periods. The final annual-aggregated data were considered to provide reasonable estimates of the mean annual water levels for each year within the period of interest. Mean water level trends in groundwater monitoring bores were estimated by simple linear regression of the mean annual water levels for the time period of interest. The fitted slopes of the linear regression models were accepted as reasonable estimates of mean water level trends in the monitoring bores. Example hydrographs with fitted linear regression models are presented in Appendix Figure C-2. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 4

Mapping only the slopes from the regression analysis can potentially give a false impression because the statistical significance of each result is not obvious. The R 2, adjusted-r 2 and F-test statistic from the regression analyses provided information on how well the linear models fitted the data and whether or not each fit was statistically significant. These results were stored in the project geodatabase for further analysis and to display spatial patterns and associations with other spatial data sets. 4.2. Seawater Intrusion Effects In coastal and estuarine areas where fresh groundwater in the Superficial Aquifer is underlain by a wedge of seawater, changes in the elevation of the groundwater level are accompanied by proportionally larger changes in elevation of the seawater-freshwater interface. In these areas, mapping of changes in watertable elevation may not be a good proxy for changes in aquifer storage because the total thickness of freshwater in the aquifer is reduced or increased from both above and below. This concept is depicted schematically in Figure 4-1 for the case of a falling watertable. Downward movement of the watertable is accompanied by upward movement of the seawater-freshwater interface and a reduction in the freshwater thickness. Δh Sea Level Monitoring Well Hydrograph t 0 t 1 Decline in freshwater thickness due to fall of the phreatic surface Δh { Monitoring Well Zh( t 0 ) Zh( t 1 ) Ground Surface Water Table Z S Seawater ρ S Freshwater ρ f Seawater - freshwater interface Δy { Zy( t1) Zb Zy( t 0 ) Base of aquifer Decline in freshwater thickness due to rise of the seawater-freshwater interface Figure 4-1: Schematic of seawater intrusion effects on freshwater thickness In this study, a simple hydrostatic relation was used to convert estimated change in the mean annual groundwater level (obtained from linear regression) to the estimated change in the mean freshwater thickness at each monitoring bore location. The applied method is described in APPENDIX D. The same methodology was applied to map the theoretical inland extent of seawater intrusion and the thickness of the coastal seawater wedge across all of the coastal and estuarine parts of the study area. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 5

Hydrostatic approximations of seawater intrusion typically over-estimate the inland extent of the seawater-freshwater interface position because they neglect hydrodynamic dispersion caused by fluid motion. Dispersive mixing of freshwater and seawater in the aquifer weakens the density gradients that cause seawater to intrude. However, calculation of the seawaterfreshwater interface position from hydrostatic considerations is mathematically simple and provides a reasonable and robust estimation of seawater intrusion at the regional scale. Assuming typical densities for fresh groundwater and seawater, a one-unit change of the inshore watertable elevation would be accompanied by an approximate 40-unit change of the seawater-freshwater interface elevation based on hydrostatic principles. For example, a watertable decline of 0.1 meters would correspond to a potential rise of the seawaterfreshwater interface of approximately 4 metres, and a potential decrease in total freshwater thickness of 4.1 metres. This is a potential change because movement of the seawaterfreshwater interface may be constrained by the base of the aquifer (see Figure 4-1). Similarly, a watertable rise of 0.1 meters would correspond to a potential increase in total freshwater thickness of 4.1 metres. The 1:40 approximation is true for a static system but if there is a hydraulic gradient discharging groundwater into the sea then the interface will be displaced seawards. 5. Results 5.1. Ten-year Trends in Groundwater Levels (1995 to 2004) A total of 543 monitoring bores within the study area had water level data that was considered suitable for fitting meaningful linear regression models (APPENDIX C). Figure 5-1 to Figure 5-3 display the estimated trends in mean superficial groundwater levels from 1995 to 2004. These results are produced from the linear regression analyses and are displayed for three different significance levels; P-value < 0.025, P-value < 0.05 and P-value < 0.1. On each map, monitoring bore locations with linear regression models that are statistically insignificant for the particular P-value criterion are not shown. At these locations, the fitted linear models were not significantly better than linear models with zero slopes. This may indicate that there is either negligible trend in mean annual water level (i.e., mean annual water level has been more or less constant); the data is curvilinear; or the data are too variable for a trend to be significantly detected. Monitoring bore sites with statistically significant slopes are plotted using colour symbols that are sized to reflect the magnitude of the estimated water level trend: Blue symbols rising Green symbols falling at less than 5 cm/yr Orange symbols falling at between 5 and 10 cm/yr Red Symbols falling at greater than 10 cm/yr A total of 314 (58%) of monitoring bore sites had P-values less than 0.025. As this criterion was relaxed from 0.025 to 0.05 to 0.1, more monitoring sites were accepted as having statistically significant trends. These additional sites generally had small slopes, so that the number of green and orange symbols was increased slightly. Irrespective of the choice of P- value criterion, all three maps provide a consistent spatial impression of mean water level trends across the study area. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 6

The mapping revealed that the Gnangara Mound (PLATE 2), northern coastal strip and central part of the Jandakot Mound were the best represented areas with respect to 1995-2004 water level data. The Serpentine Area had only a moderate density of monitoring bores with hydrographs that were suitable for ten-year trend analysis. The Safety Bay Mound and Stakehill Mound were poorly represented. Relatively few monitoring sites were located within the Swan Helena Area, Armadale Area and Byford Area. Monitoring locations were also relatively sparse within the river and coastal environs of Jandakot Mound. Mostly falling trends are evident in the northern coastal strip and central part of Gnangara Mound. The thirty-year decline in aquifer storage in the north and central parts of Gnangara Mound has been attributed to decreased rainfall, impacts of pine plantations and groundwater extraction for public and private water supply (Yesertener, 2005; DoE, 2005). Annual public extraction of groundwater from the Superficial Aquifer has decreased by about 15 GL since 1995-96. Despite the overall decrease, pumping from the northern coastal strip has increased particularly during the last five years. Pumping from the Wanneroo borefield (PLATE 3) decreased from 12.8 GL in 1995 to 8.6 GL in 2004. Annual extraction from the Pinjar borefield has been more variable, changing from 4.5 GL in 1995 to 8.0 GL in 1999 to 2.2 GL in 2004. Aquifer storage in the northern coastal strip has reduced since around 2000 in response to the start-up of the Whitfords and Quinns borefields. Pumping from the Quinns scheme commenced at 4.4 GL in 1999 and increased to 12.7 GL in 2004. Similarly, pumping from the Whitfords borefield commenced at 0.6 GL in 2000 and increased to 5.4 GL in 2004. A decline in aquifer storage is evident around the Gwelup and West Mirrabooka borefields over the past ten years. The Gwelup borefield has been pumped at between 3.3 and 7.5 GL/yr (mean 5 GL/yr) since 1975 with only moderate variations in pumping during the past ten years; from 4.1 GL in 1995 to 6.7 GL in 2004. This suggests that recent storage decline in this area is probably in response to the start-up of the West Mirrabooka scheme in around 2000. Pumping from West Mirrabooka was balanced by reduced pumping from East Mirrabooka, such that total pumping from the Mirrabooka scheme has been relatively steady at around 9 to 15 GL/yr (mean 12.2 GL/yr) since 1987. Relatively stable ten-year water level trends around the East Mirrabooka scheme may be partly attributable to this re-distribution of pumping from the east to the west. Groundwater levels have also been relatively stable in the area of Gnangara Mound between the Gwelup, Whitfords and Wanneroo borefields, east of Lake Joondalup. Groundwater levels in the Swan-Canning Estuary environs appear to have been fairly stable during the past ten years; including the southern-most part of Gnangara Mound, Cloverdale Mound and northern part of Jandakot Mound. There have been no reports of significant seawater intrusion (apart from the Belmont Racecourse) so falls have not been offset by saline intrusions. The pattern of groundwater level change in the central part of Jandakot Mound is less consistent and exhibits both stable and falling trends. Pumping from the Jandakot scheme has decreased moderately during the last five years from a mean of 6.5 GL/yr during 1995-1999 to 4.8 GL/yr during 2000-2004. Storage decline is evident within the Thompsons Lake Nature Reserve and a larger zone to the southeast of this area. Groundwater storage in the Serpentine Area has been mostly stable but there is evidence of storage decline and inferred seawater intrusion in the Safety Bay Mound and the Stakehill Mound; noting that water level data is sparse in both of these areas. 5.1.1. Comparison with Previous Results Lindsay (2004) determined thirty-year (medium-term) and ten-year (recent) changes in Superficial Aquifer groundwater levels in selected monitoring bores within metropolitan Perth. Results from the present study were checked against this previous work according to the following broad classes: watertable change was greater than +5 cm/yr (rise), watertable change was less than -5 cm/yr (fall), watertable change was between ±5 cm/yr (stable). Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 7

Ten-year water level trends for the period 1993 to 2003 were estimated by Lindsay (2004) for thirty-five monitoring bores used in the present study. Thirty-two bores (91%) had consistent ten-year water level trends in both studies according to the above criteria and three bores had different ten-year trends. The different methods employed in each study probably account for these discrepancies. Overall, there is good agreement between both studies. 5.2. Ten-year Trends in Freshwater Thickness (1995 to 2004) Figure 5-4 depicts trends in the mean freshwater thickness in the Superficial Aquifer between 1995 and 2004. Also shown is the estimated theoretical thickness of the coastal seawater wedge calculated from hydrostatic principles. Trends in freshwater thickness at monitoring sites beyond the extent of theoretical seawater intrusion are identical to the trends in water level depicted in Figure 5-2. At the other monitoring sites, trends in freshwater thickness are considerably larger than trends in water level due to theoretical movement of the seawater wedge at the base of the aquifer. Potential changes in freshwater thickness caused by seawater intrusion are most noticeable in the northern coastal strip and south of Point Peron. In the latter case, the base of the Rockingham Sand was taken as the base of the Superficial Aquifer (APPENDIX D). The large thickness of the seawater wedge in this area reflects the large thickness of unconfined sediments and is accompanied by larger thickness of freshwater. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 8

Figure 5-1: Trends in mean groundwater levels for the period 1995 to 2004; P-value < 0.025 Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 9

Figure 5-2: Trends in mean groundwater levels for the period 1995 to 2004; P-value < 0.05 Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 10

Figure 5-3: Trends in mean groundwater levels for the period 1995 to 2004; P-value < 0.1 Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 11

Figure 5-4: Trends in mean freshwater thickness for the period 1995 to 2004 overlayed on the hydrostatic approximation of seawater intrusion; P-value < 0.05 Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 12

