Hydrogeology and Groundwater Flow Model

HYDROGEOLOGY AND GROUNDWATER FLOW MODEL,

CENTRAL CATCHMENT OF BRIBIE ISLAND, SOUTHEAST QUEENSLAND

Joanne M. Jackson Bachelor of Science (Honours)

SUPERVISOR

Assoc. Professor Malcolm Cox Queensland University of Technology

A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Applied Science. 2007

School of Natural Resource Sciences

Queensland University of Technology

Brisbane, Queensland, Australia

STATEMENT OF ORIGINAL AUTHORSHIP

The work contained in this thesis has not been previously submitted for a degree or diploma at any other higher education institution. To the best of my knowledge and belief, the thesis contains no material previously published or written by another person except where due reference is made.

Signed: ……………………………………..

Joanne Jackson

Date: ……………………………………..

ABSTRACT

Bribie Island is a large, heterogeneous, sand barrier island that contains groundwater aquifers of commercial and environmental significance. Population growth has resulted in expanding residential developments and consequently increased demand for water. Caboolture Shire Council (CSC) has proposed to increase groundwater extraction by a new borefield.

Two aquifers exist within the Quaternary sandmass which are separated by an indurated sand layer that is ubiquitous in the area. A shallow aquifer occurs in the surficial, clean sands and is perched on the indurated sands. Water levels in the shallow water table aquifer follow the topography and groundwater occurs under unconfined conditions in this system. A basal aquifer occurs beneath the indurated sands, which act as a semi-confining layer in the island system. The potentiometric surface of the basal aquifer occurs as a gentle groundwater mound.

The shallow groundwater system supports water-dependent ecosystems including wetlands, native woodlands and commercial pine plantations. Excessive groundwater extraction could lower the water table in the shallow aquifer to below the root depth of vegetation on the island.

Groundwater discharge along the coastline is essential to maintain the position of the saline water - fresh groundwater boundary in this island aquifer system. Any activity that changes the volume of fresh water discharge or lowers the water table or potentiometric surface below sea level will result in a consequent change in the saline water – freshwater interface and could lead to saline water intrusion.

Groundwater level data was compared with the residual rainfall mass curve (RRMC) on hydrographs, which revealed that the major trends in groundwater levels are related to rainfall. Bribie Island has a sub-tropical climate, with a mean annual rainfall of around 1358mm/year (Bongaree station). Mean annual pan evaporation is around 1679mm/year and estimates of the potential evapotranspiration rates range from 1003 to 1293mm/year.

Flows from creeks, the central swale and groundwater discharged from the area have the potential to affect water quality within the tidal estuary, Pumicestone Passage. Groundwater within the island aquifer system is fresh with electrical conductivity ranging from 61 to 1018µS/cm while water near the coast, canals or tidal creeks is brackish to saline (1596 to 34800µS/cm). Measurements of pH show that all groundwater is acidic to slightly acidic (3.3-6.6), the lower values are attributed to the breakdown of plant material into organic acids.

Groundwater is dominated by Na-Cl type water, which is expected in a coastal island environment with Na-Cl rainfall. Some groundwater samples possess higher concentrations of calcium and bicarbonate ions, which could be due to chemical interactions with buried shell beds while water is infiltrating to depth and due to the longer residence times of groundwater in the basal aquifer.

A steady-state, sub-regional groundwater flow model was developed using the Visual MODFLOW computer package. The 4 layer, flow model simulated the existing hydrogeological system and the dominant groundwater processes controlling groundwater flow. The numerical model was calibrated against existing data and returned reasonable estimates of groundwater levels and hydraulic parameters. The model illustrated that:

The primary source of groundwater recharge is infiltration of rainfall for the upper, perched aquifer (Layer 1). Recharge for the lower sand layers is via vertical leakage from the upper, perched aquifer, through the indurated sands (Layers 2 and 3) to the semi-confined, basal aquifer (Layer 4). The dominant drainage processes on Bribie Island are evapotranspiration (15070m3/day) and groundwater seepage from the coast, canals and tidal creeks (9512m3/day). Analytical calculations using Darcy’s Law estimated that approximately 8000m3/day of groundwater discharges from central Bribie Island, approximately 16% less than the model. As groundwater flows preferentially toward the steepest hydraulic gradient, the main direction of horizontal groundwater flow is expected to be along an east- west axis, towards either the central swale or the coastline. The central swale was found to act as a groundwater sink in the project area.

ACKNOWLEGDEMENTS

I would like to thank everyone who helped in the completion of this research project. The successful completion of this study has been made possible through the practical and professional support and advice of many people, institutions and departments, in particular:

I appreciate the support, guidance and expertise of Associate Professor Malcolm Cox (principal supervisor), School of Natural Resource Sciences, Queensland University of Technology.

Queensland University of Technology Staff

Dr. Micaela Preda, Dr. Deliana Gabeva, Wathsala Kumar, Bill Kwiecien and Dr. Les Dawes.

Other Students: John Harbison, Tim Armstrong, Ken Spring, Lucy Paul and Genevieve Larsen.

Funding for this study was provided by:

Caboolture Shire Council, QM Properties and Pacific Silica.

I appreciate the assistance and data provided by:

Bureau of Meteorology

Caboolture Shire Council

Caloundra City Council

Department of Natural Resources, Mines and Energy

Forestry Plantations Queensland (previously DPI Forestry)

HLA Envirosciences Pty. Ltd

Matrix Plus Consulting Pty Limited

QM Properties

Queensland Parks and Wildlife

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TABLE OF CONTENTS

1. INTRODUCTION 1

1.1 Aims and Objectives 2

1.2 Scope of Work 3

1.2.1 Data Review 3

1.2.2 Field Work 3

1.2.3 Interpretation of Results 4

1.3 Significance of Project 4

2. BACKGROUND 7

2.1 Location 7

2.2 Topography and Vegetation 8

2.3 Climate 8

2.4 Land Use 8

2.5 Geomorphology 10

2.6 Regional Geology 12

2.6.1 Landsborough Sandstone Formation 14

2.6.2 Quaternary Sand 17

2.6.3 Indurated Sandstone 18

2.7 Regional Hydrogeology 19

2.7.1 Aquifer Recharge 20

2.7.2 Drainage 21

2.7.3 Hydraulic Parameters 22

2.8 Previous Work, Bribie Island 22

2.8.1 Groundwater Studies 22

2.8.2 Groundwater Modelling 25

3. METHODOLOGY 27

3.1 Hydraulic Monitoring Network 27

3.1.1 Climate 27

3.1.2 Monitoring Bore Network 27

3.1.3 Groundwater Quality 28

3.2 Modelling 29

3.2.1 Conceptual Model 29

3.2.2 Mathematical Modelling 30

4. RESULTS 44

4.1 Hydraulic Monitoring Data 44

4.1.1 Climate 44

4.1.2 Monitoring Bore Network 46

4.1.3 Groundwater Quality 51

4.2 Modelling 55

4.2.1 Conceptual Model 55

4.2.2 Mathematical Modelling 56

5. DISCUSSION AND SUMMARY 67

5.1 Hydraulic Monitoring 67

5.1.1 Climate 67

5.1.2 Monitoring Bore Network 67

5.1.3 Groundwater Quality 68

5.2 Modelling 70

5.2.1 Analytical Solution 70

5.2.2 Numerical Modelling 70

6. CONCLUSIONS AND FURTURE CONSIDERATIONS 75

6.1 Monitoring Bore Network 75

6.2 Groundwater Quality 76

6.3 Numerical Model 77

7. REFERENCES 80

LIST OF FIGURES

Figure 1. Location map of Bribie Island 7

Figure 2. Land use map of Bribie Island 9

Figure 3. Sea level fluctuation in the Late Quaternary 11

Figure 4. Sedimentary basins in Moreton region 13

Figure 5. Lithology of Bribie Island showing Quaternary sedimentary deposits 15

Figure 6. Hydrogeological cross section showing monitoring bores 16

Figure 7 Maximum extent of the sea during the last inter-glacial 17

Figure 8. Pumicestone Region Catchment showing Bribie Island subcatchment 20

Figure 9. Mathematical models are based on a conceptual understanding 30

Figure 10. Model configuration of central Bribie Island 33

Figure 11. Cross section of model showing the four model layers. 35

Figure 12. Topography for the whole of Bribie Island. 36

Figure 13. Boundary conditions for a) Layer 1 and b) Layers 2, 3 and 4 38

Figure 14. Location of 25 shallow monitoring bores used in the model (Layer 1) 39

Figure 15. Location of 20 deep monitoring bores used in the model (Layer 4) 40

Figure 16. Zones of hydraulic conductivities showing observation bores 41

Figure 17. Evapotranspiration zones split according to dominant vegetation type 42

Figure 18. Summary of the four types of sensitivity 43

Figure 19. Mean daily temperatures for Caloundra, Cape Moreton and Redcliffe 44

Figure 20. Average monthly rainfall on southern Bribie Island 45

Figure 21. Mean monthly rainfall compared to mean monthly pan evaporation 45

Figure 22. Location of monitoring bores used to build the geological framework 46

Figure 23. Heterogeneous sandmass of Bribie Island 48

Figure 24. Hydrograph of long-term groundwater levels and the RRMC 49

Figure 25. Cross section through central Bribie Island showing grounwater 50

Figure 26. Trilinear plot of groundwater chemistry samples 52

Figure 27. Schoeller plot of groundwater chemistry samples 53

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Figure 28. Stiff patterns overlain on the cross section through central Bribie Island 54

Figure 29. Hydraulic conductivities determined mathematically using WinPEST 59

Figure 30. Simulated water levels from steady-state model 60

Figure 31. Calculated verses observed water levels, steady-state model 62

Figure 32. Mass balance for steady-state model 62

Figure 33. Sensitivity analysis for steady-state model 66

LIST OF TABLES

Table 1. Stratigraphical succession 14

Table 2. Results of hydraulic testing 22

Table 3. Field parameters measured with a TPS meter 28

Table 4. Parameters tested for during water chemistry analysis 29

Table 5. Hydrogeological layers used in the model 35

Table 6. Groundwater physico-chemical measurements from monitoring bores 51

Table 7. Estimated groundwater discharge 56

Table 8. Zone budget for steady-state model 64

APPENDICES

Appendix A Climate Records

Appendix B Mean Pan Evaporation

Appendix C Summary of Monitoring Bore Details

Appendix D Standing Water Levels and Physico-chemical Parameters

Appendix E Groundwater Chemical Analyses

Appendix F Steady-state Groundwater Flow Model

Appendix G Observed and Calculated Water Levels - Steady-state Model

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1. INTRODUCTION Groundwater is a pervasive and vulnerable resource. Hydrogeological investigations must be conducted to enable us to sustain and protect these resources, the ecosystems that they support and to overcome problems water quality issues such as salinisation and pollution. In order to achieve these goals, we require an understanding of the fundamental processes that control groundwater quantity and quality.

Coastal zones are often densely populated areas that experience high demand for fresh water. In coastal aquifers, water quality degradation resulting from saline water intrusion is a common issue of concern.

Growing demands from industry, energy production, urban population centres and agriculture place an increasing strain on the quantity and quality of water resources. In combination with traditional hydraulic monitoring methods, mathematical modelling has emerged as an important tool used to understand groundwater flow in aquifers. In the following examples, models are used to assess various groundwater aquifers:

Aveiro Aquifer, Portugal - a Cretaceous coastal aquifer was modelled to give a better understanding of the groundwater flow conditions and the existing geochemical processes. Mathematical modelling confirmed a reduction of the naturally occurring hydraulic gradient and limited aquifer recharge from natural sources (Condesso de Melo et al, 1998).

Big Pine Key, Florida, USA – a small oceanic island with several canal developments. The study examined the types of canals that are most detrimental to the fresh groundwater supplies. It was found that the effect of the canals depended on the relative penetration and position of the development. Canals bisecting long, rectilinear islands reduced the groundwater lens volume more than canal developments at the ends of the islands (Langevin et al, 1998).

North Stradbroke Island, Queensland, Australia - a large sand island that extracts surface and ground water for town supply and for mining operations. A whole-of- island groundwater flow model was developed with MODFLOW and PEST-ASP to assist with managing the long-term sustainability of these resources (Chen, 2002).

Trinity Aquifer, Texas, USA - a multilayer, sedimentary aquifer. The groundwater flow model was developed with MODFLOW to predict water level responses to pumping and drought. This enabled the prediction of areas likely to be impacted from declining water levels in the future scenarios (Mace et al, 2000).

1.1 AIMS AND OBJECTIVES This study aimed to characterise the existing groundwater environment and to conceptualise groundwater flow processes in the central catchment of Bribie Island, near the Pacific Harbour canal estate and residential golf course developments.

The objectives of the hydrogeological study were to:

establish a geological framework for the area from existing drill hole data and downhole gamma-ray logs.

evaluate the link between the upper and lower aquifers by monitoring groundwater levels and testing groundwater quality.

integrate the data to develop a conceptual hydrogeological model for the area.

calculate a preliminary estimate of groundwater discharge from the central catchment of Bribie Island using Darcy’s Law.

simulate the dominant processes controlling groundwater flow and discharge by developing a 3D groundwater flow model in the central catchment of Bribie Island, using the Visual MODFLOW program (version 3.1 with WinPEST). The purpose of the model is to assist in understanding groundwater flows through the aquifer system in the central catchment of the island.

1.2 SCOPE OF WORK

1.2.1 Data Review The data review process involved:

acquiring and reviewing available geological and hydrogeological information. Data was sourced from the Department of Natural Resources, Mines and Water (DNRMW) database of registered bores, HLA Envirosciences Pty Ltd (on behalf of QM Properties) and Queensland University of Technology (QUT). Information reviewed included lithological logs, gamma-ray logs, results of groundwater quality and water level monitoring and hydraulic testing within monitoring bores.

acquiring and reviewing climatic information. Data was sourced from the Bureau of Meteorology (BOM), the DNRMW and University of Queensland (UQ). Information included rainfall records, temperature and pan evaporation data.

reviewing reports of previous studies undertaken in the Bribie Island region.

1.2.2 Field Work The field program was designed to obtain site-specific information in the central catchment of Bribie Island, near the Pacific Harbour residential golf course development. The field program included:

monitoring of groundwater levels within existing monitoring bores to determine static water levels; and

sampling and laboratory analysis of groundwater from selected monitoring bores within each aquifer to acquire water chemistry information.

The data gathered aimed to assist with understanding groundwater quality, groundwater occurrence and flow processes within the system and to support the development of the conceptual and numerical models.

1.2.3 Interpretation of Results The interpretation of results involved:

collating and analysing results from the field program;

interpreting geological and hydrological data to develop a conceptual model for the central Bribie Island area; and

assessing groundwater occurrence and flow processes in the central catchment of Bribie Island by developing a rudimentary 3D groundwater flow model using the Visual MODFLOW computer program.

1.3 SIGNIFICANCE OF PROJECT Bribie Island is a large, sand barrier island that contains groundwater supplies of commercial and environmental significance. There are competing demands on this groundwater system that have lead to an increased stress on the local groundwater resources. These groundwater resources are finite and must be carefully managed.

Groundwater discharge from this island aquifer system is essential to maintain the position of the saline water - fresh groundwater boundary and thus protect the aquifer system. The quantity and quality of environmental flows from creeks and groundwater discharged from the area has the potential to affect water quality within the tidal estuary, Pumicestone Passage.

Tidal wetlands and waters around Bribie Island are protected as part of Moreton Bay Marine Park. The passage provides a breeding area for fish, crabs and prawns and it contains a population of dugong that feed on its seagrass beds. The region provides an essential habitat for many species of migratory and non-migratory birds. Due to its extensive system of tidal flats, mangroves, salt marsh and claypan, the passage has been listed under the Ramsar Convention as an important site for roosting and feeding for migratory species. The Ramsar Convention is an international treaty that aims to preserve intertidal feeding banks in both hemispheres and along the flight paths of migratory bird species (South East Queensland Regional Strategy Group, 2000).

The shallow groundwater system supports water-dependent ecosystems including wetlands, native woodlands and commercial pine plantations. Commercial pine plantations and National Parks cover a significant portion of the island. Native vegetation within the National Parks largely consists of heaths, paperbark wetlands, open forests and woodlands. The vegetation on the island is phreatophytic (i.e. the plants send a root to groundwater) and utilise the shallow, perched groundwater system.

Population growth has resulted in expanding residential developments, including the Pacific Harbour canal and golf course residential estates. Population growth across the southern portion of Bribie Island has led to an increased demand for water for domestic, industrial and horticultural uses.

Caboolture Shire Council (CSC) has proposed to increase groundwater extraction to make the island self-sufficient for water supply. In late September 2006, CSC commenced test drilling and construction of production bores on the island. The CSC estimates that the new borefield could produce an environmentally sustainable yield of up to 10 megalitres of water per day.

Areas of concern that relate to an excessive extraction of groundwater along coastal zones include:

seawater infiltration into the island aquifer system. Saline water intrusion is the most common type of water quality degradation that occurs in coastal aquifers (Fetter, 2001). Saline water sources for Bribie Island include the seawater surrounding the island and surface tidal waters in natural estuaries and in artificial canals. The position of the saline water - fresh groundwater boundary is a function of the volume of fresh water discharging from the aquifer system. Any action that changes the volume of groundwater discharge or lowers the water table or potentiometric surface below sea level will result in a consequent change in the saline water – freshwater interface (Driscoll, 1986; Fetter, 2001).

impact on native vegetation (including wetlands and native woodlands) and commercial pine plantations resulting from changes to groundwater levels. Phreatophytic vegetation on the island is supported by the fresh water in the shallow groundwater system. Excessive groundwater extraction could lower the water table in the shallow aquifer below the root depth of vegetation on the island.