6. Analysis and Discussion The potential to reduce drinking water use on gardens by encouraging additional self supply from the Superficial Aquifer depends on numerous factors. The principal controls considered in this study were (a) the availability of groundwater, and (b) the proportion of garden water being supplied by scheme water. This concept is illustrated schematically in Figure 6-1. Assuming the existence of an aquifer with natural replenishment, the potential for extracting additional groundwater from the aquifer depends on bore yield, groundwater quality and the state of aquifer storage. The difference between groundwater replenishment, as affected by climate and land use, and groundwater discharge, as affected by pumping, evaporation and drainage, determines the rate of change in aquifer storage. The amount of groundwater used on gardens will depend on the relative economies of self supply and scheme water supply, as well as other factors as mentioned previously. The interest in this study was to identify areas with apparent high scheme water use and low levels of self supply, as reflected by a low density of domestic garden bores, but with reasonable prospect for increasing the level of self supply. It was assumed that existing self supply of groundwater is an expression of existing demand and, therefore, to increase the level of self supply would require the creation of new demand (e.g., through financial incentive, public education, water restrictions, etc.). Conversely, the study was also able to identify areas which are currently being used for selfsupply but which may experience problems in future due to falling groundwater levels or seawater intrusion. Land Use/Change Climate Pumping & Drainage Cost of Groundwater Supply Depth to groundwater Geology Cost of Scheme Water Supply Public Awareness Bore yield Groundwater Quality Trend in Aquifer Storage Total Water Use on Gardens Existing Self Supply of Groundwater (existing demand) No. of garden bores Secure Groundwater Source Proportion of Garden Water Supplied by Scheme Water Opportunity for Additional Self Supply ( un-assessed impact ) Regulation Figure 6-1: Opportunity for additional self supply of groundwater Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 13

6.1. Groundwater Availability Three simple categories of groundwater availability were defined based on the current state of aquifer storage and the likely effect of additional groundwater withdrawal: Rising groundwater levels - if the groundwater level is rising because recharge exceeds discharge (R > D) then the excess recharge could be extracted from the aquifer to stabilise the watertable; Stable groundwater levels - if the groundwater level is relatively stable because recharge and discharge are approximately balanced (R = D) then extracting additional groundwater will reduce aquifer storage and cause water level decline unless the extraction is offset by other factors (e.g., reduced discharge to drains, improved water use efficiency by bore users, increased room in the aquifer to accept seasonal recharge); Falling groundwater levels - if the groundwater level is already falling because discharge exceeds recharge (R < D) then extracting additional groundwater will further reduce aquifer storage and enhance water level decline. Deciding which of these situations would be acceptable, and under what circumstances, involves subjective judgements concerning equitable use and environmental impact. Figure 6-2 presents a map of groundwater availability, depicting the above categories determined for each monitoring bore location and overlayed on the theoretical seawaterfreshwater interface. All monitoring sites with mean freshwater thickness trends between ±5 cm/yr were considered to have relatively stable water levels and were classified as Stable. A P-value criterion was not used for this category, which was equivalent to assuming that all small slopes indicated negligible trends. All sites with mean freshwater thickness trends greater than 5 cm/year (rising more than 0.5 metres in ten years) and P-value less than 0.05 (significant) were classified as Rising. The remaining sites with ten-year freshwater thickness trends less than -5 cm/year (falling more than 0.5 metres in ten years) and P-value less than 0.05 were classified as Falling. On the map: blue symbols indicate Rising (R > D); green symbols indicate Stable (R D); red symbols indicate Falling (R < D); and yellow symbols indicate statistically insignificant slope (P-value > 0.05). Very few sites fell into the Rising category, which is a reflection that groundwater levels have been either stable or falling throughout the study area during the past ten years. The majority of sites fell into the categories of Stable or Falling, with apparent large-scale spatial patterns. Under the current climate, the implication is that additional self supply of groundwater would be likely to reduce aquifer storage overall, unless other factors were changed (e.g., increased recharge of stormwater, increased water use efficiency, reduced public groundwater extraction). 6.2. Spatially Interpolated Trend in Aquifer Storage Figure 6-3 shows the interpolated ten-year trend in mean freshwater thickness, as produced using a Triangulated Irregular Network (TIN). This method assumes a simple linear spatial distribution between data values. The interpolated freshwater thickness is masked at two-kilometre radii from each of the data locations (i.e., Figure 5-4). The choice of a two-kilometre mask was subjective and affects the summary statistics presented in Table 6-1 and Table 6-2. Table 6-1 indicates that the freshwater thickness beneath 14% of the study area was stable; beneath 41% was falling; and beneath 45% was undetermined. Areas with a rising trend were less than 1% of the study area. All trends in freshwater thickness between ±5 cm/yr (less than 0.5 metre change during the past ten years) were classified as Stable. To calculate the area values in Table 6-1, the study area was defined as the area enclosed by the Darling Fault and coastline and extending from two-kilometres north and south of the northern-most and southern-most data values, respectively. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 14

Table 6-2 presents a summary data for only that part of the study area occupied by Water Corporation s billing suburbs. This is about 51% of the total study area considered above. On an area basis, the freshwater thickness beneath 17% of the billing suburb area was stable; beneath 35% was falling; and beneath 48% was undetermined. Figure 6-3 highlights the large spatial gaps in the dataset, particularly in the central and southern parts of the study area. It also shows the areas that contain reasonably good spatial resolution of data. In those areas, the spatial pattern of change in aquifer storage is distinct and not associated with the suburb boundaries. For this reason, the aggregation of freshwater thickness values to suburbs to produce central estimates of change in aquifer storage beneath suburbs is not recommended. Similarly, it is not recommended to aggregate the interpolated results to suburbs due to the large variability in values within some of the suburbs and the lack of data values within others. This work was attempted but produced unsatisfactory results. Table 6-1: Summary by study area of interpolated trend in freshwater thickness (P-value < 0.05) masked at two-kilometre radii from each data value Aquifer Storage Area (Ha) Percentage of Study Area Undetermined 123,373 45.4% Rising 374 < 0.2% Stable 38,002 14.0% Falling 110,040 40.5% Total Study Area 271,789 100.0% Table 6-2: Summary by billing-suburb of interpolated trend in freshwater thickness (P-value < 0.05) masked at two-kilometre radii from each data value Aquifer Storage Area (Ha) Percentage of Billing Suburb Area Undetermined 66,702 47.7% Rising 171 < 0.2% Stable 24,387 17.5% Falling 48,439 34.7% Total Billing Suburb Area 139,699 100.0% Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 15

Figure 6-2: Trend in Superficial Aquifer storage overlayed on the estimated extent of seawater intrusion Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 16

Figure 6-3: Interpolated (TIN) trend in freshwater thickness (P-value < 0.05) with the result masked at two-kilometre radii from each data value Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 17

6.3. Opportunity for Additional Self Supply 6.3.1. Classification Figure 6-4 to Figure 6-8 depict groundwater availability superimposed on the following themes: garden bore density, per capita scheme water consumption, superficial geology, depth to groundwater below the ground surface, and groundwater isopotentials. These maps were analysed visually based on the following assumptions and interpretations: A low density of garden bores (bores per 100 households) indicates that a large proportion of garden water is supplied from scheme water; A high density of garden bores indicates that a small proportion of garden water is supplied from scheme water; A high per capita scheme water consumption and low density of garden bores is an indicator of high scheme water use on gardens; Access to groundwater may be limited by: a. Low bore yields (< 100 KL/day) in areas with predominantly clay and silt sediments; b. Drilling and equipment costs in areas of coastal limestone with large depth to groundwater 2 ; Opportunity for offsetting scheme water by developing additional self supply is low in areas outside of the billing suburbs because scheme water use on gardens is negligible in these areas. Other factors such as groundwater salinity, staining, odour and acidity; and the proximity of garden bores to wetlands, groundwater dependent ecosystems and public groundwater abstraction schemes must be considered to assess fully the opportunity to increase the number of garden bores in particular areas. Contamination of groundwater (e.g., by landfill or acid sulphate soil leachate) also may pose a risk in some locations, making these areas unsuitable for garden bores. A full assessment to the above level of detail was not conducted in this study. Further discussion about the suitability for drilling garden bores within metropolitan Perth is contained in the Perth Groundwater Atlas (2004). Each overlay map (Figure 6-4 to Figure 6-8) shows the relative opportunity for additional self supply based on the classifications in Table 6-3. For example, a suburb was classified as having high relative opportunity if aquifer storage was rising or stable, bore ownership was less than 30% and the superficial sediment was predominantly sand. A suburb was classified as having low opportunity if aquifer storage was falling, or bore ownership was greater than 60%, or the superficial sediments were predominantly silt and clay. These results are indicated by the labels L (low), M (moderate), H (high) and U (unknown) on each map. A separate coloured map of relative opportunity is presented as Figure 6-9. Areas classified as High Opportunity exhibited rising or stable ten-year water level trends, a low density of domestic garden bores, and predominantly sandy sediments. There is scope to increase the proportion of garden bore in these areas. Additional self supply would be expected to cause a reduction in aquifer storage, except in areas where maximum groundwater levels are controlled by drains and there is a component of rejected recharge. 2 However, there are a higher proportion of high socio-economic households in the coastal suburbs, so these additional costs may not be a limiting factor. The amount of iron staining and lime deposits can affect the uptake of bores. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 18

Table 6-3: Relative opportunity for additional self supply Opportunity High Moderate Low Groundwater Availability Rising / Stable Stable Falling Garden bore Density Low (< 30%) Low to moderate (0-60%) High (> 60%) Superficial geology Predominantly sand Presence of clay and silt, or limestone with large depth to groundwater Predominantly clay and silt, or limestone with large depth to groundwater Areas classified as having a Low Opportunity had combinations of falling water levels, a high density of domestic garden bores, and a predominance of clay, silt or coastal limestone with large depth to groundwater. Opportunity was judged to be low in areas with falling trends in aquifer storage because the security of the groundwater supply was uncertain. Scope to increase the proportion of garden bores in these areas is also limited because existing bore ownership is high. In areas with predominantly clay or silt sediments the opportunity to increase significantly the proportion of garden bores was considered to be low because groundwater access may be limited by low bore yields. Most garden bores in metropolitan Perth are designed to achieve flow rates of around 100-200 KL/day (Davidson, 1995). Throughout most of the coastal strip there is a negative correlation between garden bore density and the presence of limestone and large depth to groundwater. Areas classified as having Moderate Opportunity had intermediate combinations of stable trend in aquifer storage, a low to moderate density of domestic garden bores, and various proportions of clay, silt or limestone with large depth to groundwater. Areas with insufficient water level data could not be classified and were labelled as unknown. The overlay analysis neglects several factors that can have significant influence on opportunity for self supply. While there is scope for increasing the proportion of domestic garden bores in areas with High Opportunity, the scope for increasing the total number of garden bores is controlled by the number of houses and housing density. For example, Perth s central business district is classified as having a Moderate Opportunity although clearly there is negligible demand for garden water in this area. Influences of groundwater quality on self supply, including aesthetic properties such as odour and staining also are neglected. These factors could be incorporated within a more detailed overlay analysis using GIS tools but were beyond the current scope of work. For this reason the map of opportunity is considered to provide only a preliminary assessment that serves as a guide for conducting more thorough evaluations. 6.3.2. Discussion A High opportunity for additional bores is evident in the northern part of Jandakot Mound (PLATE 2), in a small area on the southwest margin of Gnangara Mound, and in two billing suburbs in the western part of the Cloverdale Area. These areas sum to approximately 8% of the total area of billing suburbs (Table 6-4). The billing suburbs of Landsdale, Winthrop, Jandakot, Canning Vale and Southern River had 2003-04 per capita scheme water consumptions greater than 140 KL/person/yr. All billing suburbs in these areas had less than 20% bore ownership in 2003-04; however, there is considerable disparity with previous bore density data in the Jandakot area. The billing suburbs Success, Atwell and Jandakot were reported as having greater than 75% of houses with bores in 1995 (Kern, unpublished). The apparent subsequent reduction in bore densities in these areas may be due to housing development during the past ten years 3. 3 Recent land releases have smaller block sizes (e.g., 500m 2 ) and larger houses making it less attractive for individuals to install their own bores. However it is common for bore ownership to increase after residents have overcome the initial costs of land purchase and house building. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 19

Although the spatial resolution of the data is limited in the areas classified as having High Opportunity, the estimated trends in aquifer storage suggest that mean annual groundwater levels have trended neither up nor down during the past ten years. This does not imply that water levels were invariant during this period, or that the storage was invariant at all locations within these areas. Table 6-4: Proportion of billing suburbs with high, moderate and low opportunities for additional self supply of groundwater Opportunity No. Billing Suburbs Area (Ha) Percentage of Area Unknown 36 19,181 10.4% Low 127 94,960 51.3% Moderate 55 55,686 30.1% High 22 15,139 8.2% Total 240 184,966 100.0% The relative opportunity is general low along the coastal margin of the study area. Falling water level trends, the presence of limestone with large depth to groundwater and an inherent risk of seawater intrusion are the main constraints on opportunity for self supply. Public groundwater extraction from the Whitfords and Quinns borefields since 1999 appear to be the main cause of falling water levels in the northern coastal strip. This is to be expected given the recent commencement of extraction with a new equilibrium still to be established. There is a lack of water level data in the Rockingham-Warnbro locale; however, this area was considered to have low relative opportunity due to the combination of moderate-to-high garden bore density and a high risk of seawater intrusion affecting bores close to the coast or screened deep within the aquifer. Per capita scheme water consumption is very low throughout this area, suggesting that the number of domestic garden bores might be under estimated. There is also inconsistency with previously reported (Kern, unpublished) bore density values, which were all greater than 75% in this area in 1995. Again, recent housing development may account for some of this difference. There is a mixture of low, moderate and unknown opportunities within the central part of the study area around the Swan-Canning Estuary environs. Water level monitoring sites that are suitable for determining ten-year water level trends are sparse throughout this area but present a reasonably consistent pattern of stable aquifer storage during the past ten years. The pattern of low opportunity mainly reflects the pattern of high garden bore density (greater than 60% bore ownership). Similarly, the pattern of moderate opportunity mostly reflects the pattern of moderate garden bore density. Opportunity for self supply could not be assessed in the eastern half of the Cloverdale Area and near Canning River (east) due to the absence of water level data in these areas. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 20

Figure 6-4: Trend in Superficial Aquifer storage overlayed on garden bore density 2003-04 Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 21

Figure 6-5: Trend in Superficial Aquifer storage overlayed on per capita scheme water consumption 2003-04 Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 22

Figure 6-6: Trend in Superficial Aquifer storage overlayed on superficial geology Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 23

Figure 6-7: Trend in Superficial Aquifer storage overlayed on depth to groundwater (May 2003) Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 24

Figure 6-8: Trend in Superficial Aquifer storage overlayed on groundwater isopotentials (May 2003) Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 25

Figure 6-9: Relative opportunity for additional self supply of groundwater Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 26

7. Conclusions The opportunity for additional self supply of groundwater from the Superficial Aquifer is highly variable across metropolitan Perth. Water level changes in groundwater monitoring bores indicate that the ten-year trend in mean freshwater thickness beneath approximately 14% of the study area is stable; beneath approximately 41% is falling; and beneath approximately 45% cannot be determined due to a lack of water level data. Areas with a rising trend are less than 1% of the study area. Within the area of the Water Corporation s billing suburbs (51% of the above study area), the freshwater thickness beneath approximately 17% of the billing suburb area is stable; beneath approximately 35% is falling; and beneath approximately 48% cannot be determined due to a lack of water level data. A high relative opportunity for additional self supply was identified under approximately 8% of Water Corporation s billing suburbs, a moderate opportunity under approximately 30% and a low opportunity under approximately 51%. A significant proportion of billing suburbs have inadequate water level records to assess ten-year trends in aquifer storage. Some of these suburbs have low opportunity for additional self supply because of other limiting factors, such as a low likelihood of adequate bore yields. Overall, the opportunity for additional self supply of groundwater was not assessed in 36 out of 240 billing suburbs (equivalent to10% by area) due to a lack of monitoring bores and water level data in these areas. Assuming a continuation of the climate of the past ten years, it is expected that additional self supply of groundwater from the Superficial Aquifer will further reduce the aquifer storage overall. This will increase the general risks of seawater intrusion, loss of urban wetlands and the need for some existing bores to be deepened. Areas with high existing bore ownership (indicating more reliance on self supply) and falling aquifer storage could place future stresses on scheme water supplies if the groundwater supplies from the Superficial Aquifer in these areas were jeopardised. This could occur due to seawater intrusion or groundwater contamination, the need to lower garden bore intake screens in response to falling levels, or the need to protect important wetlands or groundwater dependent ecosystems. Deep superficial bores and bores located closest to the coast may be at risk from seawater intrusion if superficial groundwater levels continue to fall in these areas (e.g., Rockingham-Warnbro area and the northern coastal strip between Whitfords and Yanchep). The results obtained in this study are based on several uncomplicated assumptions that provide only a preliminary assessment of the opportunity for additional self supply. The presented classification of data into Low, Moderate and High Opportunity categories neglects potential influences of spatial variability within billing suburbs; differences in housing density and building type; groundwater aesthetic quality; potential impacts of additional bores on groundwater dependent ecosystems; risks from groundwater contamination; and regulatory and social factors that influence groundwater use. The spatial pattern of ten-year change in aquifer storage is poorly correlated to the billing suburb boundaries, which makes difficult the task of objectively overlaying the water level data with other spatial datasets that are compiled based on suburb areas. A better method could be developed using more-advanced geostatistical methods than used in this study. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 27

Judgements about the environmental impact, significance and acceptability of changes in aquifer storage are subjective and should be made based on a framework of agreed values. A rigorous examination of the significance of groundwater level trends and their management implications was beyond the scope of this study; however, it appears that the information that would be required to take this next step may be lacking. 8. Recommendations Suburbs that are identified as having high opportunity for additional self supply should be further investigated at the local scale to verify the results of this study, and to determine the factors that control existing groundwater use in these areas. Assuming that current levels of self supply are expressions of current demand, identifying these controls would provide information for designing incentives to increase demand. Local scale investigations should also be conducted in areas with falling groundwater levels to determine whether these falls are likely to pose a significant risk to groundwater dependent ecosystems, licensed and unlicensed abstraction or seawater intrusion. The numbers of garden bores within in each Perth suburb need to be re-estimated. In particular, the apparent discrepancy between 2003 and 1995 estimates of garden bores in the Jandakot and Rockingham-Warnbro areas needs to be resolved. If possible, garden bores locations should be compiled as a point dataset so that the distribution of garden bores can be determined independently of the suburb boundaries. A dedicated groundwater observation network should be established to monitor seawater intrusion in susceptible coastal areas, including monitoring the depth of the seawaterfreshwater interface at a number of strategic locations. Particular areas that should be targeted for monitoring are the Rockingham-Warnbro area where there is increasing groundwater demand due to new housing developments and easy access to groundwater; and in the northern coastal strip between Whitfords and Yanchep where groundwater extraction for public supply has increased significantly during the past five years. Large spatial gaps in the Superficial Aquifer monitoring network prevent the assessment of groundwater storage levels beneath approximately half of metropolitan Perth. Lindsay (2004) recommended the drilling of an additional twenty-eight monitoring bores into the Superficial Aquifer between Coogee-Armadale and Marmion-West Swan. This assessment of monitoring requirements should be revisited and extended to include areas further north and south (e.g., from Secret Harbour to Yanchep). The monitoring should target areas with existing high densities of garden bores to assess the impacts on aquifer storage in these areas. A comprehensive overlay analysis using GIS tools is recommended to achieve a more objective classification and assessment of opportunity for additional self supply from the Superficial Aquifer. This requires the development of a broadly-agreed set of criteria for classifying groundwater supply opportunities and risks based upon multiple factors (e.g., groundwater condition, access, cost, availability, demand, etc). An adequate set of criteria does not exist at present. The criteria develop in this study are preliminary and require development and refinement through broader input from State Government, private stakeholders and research and development organisations. An explicit set of values-based criteria against which to assess the significance of groundwater level change beneath different areas of metropolitan Perth also is needed. For example, the impact of a one-metre fall in the watertable may be judged as either acceptable or unacceptable dependent upon the local context and associated values. It has not been possible in this study to classify and map the hazard and acceptability of change in aquifer storage because the criteria on which to base an assessment are lacking. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 28

The geodatabase and datasets produced for this project are useful resources that should be updated regularly to allow storage trends in the Superficial Aquifer to be analysed on an ongoing basis. The methodology developed for this study is semi-automated and suitable for regularly producing updated maps of freshwater thickness and trend. It is recommended that a custodian for the database be identified, and that a protocol be put in place for producing annual assessments of the status and trend in superficial groundwater levels and aquifer storage beneath metropolitan Perth. Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth 29

APPENDIX A: Description of the Superficial Aquifer Geodatabase All data obtained for this project were imported into a personal geodatabase (the term used by 1 ESRI). The geodatabase is essentially a Microsoft Access database that is used to store all spatial and non-spatial data. The non-spatial data can be accessed using Microsoft Access; however, 2 ArcGIS is required to work with the spatial datasets. The advantages of using a geodatabase for this project included: All data (spatial and attribute) are stored in one location; Ability to store relationships, both attribute and topological, and attribute domains; All data are accessible using ArcGIS, which was the primary analysis tool used; Data could be accessed directly from 3 Python to enable scripting of analyses. The main disadvantage of storing the data in a geodatabase is that ArcGIS is required to work with the spatial datasets. Each dataset stored in the geodatabase is summarised in the data dictionary (Appendix Table A-1). The datasets were collated specifically for the project and reflect the types of data that were initially considered relevant. The study aims were modified during the course of the project and not all datasets were used to perform the analyses in this report. 1 Environmental Systems Research Institute (see http://www.esri.com/) 2 ArcGIS is an integrated collection of GIS software produced by ESRI (see http://www.esri.com/software/arcgis/index.html) 3 Python is an interpreted, interactive, object-oriented programming language (see http://www.python.org/). Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth A-1