Exploitation of groundwater resources has the potential to significantly alter groundwater levels and intrinsic processes. These processes may influence and even control the health of associated ecosystems.

Groundwater level monitoring and water quality testing will assist with characterising the existing groundwater environment and developing an understanding of the flow processes involved. Building a conceptual model and a rudimentary mathematical model will assist with conceptualising groundwater occurrence and flow processes in the central catchment of Bribie Island, near the Pacific Harbour developments.

2. BACKGROUND

2.1 LOCATION Bribie Island is located on the east coast of Australia, approximately 65 km north of Brisbane as shown in Figure 1. It lies parallel to the southern Queensland coastline and forms the northwestern perimeter of Moreton Bay. Bribie is separated from the mainland by the narrow, tidal estuary, Pumicestone Passage.

The island lies between 26o 49’ South and 27o 06’ South latitude and 153o 04’ 20” East and 153o 12’ 30” East longitude. Bribie covers an area of approx 150 km2, is around 30 km long and ranges from 5 to 7.5 km wide.

Ki l o m e t re s Caloundra 01020

Bribie Isla nd PUM I C ESTO N E 27°00′ PASSAG E

Ningi Moreton Island Caboolture Rive r DEC EPTION BAY

Re d c lif fe MORETON BAY Pi ne Ri ve r

Shorncliffe

North Br i sb a n e Stradbroke 27°30′ Rive r Island

153°00′ 153°30′ Figure 1. Location map of Bribie Island

2.2 TOPOGRAPHY AND VEGETATION Bribie Island is a low lying, vegetated, sand barrier island. The topographic highs occur on the beach ridge systems, with a maximum elevation of around 14m above Australian Height Datum (AHD). The ridges slope gently down into the central swale area and to the coastline.

The shallow groundwater aquifer on Bribie Island supports exotic and native, phreatophytic vegetation. Exotic, commercial pine plantations cover a large portion of the northern and central areas of Bribie. The rooting depth of mature aged pines in unsaturated soil profiles could range from 3 to 5 metres (and use up to 150ml of water a day) (K. Bubb, pers comm., 2005). Large areas of remnant native vegetation occur on the island including Acacia scrub, Banksia woodland, softwood scrub, Melaleuca forest, eucalypt woodland and heath communities. Dense stands dominated by Melaleuca quinquenervia (broad-leaved paperbark) occur mainly in the low, poorly drained areas, such as the central swale, along the western side of the island (James and Bulley, 2004). This species of vegetation usually grows best in swampy sites surrounded by open forest (Boland et al, 1992).

2.3 CLIMATE The island has a sub-tropical climate and experiences a wet summer and a dry winter. Mean annual rainfall from the Bongaree station is 1358mm/year (Bureau of Meteorology).

Pan evaporation values fluctuate with the seasons with maximum values occurring from October to January. The mean annual pan evaporation values recorded at the University of Queensland, Bribie Island weather station were 1679mm/year (DNR, 1996). Potential evapotranspiration rates were estimated from water balance models and range from 60% (~1003mm/year, Williams, 1998) to 77% (~1293mm/year, Bubb and Croton, 2000) of pan evaporation.

2.4 LAND USE Figure 2 displays the main land uses on Bribie Island which include native vegetation, exotic pine plantations, residential and recreational areas (golf clubs, parks and sports fields). Caboolture Shire Council administers the southern two thirds of the island. Urban development is restricted to southern part of Bribie, which is experiencing rapid population growth. Caloundra City Council manages the northern one third of the island, which does not contain residential areas.

Figure 2. Land use map of Bribie Island showing the extent of vegetation and development on the island (modified from Caboolture Shire Council, 2003)

There are two conservation reserves on the island, the Bribie National Park (4770ha) and the Buckleys Hole Conservation Park (87.7ha). All tidal areas and waters around the island are gazetted as the Moreton Bay Marine Park (EPA).

Bribie Island currently uses two sources to supply urban water demands. Local groundwater treated at the Bribie Water Treatment Plant supplies the southern and eastern areas, while the mainland North Pine Dam Water Treatment Plant supplies water to northern areas and meets demand above the capacity of the Bribie Water Treatment Plant (CSC). Brisbane City Council (BCC) is responsible for the operation and maintenance of the North Pine WTP.

Sewage is piped to the Sewage Treatment Plant, which is located in the southwestern corner of the water reserve on southern Bribie Island. Treated sewage is discharged into infiltration ponds south of the sewage treatment plant (Isaacs and Walker, 1983; Marszalek and Isaacs, 1988).

Currently (October – December 2006) Caboolture Shire Council is undertaking test drilling and construction of production bores on the island. Pumping tests are being conducted within the new bore field to determine yield capacities.

2.5 GEOMORPHOLOGY Moreton Bay is formed by large sand islands on its eastern side. Sea level change has dominated the geological history of Moreton Bay. Eustatic oscillations have resulted in the emergence and submergence of the coastal lowlands within an altitudinal range of approximately 150m since the beginning of the Pleistocene. Figure 3 illustrates the amplitude of the sea level rise at the conclusion of the last Ice Age, reaching a maximum height (+1.5m) around 6500 years ago. Sea levels dropped to present levels around 3000 years ago (DEH, 1993; Jones, 1992a; Lang et al., 1998).

These sea level oscillations created a series of differing environments that controlled the deposition of sediment. During periods of low sea level, the floor of Moreton Bay was exposed and rivers could incise channels and flow across the bay surface. As sea levels rose, the sediments were submerged, but while the water was still relatively shallow, waves were able to wash some sediments towards the shore to accumulate on beaches and foredunes (DEH, 1993; Jones, 1992a; Lang et al., 1998).

Figure 3. Sea level fluctuation in the Late Quaternary showing when Moreton Bay was dry (modified from Jones, M.R. (1992a); Lang et al., (1998))

Bribie Island is best considered as a low lying, sand barrier island. The island developed when a strandplain of prograded beach ridges bordering the coast was separated from the mainland by the formation of Pumicestone Passage tidal estuary. The sequence of sand dunes evolution extends from the Holocene period (less than 10,000 BP) to before the last Pleistocene interglacial period (120,000- 140,000 BP) (DEH, 1993; Cox et al., 2000b).

The evolutionary classification of depositional coastal environments is based on the relative roles of three main hydrodynamic processes: waves, tides and river outflow. In this framework, coastal barriers can be considered the basic depositional element on wave-dominated coasts. On these barriers the coastal dune, beach and shoreface are sub-environments that make up large-scale coastal accumulation features (Masselink and Hughes, 2003).

Barriers occur typically as elongated, shore-parallel sand bodies that extend above sea level. A back-barrier environment, such as an estuary or lagoon, generally occurs between the barrier and the mainland (Masselink and Hughes, 2003). In the case of Bribie Island, Pumicestone Passage formed as a passage-type estuary as a result of the development of the Bribie Island barrier (DEH, 1993; Cox et al., 2000b).

2.6 REGIONAL GEOLOGY Bribie Island is located at the edge of the Late Triassic to Early Jurassic age Nambour Basin in coastal southeastern Queensland as seen in Figure 4. The Nambour Basin is a small, intracratonic basin with rock assemblages of less than 600m thick. The western boundary of the basin is adjacent to the Palaeozoic basement rocks of the D’Aguilar Block to the northwest and the Beenleigh Block to the southeast (McKellar, 1993; Cox et al., 2000b; Geoscience Australia, 2003).

Sediment for the Nambour Basin was derived from the erosion of mountains to the south and west of the coastline. Sandy sediments with minor gravel and mud were deposited on broad plains by braided rivers in the eastern part of the region. These areas gradually subsided allowing a greater thickness of sediments to accumulate. These sediments consolidated to form the Landsborough Sandstone in the southern Nambour Basin, which forms the bedrock for the Pumicestone catchment (Willmott and Stevens, 1988; Cox et al., 2000b).

The regional basin experienced a Late Triassic Norian orogeny and the resulting uplift exposed the newly stabilised continent to erosion. Ongoing erosion carved the present landscape, depositing material in floodplains, as well as carrying sediment out to sea (Cox et al., 2000b; Geoscience Australia, 2003).

Fluvial sediments of the Early Jurassic Landsborough Sandstone Formation form the bedrock below Bribie Island, although no outcrop of this formation occurs on the island. Quaternary age (Pleistocene and Holocene) sand deposits overlie this sedimentary rock unit. Table 1 lists the stratigraphical succession for Bribie Island and Figure 5 shows the Quaternary sedimentary deposits on the island. Through the interpretation of geological logs and downhole gamma-ray logs of monitoring bores, a lithological cross section of central Bribie Island was developed and is shown in Figure 6 (Armstrong, 2006).

Figure 4. Sedimentary basins in Moreton region (modified from Geoscience Australia, 2003)

Age Lithology

Holocene accretion ridges and swales undifferentiated sediments - mainly back barrier Holocene to Pleistocene deposits of sand and mud Pleistocene accretion ridges and swales Early Jurassic Landsborough Sandstone Formation

Table 1. Stratigraphical succession (modified from Ishaq, 1980; Harbison, 1998; Spring, 2005)

2.6.1 Landsborough Sandstone Formation The Landsborough Sandstone Formation consists of Late Triassic to Early Jurassic fluviatile sedimentary rock units. McKellar (1993) details the stratigraphic relationships of the Nambour Basin.

In the southern part of the Nambour Basin, the base of the Landsborough Sandstone Formation contains pebble to cobble conglomerate together with interbedded sandstone, siltstone, shale (partly carbonaceous) and minor coal (McKellar, 1993; Cox et al., 2000b).

These lower beds are overlain by fine to coarse-grained, massive quartzose and sublabile sandstone in the southern area. These beds correlate lithologically with the basal-lower Landsborough Sandstone in northern Nambour Basin (McKellar, 1993).

The upper portion of the Landsborough Sandstone Formation consists of fine to medium-grained and relatively less quartzose (labile to sublabile) sandstone, minor conglomerate, siltstone, shale (partly carbonaceous) and coal (McKellar, 1993).

Figure 5. Lithology of Bribie Island showing Quaternary sedimentary deposits (modified from Department of Mining and Energy, 1999)

Figure 6. Hydrogeological cross section showing monitoring bores and gamma-ray logs (modified from Armstrong, 2006)

2.6.2 Quaternary Sand During the Quaternary, Australia was tectonically relatively stable. During the Pleistocene (around 120,000 years ago), before the last Ice Age, the sea level was 1 to 5m higher than present day. The Pleistocene coastline which is shown in Figure 7 lay further to the west, inland of the present coastline. This resulted in seawater covering most of the low-lying coastal areas. Between the headlands and islands of this time, sediment deposition produced low barrier sand spits. Shallow tidal sand banks (tidal deltas) accumulated behind the spits from marine sediments swept around into the calmer waters. Inland of the tidal deltas lay extensive bays of open water, which were backed by mangrove estuaries and mud flats. The bays gradually filled in with sediments of mud and sand (Willmott and Stevens, 1988).

Figure 7 Maximum extent of the sea during the last inter-glacial approximately 120,000 years ago (modified from Willmott and Stevens, 1988)

When sea levels fell during the last Ice Age, these bays and sandy tidal deltas were exposed to become dry land. River channels that flowed eastward to the sea consequently cut this area. Sea levels have not returned to this previous highstand and consequently, the sediments are preserved and form the present coastline. When the sea rose again to its present level, sands of the outer barrier spits were redistributed, except in the southern area were remnant sand ridges of this age form the core of Bribie Island (Willmott and Stevens, 1988).

Thompson (1992) delineated two types of sand deposit that typically occur along the east coast of Australia: a) Low sand ridges and swales that occur parallel to the coast. These formations were widely distributed along the east coast. b) Multiple systems of transgressive, parabolic dunes with the trailing arms of the dunes open to the onshore winds from the southeast. These dunes can also be influenced by local conditions such as bedrock morphology and smaller scale local wind patterns.

2.6.3 Indurated Sandstone Darker coloured layers of variable induration are common in the sediments of coastal lowlands of subtropical southern Queensland. These induration layers typically occur in coarsely textured, highly quartzose, base-poor parent materials such as sands which generally lack minerals with the potential to weather to crystalline clays (Thompson, 1992; Lundstrom et al., 2000). These layers occur on remanent Pleistocene beach ridges and tidal delta deposits (Jones, 1992b) and on sandy alluvial fans and floodplains along streams (Thompson et al., 1996).

Numerous processes that can result in induration include: pedogenic induration within subsurface horizons of a soil profile; groundwater induration within a sediment profile; and/or aquatic induration by direct precipitation of materials onto floors of surficial water bodies (Pye, 1982).

Pye (1982) summarised the processes involved in induration as:

the formation of soluble and colloidal substances that are subsequently leached by rainwater;

the vertical and lateral transport of substances by rainfall or groundwater to areas where rates of water flow are low;

the subsequent precipitation or flocculation of inorganic and/or organic complexes on reaching an environment with different physical or chemical conditions within the sediment or water; and

the irreversible drying of substances during periods of seasonal water table lowering.

Cox et al. (2002a) found that induration within the Moreton Bay area and on Bribie Island was mainly caused by organic carbon, Fe compounds and fine clays precipitates. These substances were carried down sand profiles, coating grains and partially filling in pore spaces. The resulting induration was both laterally and vertically variable. Because of this process, the sediments would develop variable porosity and reduced permeability. These indurated sands were found to have hydrogeological significance as they can act as a semi-confining layer that influences groundwater flows, separate groundwater bodies, and reduce storage within the aquifer (Harbison, 1998; Cox et al., 2000a; Cox et al., 2002, Armstrong, 2006).

2.7 REGIONAL HYDROGEOLOGY Bribie Island is a subcatchment of the coastal Pumicestone Region Catchment which is shown in Figure 8. This catchment adjoins the catchments of Maroochy– Mooloolah to the north, Pine Rivers to the south and the Stanley to the west.

Bribie is a low sand island of approximately 150km2 that accommodates two sandmass aquifers. Groundwater forms as a freshwater 'lens' that is stored within the intergranular spaces of the porous, Quaternary sand deposits.

There are two distinct groundwater bodies occurring on the island: a shallow, perched, unconfined aquifer; and a deeper, semi-confined, basal aquifer. A hydrogeologically significant layer of more or less impervious indurated sands, locally known as “Coffee Rock”, separates these aquifers (Harbison, 1998; Harbison and Cox, 1998; Armstrong, 2006).

2.7.1 Aquifer Recharge Rainfall is a diffuse source of recharge that replenishes Bribie Island’s groundwater reserves via direct infiltration into the porous Quaternary sand sediments. The underlying, basal aquifer is recharged by water percolating down through the Quaternary sandmass. Surface water and groundwater are fundamentally interconnected. Localised aquifer recharge may occur within low-lying areas and along the central swale where surface water can readily permeate into sediments during and following rainfall events (Harbison, 1998; Armstrong, 2006).

Figure 8. Pumicestone Region Catchment showing Bribie Island subcatchment (modified from Cox et al., 2000b)

The amount of groundwater available in a system depends on numerous factors including: the frequency of rain; the quantity, intensity and duration of rain; recharge and discharge rates; the amount of water lost back to the atmosphere; and, the amount of water used by water dependant ecology. Evapotranspiration and direct seepage from the foreshore are the dominant drainage processes on the island (Harbison, 1998; Harbison and Cox, 2000). Water quality in the Pumicestone Passage depends on the quantity and quality of the water discharged into it; this would include groundwater seepage as well as surface water flows.

Using the sodium accretion method (equivalent to the Cl accretion method in this area), Harbison (1998) calculated an aquifer recharge of 7% of the average annual rainfall for the whole island. Outside of the modelled area, on the southern, Holocene beach ridges this method gave a recharge estimated at around 13% of the average annual rainfall.

2.7.2 Drainage The primary mechanisms of groundwater discharge from Bribie Island are via evapotranspiration, groundwater discharge to sea, evaporation and stream run-off (Harbison, 1998; Harbison and Cox, 2000).

Streams are not well developed on Bribie Island and tend to be short and drain the large areas of wetland. On the western side of the island, direct drainage occurs through two mangrove swamps and a number of small tidal creeks. Two tidal creeks occur on the west coast, near the Pacific Harbour developments; Dux Creek, which has been altered by canal development; and Wright's Creek, which drains the southern portion of the central swale. In the east, Freshwater Creek in the south and two freshwater lagoons in the north provide direct drainage. The lagoons (Figure 2) are usually closed to the sea by sand deposits (Lumsden, 1964; Harbison, 1998).

Surface drainage on the island is poorly developed due to the islands low topography and the permeable nature of the sand. Surface flow occurs only after periods of heavy rainfall when the sand becomes saturated. However, because of these features, water can remain lying at the surface in the interior until it either evaporates or percolates into the sand profile (Lumsden, 1964; Harbison, 1998; Armstrong, 2006).

2.7.3 Hydraulic Parameters Hydraulic conductivity (K) is an important parameter in relation to the flow of groundwater through an aquifer system, it is defined as the capacity of a porous medium to transmit water (Driscoll, 1986). Hydraulic conductivity values determined from hydraulic tests conducted in the central catchment of Bribie Island are compared with literature values in Table 2.