Appendix Table A-1: Geodatabase data dictionary NAME SOURCE COMMENT BillingSubGroups_Polygons Water Corp Water Corporations Billing Sub Groups with Relative Supply Codes BillingSubGroups_RegionsOfInterest PUR initial Regions of Interest (obsolete) acid_sulphate_soils_shp Dept of Environment Acid Sulphate Soils coastline_wrc_arc_3d Dept of Environment Coastline contours_5m_shp Dept of Environment 5m contours of topography csiro_gwareas_request_mga_shp Dept of Environment Groundwater Areas (limited extent - obsolete) csiro_gwsubareas_request_mga_shp Dept of Environment Groundwater Sub Areas (limited extent - obsolete) d_balancing_pond_coverage Water Corp Balancing Ponds/Compensation Basins drain_catchments Water Corp Drained Catchments FlowSystems_gda9 4_shp Dept of Environment Superficial Aquifer flow systems Geology_Faults Dept of Environment Darling Fault and Gingin Scarp geomorphic_wetlands_shp Dept of Environment Geomorphic wetlands with physical classification and environmental evaluation groundwater_subareas_shp Dept of Environment Groundwater Sub Areas (complete) gw_contours_0m 0m contour from the 5m topo data set (used to build gw_min_2 TIN) gw_contours_max_shp Dept of Environment 1m groundwater contours (historical maximum - 1950s - 1970s) gw_contours_min_shp Dept of Environment 1m groundwater contours (May 2003 - end of summer) developed for Perth Groundwater Atlas (2nd Edition), 2004 gw_salinity_superficial_shp Dept of Environment Groundwater salinity of superficial formations tin_hull Clip polygon for raster surfaces (roughly the area between the coast and the scarp) tin_hull_poly Clip polygon for raster surfaces (roughly the area between the coast and the scarp) Hydro_General_DGN Dept of Environment Generalised hydrology of major rivers and brooks hydro_shp Dept of Environment Hydrography linear features (natural line features, pipelines, and point water features) hydrogeology_base_super_shp Dept of Environment Structure contour map of the base of the superficial formations (10m intervals, plus coast and geology boundaries) lga_shp Dept of Environment Local Government Authority and Locality Boundaries localities_shp Dept of Environment Localities of Western Australia (suburbs) metro_contours_1m_shp Dept of Environment 1m contours of topography for Perth Metro Area open_drain Water Corp Open Drains pipe_drain Water Corp Pipe Drains pressure_drain Water Corp Pressure Drains rcodem_poly Dept Planning & Infrastructure Town Planning Scheme - R-codes roads_shp Dept of Environment Western Australian Generic Road Centreline dataset towns_shp Dept of Environment Classified towns dataset extracted from the Geonoma database of place names XYppd_stations_200km_from_Perth_m ga94_shp EnvironmentalGeolology_Dissolved SILO EnvironmentalGeolology_RAW Dept of Environment Environmental Geology Climate Stations with Point Patched Data in the SILO database (within 200km from Perth) Environmental Geology dissolved based on code and narrative LicensedSuperficial_DrawPoints Dept of Environment Licensed Superficial Draw Points LicensedSuperficialAllocs_SubArea_ce ntroids HighSchemeUse_in_DrainCatch SchemeUse_int_DrainCatch Centroids of the Licensed Superficial Draw Points (grouped by groundwater sub area) High scheme use (>140) in drained catchments Scheme use intersected with drained catchments BaseRockSand_tr_b Dept of Environment Base of the Rockingham Sand formation (contours - 50m intervals) BaseRockSand3D_tr_b same as BaseRockSand_tr_b with 3d polylines BaseSuper_layer3_cont Dept of Environment Base of Superfical contours extending offshore (PRAMS layer 3) - 5m intervals Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth A-2

NAME SOURCE COMMENT BaseSuper3D_layer3_cont same as BaseSuper_layer3_cont with 3d polylines BaseSuperClipped_tq_b Dept of Environment Base of Superfical contours clipped to coast and scarp Form_RockSand_tr_b Dept of Environment Rockingham Sand Formations Form_Super_new_tq_b Dept of Environment Superficial Formations Isopachs_tr_20 Dept of Environment Isopachs (thickness) of the Rockingham Sand Formation (20m intervals) RockSandBnd3D boundary of Rockingham Sand Formation with estimated elevations (elevations from TIN basesuperlyr3) tinbaserocksand3d same as BaseRockSand3D_tr_b clipped to Rockingham Sand Formation boundary tinbasesuper3d same as BaseSuper3D_layer3_cont with Rockingham Sand Formation Erased bores_anno_feature_class Water Corp Water Corp Production Bore Annotations bores_anno_feature_class_polys Water Corp Water Corp Production Bore Annotation Polygons WC_production_bore_locations Water Corp Water Corp production bore locations WC_production_Label_points Water Corp Water Corp production bore lable points WINSiteDetailsPoint Dept of Environment WIN database site details for superficial wells with > 10 water level records (CONTAINS RESULTS OF LINEAR REGRESSION MODELLING, and Groundwater Availability Categories) base_sup_rck RASTER (100m) - base of superfcial and Rockingham formations basesuper_rck TIN - base of superficial formation with rockingham sand formation (built from tinbaserocksand3d, tinbasesuper3d, RockSandBnd3D) basesuperlyr3 TIN - base of superficial formation (built from BaseSuper3D_layer3_cont) dtw_2003 RASTER (100m) - Depth to groundwater May 2003 grnd_surf_z RASTER (100m) - Topography based on 5m contours ground_surf_2 TIN - Topography based on 5m Contours (built from contours_5m_shp) gw_min_2 TIN - Groundwater level (May 2003) - (built from gw_contours_0m, gw_contours_min_shp) gw_minimum RASTER (100m) - Groundwater level May 2003 tin_hull_mask RASTER (100m) - processing mask for groundwater surfaces saltwat_int_m RASTER (100m) Seawater wedge thickness (m) saltwater_int RASTER (100m) Seawater-freshwater interface AreasOfInterest Description of Initial Areas of Interest (obsolete) AverageLowDensityLotSize Water Corp Average Low Density Lot Size for Water Corp Billing Sub Groups EnvGeolCodes Major Lithological Units for Environmental Geology HousingDensity Water Corp Housing Density for Water Corp Billing Sub Groups NumberOfBores Water Corp Number of Private Bores for Water Corp Billing Sub Groups PPD_Climate_Data SILO Point Patched Climate Data from SILO SchemeConsumption0304 Water Corp Scheme consumption data for Water Corp Billing Sub Groups Summary_ActualRainFallData Summary of Rainfall data by station Summary_RelativeSupplyOpportunity Summary of Relative Supply Opportunities (total area and count) SuperficialAbstraction Water Corp Superficial Abstration for Water Corp Production Bore Fields WaterLevelsSummary Water levels summarised WaterLevelsSummaryPost1970 Water level summary for 1970+ WaterLevelsSummaryPost1995 Water level summary for 1995+ WaterLevelsSummaryPost1995_1999 Water level summary for 1995-1999 WaterLevelsSummaryPost2000_2004 Water level summary for 2000-2004 WIN_WL_Annual_Average_Table Average Annual Waterlevels WinWaterLevels Dept of Environment Waterlevels (AHD) for the WIN sites Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth A-3

APPENDIX B: Summary of Monitoring Bores SITE ID AWRC NAME P- VALUE SLOPE (m/yr) CHANGE IN FRESHWATER THICKNESS (m/yr) GROUNDWATER LEVELS 2982 T280 (O) 0.251-0.022-0.892 Statistically insignificant 2983 T280 (I) 0.243-0.022-0.914 Statistically insignificant 2984 T281 0.095-0.014-0.583 Statistically insignificant 2989 T530 (O) 0.034-0.040-1.622 Falling 2990 T530 (I) 0.040-0.038-1.565 Falling 2991 T480 0.030-0.043-1.782 Falling 2992 T481 0.032-0.042-1.738 Falling 2993 T330 (O) 0.013-0.089-0.994 Falling 2994 T330 (I) 0.016-0.075-1.241 Falling 2995 T230 (O) 0.011-0.031-0.031 Stable 2996 T230 (I) 0.023-0.028-0.028 Stable 2997 CSG6 (DR1A) 0.033-0.023-0.023 Stable 3008 CSG3 0.039 0.028 1.112 Rising 3009 T580 0.214-0.022-0.560 Statistically insignificant 3010 T581 0.177-0.024-0.636 Statistically insignificant 3011 T430 (O) 0.028-0.048-1.954 Falling 3012 T430 (I) 0.027-0.048-1.986 Falling 3013 8282 0.005-0.032-1.333 Falling 3014 T180 (O) 0.006-0.037-0.037 Stable 3015 T180 (I) 0.012-0.035-0.035 Stable 3021 T540 0.016-0.058-0.058 Falling 3022 T490 0.021-0.050-2.043 Falling 3023 T390 (O) 0.042-0.043-0.043 Stable 3024 T390 (I) 0.037-0.044-0.044 Stable 3025 T340 (O) 0.016-0.048-0.048 Stable 3026 T340 (I) 0.429-0.016-0.016 Stable 3030 T130 (I) 0.122-0.014-0.014 Stable 3032 T590 0.043-0.041-0.041 Stable 3033 T440 0.006-0.057-0.057 Falling 3034 T441 0.007-0.058-0.058 Falling 3035 T290 (O) 0.017-0.037-0.037 Stable 3038 T240 (I) 0.000-0.057-0.057 Falling 3039 T95 (O) 0.409-0.010-0.010 Stable 3040 T95 (I) 0.277-0.024-0.024 Stable 3042 T400 (O) 0.056-0.039-0.039 Stable 3043 T400 (I) 0.038-0.044-0.044 Stable 3044 T190 (O) 0.393 0.011 0.011 Stable 3045 T190 (I) 0.153 0.023 0.023 Stable 3046 T140 (O) 0.051-0.028-0.028 Stable 3048 JM41 0.000-0.076-0.076 Falling 3049 JM37 0.001-0.071-0.071 Falling 3050 T550 (O) 0.547-0.015-0.015 Stable 3051 T550 (I) 0.237-0.029-0.029 Stable 3052 T500 0.603-0.011-0.011 Stable 3053 T450 (O) 0.421-0.009-0.009 Stable 3054 T450 (I) 0.285-0.011-0.011 Stable 3055 T350 0.114-0.031-0.031 Stable 3056 T300 0.500-0.013-0.013 Stable 3057 T250 (O) 0.003-0.069-0.069 Falling 3058 T250 (I) 0.007-0.036-0.036 Stable 3063 JE12A 0.000-0.079-0.079 Falling 3065 JE12C 0.000-0.084-0.084 Falling Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth B-1