Lithology K (m/day) Reference Fine to coarse sand 10-2 – 103 1 1.2 - 11 2 Sand (unconfined, perched aquifer) 0.33 – 18.5 4 Sandstone, friable 10-3 – 1 1 0.09 – 0.25 2 Indurated sand (Coffee Rock) 0.07 – 2.5 4 1 - 25 3 Sand (semi-confined, basal aquifer) 0.13 – 4.7 4 1 Driscoll, 1986 2 Armstrong, 2006 – Slug Test 3 Armstrong, 2006 – Pumping Test 4 HLA Envirosciences – Slug Test (unpublished data, 2005)

Table 2. Results of hydraulic testing

2.8 PREVIOUS WORK, BRIBIE ISLAND Earlier groundwater studies of Bribie Island have investigated water supply and wastewater disposal issues and focused on the developed, southern portion of the island. Later studies have considered the whole island.

Previous investigations on Bribie Island are summarised below.

2.8.1 Groundwater Studies In 1962, 6 production bores and a 2.2ML/day water treatment plant (WTP) were installed to southwest of Woorim (Harbison, 1998). The Geological Survey of Queensland conducted a hydrogeological investigation in 1963 – 1964, which

included drilling 31 holes (typically to 14m) in southern Bribie Island (Lumsden, 1964). Water balance analysis estimated that groundwater seepage (45%) and evapotranspiration (50%) accounted for the bulk of the total rainfall removed from the system; a potential yield of 25% of total rainfall was estimated. That study recorded average hydraulic conductivities of 4m/day and 13m/day from permeameter tests and grain size distribution, respectively. Lumsden (1964) recommended that an area of 2.6km2 be set aside as a water reserve. This area was gazetted in 1970, in the southeast of the island, south of the Bongaree-Woorim road (Harbison, 1998).

An additional 21 extraction bores were drilled within the water reserve in 1966 – 1967. In 1971, due to continued problems with iron fouling of production bore screens, groundwater extraction in the water reserve was changed to pumping from a trench (approximately 3km long and 5m deep) (Isaacs and Walker, 1983; Harbison, 1998).

John Wilson and Partners (1979) reviewed the performance and capacity of the water reserve to supply an increased water treatment capacity of 6.6ML/day. Recommendations from the investigation included extending the trench system within the reserve and extending sewage disposal south of the water reserve to limit groundwater flow out of the reserve. Water balance analysis estimated 42% of rainfall recharged the aquifer and hydraulic conductivities within the water reserve ranged from 13 to 30m/day.

In 1979 – 1980, the Geological Survey of Queensland conducted a second hydrogeological investigation (Ishaq, 1980) in southern Bribie Island. As part of the investigation, 26 holes were drilled and completed as observation bores. Ishaq (1980) determined an average hydraulic conductivity of 17m/day from grain size distribution. Analysis of pumping test data from two bores (from John Wilson and Partners, 1966) determined hydraulic conductivity results of 15 and 75m/day. Water balance analysis suggested of the total rainfall, 13% recharged the aquifer, 82% was removed through evapotranspiration and 5% was lost through surface runoff. Ishaq (1980) assumed that potential evapotranspiration was equal to 63% of pan evaporation.

The Department of Environment and Heritage (1993) completed an Integrated Management Study of Pumicestone Passage and its catchment and groundwater resources, which included Bribie Island.

In 1992, the Water Resources Commission completed 23 observation bores (14100079 – 14100101) across the island. Aquifer stratigraphy was examined and the base of the Quaternary aquifer was identified in drill logs and with downhole gamma-ray logs. Estimates from the report include a specific yield of 0.17, groundwater storage volume of 2.1x106ML, and a sustainable yield of 25,000ML/year. Regular monitoring of groundwater levels and water chemistry has continued since 1992 (DNRMW database). The GSQ recovered 11 bores (14100102 – 14100112) and installed 5 new bores (14100113 – 14100117) and a gauge board (14100118) in the extraction trench in 1994.

In 1995, the Department of Natural Resources completed a report that aimed to understand effects caused by changes in land use on Bribie Island. An additional 6 observation bores (14100119 - 14100124) were installed in northern Bribie Island and a whole of island, groundwater model was constructed (DNR, 1996). A further 5 observation bores (14100125 - 14100130) were installed by DNR.

Harbison (1998) completed a research project with QUT investigating groundwater occurrence and chemistry on Bribie Island. He developed a hydrogeological conceptual model that recognised the significance of the indurated sands. The indurated sand layer was found to control infiltration, the degree of aquifer confinement and aquifer storage within the island aquifer system. Chemical analysis of rainwater and groundwater recorded Na-Cl type water, with calcium and bicarbonate enrichment in recent sand deposits (Harbison, 1998; Harbison and Cox, 1998).

Paul (2003) as part of a research project with QUT studied the environmental quality of ground and surface waters in the central catchment of Bribie Island. Paul found that shallow groundwater and surface water were closely related and that water chemistry of the different water bodies was linked through groundwater flow processes.

Armstrong (2006) installed 21 single and nested, monitoring bores across an east – west transect in central Bribie Island as part of a QUT research project. He investigated the affect of aquifer properties and heterogeneity on groundwater

occurrence and migration. Hydraulic testing of the aquifer system confirmed that the indurated sand layer had a lower hydraulic conductivity than the upper, unconfined and the basal, semi-confined aquifers. The indurated sand layer impeded groundwater migration, resulted in the elevated shallow water table aquifer, and caused local semi-confinement of the basal aquifer. Water quality analysis recorded a relationship between surface water and the shallow, unconfined groundwater that is important to the wetland areas of the island (Armstrong and Cox, 2002; Armstrong, 2006).

2.8.2 Groundwater Modelling Isaacs and Walker (1983) built a finite-difference, numerical model for southern Bribie Island. They assumed a constant hydraulic conductivity of 25m/day and a recharge rate of 300mm/year (approximately 22%). Marsalek and Isaacs (1988) conducted a field investigation to assess the effects of the treated effluent recharge on groundwater quality and found that effluent tends to sink to the bottom of the aquifer.

DNR (1996) constructed a whole of island, steady-state groundwater flow model using the MODFLOW package (USGS) with the PMWIN graphical interface. The aquifer was modelled as a single layered, unconfined aquifer. Calibration of the model involved using the PEST package (inverse problem solver) to determine the recharge and hydraulic conductivity values, to achieve the best match between observed and calibrated water levels.

DNR developed steady-state and transient groundwater flow models to investigate the removal of commercial pine plantations and for resource management associated with current and proposed groundwater developments (Werner, 1998a; Werner and Williams, 1999). The whole-of-island model was conceptualised as a single unconfined aquifer layer. Werner (1998a) acknowledged that peaty layers and clay lenses caused some semi-confined regions and isolated groundwater perching. A block centred, finite difference, MODFLOW model was constructed. Recharge, hydraulic conductivity and specific yield were mathematically calibrated to historical groundwater levels using the PEST package. Zones of spatially invariant hydraulic conductivity were assigned, calibrated and produced values that ranged from 5 to 150m/day. Aquifer recharge was calibrated at 22% of annual rainfall and potential evapotranspiration rates were estimated from a bucket model

(Williams, 1998). The ratios of potential evapotranspiration rates to historical pan evaporation rates ranged from 0.45 to 0.65. Steady-state analysis identified the central swale as a region of net groundwater discharge and found that losses to fixed head cells (coastline, canals and lagoons) was the dominate discharge process for the modelled aquifer.

Werner (1998b) produced a supplementary report that investigated the effect of a proposed groundwater extraction bore field. The MODFLOW model adopted most of the basic model parameters from the principal groundwater investigation (Werner 1998a); alterations covered the bore field proposed by Caboolture Shire Council.

Evans et al. (2002) conducted an impact assessment of the bore field proposed by Caboolture Shire Council. The evaluation considered factors including safe yield with respect to security of supply and prevention of seawater intrusion, ecological impacts and acid sulphate soil surveys. The groundwater model developed by the Department of Natural Resources (Werner 1998b) was used and refined to optimise the bore field arrangement. A sustainable groundwater extraction rate of 7ML/d was suggested. This rate did not conflict with current forestry operations and adjacent areas of national park.

As part of a research project with QUT, Spring (2005) developed a quasi three- dimensional, steady-state, whole-of-island groundwater flow model of Bribie Island using MODFLOW-96. The model was conceptualised as a two-aquifer system separated by a heterogeneous, indurated sand layer. Hydraulic conductivity, drainage and evapotranspiration parameters were calibrated using the PEST package. The technique of pilot point parameterisation was used to mathematically calibrate the hydraulic conductivities and VCONT layer across the island to achieve a better fit of observed water levels. A difference in the hydraulic heads in the upper, unconfined layer was reported as reflecting an increased movement of groundwater through the underlying indurated sands. Spring (2005) found that evapotranspiration removed a significant amount of rainfall from the system before recharge to the aquifer. The central swale was found to be a significant discharge feature and as well as groundwater seepage (Spring et al., 2004; Spring, 2005).

3. METHODOLOGY Monitoring of groundwater levels, the analysis of groundwater quality and testing of aquifer hydraulic properties is required to determine the performance of a groundwater system in response to natural and induced conditions. These parameters were used to assist with developing a conceptual model for central Bribie Island and are summarised below.

3.1 HYDRAULIC MONITORING NETWORK

3.1.1 Climate Climate averages were collected from the Bureau of Meteorology for three stations in the area: Caloundra, Cape Moreton and Redcliffe. Rainfall records were obtained from the Bureau of Meteorology for two weather stations on Bribie, Bongaree Bowls Club and Bribie Island University of Queensland, both of which have been decommissioned (Appendix A). Rainfall data was also acquired from the Department of Natural Resources, Mines and Water (DNRMW) from an automatic tipping bucket rainfall gauge located in east central Bribie at Bore 14100090.

Mean daily pan evaporation values were recorded from 1970 to 1993 at the University of Queensland Bribie Island weather station (Appendix B).

3.1.2 Monitoring Bore Network DNRMW maintain a groundwater monitoring bore network across Bribie Island. A bore search of the DNRMW database for registered bores was completed on Bribie Island and data from 52 bores (14100079 – 130) was found.

Data was also acquired from HLA Envirosciences (2002), who had installed a groundwater monitoring network across the Pacific Harbour area on behalf of QM Properties (MW1S – 27S and MW 3D – 19D). In 2001, as part of a QUT research project, Armstrong (2006) installed 21 nested monitoring bores across central Bribie Island (14100131 - 151). Data acquired from the above sources included lithological information, bore construction details, elevations, water levels and water chemistry.

Fieldwork was conducted on Bribie Island in May, July, September and November 2003. At selected locations across the central catchment area, standing water levels were measured with a dipmeter (100m long) and physico-chemical parameters were measured using a TPS 90 FL microprocessor, multi-probe, field analyser.

3.1.3 Groundwater Quality In May and November 2003, a groundwater sampling program was conducted at 27 monitoring bores in the central Bribie Island area. To ensure a representative sample of the aquifer was collected, all monitoring bores were purged of three water bore volumes using a submersible pump or a bailer (in low flowing bores) prior to collecting a sample. Polyethylene sample bottles (500mL) had been prepared in the laboratory with a wash of 1:3 diluted HNO3. Two sample bottles were used per bore, one for anion analysis and the other for cation analysis. The cation sample bottle was acidified with 1mL HNO3 to slow chemical reactions. Physico-chemical parameters of the groundwater were measured in the field with a TPS meter and parameters recorded are listed in Table 3.

Parameters Analysis Physico-chemical EC (µS/cm), Eh (mV), DO (ppm), pH and temperature EC = Electrical Conductivity Eh = Oxidation Reduction Potential (Redox Potential) DO = Dissolved Oxygen

Table 3. Field parameters measured with a TPS meter

All samples were preserved at below 4oC by storing them with ice during the day and in a refrigerator at night. Water quality analysis of samples for major ions and metals was conducted in the School of Natural Resource Sciences (NRS) chemical laboratory. Alkalinity was determined by acid titration. Cations were analysed with the Varian Liberty 200 Inductively Coupled Plasma – Optical Emission Spectrometer (ICP-OES) and anions were analysed with the DX300 Dionex Ion Chromatograph. Ions and metals tested for are listed in Table 4.

Method Analysis

ICP – OES Na, K, Ca, Mg, Fe, Al, Mn, Zn and SiO2

Acid titration HCO3

Ion Chromatography Cl, F, Br, NO3, PO4 and SO4

Table 4. Parameters tested for during water chemistry analysis

3.2 MODELLING

3.2.1 Conceptual Model A conceptual model is built on an understanding of how an aquifer system works. The model must simplify the real world complexity to a minimum level that is appropriate to the scale of the project, for example regional or local. Simplification depends on the end product required, the amount of available data and the current level of understanding. Building a conceptual model is an iterative process that can identify gaps in the data which you can try to improve with further data gathering.

A conceptual model provides a simplified representation of a hydrogeologic system and the flow processes present. The model describes factors including the system geometry, physical and hydraulic boundaries and hydraulic parameters.

A complex geological model is simplified into a hydrogeological model which recognises hydrostratigraphic units. The aquifer units and semi-confining layers are portrayed in three dimensional space. The geological framework for the central catchment of Bribie Island was established from analysis of drill hole data and downhole gamma-ray logs, utilising cross sections and 3D cross sections with the HydroGeo Analyst computer program.

It is necessary to identifying physical boundaries including faults, impermeable strata and permanent bodies of water such as lakes and oceans within the boundary domain. As Bribie is an island, the sea to the east and west of the model area was used as a natural boundary. The less permeable indurated sands are a hydrogeologically significant layer in the Bribie model.

Hydraulic boundaries such as groundwater divides can be used to limit the extent of the model where available. Streamlines are essentially a boundary since flow can only occur parallel to them, i.e. no flow can enter the model domain normal to a streamline. This artificial barrier was used to the north and south of the model of

the central area of Bribie Island as flow in this area is predominantly along an east- west axis.

Results from hydraulic tests and well as monitoring of groundwater levels and groundwater quality were taken into account when developing the conceptual model. These factors assisted with understanding groundwater occurrence and flow processes in the area. This helped to clarify the relationship between the upper and lower aquifers and the impact of the indurated, sand layer, which lay between the two aquifer systems.

3.2.2 Mathematical Modelling Models simulate groundwater occurrence and movement in the subsurface environment. A model represents a simplified form of the real-world aquifer system and assists with understanding and managing a groundwater resource (Bear et al, 1992). Mathematical models are based on a conceptual understanding of the aquifer system and they depend on the solution of basic mathematical equations as shown in Figure 9. Analytical models provide the simplest approach to modelling while numerical modelling can represent more complex systems.

Figure 9. Mathematical models are based on a conceptual understanding of the aquifer system as expressed by mathematical equations (modified from Mercer and Faust, 1981)

Analytical Solution

The simplest mathematical model of groundwater flow is Darcy’s Law (equation 1) which is an equation that describes the flow of groundwater. Groundwater flow through a vertical section of an aquifer can be calculated using Darcy’s Law (Driscoll, 1986):

KA(h − h ) Q = 1 2 Equation 1 L

where:

Q = flow (m3/day) K = hydraulic conductivity averaged over the height of the aquifer (m/day) A = area (m2) h1-h2 = difference in hydraulic head (m) L = distance along the flowpath between the points where h1 and h2 are measured (m) An analytical solution of the aquifer system in the central catchment of Bribie Island was used to assist with understanding the groundwater flow processes at a rudimentary level. The results obtained by using Darcy’s Law were later compared to the model results to verify the findings from numerical model.

Numerical Modelling

Numerical models are used to represent complex processes (Hill, 1998). Numerical models are used when complex boundary conditions exist or where the value of parameters varies within the model (Zheng and Bennett, 1995).

Due to the complicated subsurface environment, conditions can rarely be replicated completely by mathematical expressions. Simplifying assumptions are usually made to solve flow equations for appropriate boundary and initial hydrologic conditions. Assumptions include; the aquifer being homogeneous; isotropic; and infinite in areal extent. Simplification reduces the accuracy of the model (Driscoll, 1986).

The Visual MODFLOW (version 3.1.0) computer package was available for use to build a groundwater flow model over the central catchment of Bribie Island. Visual MODFLOW is a three-dimensional, finite-difference, Layer Property Flow (LPF)

package built on the MODFLOW-2000 module (Harbaugh et al., 2000). MODFLOW is a computer program developed by the U.S. Geological Survey (USGS) that simulates three-dimensional ground-water flow through a porous medium by using a finite-difference method (McDonald and Harbaugh, 1988).

Visual MODFLOW is built on the MODFLOW-2000 module, which requires the direct definition of the complete geometry of the each cell (including vertical cell geometry), unlike previous MODFLOW versions (Harbaugh et al, 2000). The available version of Visual MODFLOW did not support all of the features and analysis capabilities of MODFLOW-2000 including the Observation Process, the Sensitivity Process and the Parameter Estimation Process. Visual MODFLOW does support the PEST package (Doherty, 1994) which is a powerful and robust parameter estimation program.

PEST is an acronym for Parameter ESTimation. PEST optimises a set of user- defined model parameters to minimize the calibration residuals from a set of user- defined observations. PEST guides the model calibration process towards the most reasonable set of parameter values in order to achieve a better calibration result. Visual MODFLOW supports the optimisation of the model flow properties conductivity, storage, and recharge (Waterloo Hydrogeologic, 1995). When generating parameters using an inverse solution, exercise caution in order to generate realistic values for aquifer parameters.

The average conditions within the central Bribie Island area were simulated by Visual MODFLOW using the steady-state option. The model does not include seasonal variability and does not attempt to model the fresh water-salt water interface. These limitations are discussed in the sensitivity and uncertainty assessment.

Spatial Discretisation and Boundary Conditions

Defining the physical configuration of the model involves delineating the areal extent and thickness of the aquifers and defining the number of layers and the boundary conditions within the aquifer systems (Fetter, 2001).

The model extends approximately 7.5km in a north-south direction and 8.5km in the east-west direction. The co-ordinate system is MGA Zone 56 (GDA 94). The model grid is aligned 16.9 degrees west of north to align the model grid with the dominant direction of groundwater flow. Layers consisted of 75 rows and 85 columns of

model cells the size of 100m x 100m. The model configuration for the Bribie model is shown in Figure 10.

Figure 10. Model configuration of central Bribie Island

There are three ways of representing a semi-confining layer in multi-aquifer simulations. The first and simplest is the quasi-three-dimensional approach. In this situation, the semi-confining layer is not explicitly represented. It is simply incorporated as a leakage term (VCONT) between adjacent layers. This effectively ignores storage within the semi-confining bed and assumes an instantaneous response in the unstressed aquifer. This analysis is appropriate for steady-state simulations or systems with very thin semi-confining beds with limited storage properties (Anderson, 1993).

Visual MODFLOW requires the top and bottom elevations for each grid cell in the model and it requires hydraulic conductivity values (Kx, Ky and Kz) for each grid

cell. Visual MODFLOW uses this information to calculate the interlayer leakage (VCONT) values. As a result, a VCONT value could not be entered into the model to simulate the leakance through the semi-confining layer between the two aquifers, as Spring (2006) did in his regional model of the island.

A second approach is to discretise the semi-confining bed as a separate layer. This considers the storage within the semi-confining layer but generally does not provide a good approximation of the gradient within the confining bed (Anderson, 1993). When this method was utilised for the Central Bribie Island area, the numerical model would not converge.

The third method is to discretise several layers within the confining bed to approximate the gradient. The modeller must weigh the benefits of including gridding in an area where there is limited data and interest in hydraulic heads (Anderson, 1993). The benefits for the central Bribie Island model of discretising separate layers were convergence and stability of the model.

The model defines four layers: 1) the surficial sand; 2) and 3) the indurated sand layer; and 4) the basal sand layer. Figure 11 shows a sample cross section through the model of the island. The bedrock Landsborough Sandstone was not included in the model because there was no hydrogeological information from this unit as none of the piezometers penetrated to this depth. The bedrock contact was treated as a no flow boundary as it is believed that no groundwater flows upward from this stratigraphy.

The topography of the island (ground surface) was generated from topographic data supplied by the Caboolture Shire and Caloundra City Councils combined with bore hole elevations from DNRMW, HLA and QUT bores and is shown in Figure 12. The surfaces representing the base of layers 1, 3 and 4 were gridded from data points delineated by interpretation of drill log data and downhole gamma-ray logs. Surfaces were contoured using the Surfer contouring software and imported into Visual MODFLOW. Layer 3 was created by splitting the distance between the base of Layer 1 and top of Layer 4 into two individual layers (Layer 2 and 3). The base of the model represents the contact between Quaternary sediments and the underlying Jurassic Landsborough Sandstone, which represents bedrock in the area.

Figure 11. Cross section of model showing the four model layers. The base of the model is the sandstone bedrock.

All layers were assigned as confined/unconfined – variable S and T (Table 5).

Geological Model Model layer Model layer Aquifer type unit layer type thickness Surficial sand Layer 1 Unconfined 4 – 10 m Confined / Indurated Layers 2 Semi-confining unconfined, 1.5 – 7 m sand and 3 layer variable S,T Basal sand Layer 4 Semi-confined 5 – 35 m

Table 5. Hydrogeological layers used in the model

There are three types of boundary conditions commonly used in groundwater models: specified head, specified flow, and head dependent flow. In specified head boundaries (Dirichlet Conditions), the head remains constant and water will flow into and out of the model domain depending on the head distribution developed near the boundary. Bodies of water, for example lakes and the ocean, are commonly represented as constant head boundaries. Caution is to be used when applying this type of boundary as it can act as an infinite source of water which may not match the real world conditions. Specified flow boundaries (Neuman Conditions) have a fixed flux of water assigned along the boundary. An example of this are no flow boundaries, such as groundwater divides and impermeable barriers, which are

given a specified flux that is set to zero. In head dependent flow boundaries (Cauchy Conditions), flow across the boundary is determined by a prescribed head outside of the model domain, heads calculated within the model, and some form of hydraulic resistance to flow in between.

12 11 10 9 8 7 6 m 5 (AHD) 4 3 2 1 0

Figure 12. Topography for the whole of Bribie Island. Oblique view of elevation data created using Surfer contouring package.

The allocation of the boundary conditions attempted to correspond with natural hydrogeologic boundaries in order to minimise the influence of model boundaries on simulation results. The boundary conditions used in the model are displayed in Figure 13.

Cells representing Pumicestone Passage and the Coral Sea were assigned as inactive. Coastline cells, the Pacific Harbour canal system and tidal creeks were assigned as fixed-head cells with a hydraulic head value of 0.3m (AHD), a typical groundwater level along low-energy coasts (Harbison and Cox, 2002). Lagoons were assigned as fixed-head cells with a hydraulic head value of 0.7m (AHD) (Harbison, 1998).

The fixed head cells along the coast were assigned to give an approximation of the interface between salt water and the less dense freshwater. This numerical model was developed to simulate groundwater flow in central Bribie Island and does not attempt to specifically map the fresh water - saltwater boundary along the coastline.

Artificial boundaries were created at the northern and southern boundaries of the model, as there were no natural groundwater divides in the central catchment of Bribie Island. They were assigned as general head boundaries as they were in full hydraulic contact with the aquifer. The hydraulic head at the boundary was set at 0.3m and conductance values ranged from 0.012 to 0.5m2/day. Initial conductance values were determined using equation 2; however, these values were too high resulting in lowered groundwater levels. The conductance values were reduced manually until a better calibration was achieved.

(L *W ) * K C = Equation 2 D

where:

C = conductance (m2/day) (L*W) = is the surface area of the grid cell face exchanging flow with the external source/sink (m2) K = average hydraulic conductivity of the aquifer material separating the external source/sink from the model grid (m/day)

D = is the distance from the external source/sink to the model grid (m)

Drain cells were assigned along the central swale within Layer 1. Drainage was set at 750m2/day, with a drainage depth of 1m below ground level. This was designed to mimic loss of water from the model domain via evapotranspiration by vegetation and evaporative processes along the swale.

The loss of groundwater from the model domain via direct seepage from the canals was simulated by assigning drain cells in the canal estates within Layer 1. Drainage of 1000m2/day was initially set, with a drainage depth of 1m below the land surface. Initial attempts to assign these cells as fixed head cells failed due to the proposed fixed head elevation (0.3m) lying below the bottom elevations of some cells in this area, which the computer program would not accept.

Figure 13. Boundary conditions for a) Layer 1 and b) Layers 2, 3 and 4 for central Bribie Island using model layers shown in Figure 11.

Monitoring Bores

DNRMW, HLA and QUT monitoring bores are represented in the model as observation points. The locations of the monitoring bores in the upper, perched aquifer are shown in Figure 14 and the bores in the basal aquifer are shown in Figure 15. Within the model, Layer 1 (the shallow, unconfined aquifer) contained 25 monitoring bores and Layer 4 (the basal, semi-confined aquifer) contained 20 monitoring bores. The bores were used as model calibration points to achieve calibration in steady-state.

Initial Hydraulic Heads

Initial hydraulic heads for the model were subset from the whole island steady-state model completed by Spring (2005). The head data for Layers 1 and 4 was contoured in Surfer and then imported into Visual MODFLOW.

Figure 14. Location of 25 shallow monitoring bores used in the model (Layer 1)

Figure 15. Location of 20 deep monitoring bores used in the model (Layer 4)

Hydraulic Conductivities

Initial steady-state hydraulic conductivities were spatially invariant and based on field test results conducted by Armstrong (2006) and HLA (2002). This method resulted in a poor calibration between the field and the simulated water levels. Zones were established as shown in Figure 16 and the parameter optimisation software WinPEST was used to estimate the distribution of hydraulic conductivities. Observed groundwater levels were matched to hydrologic inputs through the process of inverse parameter estimation. Inverse modelling helps with determination of parameter values that produce the best possible fit to the available observations (Hill, 1998). This was a valuable time-saving tool which enhanced the model calibration. However caution should be exercised when using inverse problem solving otherwise the program can generate unrealistic values for aquifer

parameters. Therefore the calibrated hydraulic conductivity values in the model were restricted to between 1 and 110m/day.

Figure 16. Zones of hydraulic conductivities showing observation bores

Recharge and Evapotranspiration

Recharge was applied across the model domain as a percentage of the annual rainfall and it was assumed that it did not vary spatially within the model. The initial aquifer recharge rate of 95mm/year (7% of the average annual rainfall) (Harbison, 1998) was applied to the model domain. Factors including evapotranspiration, surface water runoff and interception by vegetation are expected to account for the remainder of the rainfall (around 93%). Recharge of the aquifer was increased to 218mm/year (16% of the average annual rainfall) when potential evapotranspiration was included into the model.

Evapotranspiration (ET) is expected to make up a large portion of the total groundwater discharge for Bribie Island. Estimations of ET rates from water balance models range from 60% (1003mm/year, Williams, 1998) to 77% (1293mm/year, Bubb and Croton, 2000) of the pan evaporation (1679mm/year). The bulk of rainfall removal occurs before recharge of the groundwater system.

The ET parameters were split into 3 zones which are displayed in Figure 17. Divisions were based on the dominant vegetation types on the island: pine plantation, swale and National Park. ET rates range from 180 to 270mm/year depending on the vegetation type. The rooting depth of mature aged pines in unsaturated soil profiles could range from 3 to 5 metres (K. Bubb, pers comm., 2005), so the extinction depth in the pine plantation areas was set at 3m. Extinction depth in the swale and National Park areas was set at 2.5m.

Figure 17. Evapotranspiration zones split according to dominant vegetation type as shown in example photographs

Model Calibration and Sensitivity Assessment

Model calibration is undertaken to refine a models representation of the hydrogeologic framework, hydraulic properties, and boundary conditions to achieve

a desired degree of correspondence between the model simulations and observations of the groundwater flow system (ASTM, 1996).

Visual MODFLOW supports the PEST package (Doherty, 1994) and can optimise hydraulic conductivity, storage, and recharge (Waterloo Hydrogeologic, 1995). PEST was used to optimise hydraulic conductivity in the model to minimize the calibration residuals from the water level observations. The calibrated horizontal hydraulic conductivity values were restricted to between 1 and 110m/day. Due to the variability in time and period of water level records, an average water level per monitoring bore was used for the calibration of the steady-state model.

The conductance values for the general head boundaries at the northern and southern boundaries of the model were reduced manually until a better calibration was achieved. The conductance values ranged from 0.012 to 0.5m2/day.

Sensitivity analysis is defined as the quantitative evaluation of the impact or uncertainty in model inputs on the degree of calibration of a model and on its results or conclusions (ASTM, 1994). When user-defined parameters within the model are varied, it is possible to determine how sensitive the model is to these changes. There are four types of sensitivity which are illustrated in Figure 18. Sensitivity type is characterised by whether the changes to the calibration residuals and model conclusions are significant or insignificant.

Sensitivity assessment was conducted on the following model inputs: evapotranspiration and drain parameters and general head boundary conductance.

Figure 18. Summary of the four types of sensitivity (modified from ASTM, 1994)

4. RESULTS

4.1 HYDRAULIC MONITORING DATA

4.1.1 Climate Bribie Island has a sub-tropical climate and experiences a wet summer and a dry winter. Figure 19 reveals that the maximum temperatures in the Moreton Bay area range from 19°C in winter and 28°C in summer.

30 Caloundra 25

20 C o 15 Temp Temp 10

0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

30 Cape Moreton 25

20 C o 15 Temp Temp 10

0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

30 Redcliffe 25

20 C o 15 Temp Temp 10

0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Mean daily maximum temperature (oC) Mean daily minimum temperature (oC) Figure 19. Mean daily temperatures for Caloundra, Cape Moreton and Redcliffe

Rainfall records shown in Figure 20 reveal a seasonal trend in the data with a peak period for rainfall occurring over summer and early autumn (December through March). The mean annual rainfall from the Bongaree station, which operated for

nearly 59 years, is 1358mm/year. The mean monthly pan evaporation values from the University of Queensland Bribie Island weather station (1970 – 1995) were compared to mean monthly rainfall from the nearby Bongaree station in Figure 21. Pan evaporation values exhibit seasonal fluctuations and usually exceed rainfall from July through January. The mean annual pan evaporation was measured as 1679mm/year.

250 Bore 14100090 Bongaree Station University of Qld 200

150

100 Mean Monthly Rainfall Monthly Mean (mm)

0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 20. Average monthly rainfall on southern Bribie Island

Figure 21. Mean monthly rainfall compared to mean monthly pan evaporation

4.1.2 Monitoring Bore Network Data from all monitoring bores was used to develop a geological framework for the central catchment of Bribie Island. The monitoring bores located within the central area of Bribie Island are summarised in Appendix C and locations of all bores are illustrated in Figure 22.

Figure 22. Location of monitoring bores used to build the geological framework

Lithological data from different sources (DNRMW, HLA and QUT) was collated and interpreted to unify the data. Different naming conventions were used for lithology in the various drilling programs conducted over many years. For example, material in the upper profile that was described variably as sandstone, indurated sand or “Coffee Rock” in previous drill hole logs were grouped into an indurated sand assemblage.

Data was plotted in 3-dimensional space and interpolations of lithological data between monitoring bores were made using the HydroGeo Analyst computer package. Figure 23 shows the results of the process and graphically displays the heterogeneous nature of the Bribie Island sandmass.

Standing water levels were recorded between May and November 2003 to obtain site specific information to assist with understanding the groundwater flow processes in the central catchment of Bribie Island (Appendix D).

Hydrograph analysis is an important method of presenting periodic measurements (time series) of groundwater levels as the graphs display baseline trends in the data. When recharge and discharge within an aquifer system are in balance, hydrographs show that water level data can vary significantly from year to year, but will remain relatively stable over the long term. When rainfall is inadequate to compensate for discharges from the aquifer, such as during droughts or due to excessive pumping, the water level will fall over time.

Figure 24 shows a hydrograph of water levels recorded from a selection of representative monitoring bores with long-term data. Groundwater levels are plotted with a residual rainfall mass curve (RRMC) calculated for the site 14100090 (automatic tipping bucket rainfall gauge). The RRMC shows the cumulative difference between the rainfall recorded for a month and the average rainfall for each month. This curve is used to illustrate trends in rainfall to assist with the detection of seasonal and longer-term climatic variations. An increase in the RRMC indicates periods of above average rainfall and decreases indicate periods of below average rainfall. As can be seen in Figure 24, the groundwater levels, in the shallow and basal monitoring bores, mimic the trends of the RRMC.

In Figure 25 groundwater levels recorded across the central Bribie Island transect are overlain on the hydrogeological cross section. This figure displays the lithology

of the area and the two aquifers present: the shallow water table of the perched aquifer and the deeper potentiometric surface of the basal, semi-confined aquifer.

Figure 23. Heterogeneous sandmass of Bribie Island The HydroGeo Analyst computer package was used to show a) the lithology of individual bores and b) the interpolation between bores.

Figure 24. Hydrograph of long-term groundwater levels and the RRMC

Figure 25. Cross section through central Bribie Island showing grounwater levels and piezometer locations (modified from Armstrong, 2006)

4.1.3 Groundwater Quality Physico-chemical parameters were recorded from a selection of monitoring bores in central Bribie Island when measuring water levels and collecting groundwater samples. A summary of the recorded physico-chemical parameters is listed in Table 6 (Appendix D). Groundwater monitoring bores near coastal areas, canal developments or tidal creeks were found to have an increased electrical conductivity (EC) compared to the fresh groundwater within the aquifers. The average pH values of groundwater within the upper aquifer and indurated sand layer were slightly more acidic than the lower semi-confined aquifer.

EC EC Monitoring Bores pH pH µS/cm µS/cm range average range average Upper, perched aquifer 61 - 590 229 3.4 - 6.6 4.1 Indurated sand layer 90.2 - 294 169 3.5 - 3.9 3.7 Basal, semi-confined aquifer 76.4 - 1018 317 3.7 - 5.8 4.9 Near coast, canals or tidal creeks 1596 - 34800 14748 3.3 - 6.5 5.1

Table 6. Groundwater physico-chemical measurements from monitoring bores

Groundwater samples were collected from selected monitoring bores across the project area and analysed in the QUT laboratory (Appendix E). An ion balance was calculated for each sample. An ion balance represents a summation of negative and positive ions; expressed as equivalents [(sum of cations - sum of anions) / sum of cations and anions]. An analysis returning an ion balance exceeding 5% was regarded as poor (inaccurate). Water chemistry results completed in this study were compared and combined with existing water chemistry records. One analysis per bore was selected as a representative sample of that monitoring bore for presentation in the following graphs.

The major ions of groundwater from monitoring bores within the central Bribie Island area are plotted on a Trilinear diagram shown in Figure 26. Trilinear plots display data based on the percentage of major cations and anions of a water sample. This plot can reveal useful properties and relationships of different groundwater groups.

Trilinear diagrams can indicate samples with similar chemical compositions, via the clustering of data points.

The Trilinear plot of groundwater samples within the central catchment of Bribie Island shows that the dominant water type in this area is Na-Cl type water. A number of groundwater samples, predominantly from the basal aquifer, display an increase in calcium and bicarbonate ions.

Figure 26. Trilinear plot of groundwater chemistry samples

Ion concentrations of groundwater samples plotted on a Schoeller Plot display and compare analyte concentrations in a graphical form that can differentiate hydrochemical water types. Unlike trilinear diagrams, the Schoeller diagram displays the actual concentration of chemical constituents on a single diagram. Figure 27 shows that groundwater from the basal aquifer tends to possess higher concentrations of calcium and bicarbonate ions.