SITE ID AWRC NAME P- VALUE SLOPE (m/yr) CHANGE IN FRESHWATER THICKNESS (m/yr) 3068 T600 (I) 0.221-0.021-0.021 Stable 3069 T200 (O) 0.011-0.046-0.046 Stable 3070 T200 (I) 0.055-0.034-0.034 Stable 3071 JM42 0.000-0.087-0.087 Falling 3073 JM49 0.153-0.010-0.010 Stable 3075 T560 (O) 0.331-0.018-0.018 Stable 3076 T560 (I) 0.323-0.018-0.018 Stable 3077 T510 0.371-0.011-0.011 Stable 3078 T410 0.184-0.027-0.027 Stable 3080 T150 (O) 0.004-0.075-0.075 Falling 3081 T150 (I) 0.001-0.095-0.095 Falling 3083 JM48 0.001-0.107-0.107 Falling 3085 T105 (I) 0.240-0.036-0.036 Stable 3086 JE13 0.005-0.062-0.062 Falling 3090 T460 0.831 0.005 0.005 Stable 3091 T360 0.074-0.045-0.045 Stable 3092 T310 0.013-0.076-0.076 Falling 3093 T260 (O) 0.598-0.010-0.010 Stable 3094 T260 (I) 0.469 0.019 0.019 Stable 3099 T210 (O) 0.302-0.024-0.024 Stable 3100 T210 (I) 0.153-0.021-0.021 Stable 3101 T160 (O) 0.047-0.039-0.039 Stable 3103 JM44 0.021-0.067-0.067 Falling 3104 JM39 0.010-0.088-0.088 Falling 3105 T570 0.283-0.033-0.033 Stable 3106 T520 (O) 0.450-0.019-0.019 Stable 3107 T520 (I) 0.361-0.022-0.022 Stable 3108 T420 0.242-0.020-0.020 Stable 3109 T370 0.142-0.036-0.036 Stable GROUNDWATER LEVELS 3112 T470 0.074-0.055-0.055 Statistically insignificant 3113 T270 0.853-0.003-0.003 Stable 3115 T170 0.002-0.175-0.175 Falling 3116 T120 (O) 0.000-0.222-0.222 Falling 3117 T120 (I) 0.000-0.120-0.120 Falling 3130 T65 (O) 0.008-0.039-0.039 Stable 3131 T65 (I) 0.009-0.037-0.038 Stable 3148 BM2C 0.002-0.061-0.061 Falling 3151 BM2A 0.044-0.032-0.032 Stable 3154 JM28 0.722-0.005-0.005 Stable 3155 JM24 0.135 0.022 0.022 Stable 3157 JM17 0.722 0.006 0.006 Stable 3158 T40 (I) 0.194-0.017-0.017 Stable 3161 JM13 0.244-0.030-0.030 Stable 3164 JM47 0.029-0.023-0.023 Stable 3165 BM5A 0.004-0.036-0.036 Stable 3173 JM33 0.037-0.052-0.052 Falling 3181 JE6C 0.044 0.036 0.036 Stable 3183 JE6A 0.054 0.033 0.033 Stable 3186 JE7C 0.037 0.042 0.042 Stable 3194 J310 0.669-0.010-0.010 Stable 3196 JM12 0.426-0.017-0.017 Stable 3197 JE8A 0.539-0.012-0.012 Stable 3199 JM29 0.005-0.059-0.059 Falling 3201 JM18 0.176 0.027 0.027 Stable 3204 JE1A 0.779 0.009 0.009 Stable Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth B-2

SITE ID AWRC NAME P- VALUE SLOPE (m/yr) CHANGE IN FRESHWATER THICKNESS (m/yr) 3205 JE1B 0.601 0.010 0.010 Stable 3211 T90 (I) 0.655 0.018 0.018 Stable 3212 JE10C 0.310 0.032 0.032 Stable 3219 WR2C 0.074-0.042-0.042 Stable 3228 SE5 0.000-0.295-0.295 Falling 3327 TM7A 0.000-0.079-0.079 Falling 3331 TM16A 0.818 0.004 0.004 Stable 3333 TM16C 0.335 0.015 0.015 Stable GROUNDWATER LEVELS 3335 JE14A 0.244 0.085 0.085 Statistically insignificant 3337 JE14C 0.352 0.048 0.048 Stable 3347 TD4 0.031 0.058 0.058 Rising 3373 TD29 0.019-0.057-0.057 Falling 4343 T110 (O) 0.315-0.030-0.030 Stable 4344 T110 (I) 0.105-0.052-0.052 Statistically insignificant 4347 GE2 0.396 0.007 0.289 Statistically insignificant 4348 GD4 0.548-0.006-0.006 Stable 4349 793 0.305-0.013-0.013 Stable 4354 7597 0.080-0.024-0.024 Stable 4355 JP1 0.015-0.056-0.056 Falling 4357 142 0.051-0.026-0.932 Statistically insignificant 4358 GE1 0.231-0.012-0.012 Stable 4361 8279 0.089 0.043 0.043 Stable 4362 GE3 0.435-0.012-0.012 Stable 4370 GD5 0.012-0.034-0.034 Stable 4372 GM22 0.007-0.079-0.079 Falling 4373 8525 0.000-0.216-0.216 Falling 4374 GM17 0.000-0.148-0.148 Falling 4375 GCM 0.000-0.168-0.168 Falling 4376 GM13 0.000-0.236-0.236 Falling 4377 GM8 0.000-0.161-0.161 Falling 4378 GM9 0.002-0.121-0.121 Falling 4379 GM4 0.005-0.089-0.089 Falling 4380 GM1 0.002-0.108-0.108 Falling 4381 7593 0.004-0.087-0.087 Falling 4386 GE4 0.009-0.037-0.037 Stable 4391 GM26 0.019-0.046-0.046 Stable 4416 GM23 0.104-0.120-0.121 Statistically insignificant 4420 GM31 0.000-0.179-0.179 Falling 4421 GM30 0.001-0.203-0.203 Falling 4432 GM14 0.000-0.252-0.252 Falling 4435 GM29 0.000-0.180-0.180 Falling 4441 GM11 0.001-0.169-0.169 Falling 4447 GM2 0.002-0.135-0.135 Falling 4448 GM6 0.002-0.162-0.162 Falling 4451 GM3 0.002-0.149-0.149 Falling 4452 WH260 0.000-0.068-0.068 Falling 4453 459 0.068-0.018-0.018 Stable 4454 8283 0.004-0.037-0.037 Stable 4455 T10 (O) 0.004-0.092-0.092 Falling 4462 GM27 0.003-0.130-0.130 Falling 4463 GM28 0.001-0.092-0.092 Falling 4468 GM24 0.005-0.082-0.082 Falling 4479 GM20 0.021-0.085-0.086 Falling 4481 GM32 0.002-0.141-0.141 Falling 4483 GM15 0.001-0.157-0.158 Falling Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth B-3

SITE ID AWRC NAME P- VALUE SLOPE (m/yr) CHANGE IN FRESHWATER THICKNESS (m/yr) 4484 GM16 0.003-0.190-0.190 Falling 4485 GM12 0.002-0.254-0.254 Falling 4486 GM7 0.005-0.296-0.296 Falling GROUNDWATER LEVELS 4491 GF6 0.841 0.002 0.083 Statistically insignificant 4502 GD6 0.848-0.002-0.002 Stable 4504 GM25 0.001-0.114-0.114 Falling 4511 643 0.012-0.050-0.050 Falling 4512 GD7 0.079-0.035-0.035 Stable 4513 MM40 0.001-0.125-0.125 Falling 4514 MM34 0.001-0.232-0.232 Falling 4515 MM28 0.000-0.174-0.174 Falling 4518 JM19 0.162-0.033-0.033 Stable 4519 8284 0.295-0.017-0.017 Stable 4520 JM45 0.457-0.014-0.014 Stable 4521 JM7 0.011-0.049-0.049 Stable 4522 JM2 0.003-0.067-0.067 Falling 4524 T30 (I) 0.001-0.071-0.071 Falling 4525 T5 (O) 0.120 0.028 0.028 Stable 4526 T5 (I) 0.148-0.044-0.044 Stable 4528 1081 0.465 0.011 0.011 Stable 4541 125 0.184-0.027-0.027 Stable 4545 637 0.071-0.026-0.026 Stable 4547 MM66 0.008-0.071-0.071 Falling 4557 MM68 0.001-0.115-0.115 Falling 4575 JE4C 0.013-0.085-0.085 Falling 4586 JM26 0.049-0.038-0.038 Stable 4588 JM14 0.045-0.060-0.061 Falling 4589 JM8 0.026-0.058-0.058 Falling 4595 JM3 0.027-0.048-0.048 Stable 4596 JM4 0.014-0.044-0.044 Stable 4618 7970 0.054 0.019 0.019 Stable 4624 MM67 0.454-0.013-0.014 Stable 4625 649 0.079-0.022-0.022 Stable 4630 MM36 0.810 0.006 0.006 Stable 4664 GN5 0.000-0.089-0.089 Falling 4673 GD10 0.026-0.043-0.043 Stable 4674 JM35 0.066 0.075 0.075 Statistically insignificant 4675 JM31 0.017-0.036-0.036 Stable 4676 JM27 0.959-0.001-0.001 Stable 4678 JM22 0.815-0.004-0.004 Stable 4695 JM5 0.028-0.033-0.033 Stable 4712 149 0.064-0.028-0.028 Stable 4718 3020 0.117-0.033-0.033 Stable 4722 678 0.239-0.007-0.007 Stable 4726 2069 0.931-0.002-0.002 Stable 4766 MM25 0.022-0.042-0.042 Stable 4781 JM36 0.680-0.011-0.011 Stable 4783 T80 (O) 0.646 0.005 0.005 Stable 4784 T80 (I) 0.033-0.038-0.038 Stable 4785 JM23 0.305-0.014-0.014 Stable 4786 JM16 0.003-0.064-0.064 Falling 4790 2436 0.011-0.031-0.031 Stable 4808 144B 0.228-0.013-0.013 Stable 4815 821 0.341-0.019-0.019 Stable 4816 MM43 0.013-0.034-0.034 Stable Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth B-4