Figure 27. Schoeller plot of groundwater chemistry samples

In Figure 28 groundwater analyses are displayed as Stiff Patterns plotted on the cross section through central Bribie Island. A polygonal shape is created by plotting ions in milliequivalents per litre on either side of a vertical zero axis; cations are plotted on the left and anions on the right. Na-Cl water is the dominant water type in the area. Calcium and bicarbonate ions are at higher concentrations in a couple of samples in the coarse sands in the basal aquifer.

Figure 28. Stiff patterns overlain on the cross section through central Bribie Island (modified from Armstrong, 2006)

4.2 MODELLING

4.2.1 Conceptual Model Models are used to represent a simplified form of reality to assist with developing an understanding of the groundwater resource. Mathematical models are based on a conceptual understanding of the physical system to be modelled. A conceptual model involves the conceptualisation of the geology and hydrology of a groundwater system.

As discussed in Chapter 2, Bribie Island is composed of Quaternary sand deposits that overlie bedrock of the Early Jurassic Landsborough Sandstone Formation. Groundwater on Bribie Island occurs as a freshwater 'lens' within the intergranular spaces of the heterogeneous, sand deposits. Two distinct groundwater bodies occur on the island: a shallow, perched, unconfined aquifer and a deeper, semi- confined, basal aquifer. A hydrogeologically significant layer of indurated sand, locally known as “Coffee Rock”, separates these aquifers (Harbison, 1998; Harbison and Cox, 1998; Spring, 2005; Armstrong, 2006). Hydraulic conductivity results from field testing on Bribie Island range from 0.3 to 18.5m/day for the shallow, perched aquifer and 1 to 25m/day for the basal, semi-confined aquifer.

Bribie Island’s groundwater aquifers are recharged via direct infiltration of rainwater into the porous sands. Using the sodium accretion method, Harbison (1998) calculated an aquifer recharge of 7% of the average annual rainfall for this part of the island.

Evapotranspiration and groundwater discharge to the sea dominate groundwater discharge processes on Bribie. Other drainage mechanisms include evaporation, surface run-off and some direct drainage from tidal creeks along west coast (Harbison, 1998; Harbison and Cox, 2000).

4.2.2 Mathematical Modelling

Analytical Solution An analytical solution is the simplest approach to modelling. A preliminary estimate of groundwater discharge at the coast was calculated using Darcy’s Law. The area assessed covered the same area as the groundwater flow model. The input values and results from this analysis are listed in Table 7. The estimate of groundwater discharge from the central catchment of Bribie Island totalled approximately 8000m3/day. These results depend on evaluation of the thickness of the sand layers on the island and representative hydraulic conductivities gained from field testing. Discharge results were not directly verified with field data and are therefore are unlikely to be very accurate.

KA(h1 − h2 ) Q = L Shallow Indurated Basal Units Sands Sand Sands

# # K mean m/day 6.4 0.4 13*

3 A mean m 193500 279500 860000

(h1-h2) mean m 4.5 2.5 1.5

L mean m 2875 2875 2875 Q = discharge m3/day 2000 100 6000 # Average from Slug Tests (QUT and HLA) * Average from Pumping Tests (QUT)

Table 7. Estimated groundwater discharge

Numerical Modelling A rudimentary steady-state groundwater flow model was developed for the central area of Bribie Island. The model was designed to investigate recharge, hydraulic properties, boundary conditions, discharge, flow budget and the sensitivity of model parameters on model results.

Model Calibration

Model calibration is the process of refining selected model input parameters to achieve an acceptable degree of correspondence between the model simulation and observations of the groundwater flow system (ASTM, 1994). Calibrations were based on achieving the best fit between simulated groundwater levels and water levels recorded from field observation. Calibration simulations were performed using inverse problem solving with the WinPEST package, which is included with the Visual MODFLOW program.

The study included qualitative and quantitative measures of calibration. Qualitative measures include the comparison of expected water level contours, hydraulic gradients and flow directions with those simulated by the model. Quantitative measures involve calculating differences in observed and predicted water levels within the model.

Initial sensitivity analysis revealed that water levels were most sensitive to recharge rates and hydraulic conductivity. The model calibration was found to be nonunique in that the model could be calibrated if both the recharge rate and the hydraulic conductivity were increased concurrently.

Subsequent calibration focused on adjustment to hydraulic conductivity values, based on the assumption that uncertainties in the infiltration rate were small relative to uncertainties in hydraulic conductivity. Initially hydraulic conductivity was based on field hydraulic tests conducted in the area and was assumed to be spatially invariant. This method resulted in a poor calibration and the model was unable to simulate realistic water levels, especially in the upper, perched aquifer and for some hydraulic values the model would not converge. Numerous discrete zones were adopted for calibrating the hydraulic conductivities.

Calibrated horizontal hydraulic conductivities were limited between 1 and 110m/day and vertical hydraulic conductivities between 0.0001 and 1.1m/day. Figure 29 displays the mathematically derived hydraulic conductivities.

The pattern of water level contours and groundwater flow predicted by the calibrated model are qualitatively similar to the inferred water levels expected by the conceptual model. Groundwater flows are parallel to the steepest gradient in the study area. Flow direction is dominated by east–west flow from the topographically higher beach ridges down to the low-lying swale and coastal areas.

The calibrated steady-state model for the central catchment of Bribie Island simulates the observed groundwater levels and the groundwater flow processes in the area (Appendix F). Water levels simulated by the steady-state model are presented in Figure 30 and Appendix G contains the simulated and observed water levels. A scattergram of observed heads verses modelled heads for the steady- state calibration is included in Figure 31.

The normalised root mean square value from the optimised steady-state model was 4.5%, a value that represents the collective error in the model outputs. This value was based on measured (actual) verses predicted water levels and should be less than 5 percent (L. Luba, pers comm., 2005). The correlation coefficient is 0.99; this value tends to 1 for perfect calibrations (Middlemis, 2000). The absolute residual mean for the steady-state model is 0.21m. The maximum residual in the model between assumed and simulated water levels is +0.94m at monitoring bore 14100135.

Figure 29. Hydraulic conductivities determined mathematically using WinPEST Figures show: a) Kx and Ky for Layer 1; b) Kz for Layer 1; c) Kx and Ky for Layers 2 and 3; Kz for Layers 2 and 3; e) Kx and Ky for Layer 4; and f) Kz for Layer 4.

Figure 30. Simulated water levels from steady-state model showing monitoring bores: a) shallow, unconfined; and b) basal, semi-confined aquifers.

Water Budget

In addition to the calculated hydraulic heads, MODFLOW uses computed heads to develop a mass balance (volumetric balance). This provides a check on the accuracy of the numerical solution. A good mass balance may not guarantee an accurate solution, however a poor mass balance usually indicates problems within the model. Although models are rarely useful for quantitative predictions of consequences (Voss, 1998), data in the mass balance contains useful information used to identify the relative importance of flows into and out of the system (Anderson, 1993).

The mass balance graph shown in Figure 32 plots the volume of water entering and leaving the system through the flow boundary conditions. The final steady-state model produced a mass balance error of 0 %. The percent discrepancy of a model should be less than 1 percent (Anderson, 1993).

As anticipated, the mass balance data shows that rainfall is the primary model input with 25163m3/day. There is a relatively insignificant input from the constant head boundaries of 5m3/day. Model outputs are dominated by evapotranspiration (15070m3/day) and groundwater discharge from constant head boundaries (9512m3/day). Minor losses occur via drains (397m3/day) and flow across the northern and southern general head boundaries (189m3/day).

Harbison (1998) estimated that 7% of annual rainfall (1358mm/year) infiltrates into the Pleistocene sands on Bribie Island. For the central catchment of the island this equates to approximately 11215m3/day. When losses from the modelled system via evapotranspiration and drains are subtracted from the rainfall recharge, the amount that enters the aquifer system is around 9696m3/day, around 13.5% less than anticipated. The modelled groundwater discharge from the constant head boundaries was 9512m3/day, around 16% more than the preliminary estimate of 8000m3/day, determined from Darcy’s Law flow equation.

Figure 31. Calculated verses observed water levels, steady-state model

Figure 32. Mass balance for steady-state model

The flow zone budget data in Table 8 outlines the flow rates of water entering and leaving user-defined zones through flow boundary conditions and through other user-defined zones. This provides information related to groundwater movement in areas outlined by the modeller. Five zones of interest were delineated: zones 1 – 3 in the upper aquifer (representing three different vegetation groups - National Park, swale and pine plantation, respectively); zone 4 in the indurated, sand layer; and zone 5 in the basal aquifer.

Rainfall was the dominant recharge process for Layer 1 (perched aquifer, zones 1 - 3) of the model while for the lower sands (Layers 2, 3 and 4, zones 4 and 5) recharge was via vertical leakage of water from the overlying sand layers.

Groundwater discharge from Layer 1 of the model is dominated by evapotranspiration (15070m3/day) followed by groundwater discharge at constant head boundaries (2596m3/day). Evapotranspiration does not remove groundwater from the lower layers 2, 3 and 4. Layers 2 and 3, representing the indurated sands, have minor losses via seepage at the coast (60m3/day) and via flow across the general head boundaries (18m3/day). The dominant process to remove groundwater from layer 4 (the basal, semi-confined aquifer) is via groundwater discharge to the coast (6856m3/day) plus with minor flow occurring across the northern and southern general head boundaries (80m3/day).

Mathematical analysis estimated that groundwater discharge from the aquifer system would be around 2000, 100 and 6000m3/day from the shallow, perched aquifer, the indurated sands and the basal, semi-confined aquifer, respectively. The modelled outputs are comparable to the results determined from analytical solution.

Layer 1 National Pine Layer 2 & 3 Layer 4 Park & Swale Plantation remainder Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 IN: Flow (m3/day) Constant Head 4.8 ------Head Dep Bounds ------Recharge 15511.0 2215.8 7435.9 -- -- Zone 2 to 1 Zone 1 to 2 Zone 1 to 3 Zone 1 to 4 Zone 4 to 5

= 31.4 = 51.5 = 182.2 = 3787.7 = 6953.0 Zone 3 to 1 Zone 3 to 2 Zone 2 to 3 Zone 2 to 4

= 182.4 = 136.2 = 5.6 = 968.0 Zone 4 to 1 Zone 4 to 2 Zone 4 to 3 Zone 3 to 4

= 54.2 = 0.0 = 0.0 = 2308.3 Zone 5 to 4

= 21.4 Total IN 15784 2403.5 7623.7 7085.4 6953.0 OUT: Flow (m3/day) Constant Head 2595.9 -- -- 59.6 6856.4 Drains 397.1 ------ET 8728.7 1386.4 4954.6 -- -- Head Dep Bounds 40.6 12.0 42.2 18.3 75.6 Zone 1 to 2 Zone 2 to 1 Zone 3 to 1 Zone 4 to 1 Zone 5 to 4

= 51.5 = 31.4 = 182.4 = 54.2 = 21.4 Zone 1 to 3 Zone 2 to 3 Zone 3 to 2 Zone 4 to 2

= 182.2 = 5.6 = 136.2 = 0.0 Zone 1 to 4 Zone 2 to 4 Zone 3 to 4 Zone 4 to 3

= 3787.7 = 968.0 = 2308.3 = 0.0 Zone 4 to 5

= 6953.0 Total OUT 15784 2404 7624 7085 6953 IN - OUT 0.033 -0.004 0.017 0.2 -0.244 % discrepancy 0.00 0.00 0.00 0.00 0.00

Table 8. Zone budget for steady-state model

Uncertainty and Sensitivity Assessment

Sensitivity analysis is undertaken to determine model sensitivity to factors that affect groundwater flows and data uncertainty. In sensitivity analysis, results from the base-case model simulation are compared with the results of other model runs after altering various parameters. Evaluations are based on the degree to which the model output changes for a given change in input.

Sources of uncertainty in numerical models can include geological, parameter (e.g. hydraulic conductivity and recharge) and boundary condition uncertainty (Fabritz, et al., 1998). Geological uncertainty relates to the degree to which the stratigraphy assumed in the model represents the geology of the area. The southern portion of the model contains few piezometers (3 in the upper aquifer and 3 in the lower aquifer) and as such has higher uncertainty than the northern portion of the model.

Parameter and boundary condition uncertainty describe the uncertainty in the model from imposed parameters and by characterisation of hydrogeologic conditions along the boundary of the model. Recharge was one of the better-defined parameters of the model. The recharge rate has a large affect on the total volume of water that enters the flow field. Hydraulic conductivity was determined using a reverse, parameter estimation technique within a restricted range of values. Altering hydraulic conductivities in the Bribie model resulted in non-convergence.

Sensitivity analysis was conducted on five parameters within the model and the results are displayed in Figure 33. The diagrams plot the normalised root mean square and simulated water levels from monitoring bores MW3s (perched aquifer) and MW3d (basal aquifer). Changes to ET rate, ET extinction depth and general head boundary conductance cause a significant change to the models calibration, while changes to drain conductance and elevation do not have any significant impact on the models calibration.

Figure 33. Sensitivity analysis for steady-state model The figures show simulated water levels in monitoring bores MW3s and MW3d and the normalised RMS for the model.

5. DISCUSSION AND SUMMARY

5.1 HYDRAULIC MONITORING

5.1.1 Climate Bribie Island has a sub-tropical climate with the following features.

Temperature maximums for the area range from 19°C in winter up to 28°C in summer.

Mean annual rainfall is around 1358mm/year at Bongaree station which is located in the southwest of Bribie Island. Rainfall is seasonal with peak rainfall occurring over summer and early autumn (December through March).

Mean annual pan evaporation is around 1679mm/year. Pan evaporation values fluctuate with the seasons and usually exceed rainfall from July through January.

Potential evapotranspiration rates were estimated to range from 60% (~1003mm/year) to 77% (~1293mm/year) of the pan evaporation.

5.1.2 Monitoring Bore Network Data from various sources (DNRMW, HLA and QUT) was collated and interpreted in order to conceptualise the hydrogeological system in the central catchment of Bribie Island.

Lithological data was interpreted and the various stratigraphic descriptions from the different sources were standardised to allow comparison of data. The resulting interpretation was plotted in 3-dimensional space using the HydroGeo Analyst computer package. This process highlighted that the Quaternary sandmass in central Bribie Island was spatially heterogeneous in both lateral and vertical extent.

The sandmass aquifer system in central Bribie Island contains fine to coarse sands, clayey sands, clay bands and the hydrogeologically significant indurated sands. The indurated sands affect groundwater flow on the island by impeding the infiltration of water into the sandmass. This indurated layer separates the two groundwater systems, causes perching of groundwater above this horizon and results in the semi-confinement of the basal aquifer.

Groundwater levels recorded in the field across central Bribie Island show a distinct separation between the shallow, perched aquifer and the basal, semi-confined aquifer.

groundwater in the surficial, clean sands is perched on the indurated, Quaternary sands and occurs under unconfined conditions. The water table mirrors the topography and water levels range from around 1 to 7.3mAHD.

the indurated sands act as a semi-confining layer causing the groundwater in the basal sands to occur under semi-confined conditions. The potentiometric surface of the basal aquifer occurs as a gentle groundwater mound and water levels range from around 1.3 to 2.9mAHD.

Hydrograph analysis of long-term, groundwater level data reveals baseline trends in the data. This data was compared to the residual rainfall mass curve (RRMC) for the station near bore 14100090 (BoM station 540055). The comparison revealed that groundwater levels, in the shallow and basal monitoring bores, mimic trends displayed by the RRMC. Hydrographs revealed that major trends in groundwater levels are predominantly related to recharge by rainfall.

Groundwater flows preferentially toward the steepest hydraulic gradient. In the upper, perched aquifer, the sides of the beach ridges offer the steepest gradient in central Bribie Island. It is anticipated that the main horizontal direction of groundwater flow is along an east-west axis, towards the low-lying central swale or the coastline. The lower basal aquifer forms a gentle groundwater mound, with water flowing east and west to the coastline to discharge via groundwater seepage off the coast. As flow can only occur parallel to streamlines, the north-south flow along the length of the island would be nominal compared to flow along the east- west axis.

5.1.3 Groundwater Quality Groundwater chemistry investigates the processes that control the groundwater quality. Physico-chemical measurements and water chemistry analyses for the central catchment of Bribie Island revealed fresh groundwater of acidic to slightly acidic quality.

Electrical conductivity readings of groundwater from the upper aquifer, the indurated sand layer and the basal aquifer ranged from 61 to 1018µS/cm. This reveals that groundwater within the island aquifer system is fresh. Groundwater from monitoring

bores near the coast, canals or tidal creeks was found to have an increased electrical conductivity. Electrical conductivity readings were brackish to saline and ranged from 1596 to 34800µS/cm. Predominantly the groundwater on Bribie is fresh even though the island is surrounded by seawater. However the elevated conductivity in some samples indicates the vulnerability of this type of groundwater system to seawater encroachment.

Measurements indicate that the pH of groundwater is acidic to slightly acidic (3.3- 6.6). This has been attributed to the breakdown of plant material into organic acids (Harbison, 1998; Armstrong, 2006). The average pH values of groundwater within the upper aquifer (4.1) and indurated sand layer (3.7) were slightly more acidic than the lower semi-confined aquifer (4.9).

Groundwater chemistry analysis can indicate samples with similar chemical compositions, via the clustering of data points, and show trends occurring within groundwater groups. Groundwater samples from aquifers in central Bribie Island show that groundwater from both aquifers is dominated by Na-Cl type water. This is to be anticipated in a coastal island environment where the primary mechanism of groundwater recharge is coastal rainfall containing cyclic salt.

Quartz, the dominant mineral on the island, belongs to the silicate group of minerals which are slow to chemically react with water. Some minerals are more soluble and react fast upon contact with water, for example carbonate minerals (Appelo and Postma, 2005). A number of groundwater samples from the basal aquifer possess higher concentrations of calcium and bicarbonate ions. Enrichment of Ca and

HCO3 could be due to chemical interactions with shell material while water is infiltrating to the lower levels. The longer residence times of groundwater in the basal aquifer may also be a factor.

Groundwater recharge of the Bribie Island aquifers is via the infiltration of coastal rainfall into the upper sand unit and vertical leakage of groundwater into the underlying sand units. This common recharge source is reflected by the similarity of the physico-chemical parameters and the water chemistry results. However, the separation of the two aquifers by semi-confining, indurated sands enables chemical interactions to alter the groundwater, resulting in subtle, localised differences in the groundwater quality.

5.2 MODELLING

5.2.1 Analytical Solution Mathematical analysis was used to make a preliminary estimate of groundwater discharge from the central portion of Bribie Island. Darcy’s Law is an equation that describes the flow of groundwater in a system. This equation was used for a rudimentary assessment of the discharge from the central area of the island.

Groundwater discharge from the aquifer system in the central catchment of the island is approximately 8000m3/day. Discharge from the upper, perched aquifer was in the order of 2000m3/day and 6000m3/day discharged from the basal, semi- confined aquifer. The larger volume of groundwater discharge from the basal aquifer is attributed to the larger volume of this aquifer and its higher hydraulic conductivity rates.

A minor volume of groundwater discharges from the indurated sands (approximately 100m3/day). This is expected as this layer occupies a small volume in the sandmass and has the lowest recorded hydraulic conductivity values. The process of induration has resulted in the infilling of pore spaces between sand grains which has reduced the hydraulic conductivity and available storage of the sand.

Darcy’s Law was used to calculate an initial estimate of discharge from the central area of Bribie Island. The heterogeneous nature of the sand, variations in the thickness and hydraulic conductivity of the aquifers were not taken into account. The simplifications introduced uncertainty into the discharge calculations.

5.2.2 Numerical Modelling A steady-state groundwater flow model was developed and calibrated against existing groundwater level data collected during field programs. The model was developed to simulate the existing hydrological system and the dominant groundwater processes controlling groundwater flow.

The main direction of horizontal groundwater flow in the model was along an east- west axis, from the beach ridges towards either the central swale or the coastline. This was expected from the conceptual model as groundwater flows preferentially toward the steepest hydraulic gradient. Due to the heterogeneous and anisotropic nature of the sandmass on Bribie Island, it is anticipated that the model represents

the overall flow regime in the area but that it is unlikely to model the local flows accurately.

Groundwater in the upper, perched aquifer mirrored the topography of the sand ridges. Water levels range from zero at the coastline up to 8.5mAHD in the higher beach ridges. The simulated potentiometric surface of the basal aquifer was a gentle groundwater mound with the highest water level (3mAHD) centrally located in the north of the study area. This correlates with the expected water level contours determined from field investigations.

Groundwater levels in the model in the upper, perched aquifer and the basal, semi- confined aquifer were found to be lower along the coastal areas and in the vicinity of the central swale. This matches patterns in water levels revealed in field studies which are attributed to proximity to groundwater discharge locations and mechanisms. Direct discharge along the coastline and groundwater seepage off the coast are significant groundwater discharge mechanisms on Bribie. The central swale acts as a local groundwater sink that supports wetlands which are reliant on shallow groundwater. Any change that alters the shallow groundwater levels has the potential to negatively impact on this native vegetation, which usually grows best in swampy, freshwater sites (Boland et al, 1992).

Water Budget

The calibrated groundwater model produced an estimated groundwater budget for the model domain. The primary source of groundwater recharge is infiltration of rainfall for the upper, perched aquifer (Layer 1) and percolation of groundwater into the lower indurated sands (Layers 2 and 3) and the semi-confined, basal aquifer (Layer 4). An insignificant amount of water enters the Bribie aquifers from constant head boundaries (5m3/day). However the Visual MODFLOW modelling package is not able to model the freshwater-seawater interface so this value is unlikely to adequately represent the water interface at the coast.

While Bribie Island aquifers form groundwater mounds above sea level, they restrict saline water intrusion into the aquifer system but this balance needs to be constantly monitored to protect the existing balance. Any change that lowers the water table or potentiometric surface of the aquifers has the potential to alter the seawater-fresh groundwater boundary. Excessive extraction of groundwater via extraction bores or reduction in recharge due to drought or changes to land use

could lower the groundwater levels within the aquifer system. The potential for induced seawater intrusion into the island was not investigated in this study but would be a good topic for future research.

The flow budget describes how much water leaves the groundwater system under steady-state conditions. The dominant drainage processes on Bribie Island are evapotranspiration (Layer 1 only - 15070m3/day) and groundwater seepage along the coast, from canals and tidal creeks (all layers - 9512m3/day). Groundwater enters the sea through offshore sediments in the Pumicestone Passage and the Coral Sea. Analytical calculations offer an estimate of around 8000m3/day of groundwater discharged from central Bribie Island, approximately 16% less than the model. The drain cells in Layer 1 and flow across the general head boundaries in Layers 2, 3 and 4 remove minor amounts of water from the system. Any natural or anthropogenic change that significantly reduces groundwater seepage from the coastline has the potential to alter the seawater - fresh groundwater boundary. This could result in the degradation of the freshwater aquifer system due to saline water intrusion. Changes to the quantity and quality of environmental flows discharging into Pumicestone Passage have the potential to impact ecosystems within the area.

Uncertainty and Sensitivity Assessment

Sources of uncertainty in numerical models can include geological, parameter (e.g. hydraulic conductivity and recharge) and boundary condition uncertainty. Geological uncertainty relates to the degree to which the stratigraphy assumed in the model represents the geology of the area. Parameter and boundary condition uncertainty describe the uncertainty in the model from imposed parameters and by characterisation of hydrogeologic conditions along the boundary of the model.

There is considerable generalisation involved in the representation of the sand layers in the model. The three sand layers are: the younger upper, clean sands; the indurated sand layer; and the lower basal sands. The southern half of the model has a limited number of piezometers in both the upper, perched and basal, semi- confined aquifer systems. The east-west transect installed by QUT and the monitoring network in the Pacific Harbour area give good information about the stratigraphy in the northern area. The northern portion of the model has 22 of the 25 piezometers in the upper aquifer and 17 of the 20 piezometers in the basal aquifer. It was neither possible nor necessary to complete further monitoring bores

in the southern half of the study area due to budgetary constraints. Further drilling would have confirmed the heterogeneity of the sand package but this information was unlikely to add significantly to the current model as data would have to have been simplified to mathematically model the system. The delineation of the different sand units does not significantly affect the overall water budget in terms of the amount of water that is discharged to the sea or Pumicestone Passage. However, the lack of data may influence the representation of local conditions such as flow directions or water levels in the south of the model.

The recharge rate has a large affect on the total volume of water that enters the model. The groundwater model reveals a non-unique relationship; an increase in the recharge rate causes a proportional increase in the evapotranspiration and groundwater discharge along the coastal zone. As there were good records for this parameter the data was not altered significantly.

There is uncertainty associated with the hydraulic conductivity parameters within the model, especially for the indurated sand layer as there are few monitoring piezometers targeting this interval. The hydraulic conductivities determined from parameter estimation methods were limited between 1 and 110m/day (horizontal) and between 0.0001 and 1.1m/day (vertical) to keep the values within limits of field test data and published values for similar sedimentary units. The uncertainties associated with the hydraulic conductivity combined with the heterogeneity and anisotropy of the sandmass cause uncertainties in direction and magnitude of flows at a local scale. However, it is unlikely that the hydraulic conductivity values within specific sand units will differ by more than an order of magnitude from the actual field value.

The most important source of uncertainty in the model arises from the salt water boundary not being integrated in the model. A source of boundary condition uncertainty arises from treating the coastline as a constant head boundary. The proportion of groundwater that discharges to these boundaries is dependent upon the assigned head value and/or the hydraulic conductivities values for the sediments near the coast. Sea water does extend into the Bribie Island aquifer and interacts with the fresh aquifer. This is revealed by water quality samples collected along the coastal areas and near tidal streams which have elevated electrical conductivities. The model simulates the dominant processes controlling groundwater flow and discharge in the central catchment of Bribie Island but does

not incorporate the interaction between the freshwater – sea water along the coast due to limitations of the software package. Groundwater levels along the coast are influenced by sea water levels and tidal surges, which the model does not take into account.

After modification of select parameter values during sensitivity analysis, the model still shows the same basic behaviour. This includes the presence of groundwater divides along the higher beach ridges, flow gradients from the higher beach ridges down to the coast or swale areas and a dominant groundwater flow direction along an east-west axis.

6. CONCLUSIONS AND FUTURE CONSIDERATIONS

6.1 MONITORING BORE NETWORK There is a scarcity of data in the southern portion of the project area, near the central swale and within the hydrogeologically significant indurated sand layer. There are few existing monitoring bores in the southern portion of the model and the bores present are not nested. There is limited information on the nature of the indurated sands in the southern area. Water levels in the shallow and basal aquifers cannot be observed and compared, and the paucity of data reduces the accuracy of the model in the south. The model assumes the same stratigraphy in the south as that in the north, which cannot be verified with the current reach of piezometers in the south.

The central swale acts as a groundwater sink in the area and is of environmental significance as it supports paperbark wetlands. Due to the environmental significance of this feature and its role as a drainage feature on the island, there are insufficient monitoring bores along the length of this feature to monitor water levels and water quality discharging into Pumicestone Passage.

The indurated sand layer is not considered a primary water producing unit within the Bribie sandmass and as a result limited data exists for the layer. However, this horizon is hydrogeologically significant to groundwater flow within the aquifer system and the induration process reduces available storage within the Bribie sandmass. Further information on the extent, specifically in the south, and the hydraulic parameters of this unit are required in order to improve understanding of the role and impact of the indurated sands within the aquifer system.

Monitoring bores are more useful where nested bore sites exist i.e. bores that are screened at various depths in the aquifer system at the same location. This setup assists with defining the different water quality parameters, groundwater levels and hydraulic gradients in the separate aquifers. As shown in this project and others preceding it, Bribie Island possesses separate but interconnected aquifers. It is recommended that any future monitoring bores be installed as nested bore sites. Bores should be screened in the shallow aquifer, the basal aquifer, and in the indurated sands.

Hydraulic testing is recommended at other locations within the different sand units on Bribie Island. This will provide improved constraints on parameter estimation methods used in the mathematical model.

The existing monitoring bore network should be maintained and monitoring continued on a regular basis.

6.2 GROUNDWATER QUALITY Groundwater recharge is via the infiltration of coastal rainfall into the surfical sands and percolation of groundwater into the lower sand units across the island. Analyses of groundwater from the two aquifers revealed an overlap of physico- chemical parameters and water chemistry results which reflects the interconnection of the aquifer systems. Groundwater from the island was dominated by fresh and acidic to slightly acidic quality water.

Groundwater samples reflect the coastal environment setting with groundwater dominated by Na-Cl type water. A number of samples from the basal aquifer possessed higher concentrations of calcium and bicarbonate ions. This enrichment could be due to chemical interactions with shell material in the sedimentary units and longer residence times of groundwater in the basal aquifer could be a factor.

There are insufficient monitoring bores located along coastal areas to enable monitoring of the fresh water-seawater interface. Due to the growing demands placed on this aquifer, this lack of monitoring presents a risk to the fresh groundwater system. Monitoring of the interface, spatially and temporally, is required to protect this water resource against deterioration from saltwater intrusion.

Environmental flows from tidal creeks and canals and groundwater discharge from the coastal areas has the potential to affect water quality within the tidal estuary, Pumicestone Passage. Monitoring of groundwater quality should continue on a regular basis in areas of groundwater discharge, including the central swale area and at locations along the coast.

6.3 NUMERICAL MODEL A steady-state, sub-regional, groundwater flow model was developed to simulate the existing hydrological system and the dominant processes that control groundwater flow. The conceptual model and subsequent numerical model were developed based on historical data, information from previous investigations and data gather as part of this study, including water level and water quality data.

The numerical model was calibrated against existing data and returned reasonable estimates of groundwater levels and hydraulic parameters. The model converges rapidly and is stable. Hydrogeological processes, especially flow characteristics, are verified by the simple model of central Bribie Island.

All numerical groundwater flow models have limitations that are associated with: the quality and quantity of data; assumptions and simplifications used to develop the model; and the scale of the model.

Some of the data input into the model were based on limited information, such as the stratigraphy and water levels in the southern portion of the model and the hydraulic parameters of the indurated sand layer. Greater stratigraphic and water level control could be achieved by installing more monitoring bores in the south. Water levels and therefore the calibration are affected by the distribution of the water level data. As a result the model will be biased to areas where there is a higher density of water level readings.

A numerical groundwater flow model gives an approximation of the aquifer. Assumptions made while constructing the model, such as a homogeneous, isotropic sand mass were used to simplify the model. The calibrated steady-state model does a reasonable job of matching the water level distribution in the central Bribie Island area. However, due to the assumptions and limited data on the indurated sands, it is unlikely that the local flows will be accurately represented by the model. The model is unlikely to be accurate near the coastline where inaccuracies may be introduced by boundary condition approximations.

The model provides insight into the groundwater system in terms of water budgets and groundwater flow directions. However, it should be viewed as a basic model that could be improved with additional data. The model can be used to identify and prioritise gaps that exist in the data. Specific areas in which improvements may be beneficial are summarised below.

Additional sensitivity studies to prioritise data collection in the central Bribie Island area. Additional studies could identify areas that are most significant in terms of defining stratigraphy and hydrogeologic parameters. The model could identify areas in which water levels measurements would be most valuable in terms of constraining the stratigraphy and input parameters.

Transient modelling to evaluate effects of seasonal fluctuations. The current model is a steady-state model which estimates flow under average conditions. It could be run as a transient model to evaluate the impact of seasonal changes on the groundwater system. This might be useful to evaluate the effects of seasonal changes to the shallow groundwater and its consequent interaction with the phreatophytic vegetation.

Refining hydraulic conductivity based on different sand units, both vertically within the sand column and horizontally across the central area, specifically in the southern portion. The model by necessity assumes averages across large areas with limited data to validate against. While this may not affect the average water budget, it may affect the local flow directions and flow rates.

Developing a model with a computer package that allows for the modelling of the freshwater-saltwater interface. The potential for seawater intrusion into the fresh aquifer system was not investigated in this study but it would be a topic for future research. Seawater intrusion into sand aquifers in coastal settings is a significant process with respect to water level predictions and protection of water quality. This process was not model in the central Bribie Island model as Visual MODFLOW is not able to model density dependent flow (i.e. freshwater-seawater interface) and due to the lack of monitoring bores along the coast. It is unlikely that the model accurately predicts groundwater levels near the coast.

In a number of aquifers around the world, natural groundwater resources have been impacted by the extraction of groundwater for human supply. Groundwater extraction can lower water levels and cause saltwater intrusion into productive aquifers in coastal settings. Changes to the quantity and quality of environmental flows discharging into Pumicestone Passage could impact ecosystems within the tidal estuary and potentially areas of Moreton Bay.

We need to understand the processes in coastal aquifers and develop an adequate monitoring bore network to research and ultimately protect these resources. Further aquifer studies with adequate field monitoring and subsequent recalibration of the model will improve performance and increase accuracy of the central Bribie Island model.