SITE ID AWRC NAME P- VALUE SLOPE (m/yr) CHANGE IN FRESHWATER THICKNESS (m/yr) 4822 MM31 0.000-0.089-0.089 Falling 4826 GN10 0.104-0.037-0.037 Stable 4834 MM53 0.098-0.020-0.020 Stable 4846 8285 0.605 0.011 0.011 Stable 4849 2288 0.023-0.072-0.072 Falling 4851 MM38 0.048-0.029-0.029 Stable 4852 MM46 0.079-0.039-0.039 Stable 4854 M60 0.238-0.018-0.018 Stable 4857 MP3B 0.035-0.043-0.043 Stable 4858 MP3C 0.038-0.018-0.018 Stable 4859 MM33 0.060-0.025-0.025 Stable 4861 MP2B 0.003-0.047-0.047 Stable 4862 MP2C 0.010-0.032-0.032 Stable 4863 MP2D 0.009-0.035-0.035 Stable 4866 MM49B 0.097-0.031-0.031 Stable 4872 MM54B 0.866 0.002 0.002 Stable 4874 MM26 0.426 0.014 0.014 Stable 4879 T85 0.385-0.024-0.025 Stable 4880 T75 0.110 0.020 0.020 Stable 4883 675B 0.036-0.018-0.018 Stable 4884 GD8 0.169-0.036-0.036 Stable 4885 MM44B 0.543-0.002-0.002 Stable 4886 MM45 0.380 0.022 0.023 Stable 4887 MM47 0.103-0.024-0.024 Stable 4888 MM47A 0.850-0.006-0.006 Stable 4890 M80B 0.028-0.033-0.033 Stable 4891 M80C 0.034-0.031-0.031 Stable 4892 M81 0.017-0.059-0.059 Falling 4900 MM55B 0.478-0.010-0.010 Stable 4902 MM56B 0.566 0.008 0.008 Stable 4904 MM27 0.520-0.015-0.015 Stable 4910 T115 0.513-0.018-0.018 Stable 4911 MM48 0.007-0.058-0.058 Falling 4912 MM48A 0.012-0.046-0.046 Stable 4913 MM51A 0.003-0.069-0.069 Falling 4916 MM52 0.857 0.003 0.003 Stable 4917 MM57 0.000-0.166-0.166 Falling 4918 M290 0.404 0.038 0.038 Stable 4921 JP14 0.007-0.031-0.082 Falling 4922 JP21 0.000-0.074-0.074 Falling 4925 JP15 0.000-0.074-0.074 Falling 4926 JP19 0.000-0.277-0.277 Falling GROUNDWATER LEVELS 4932 JP7 0.200-0.010-0.249 Statistically insignificant 4935 PM29 0.000-0.255-0.255 Falling 4937 JP4 0.027-0.042-0.042 Stable 4938 GE7 0.013-0.047-0.047 Stable 4941 PM34 0.000-0.245-0.245 Falling 4942 PM33 0.000-0.241-0.241 Falling 4943 JP17 0.000-0.174-0.174 Falling 4944 PM31 0.000-0.254-0.254 Falling 4945 YY1 (I) 0.000-0.277-0.277 Falling 4946 YY1 (O) 0.000-0.320-0.320 Falling 4954 PM32 0.000-0.256-0.257 Falling 4955 P270 0.000-0.247-0.247 Falling 4956 P280 0.000-0.265-0.265 Falling Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth B-5

SITE ID AWRC NAME P- VALUE SLOPE (m/yr) CHANGE IN FRESHWATER THICKNESS (m/yr) 4957 P290 0.000-0.264-0.264 Falling 4958 P300 0.000-0.252-0.252 Falling 4959 P310 0.000-0.280-0.280 Falling 4968 WH100 0.000-0.128-0.128 Falling 4969 JP20B 0.001-0.036-0.036 Stable 4970 JP20C 0.003-0.032-0.032 Stable 4971 JP18C 0.000-0.072-0.072 Falling 4973 JP11 0.000-0.176-0.176 Falling 4974 PM36 0.000-0.265-0.265 Falling 4975 JP13 (I) 0.000-0.224-0.224 Falling 4977 PM35 0.000-0.226-0.226 Falling 4979 JP16 0.012-0.110-0.111 Falling 4980 P250 0.000-0.243-0.243 Falling 4981 JP16A 0.000-0.234-0.234 Falling 4982 JP16B 0.000-0.240-0.240 Falling 4983 JP16C 0.000-0.223-0.223 Falling 4985 PM19 0.000-0.303-0.303 Falling 5002 8281 0.005-0.047-0.047 Stable 5003 WM16 0.057-0.030-0.030 Stable 5004 MS9 0.000-0.080-0.080 Falling 5005 WM11 0.000-0.159-0.159 Falling 5006 WM4 0.000-0.141-0.142 Falling 5008 P220 0.003-0.081-0.081 Falling 5011 PM37 0.000-0.181-0.181 Falling 5012 PCM21 0.000-0.227-0.227 Falling 5018 WH230 0.000-0.044-0.044 Stable 5019 WH310 (O) 0.089 0.012 0.012 Stable 5020 GD2 0.314 0.017 0.017 Stable 5024 WM22 0.000-0.041-0.041 Stable 5025 WM18 0.000-0.040-0.040 Stable 5026 MS10 0.000-0.058-0.058 Falling 5029 MS7 0.000-0.054-0.054 Falling 5031 JP9 0.000-0.069-0.069 Falling 5036 WM9 0.000-0.110-0.110 Falling 5037 GN19 0.000-0.121-0.121 Falling 5038 PM24 0.004-0.049-0.049 Stable 5039 PM23 0.001-0.090-0.090 Falling 5055 MM14 0.002 0.053 0.053 Rising 5056 GN8 0.252 0.010 0.010 Stable 5057 WM28 0.663-0.004-0.004 Stable 5075 MS14 0.001-0.049-0.049 Stable 5077 MT1S 0.000-0.056-0.056 Falling 5078 MT1I 0.000-0.056-0.056 Falling 5079 MT1D 0.000-0.057-0.057 Falling 5084 MT3I 0.000-0.050-0.050 Falling 5085 MT3D 0.000-0.049-0.049 Stable 5086 MT3S 0.001-0.039-0.039 Stable 5091 PM25 0.001-0.064-0.064 Falling 5094 GN23 0.001-0.204-0.204 Falling 5097 PM6 0.000-0.338-0.338 Falling 5102 JB4 0.063-0.048-0.048 Stable 5103 JB5 0.003-0.052-0.052 Falling 5104 JB12A 0.001-0.048-0.048 Stable 5105 JB12B 0.000-0.057-0.057 Falling 5106 JB12C 0.005-0.039-0.039 Stable GROUNDWATER LEVELS Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth B-6

SITE ID AWRC NAME P- VALUE SLOPE (m/yr) CHANGE IN FRESHWATER THICKNESS (m/yr) 5109 JB10A 0.004-0.043-0.043 Stable 5110 JB10B 0.009-0.038-0.038 Stable 5111 JB10C 0.005-0.040-0.040 Stable 5130 GN15 0.000-0.110-0.111 Falling 5133 WM31 0.000-0.165-0.165 Falling 5135 WM5 0.000-0.248-0.248 Falling 5144 PM12 0.000-0.213-0.214 Falling 5145 PM9 0.000-0.183-0.183 Falling 5152 MM15 0.816-0.004-0.004 Stable 5156 GN1A 0.956-0.001-0.001 Stable 5157 GN11 0.004-0.041-0.041 Stable 5158 WM23 0.046-0.042-0.042 Stable 5161 JB9A 0.004-0.035-0.035 Stable 5162 JB9B 0.001-0.044-0.044 Stable 5163 JB9C 0.001-0.045-0.045 Stable 5166 WM13 0.000-0.144-0.144 Falling 5173 WM3 0.449-0.021-0.021 Stable 5174 WM1 0.000-0.166-0.166 Falling 5175 PM7 0.000-0.255-0.255 Falling 5176 MM16 0.862-0.003-0.003 Stable 5184 MM9 0.020-0.027-0.027 Stable 5186 WM24 0.000-0.118-0.118 Falling 5188 NR7A 0.000-0.089-0.089 Falling 5189 NR7B 0.002-0.102-0.102 Falling 5190 NR7C 0.000-0.107-0.107 Falling 5196 WM35 0.000-0.101-0.101 Falling 5201 WM6 0.002-0.090-0.090 Falling GROUNDWATER LEVELS 5202 GN20 0.261-0.076-0.076 Statistically insignificant 5205 PM13 0.000-0.184-0.184 Falling 5206 PM11 0.000-0.204-0.204 Falling 5214 MM17 0.163-0.028-0.028 Stable 5215 GN2 0.312-0.032-0.032 Stable 5223 GD11 0.570-0.011-0.011 Stable 5224 MM10 0.016-0.071-0.071 Falling 5225 GN4 0.009-0.104-0.104 Falling 5230 GN18 0.117-0.103-0.103 Statistically insignificant 5231 WM41 0.085-0.109-0.109 Statistically insignificant 5242 WM40 0.099-0.130-0.130 Statistically insignificant 5246 GN13 0.229-0.066-0.066 Statistically insignificant 5248 NR9C 0.017-0.084-0.084 Falling 5249 WM2 0.000-0.131-0.131 Falling 5250 GG1 (I) 0.000-0.235-0.235 Falling 5251 GG1 (O) 0.000-0.239-0.239 Falling 5252 NR1A 0.000-0.234-0.234 Falling 5253 NR1B 0.000-0.234-0.234 Falling 5254 NR1C 0.000-0.273-0.273 Falling 5255 PM8 0.000-0.222-0.222 Falling 5259 MM18 0.225-0.023-0.023 Stable 5274 GN12 0.012-0.163-0.163 Falling 5275 WM33 0.007-0.178-0.178 Falling 5277 NR12C 0.003-0.075-0.075 Falling 5278 NR12A 0.005-0.100-0.100 Falling 5279 NR12B 0.004-0.100-0.100 Falling 5280 NR5A 0.002-0.098-0.098 Falling 5281 NR5B 0.003-0.100-0.100 Falling Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth B-7