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APPENDIX A

Climate Records

Rainfall Stations Bongaree Bowls University of Dept. of Natural Club Queensland Resources & Mines Bore 14100090 Station Number 040027 040685 540055 Duration of 1931 - 1990 1978 - 1993 1993 - present Records Years of Record 59 15 11 Minimum 725.8 940.1 924.0 Rainfall (mm) Maximum 2471.2 1639.0 2344.0 Rainfall (mm) Average 1358.2 1287.3 1362.6 Rainfall (mm)

Stations Redcliffe Cape Moreton Caloundra Council Lighthouse Signal Station Station Number 040697 040043 040040 Duration of 1981 - present 1869 - present 1899 - present Records Years of Record 24 136 106

APPENDIX B

Mean Pan Evaporation

University of Qld (1970 – 1993) E E Days pan pan (mm/day) (mm/month) January 31 6.2 192.2 February 28 5.4 151.2 March 31 4.8 148.8 April 30 3.9 117.0 May 31 2.9 89.9 June 30 2.6 78.0 July 31 2.7 83.7 August 31 3.5 108.5 September 30 4.7 141.0 October 31 5.5 170.5 November 30 6.1 183.0 December 31 6.5 201.5 Annual 365 4.6 1679.0

APPENDIX C

Summary of Monitoring Bore Details

Natural Relative Top of Bottom of Bottom of Bore Id. Easting Northing Source Elevation Elevation screen screen hole MGA Zone 56 (GDA 94) m (AHD) m (AHD) m m m 14100079 508273 7021931 2.26 2.78 1.6 5.0 8.0 DNRMW 14100080 509460 7022453 1.57 2.09 1.0 5.5 12.0 DNRMW 14100081 510371 7023867 1.77 2.30 1.5 5.5 12.0 DNRMW 14100082 511889 7024604 6.65 7.17 11.5 17.5 22.0 DNRMW 14100083 509371 7014423 1.49 1.98 5.5 11.5 17.0 DNRMW 14100084 510832 7015006 2.96 3.37 7.0 13.0 19.6 DNRMW 14100085 512240 7016943 2.32 2.77 8.0 14.0 19.6 DNRMW 14100086 514225 7017526 3.51 3.94 11.5 17.5 24.2 DNRMW 14100087 513337 7011619 3.51 3.88 18.6 30.6 35.0 DNRMW 14100088 514053 7012117 8.43 8.86 34.0 40.0 42.6 DNRMW 14100089 515709 7012636 5.62 6.02 33.0 41.0 46.0 DNRMW 14100090 516314 7012892 3.58 3.95 16.0 22.0 38.0 DNRMW 14100090 516314 7012892 3.58 3.95 28.0 34.0 38.0 DNRMW 14100090 516314 7012892 - 4.88 - - - DNRMW 14100091 513828 7007465 1.67 2.07 3.5 7.5 10.4 DNRMW 14100092 515309 7008251 7.04 7.44 12.0 16.0 24.2 DNRMW 14100093 516282 7009216 5.70 - 12.0 24.0 35.0 DNRMW 14100094 515615 7004079 1.93 2.31 6.5 11.5 15.0 DNRMW 14100095 517047 7004385 6.08 6.55 10.0 13.0 19.6 DNRMW 14100096 517818 7004599 5.69 6.11 11.0 15.0 19.6 DNRMW

Natural Relative Top of Bottom of Bottom of Bore Id. Easting Northing Source Elevation Elevation screen screen hole MGA Zone 56 (GDA 94) m (AHD) m (AHD) m m m 14100097 518122 7005306 5.71 6.06 13.0 18.0 28.8 DNRMW 14100098 520189 7005672 5.11 5.50 16.0 19.0 24.0 DNRMW 14100099 518122 7005183 5.71 6.03 4.1 7.1 7.1 DNRMW 14100100 515693 7012648 5.62 6.06 14.0 20.0 20.0 DNRMW 14100101 514038 7012112 8.43 8.83 12.0 20.0 20.0 DNRMW 14100102 518670 7003367 3.47 3.69 0.0 10.1 10.1 DNRMW 14100102 518670 7003367 - 3.76 - - - DNRMW 14100103 520186 7004318 3.95 4.31 0.0 6.6 6.6 DNRMW 14100104 518036 7002845 2.80 3.04 0.0 4.2 4.2 DNRMW 14100104 518036 7002845 - 3.16 - - - DNRMW 14100105 517761 7003122 3.92 4.30 0.0 9.1 9.1 DNRMW 14100106 518234 7006290 3.82 4.05 7.6 8.2 8.2 DNRMW 14100106 518234 7006290 3.96 4.20 - - - DNRMW 14100107 517792 7005307 4.14 4.54 7.6 8.2 8.2 DNRMW 14100107 517792 7005307 - 5.15 - - - DNRMW 14100108 517655 7006107 3.59 3.89 7.1 7.7 7.7 DNRMW 14100108 517655 7006107 - 4.45 - - - DNRMW 14100109 518373 7007336 2.70 3.03 7.4 8.0 8.0 DNRMW 14100110 517713 7008014 5.12 5.54 13.8 14.4 14.4 DNRMW 14100111 516972 7009800 4.59 4.89 11.7 12.3 12.3 DNRMW

Natural Relative Top of Bottom of Bottom of Bore Id. Easting Northing Source Elevation Elevation screen screen hole MGA Zone 56 (GDA 94) m (AHD) m (AHD) m m m 14100112 515879 7006791 6.47 6.82 8.2 8.8 8.8 DNRMW 14100112 515879 7006791 - 7.49 - - - DNRMW 14100113 517660 7005035 3.98 4.65 0.0 3.8 3.8 DNRMW 14100114 516239 7009368 5.67 6.23 0.0 3.9 3.9 DNRMW 14100115 515031 7010068 6.31 6.96 0.0 3.8 3.8 DNRMW 14100116 515215 7006738 1.55 2.18 0.0 5.3 5.3 DNRMW 14100117 516222 7005001 2.87 2.90 0.0 1.5 1.5 DNRMW 14100118 519005 7006228 - 1.58 - - - DNRMW 14100119 513559 7013404 9.50 10.05 20.0 26.0 28.5 DNRMW 14100119 513559 7013404 - 10.03 - - - DNRMW 14100120 513371 7017342 10.34 10.87 20.0 23.0 23.3 DNRMW 14100120 513371 7017342 10.37 10.81 - - - DNRMW 14100121 513070 7020327 9.32 9.89 20.0 23.0 23.5 DNRMW 14100122 511739 7012052 6.53 6.97 18.5 21.5 22.0 DNRMW 14100123 511112 7019436 6.37 6.84 7.0 10.0 11.3 DNRMW 14100124 511114 7021498 6.86 7.33 16.0 19.0 19.3 DNRMW 14100125 513559 7013404 9.50 - - - 28.5 DNRMW 14100126 511895 7012207 6.44 6.81 3.0 4.0 4.9 DNRMW 14100127 511112 7019498 6.50 7.32 2.9 4.4 4.7 DNRMW 14100128 510860 7014945 2.95 3.42 - - - DNRMW

Natural Relative Top of Bottom of Bottom of Bore Id. Easting Northing Source Elevation Elevation screen screen hole MGA Zone 56 (GDA 94) m (AHD) m (AHD) m m m 14100128 510860 7014945 3.01 3.51 1.2 1.7 1.7 DNRMW 14100129 512264 7011835 - - - - - DNRMW 14100130 513199 7011681 4.05 4.81 0.4 0.9 0.9 DNRMW 14100131 515146 7010749 6.33 6.73 2.6 5.6 6.1 QUT 14100132 515443 7010894 5.70 6.18 2.6 5.6 6.1 QUT 14100133 515664 7010969 5.32 5.71 2.6 5.6 6.6 QUT 14100134 516438 7011217 4.30 4.73 1.0 4.0 6.6 QUT 14100135 516666 7011284 3.17 3.82 0.2 3.0 10.5 QUT 14100136 516040 7012805 4.09 4.49 33.5 39.5 43.6 QUT 14100137 516030 7012800 4.16 4.67 0.2 3.2 3.2 QUT 14100138 515717 7012656 5.79 6.40 1.8 4.8 5.5 QUT 14100139 515188 7012486 6.66 7.14 2.7 5.7 6.1 QUT 14100140 514731 7012328 7.62 8.07 23.3 29.3 44.3 QUT 14100141 514721 7012325 7.53 8.00 2.0 5.0 6.5 QUT 14100142 514028 7012110 8.19 8.69 1.7 4.7 6.7 QUT 14100143 514028 7012098 8.08 8.45 7.0 10.0 10.7 QUT 14100144 513078 7011843 3.84 4.25 22.0 28.0 35.9 QUT 14100145 513083 7011853 3.96 4.41 0.2 2.7 3.2 QUT 14100146 512452 7011906 3.67 4.08 1.0 4.0 5.4 QUT 14100147 512447 7011911 3.74 4.13 20.0 26.0 32.0 QUT

Natural Relative Top of Bottom of Bottom of Bore Id. Easting Northing Source Elevation Elevation screen screen hole MGA Zone 56 (GDA 94) m (AHD) m (AHD) m m m 14100148 511873 7012200 6.48 6.83 15.0 21.0 27.0 QUT 14100149 511860 7011751 4.80 5.18 0.5 3.5 3.5 QUT 14100150 511855 7011746 4.79 5.24 4.0 7.0 7.0 QUT 14100151 511855 7011756 4.72 5.19 27.0 33.0 34.9 QUT MW 1S 514483 7010444 7.61 7.80 - - 6.0 HLA MW 2S 514541 7010513 - 7.36 - - 5.0 HLA MW 3S 514922 7010622 6.63 6.93 - - - HLA MW 3D 514911 7010622 6.69 7.05 17.0 20.0 21.0 HLA MW 4S 513978 7010331 5.19 5.52 - - - HLA MW 4D 513968 7010329 5.23 5.81 19.0 22.0 23.0 HLA MW 5S 513759 7010794 5.11 5.54 - - - HLA MW 5D 513768 7010804 5.11 5.62 16.8 19.8 21.0 HLA MW 6S 514051 7011182 6.58 7.07 - - - HLA MW 6D 514043 7011171 6.58 6.91 20.0 23.0 24.0 HLA MW 7S 514816 7009985 6.72 7.31 - - - HLA MW 7D 514818 7009973 6.70 7.15 25.0 28.0 29.0 HLA MW 8S 514984 7011115 7.82 8.09 - - - HLA MW 8D 514991 7011107 7.76 8.31 19.0 22.0 23.0 HLA

Natural Relative Top of Bottom of Bottom of Bore Id. Easting Northing Source Elevation Elevation screen screen hole MGA Zone 56 (GDA 94) m (AHD) m (AHD) m m m MW 09D 514010 7010957 5.80 6.35 4.5 5.5 8.0 HLA MW 10D 514112 7010403 5.83 6.33 4.5 5.5 8.0 HLA MW 11D 514105 7010112 5.07 5.64 10.0 11.0 12.0 HLA MW 12D 514299 7010611 8.19 8.75 13.5 14.5 17.0 HLA MW 13D 514490 7010966 6.83 7.36 11.8 12.8 17.0 HLA MW 14D 514529 7010693 6.59 7.19 4.0 5.0 10.0 HLA MW 15D 514697 7010221 6.63 7.13 4.0 5.0 9.5 HLA MW 16D 514814 7010962 7.00 7.59 5.0 6.0 9.3 HLA MW 17D 514833 7010114 6.60 7.10 10.2 11.2 13.7 HLA MW 18D 514780 7010561 6.53 7.11 12.0 13.0 14.1 HLA MW 19D 515008 7010109 6.59 7.15 21.5 22.5 31.1 HLA MW 09S 513810 7010610 5.45 5.97 1.8 2.3 4.0 HLA MW 10S 514004 7010745 5.96 6.47 2.0 2.5 3.9 HLA MW 11S 514080 7010538 5.99 6.49 1.5 2.0 3.3 HLA MW 12S 514101 7010114 5.03 5.56 2.0 2.5 2.7 HLA MW 13S 514102 7010278 5.67 6.19 1.7 2.2 3.2 HLA

Natural Relative Top of Bottom of Bottom of Bore Id. Easting Northing Source Elevation Elevation screen screen hole MGA Zone 56 (GDA 94) m (AHD) m (AHD) m m m MW 14S 514304 7010609 8.19 8.70 3.0 3.5 4.2 HLA MW 15S 514302 7011012 8.34 8.86 3.0 3.5 5.0 HLA MW 16S 514423 7010113 8.00 8.57 3.5 4.0 5.8 HLA MW 17S 514463 7011102 6.75 7.30 1.3 1.8 3.5 HLA MW 18S 514562 7010611 6.71 7.23 1.5 2.0 3.3 HLA MW 19S 514611 7010766 6.67 7.19 1.3 1.8 4.0 HLA MW 20S 514693 7010223 6.68 7.20 1.8 2.3 3.3 HLA MW 21S 514753 7010115 6.52 7.08 1.8 2.3 3.0 HLA MW 22S 514761 7010991 7.12 7.65 1.4 1.9 3.0 HLA MW 23S 514808 7009977 6.43 6.96 6.0 6.5 9.3 HLA MW 24S 514932 7010927 6.69 7.21 1.0 1.5 3.0 HLA MW 25S 515000 7010408 6.17 6.67 1.0 1.5 10.0 HLA MW 26S 515006 7010111 6.58 7.11 2.3 2.8 2.8 HLA MW 27S 515076 7010694 6.71 7.23 1.3 1.8 2.1 HLA

APPENDIX D

Standing Water Levels and Physico-chemical Parameters

Bore Id SWL EC pH Eh D.O. Temp. Colour Odour Date (m b ToC) (µS/cm) (mV) (ppm) (oC) 088 6.30 402 5.76 161 0.96 22.0 Clear N 17/07/03 088 6.47 376 5.65 150 0.56 22.9 Crystal clear N 24/09/03 088 6.58 344 5.64 204 1.35 22.4 Crystal clear N 13/11/03 092 6.92 315 5.62 218 1.77 20.1 Medium brown N 14/05/03 092 6.58 320 5.31 234 1.24 21.4 Milky, almost clear Y 16/07/03 092 6.56 307 5.22 246 0.72 22.2 Milky clear N 15/09/03 092 6.79 307 5.28 272 1.12 22.7 Milky clear N 11/11/03 101 6.34 193 4.85 240 0.96 21.8 Almost clear Y 17/07/03 101 6.50 93 4.60 258 0.82 23.4 Weak tea Y 24/09/03 101 6.69 101.8 5.30 236 0.66 22.7 Weak tea N 13/11/03 112 4.94 331 6.55 135 3.17 21.0 Clear / slightly brown Y 15/05/03 112 4.98 287 5.02 174 0.92 21.6 Dark tea Y 16/07/03 112 5.09 264 5.25 162 0.73 22.2 Weak tea Y 15/09/03 112 5.43 262 5.14 185 1.1 22.3 Weak tea Y 11/11/03 114 0.96 216 3.77 270 1.00 21.2 Dark tea Y 17/07/03 114 1.28 178 4.23 281 0.85 20.4 Dark tea Y 15/09/03 114 1.46 180.4 4.09 284 0.97 22.4 Tea Y 11/11/03 115 0.70 362 3.62 323 3.64 21.1 Dark brown Y 14/05/03 115 0.72 335 3.71 309 2.32 21.1 Dark tea Y 16/07/03 115 1.09 319 3.67 319 0.87 21.0 Dark tea Y 15/09/03 115 1.31 319 3.74 331 1.08 22.4 Dark tea Y 11/11/03

Bore Id SWL EC pH Eh D.O. Temp. Colour Odour Date (m b ToC) (µS/cm) (mV) (ppm) (oC) 116 0.88 24300 6.52 139 1.73 21.3 Light brown N 15/05/03 116 1.35 18350 5.95 155 2.16 21.0 Milky, light brown saline 16/07/03 116 1.61 16420 5.45 176 2.34 21.1 Milky clear N 15/09/03 116 1.55 17720 5.59 187 1.98 21.5 Milky clear N 11/11/03 126 3.36 74 4.48 335 0.75 22.0 Dark tea Y 24/09/03 126 3.52 106.1 4.48 398 1.21 23.9 Tea Y 13/11/03 129 1.76 68 4.85 336 3.63 20.7 Dark murky brown Y 24/09/03 129 2.20 65.8 4.51 364 0.97 21.9 Dark murky brown Y 13/11/03 131 1.00 67 4.06 319 3.66 20.4 Dark brown N 14/05/03 131 1.08 63 4.19 320 4.35 19.8 Dark brown Y 15/07/03 131 1.38 61 4.60 323 0.89 21.2 Light murky brown Y 24/09/03 131 1.49 62.2 4.30 310 1.04 23.2 Lt murky brown Y 12/11/03 132 1.10 396 3.85 306 0.75 20.5 Dark murky brown Y 24/09/03 132 1.03 403 3.67 321 2.38 22.1 Dark brown Y 12/11/03 133 0.89 373 3.64 349 4.83 20.4 Dark murky brown Y 24/09/03 133 1.90 314 3.68 356 4.02 23.8 Dark brown Y 12/11/03 139 1.33 398 4.28 269 0.72 21.2 Dark murky brown Y 24/09/03 139 1.35 402 4.38 255 0.89 21.8 Dark murky brown Y 13/11/03 140 5.37 321 4.99 212 2.07 21.5 Clear tea N 17/07/03 140 5.55 303 4.91 250 0.60 22.7 Clear N 24/09/03 140 5.65 307 4.80 250 0.62 22.4 Clear N 13/11/03

Bore Id SWL EC pH Eh D.O. Temp. Colour Odour Date (m b ToC) (µS/cm) (mV) (ppm) (oC) 141 0.97 170 4.49 250 1.41 19.2 Dark brown, muddy Y 17/07/03 141 1.26 168 4.33 282 0.81 20.6 Dark murky brown Y 24/09/03 141 1.23 188.4 4.63 281 0.98 22.8 Dark murky brown Y 13/11/03 142 1.20 83 4.18 265 3.48 19.7 Medium brown Y 14/05/03 142 1.26 72 4.80 250 3.82 19.4 Dark brown, muddy Y 17/07/03 142 1.68 69 4.34 266 0.68 21.5 Dark murky brown Y 24/09/03 142 1.79 70.7 4.44 256 1.29 22.7 Dark murky brown Y 13/11/03 143 4.89 99 3.90 356 3.21 -19.3 Dark brown Y 14/05/03 143 5.02 105 3.89 290 0.54 22.4 Dark brown Y 17/07/03 143 5.40 121 3.72 295 0.64 22.8 Dark murky brown Y 24/09/03 143 5.60 90.2 3.80 286 0.76 22.3 Dark murky brown Y 13/11/03 144 2.12 1018 4.87 259 0.82 20.2 Dark tea Y 17/07/03 144 2.42 882 5.10 235 0.62 21.4 Dark tea N 24/09/03 144 2.70 941 5.18 266 1.03 21.1 Tea Y 13/11/03 145 1.30 154 3.70 372 3.41 18.3 Dark brown N 17/07/03 145 1.51 142 3.78 339 1.29 20.4 Light murky brown Y 24/09/03 145 1.59 146.6 3.69 344 1.96 21.8 Med murky brown Y 13/11/03 146 1.88 64 4.36 298 3.92 22.8 Dark murky brown Y 24/09/03 146 2.17 64.6 4.18 270 0.83 23.2 Dark murky brown Y 13/11/03 147 2.04 86 4.66 253 1.05 21.5 Weak tea Y 17/07/03 147 2.36 83 4.73 255 0.50 22.4 Weak tea Y 24/09/03