SITE ID AWRC NAME P- VALUE SLOPE (m/yr) CHANGE IN FRESHWATER THICKNESS (m/yr) 5282 NR5C 0.001-0.087-0.087 Falling 5283 NR5D 0.002-0.098-0.098 Falling 5284 WM7 0.001-0.084-0.084 Falling 5285 GN29 (O) 0.002-0.076-0.076 Falling 5286 GN29 (I) 0.001-0.098-0.098 Falling 5287 NR3C 0.002-0.086-0.087 Falling 5288 NR3B 0.002-0.099-0.099 Falling 5289 NR3A 0.001-0.096-0.096 Falling 5290 NR8C 0.009-0.064-0.064 Falling 5295 MM58 0.673-0.008-0.008 Stable 5296 GN3 W 0.831 0.012 0.012 Stable 5306 GN3 E 0.857 0.011 0.011 Stable 5308 L10C 0.721-0.012-0.012 Stable GROUNDWATER LEVELS 5309 L10A 0.081-0.093-0.093 Statistically insignificant 5310 GN17 0.019-0.138-0.138 Falling 5318 WEP1 0.020-0.139-0.139 Falling 5319 WM32 0.002-0.218-0.218 Falling 5321 L200C 0.005-0.122-0.122 Falling 5322 GN22 0.001-0.088-0.089 Falling 5323 NR6C 0.000-0.084-0.084 Falling 5324 WM8 0.003-0.059-0.059 Falling 5325 NR10C 0.003-0.074-0.074 Falling 5327 MM19 0.657-0.011-0.011 Stable 5328 M360 0.251-0.025-0.025 Stable 5330 MM12 0.008-0.101-0.101 Falling 5351 L30C 0.040-0.024-0.024 Stable 5352 L110C 0.026-0.052-0.052 Falling 5355 L120C 0.004-0.059-0.059 Falling 5358 L220A 0.002-0.054-0.054 Falling 5359 L220C 0.003-0.047-0.047 Stable 5360 GN21 0.009-0.048-0.048 Stable 5361 NR4C 0.007-0.058-0.058 Falling 5362 NR2C 0.000-0.104-0.104 Falling 5365 MM60 0.011-0.178-0.178 Falling 5366 MM59B 0.030-0.045-0.045 Stable 5372 PB3 0.023-0.028-0.028 Stable 5374 L50C 0.935-0.001-0.001 Stable 5375 PB2 0.001-0.033-0.033 Stable 5376 PB1 0.003-0.038-0.038 Stable 5378 L130C 0.004-0.047-0.047 Stable 5382 L240C 0.050-0.033-0.033 Stable 5383 NR11C 0.014-0.040-0.040 Stable 5384 GN24 0.000-0.047-0.047 Stable 5385 GN31 0.001-0.056-0.056 Falling 5403 GN14 0.644 0.003 0.003 Stable 5404 L80A 0.234-0.067-0.067 Statistically insignificant 5405 L80C 0.112-0.116-0.116 Statistically insignificant 5406 L160C 0.197-0.029-0.029 Stable 5409 L260C 0.234-0.013-0.013 Stable 5413 GD17 0.688-0.007-0.007 Stable 5414 GD20 0.003-0.107-0.107 Falling 5415 GD12 0.041-0.076-0.076 Falling 5416 L90A 0.002-0.126-0.126 Falling 5417 L90C 0.015-0.036-0.036 Stable 5418 GD14 0.917 0.002 0.002 Stable Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth B-8

SITE ID AWRC NAME P- VALUE SLOPE (m/yr) CHANGE IN FRESHWATER THICKNESS (m/yr) 5420 L170C 0.954 0.001 0.001 Stable 5422 L280A 0.133-0.025-0.025 Stable 5423 L280C 0.156-0.022-0.022 Stable 5424 GD19 0.000-0.131-0.131 Falling 5425 GD13 0.874-0.005-0.005 Stable 5433 JP22 0.630-0.002-0.002 Stable 5447 TM12C 0.000-0.096-0.096 Falling 5450 TM7C 0.000-0.074-0.074 Falling 5451 TM14C 0.018-0.038-0.038 Stable 5452 TM4C 0.004-0.063-0.063 Falling 5453 TM2C 0.012-0.065-0.065 Falling 5457 TM13C 0.001-0.058-0.058 Falling 5462 TM6C 0.472 0.011 0.011 Stable 5490 PVEG1 0.000-0.152-0.152 Falling 5491 PVEG2 0.000-0.161-0.161 Falling 5492 PVEG3 0.000-0.172-0.172 Falling 5506 L300A 0.370-0.022-0.022 Stable 5510 L320C 0.005-0.062-0.062 Falling 5517 L340A 0.093-0.025-0.025 Stable 5518 L340C 0.093-0.032-0.032 Stable 5528 1005 REDRILL 0.120-0.032-0.032 Stable 5544 GM34 0.001-0.172-0.172 Falling 5546 GM33 0.001-0.136-0.136 Falling 5548 GM35 0.000-0.180-0.180 Falling 5553 2025A 0.041-0.034-0.034 Stable 5555 LN19-89 0.000-0.123-0.123 Falling 5558 LN12-89 0.000-0.164-0.165 Falling 5563 LN8-89 0.000-0.147-0.147 Falling 5570 LN3-89 0.000-0.149-0.149 Falling 5571 LN24-89 0.000-0.132-0.132 Falling 5575 LN14-89 0.000-0.175-0.175 Falling 5576 LN22-89 0.000-0.171-0.171 Falling 5577 LN23-89 0.000-0.173-0.173 Falling 5578 LN16-89 0.000-0.151-0.151 Falling 5579 LN17-89 0.000-0.153-0.153 Falling GROUNDWATER LEVELS 5582 LN2-89 0.209-0.052-0.052 Statistically insignificant 5583 LN32-89 0.000-0.146-0.146 Falling 5724 QC 14-89 0.000-0.101-2.913 Falling 5725 QG 15-89 0.002-0.063-1.453 Falling 5727 QU 21-89 0.062-0.029-0.611 Statistically insignificant 5729 QJ 17-89 0.000-0.075-1.719 Falling 5732 QL 18-89 0.001-0.081-1.083 Falling 5736 QQ 24-89 0.023-0.039-1.100 Falling 5737 QV 26-89 0.007-0.077-0.077 Falling 5739 QB 27-89 0.004-0.031-1.260 Falling 5740 EG 2-89 0.006-0.034-0.209 Falling 5741 EI 1-89 0.035-0.036-0.036 Stable 5742 EF 3-89 0.657-0.004-0.162 Statistically insignificant 5743 EE 4-89 0.769 0.004 0.144 Statistically insignificant 5744 EK 5-89 0.022-0.026-0.026 Stable 5745 EA 7-89 0.158-0.012-0.012 Stable 5746 EL 6-89 0.000-0.053-0.053 Falling 5747 EO 8-89 0.000-0.052-0.421 Falling 5749 ER 11-89 0.197 0.033 0.688 Statistically insignificant 5750 EQ 10-89 0.015-0.032-0.777 Falling Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth B-9

SITE ID AWRC NAME P- VALUE SLOPE (m/yr) CHANGE IN FRESHWATER THICKNESS (m/yr) 5751 EZ 12-89 0.000-0.072-0.278 Falling GROUNDWATER LEVELS 5754 ES 30-89 0.392-0.011-0.444 Statistically insignificant 5755 EH 32-89 0.003-0.035-0.653 Falling 5756 ET 31-89 0.000-0.055-2.117 Falling 6152 2-87 0.000-0.243-0.243 Falling 6154 4-87 0.002-0.158-0.158 Falling 6224 2-85 0.323-0.043-0.043 Stable 6230 8-85 0.061-0.071-0.071 Statistically insignificant 6232 10-85 0.000-0.227-0.227 Falling 6233 11-85 0.000-0.236-0.236 Falling 6237 15-85 0.020 0.068 0.068 Rising 7915774 QX 1-90 0.008-0.052-0.390 Falling 9371196 WF1 0.079-0.028-0.223 Statistically insignificant 9371204 WF2 0.124-0.018-0.018 Stable 9371212 WF3 0.041-0.035-0.035 Stable 9371220 WF4 0.010-0.063-0.063 Falling 9371228 WF5 0.014-0.070-0.070 Falling 9371236 WF6 0.009-0.070-0.070 Falling 9371244 WF7 0.015-0.080-0.080 Falling 9371252 WF8 0.006-0.064-0.064 Falling 9371260 WF9 0.000-0.148-0.148 Falling 9371268 WF10 0.000-0.139-0.139 Falling 9371276 WF11 0.002-0.118-0.118 Falling 9371284 WF12 0.018-0.084-0.084 Falling 9371292 WF13 0.204-0.018-0.400 Statistically insignificant 9373997 LB2 0.001-0.071-0.071 Falling 9387429 LB5 0.000-0.069-0.069 Falling 9938733 LB14 0.000-0.062-0.062 Falling 9963955 T140 (I) 0.062-0.041-0.041 Stable 10022425 T61 (I) 0.045-0.066-0.066 Falling 10022433 T21 (I) 0.133-0.035-0.035 Stable 10022441 T161 (I) 0.017-0.041-0.041 Stable 10022448 BM5C 0.000-0.025-0.025 Stable 10022456 JE17C 0.084 0.016 0.016 Stable 10022463 JE18C 0.586-0.013-0.013 Stable 10022470 JE21C 0.075-0.047-0.047 Stable 10117829 JE19C 0.360-0.014-0.014 Stable 10117850 JE20C 0.002-0.055-0.055 Falling 10307645 CW1 0.000-0.221-0.221 Falling 10308029 CW4 0.000-0.262-0.262 Falling 10406970 JM51 0.143 0.060 0.060 Statistically insignificant 11188896 JE23C 0.018-0.056-0.056 Falling 11188904 JE22C 0.001-0.063-0.063 Falling 11550412 JM52 0.005-0.046-0.046 Stable 11551298 BL8530 0.001-0.030-0.030 Stable 12078898 SP1-1A 0.002 0.036 0.036 Stable 12078901 SP1-1B 0.004 0.034 0.034 Stable 12078904 SP1-1C 0.009 0.030 0.030 Stable 12282948 GNM17A (SEMINIUK D8S) 12282951 GNM17B (SEMINIUK D8D) 0.094-0.027-0.027 Stable 0.001-0.045-0.045 Stable 20031115 JP3D 0.000-0.107-0.454 Falling Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth B-10

APPENDIX C: Method for Fitting Linear Trends A simple and robust method was required to estimate trends in groundwater levels during an arbitrary time period of interest. Due to the large amount of available monitoring data, a semiautomated approach was developed to make the task manageable. The Python scripting language was used to access water level data directly from the project geodatabase and to process this data via direct calls to the statistical software package 1 R. C.1. Removal of Outliers Outliers can be identified both visually and using statistical tests. The z-score test (Mendenhall and Sincich, 1992) was used in this study. All results were verified manually. For each monitoring bore hydrograph, an outlier analysis was performed by fitting a 4 th order polynomial to the raw groundwater level data and then calculating a population of residuals as the differences between the raw data points and fitted polynomial. By applying the z-score test to the residuals, all data points with residual values greater than three standard deviations were marked as potential outliers and then examined manually. Examples are presented in Appendix Figure C-1. In these graphs, potential outliers are all data points lying outside of the outlier bounds (green lines) which are drawn at three standard deviations from the fitted polynomial (blue line). The applied formulas were: Data (water level reading): x i 4 3 2 Fitted polynomial: y = ax + bx + cx + dx e i i i i i + Residual: ri = yi xi 1 n Residual mean: r = i = r 1 i n Residual standard deviation: s = Residual z-score: z i = ( r r ) i s 1 ( n 1) ( r ) n 2 i = i r 1 Using a 4 th order polynomial was convenient for capturing longer-period peaks and troughs in curvilinear time series; however, outliers at the beginnings and ends of time series were sometimes overlooked if the 3 rd or 4 th order terms of the polynomial regression model could accommodate these end points. These outliers were identified visually. Verified outliers were excluded from all subsequent data processing and analyses. 1 R is a free software environment for statistical computing and graphics (see http://www.r-project.org/index.html) Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth C-1

Appendix Figure C-1: Examples of verified outliers: water level data (symbols); fitted 4 th order polynomial (blue line); outlier bounds at three standard deviations from the fitted polynomial (green lines) The following algorithm was used for coding the outlier analysis: For each monitoring bore # get water levels records for the period of interest # fit a fourth-order polynomial to the data # calculate the residuals # calculate mean and standard deviation of the residuals for each water level record # calculate the z-score (see note) if abs(z-score) > 3 then # store water level record as a potential outlier # plot results of the analysis Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth C-2

C.2. Aggregation of Data to Mean Annual Water Levels Mean-daily groundwater levels were first calculated for all days with measured water levels during the period of interest. These daily averages were then averaged in time over each month to obtain mean-monthly groundwater levels. The same procedure was repeated to calculate mean-semester and mean-annual groundwater levels. The aggregation process was implemented within the geodatabase using Structured Query Language (SQL). Verified outliers were excluded from this processing. C.3. Linear Regression The following rules were used to identify monitoring bores with water level records suitable for performing meaningful linear regressions. To qualify for analysis, monitoring bores required: A mean annual water level in the first year of the period of interest; A mean annual water level in the last year of the period of interest; Mean annual water levels in at least 80% of years within the period of interest. Monitoring bores that did not meet these criteria were excluded from the analysis. Appendix Figure C-2: Example linear regression models: water level data with outliers removed (black symbol); aggregated mean annual water levels (blue symbols); linear regression (blue line) Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth C-3

Linear regression models were fitted using the Python scripting language to access the project geodatabase and call the statistical software package R. Example hydrographs with fitted linear regressions are presented in Appendix Figure C-2. Black symbols joined by a red line indicate the raw water level data; blue symbols are aggregated mean annual water levels; and the blue line is the fitted linear model. C.4. Statistical Tests Results from the linear regression analysis can be displayed for various significance levels based on the P-values (Mendenhall and Sincich, 1992). The P-value, or probability value, was obtained from the F-test statistic and signifies the overall sufficiency of the linear regression model. A small P-values indicates that the model is a useful predictor, while a large P-value indicates that the model is a poor predictor and does not forecast the data significantly better than a linear model with a zero slope. The R squared and adjusted R squared statistics are correlation coefficients that measure how well the linear model explains variation in the observed data. To estimate the correlation coefficients and significance of each linear regression model the following formulas were applied: Data (water level reading): x i Linear regression model: y = mx b, where m is slope and b is the intercept. i i + Error: ei = yi xi 1 n Linear model mean: y = i = y 1 n Sum of the Squares Model: SSM = n = ( y ) Sum of the Squares Error: SSE = i = e 1 i i n 2 i i y 1 2 Mean Squared Model: MSM = SSM Mean Squared Error: 1 MSE = n ( 2) SSE Mean Squared Total: MST = MSM + MSE SSE Rsquared: R 2 = 1 SST SSE n 1 Adjusted R squared: R 2 = 1 SST n 2 F-test statistic: MSM F - ratio = MSE Probability Value: p - value = P ( F(1, n 2) F - ratio) Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth C-4

The null hypothesis is that the slope of the linear regression model is zero (i.e. H 0 : m = 0) and the alternate hypothesis is that the slope is non-zero (i.e. H a : m 0). For simple linear regression the F-test statistic has an F distribution with degrees of freedom (1, n-1). The P- value indicates the probability of observing strictly by chance an F distribution value that is greater than or equal to the calculated F-ratio. The following significance values are commonly used (Weisstein, 2005): ( δ ) 0. 05 significant", 0.01 P ( δ ) 0. 05 is "significant" and P ( δ ) 0. 01 is "highly significant". P is "not A bubble plot representation of the linear regression results was developed to gain a better statistical understanding of the results and to select an appropriate cut-off value for classifying significance. Appendix Figure C-3 is the bubble plot from the regression analysis of ten-year water levels trends from 1995 to 2004. The plot displays the P-value, adjusted-r 2 and fitted linear slope (bubbles) for all sites. P-Value, Adjusted R-Squared and Absolute Slope Adjusted R Squared 1.00 0.90 0.80 0.70 0.60 0.50 0.40 AbsSlope(m/yr) Bubble size is determined by Absolute Value of Slope P-Value < 0.025 and R-squared > 0.4 0.30 0.20 0.10 0.00 0.00 0.05 0.10 0.15 0.20 0.25 0.30 P-Value Appendix Figure C-3: Bubble plot from linear regression of 1995-2004 water level trends Results from this analysis are presented spatially in Section 5.1. of the main report. Maps of mean annual water level change from 1995 to 2004 were produced for three different significance levels: P-value < 0.01, P-value < 0.025, and P-value < 0.05. Appendix Table C-1: Slopes with P-value < 0.025; linear regression of 1995-2004 water levels Fitted Slope (S) m/yr Number of Sites S -0.05 75-0.1 S < -0.05 111-0.2 S < -0.1 79-0.3 S < -0.2 46 S < -0.3 3 Total 314 Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth C-5

In this example it can be seen that most large slopes (large bubbles) have P-value less than 0.025. Out of 543 monitoring bores that had suitable water level data for performing a linear regression, 314 (58%) had P-values greater than 0.025 (Appendix Table C-1and Appendix Figure C-4). All regression models with P-values below this cut-off had adjusted-r 2 values greater than 0.4. Increasing the P-value cut-off to 0.05 would add a set of points that have relatively low slopes. Further increasing the cut-off to above 0.05 would introduce additional sites that have higher slopes that are not well correlated or as significant. On this basis, it is reasonable to set a P-value cut-off up to 0.05 but not higher. Setting the P-value cut-off at 0.025 provides the greatest level of certainty without the loss of too much information. The histogram in Appendix Figure C-4 depicts slopes from the 314 monitoring bore sites that have P-values less than 0.025. While this representation of the results neglects spatial bias caused by the non-uniform distribution of monitoring bore sites, it nevertheless indicates a skew in the direction of negative slope. This suggests that groundwater levels are generally falling. The histogram in Appendix Figure C-5 includes all 543 monitoring bore sites, and reveals that a large number of sites have almost zero slopes. Again, it is skewed to the left and indicates that more sites have falling water levels. Histogram of Slope with P-Value < 0.025 Frequency 0 20 40 60 80 100-0.3-0.2-0.1 0.0 0.1 Slope(m/yr) Appendix Figure C-4: Histogram of slope with P-value < 0.025 from linear regression of 1995-2004 water level trends Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth C-6

Histogram of Slope Frequency 0 50 100 150 200-0.3-0.2-0.1 0.0 0.1 Slope(m/yr) Appendix Figure C-5: Histogram of slope (all sites) from linear regression of 1995-2004 water level trends Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth C-7

APPENDIX D: Methodology for Estimating Seawater Intrusion Effects A simple hydrostatic relation was used to convert the estimated changes of mean annual groundwater levels (APPENDIX C) to estimated changes of total freshwater thickness. The same method was applied spatially to map the theoretical extent of seawater intrusion and thickness of the coastal seawater wedge across all of the study area. While the method described below was applied across all of the study area for computational convenience, it is important to stress that only areas that are adjacent to the ocean and Swan-Canning Estuary are susceptible to seawater intrusion. D.1. Change in Mean Freshwater Thickness Change in total mean freshwater thickness at monitoring bore locations was calculating as the difference between the mean freshwater thicknesses at the start and end of the time period of interest. A linear regression model was used to estimate both the mean water level and the corresponding hydrostatic position of the seawater-freshwater interface. If the theoretical seawater-freshwater interface position was found to be below the base of the aquifer then the estimated freshwater thickness was reduced accordingly. For the purpose of estimating seawater intrusion, the base of the Rockingham Sand was taken as the base of the Superficial Aquifer where this unit underlays the Superficial Aquifer. The Ghyben-Herzberg approximation is a simple hydrostatic relation based on the typical density difference between freshwater and seawater. In a freshwater aquifer, it predicts that the depth to an abrupt seawater-freshwater interface will be approximately forty times the height of the groundwater elevation above mean sea level. The mathematical formula is: 1 hs = h f = 40h ρ ρ s f f where h s is the depth of freshwater below sea level, h f is the depth of freshwater above sea level, ρ s = 1.025 Kg/L is the density of seawater and ρ f = 1.0 Kg/L is the density of freshwater. The algorithm used to adjust freshwater thickness for seawater intrusion is listed following: # MAIN for each monitoring bore site base_super = base of the superficial aquifer for this site # calculate water levels at the start and end of the period of interest from the linear regression wl(t0) = groundwater level from linear regression model at start of period wl(t1) = groundwater level from linear regression model at end of period # calculate the freshwater thickness at the start and end of the period of interest th(t0) = calculate_thickness( wl(t0), base_super) th(t1) = calculate_thickness( wl(t1), base_super) # calculate change in the freshwater thickness delta_th = th(t1) - th(t0) # update geodatabase with delta_th # END MAIN Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth D-1

# Function to calculate freshwater thickness calculate_thickness(waterlevel, base_super) # calculate the position of the seawater-freshwater interface saltwater_interface = -40 * waterlevel # calculate the potential freshwater thickness that is occupied by basement x = base_super - saltwater_interface # check whether the basement is below the potential seawater-freshwater interface if x < 0 then x = 0 # calculate freshwater thickness fresh_water_thickness = waterlevel - saltwater_interface x return fresh_water_thickness # END calculate_thickness D.2. Regional Mapping of the Seawater-Freshwater interface The same hydrostatic approximation was used to map the theoretical extent and thickness of the seawater wedge across all of the study area. Surfaces of watertable elevation and base of aquifer elevation were produced by building Triangulated Irregular Networks (TINs) from contour datasets. The TINs were converted to the following raster surfaces, which are contained in the project geodatabase: Groundwater levels converted from May 2003, 1-metre contour data, as produced by the Department of Environment (APPENDIX A); Base of Superficial Aquifer elevations converted from 5-metres contour data, as produced by Department of Environment for the Perth Regional Aquifer Modelling System (PRAMS) Base of Rockingham Sand converted from 50-metres contour data, as produced by Department of Environment for the Perth Regional Aquifer Modelling System (PRAMS) Assuming that mean sea level elevation is approximately zero, the theoretical elevation of the seawater-freshwater interface was calculated as: For all raster cells saltwater_interface = -40 * groundwater_level The maximum inland extent of the seawater-freshwater interface (i.e., position of the toe of the seawater wedge) was then calculated as: For all raster cells if saltwater_interface > basement then saltwater_intrusion_extent = true else saltwater_intrusion_extent = false end if Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth D-2

Lastly, the thickness of the seawater wedge was calculated: For all raster cells if saltwater_interface > basement then saltwater_wedge_thickness = saltwater_interface - basement else saltwater_wedge_thickness = 0 end if Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth D-3

PLATE 1: Topography Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth I

PLATE 2: Superficial Aquifer flow areas Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth II

PLATE 3: Water Corporation production bores (not all of these bores are commissioned) Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth III

PLATE 4: Main drain network and surface catchments Opportunity for Additional Self Supply of Groundwater from the Superficial Aquifer beneath Metropolitan Perth IV