Bore Id SWL EC pH Eh D.O. Temp. Colour Odour Date (m b ToC) (µS/cm) (mV) (ppm) (oC) 147 2.62 78 4.46 275 1.17 22.0 Weak tea Y 13/11/03 148 4.64 76 4.38 310 0.74 22.6 Weak tea Y 24/09/03 148 4.90 78.1 4.54 334 0.68 23.2 Weak tea Y 13/11/03 149 1.19 224 3.52 310 1.14 19.3 Dark murky brown Y 24/09/03 149 1.31 214.8 3.53 332 1.4 22.2 Dark murky brown Y 13/11/03 150 1.25 294 3.56 307 5.52 19.9 Dark muddy brown Y 17/07/03 150 2.15 237 3.51 311 1.80 19.8 Dark murky brown Y 24/09/03 150 2.47 234 3.48 317 1.63 21.4 Dark murky brown Y 13/11/03 151 3.31 210 3.81 289 0.83 21.2 Dark tea Y 17/07/03 151 3.62 203 3.68 291 0.73 21.9 Dark tea Y 24/09/03 151 3.87 205.9 3.77 288 0.9 21.7 Dark tea Y 13/11/03 MW 1S 1.07 152 4.13 334 3.35 20.0 Dark brown Y 15/07/03 MW 1S 1.38 128 4.25 348 3.41 19.8 Murky choc brown Y 16/09/03 MW 1S 1.58 137.9 4.23 348 2.21 22.3 Dark murky brown Y 12/11/03 MW 3S 0.75 399 4.31 262 2.33 20.3 Dark brown, muddy Y 15/07/03 MW 3S 1.40 387 4.45 273 3.75 19.8 Murky choc brown Y 16/09/03 MW 3S 1.59 493 4.30 287 1.17 22.8 Dark murky brown Y 12/11/03 MW 4D 4.64 393 5.33 269 4.66 19.6 Clear / slightly brown N 14/05/03 MW 4D 4.67 386 4.61 304 1.40 21.2 Milky N 15/07/03 MW 4D 4.98 390 5.24 262 0.79 21.5 Milky clear N 16/09/03 MW 4D 5.12 392 4.94 294 0.97 22.4 Clear N 12/11/03

Bore Id SWL EC pH Eh D.O. Temp. Colour Odour Date (m b ToC) (µS/cm) (mV) (ppm) (oC) MW 4S 1.89 233 4.00 410 4.34 - Dark brown N 14/05/03 MW 4S 1.87 294 3.61 443 5.50 18.3 Dark brown, muddy Y 15/07/03 MW 4S 2.50 308 3.52 423 6.77 19.1 Murky choc brown Y 16/09/03 MW 4S 2.53 353 3.45 454 1.94 22.0 Dark murky brown Y 12/11/03 MW 5D 4.17 263 4.52 296 1.36 20.4 Very clear N 15/07/03 MW 5D 4.37 258 5.06 273 0.81 21.5 Crystal clear N 16/09/03 MW 5D 4.65 254 4.51 326 1.18 22.2 Crystal clear N 12/11/03 MW 5S 1.34 277 3.95 346 5.35 20.0 Dark brown, muddy Y 15/07/03 MW 5S 1.64 263 3.73 358 4.52 19.4 Murky choc brown Y 16/09/03 MW 5S 1.75 259 3.71 397 2.48 23.2 Dark murky brown Y 12/11/03 MW 6D 5.33 364 4.88 277 1.20 20.8 Milky N 15/07/03 MW 6D 5.43 354 5.41 239 0.73 21.6 Milky clear N 16/09/03 MW 6D 5.70 361 5.39 255 0.94 22.4 Milky clear N 12/11/03 MW 6S 0.64 220 4.53 296 1.91 20.3 Dark brown, muddy Y 15/07/03 MW 6S 0.98 203 4.57 281 2.93 19.8 Murky choc brown Y 16/09/03 MW 6S 1.06 206.9 4.32 310 0.89 21.8 Dark murky brown Y 12/11/03 MW 8D 5.89 343 5.07 254 4.22 - Clear / slightly brown N 14/05/03 MW 8D 5.94 350 4.86 260 1.49 21.9 Milky Y 15/07/03 MW 8D 6.03 409 5.02 269 0.76 22.5 Milky clear N 16/09/03 MW 8D 6.22 379 4.50 292 1.05 22.7 Milky clear N 12/11/03 MW 8S 1.46 130 3.55 324 4.21 -14.3 Medium brown N 14/05/03

Bore Id SWL EC pH Eh D.O. Temp. Colour Odour Date (m b ToC) (µS/cm) (mV) (ppm) (oC) MW 8S 1.52 120 3.85 333 3.17 21.2 Dark brown, muddy Y 15/07/03 MW 8S 1.73 111 3.85 343 3.68 21.1 Murky choc brown Y 16/09/03 MW 8S 1.88 120.2 3.77 346 1.38 23.4 Lt murky brown Y 12/11/03 MW 11-1D 4.80 34800 6.06 215 0.22 22.9 Dark brown Y 15/05/03 MW 11-1D 6.37 ------16/07/03 MW 11-1D 6.23 ------15/09/03 MW 11-1D 4.86 26400 5.19 227 2.99 23.9 Dark murky brown N 12/11/03 MW 11-1S 1.59 14400 3.55 480 3.64 21.9 Dark brown Y 15/05/03 MW 11-1S 2.60 ------16/07/03 MW 11-1S 2.33 ------15/09/03 MW 11-1S 1.99 13650 3.25 427 3.26 24.6 Dark murky brown N 12/11/03 MW 11D 4.80 248 4.78 262 0.75 20.2 Clear tea N 15/07/03 MW 11D 4.97 233 5.01 247 0.89 21.6 Tea N 16/09/03 MW 11D 5.15 238 4.83 277 0.95 22.0 Tea Y 12/11/03 MW 12S 1.38 344 3.39 348 2.81 18.7 Dark brown, muddy Y 15/07/03 MW 12S 1.72 331 3.44 347 4.58 19.8 Murky choc brown Y 16/09/03 MW 12S 1.89 304 3.47 332 0.84 22.0 Dark murky brown Y 12/11/03 MW 15S 1.59 112 3.79 325 4.59 20.6 Medium brown Y 15/07/03 MW 15S 1.91 112 3.76 330 5.51 20.0 Light murky brown Y 16/09/03 MW 15S 2.13 108.2 3.77 327 1.33 22.8 Light brown Y 12/11/03 MW 16D 0.89 268 4.10 285 1.71 20.6 Dark brown, muddy Y 15/07/03

Bore Id SWL EC pH Eh D.O. Temp. Colour Odour Date (m b ToC) (µS/cm) (mV) (ppm) (oC) MW 16D 1.14 250 4.21 300 0.88 20.3 Murky choc brown Y 16/09/03 MW 16D 1.33 253 4.51 316 2.02 21.9 Dark murky brown Y 12/11/03 MW 22S 0.89 314 3.83 317 4.80 18.7 Dark brown, muddy Y 15/07/03 MW 22S 1.16 313 3.55 322 6.19 19.3 Light murky brown Y 16/09/03 MW 22S 1.32 310 3.58 324 2.4 23.6 Dark murky brown Y 12/11/03 QM 114 1.16 5310 4.90 222 0.29 23.6 Dark brown Y 15/05/03 QM 114 1.41 2085 5.06 204 1.59 19.9 Dark brown, muddy Y 15/07/03 QM 114 1.56 1596 4.85 237 4.30 22.3 Murky choc brown Y 15/09/03 QM 114 1.54 1950 4.79 285 3.01 25.6 Dark murky brown Y 11/11/03 Slnder Dr 5.31 308 3.64 285 0.81 22.8 Dark tea Y 16/07/03 Slnder Dr 5.44 284 3.60 326 0.71 23.5 Dark tea Y 15/09/03 Slnder Dr 5.91 330 4.01 347 1.05 23.2 Dark tea Y 11/11/03 TCLP nth 4.69 397 4.21 300 4.17 23.4 Dark brown Y 15/05/03 TCLP nth 4.90 590 4.15 274 5.33 22.7 Dark brown Y 16/07/03 TCLP nth 4.97 413 4.18 289 5.73 22.6 Murky choc brown Y 15/09/03 TCLP nth 5.09 384 4.14 305 3.08 23.7 Dark murky brown Y 11/11/03 W Patch 2.68 130 6.33 264 4.25 20.9 Dark tea N 15/05/03 W Patch 2.83 186 4.92 398 1.76 16.1 Tea Y 15/07/03 W Patch 2.93 132 4.60 377 0.93 21.5 Dark tea N 15/09/03 W Patch 2.59 152.1 4.86 386 1.41 22.0 Tea Y 11/11/03

APPENDIX E

Groundwater Chemical Analyses

Sample Id. Na K Mg Ca Sr Mn Fe Zn Cu F Cl Br SO4 NO3 NO2 HCO3 mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L 14100087 44.0 1.4 4.4 1.7 0.04 2.70 0.10 71.0 2.0 0.5 16.5 14100087 63.0 2.4 5.5 3.4 0.17 8.50 0.00 97.0 23.0 2.4 9.2 14100088 57.0 4.3 6.0 7.7 0.05 5.00 0.10 68.0 2.2 0.5 98.0 14100088 64.0 5.3 8.2 14.0 0.30 9.00 0.15 82.0 4.5 0.0 124.4 14100088 49.2 4.6 7.1 8.7 0.00 0.25 0.03 0.08 0.08 50.2 0.0 3.3 104.9 14100088 51.4 4.9 6.9 6.4 0.03 0.10 0.03 0.00 0.01 46.6 0.0 0.0 111.8 14100088 49.1 5.3 6.8 6.2 0.07 0.04 12.15 0.04 0.00 0.05 46.4 0.11 0.2 0.3 99.8 14100088 47.2 4.2 6.9 6.5 0.03 0.00 0.07 0.00 0.07 46.5 0.0 0.0 108.7 14100088 49.2 5.4 7.0 6.6 0.08 0.04 12.37 0.03 0.01 0.01 52.4 0.12 1.4 1.1 120.0 14100088 51.3 4.6 6.0 6.3 0.01 0.00 0.01 0.07 0.10 47.3 0.0 0.0 111.8 14100089 53.0 5.9 9.0 12.0 0.22 6.90 0.10 80.0 2.0 0.5 105.0 14100089 81.0 4.3 33.0 51.0 8.60 13.00 0.00 72.0 1.0 0.5 451.3 14100089 52.4 3.7 13.9 20.5 3.03 0.21 0.00 0.06 0.03 69.2 0.0 0.0 159.7 14100089 46.6 4.1 8.7 15.8 1.80 0.00 0.01 0.00 0.00 65.7 0.0 0.0 110.1 14100089 43.7 4.7 6.6 11.1 0.11 0.88 15.92 0.02 0.00 0.04 62.8 0.15 0.1 0.1 88.3 14100089 41.8 3.9 6.9 11.7 0.80 0.00 0.15 0.00 0.02 65.2 0.5 0.0 83.2 14100089 43.5 5.1 6.8 11.2 0.12 0.85 16.43 0.03 0.01 0.13 61.4 0.18 0.6 0.2 110.0 14100089 43.6 4.6 6.5 9.9 0.47 0.00 0.03 0.04 0.03 65.8 0.0 0.0 79.9 14100090 53.0 4.3 4.5 4.1 0.04 0.02 0.10 95.0 2.0 0.5 16.5 14100090 43.0 2.5 3.2 3.3 0.08 2.00 0.00 70.0 6.4 0.0 4.8 14100090 44.0 2.8 3.4 1.6 0.05 2.30 0.00 64.0 5.7 0.0 19.7 14100090 45.3 4.2 3.6 4.3 0.03 3.58 0.16 0.03 0.01 72.9 0.4 3.9 20.2 14100090 34.1 2.9 2.7 2.2 0.02 2.80 0.07 0.00 0.00 58.9 0.9 0.0 17.1 14100090 43.7 3.9 3.7 4.6 0.04 4.28 0.91 0.01 0.00 75.9 1.1 0.0 29.8 14100090 37.5 3.2 2.9 3.2 0.02 0.02 0.56 0.49 0.01 66.1 3.2 0.0 17.5 14100091 350.0 15.5 63.0 55.0 2.00 23.00 0.20 550.0 120.0 1.0 320.0 14100091 150.0 9.4 28.0 26.0 3.40 2.30 0.50 215.0 74.0 0.5 200.0 14100092 65.0 3.0 11.0 19.0 0.60 8.30 0.10 96.0 29.0 0.5 84.0 Sample Id. CO3 PO4 Al SIO2 B Site Cond pH Date T(Wa) Depth colour HARD TURB mg/L mg/L mg/L mg/L mg/L µS/cm 14100087 0.0 19.0 deep 280 4.8 11 Feb 92 30 22 14100087 0.0 90.0 deep 370 5.0 03 Mar 92 25 31 14100088 0.0 17.0 deep 385 6.6 07 Feb 92 40 44 14100088 0.0 20.0 deep 420 6.4 03 Mar 92 27 69 14100088 0.1 0.00 16.0 0.10 deep 320 7.1 06 Sep 95 17 51 13 14100088 0.0 0.00 16.0 0.10 deep 325 6.6 08 Aug 96 29 44 27 14100088 0.02 0.02 deep 374 6.6 14 Sep 00 23.4 14100088 0.0 0.01 17.0 0.07 deep 327 6.7 15 May 01 20 3 45 268 14100088 0.00 0.00 24.3 deep 326 5.6 19 Sep 01 21.6 14100088 0.0 0.01 18.0 0.09 deep 326 6.4 07 Aug 02 20 2 40 3 14100089 0.0 14.0 deep 410 5.1 06 Feb 92 41 67 14100089 0.1 24.0 deep 830 6.2 03 Mar 92 27 263 14100089 0.4 0.00 21.0 0.10 deep 454 7.6 06 Sep 95 19 108 3 14100089 0.0 0.00 19.0 0.00 deep 384 6.4 09 Aug 96 20 75 66 14100089 0.03 0.00 deep 390 5.7 14 Sep 00 23.2 14100089 0.0 0.00 20.0 0.05 deep 347 6.3 17 May 01 20 6 58 108 14100089 0.00 0.14 27.7 deep 364 5.9 19 Sep 01 21.2 14100089 0.0 0.00 19.0 0.06 deep 340 6.1 07 Aug 02 30 1 51 36 14100090 0.0 10.0 deep 325 6.1 19 Feb 92 34 29 14100090 0.0 24.0 deep 236 5.2 03 Mar 92 19 21 14100090 0.0 21.0 deep 245 5.5 03 Mar 92 27 18 14100090 0.0 0.00 13.0 0.10 deep 324 5.7 06 Sep 95 93 26 3 14100090 0.0 0.08 15.0 0.00 deep 240 5.7 09 Aug 96 101 17 6 14100090 0.0 0.02 13.0 0.03 deep 315 5.8 17 May 01 20 118 27 13 14100090 0.0 0.00 15.0 0.04 deep 260 5.6 07 Aug 02 20 4 20 9 14100091 0.0 36.0 shallow 2350 6.0 07 Feb 92 7 397 14100091 0.0 31.0 shallow 1100 6.2 02 Mar 92 5 180 14100092 0.0 14.0 deep 510 4.9 07 Feb 92 16 93 Sample Id. Na K Mg Ca Sr Mn Fe Zn Cu F Cl Br SO4 NO3 NO2 HCO3 mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L 14100092 49.0 2.3 6.7 12.0 1.20 12.00 0.00 75.0 5.4 0.0 84.3 14100092 41.2 1.7 5.4 4.2 0.12 0.27 0.16 0.05 0.00 66.9 2.1 0.0 13.3 14100092 42.7 2.0 5.1 3.0 0.11 0.34 0.12 0.01 0.00 70.7 1.1 0.0 15.8 14100092 39.8 1.7 5.5 4.9 0.07 2.42 0.13 0.00 0.00 69.2 2.0 0.0 33.1 14100092 38.4 1.8 5.0 3.0 0.02 0.27 0.08 0.06 0.00 69.0 0.6 0.0 16.0 14100100 57.0 2.5 9.0 6.4 0.08 0.15 0.10 105.0 2.0 0.5 29.5 14100100 53.0 1.2 6.9 2.9 0.10 2.70 0.00 89.0 0.0 0.0 21.7 14100100 52.2 1.6 5.8 2.3 0.03 0.34 0.12 0.04 0.00 89.9 2.9 0.0 7.0 14100100 52.6 1.3 7.0 2.9 0.04 0.54 0.10 0.00 0.00 92.2 0.9 0.0 14.9 14100100 54.9 1.4 8.0 1.0 0.02 0.01 0.73 0.00 0.00 0.02 99.2 0.31 0.7 0.2 18.0 14100100 54.3 1.3 7.2 1.2 0.02 0.46 0.06 0.00 0.00 99.7 2.1 0.0 0.0 14100100 55.5 2.3 4.3 0.8 0.01 0.00 0.39 0.04 0.00 0.11 102.1 0.25 0.6 0.3 0.6 10.0 14100100 50.1 1.5 6.4 1.2 0.02 0.01 0.42 0.03 0.01 0.09 86.5 0.23 37.0 0.2 7.5 14100100 55.7 1.5 7.7 1.5 0.01 0.39 0.20 0.18 0.00 97.6 2.2 0.0 0.0 14100101 41.0 2.4 8.2 10.5 0.05 0.70 0.10 77.0 2.0 0.5 26.0 14100101 24.0 1.3 5.3 5.0 0.10 3.50 0.00 30.0 0.0 0.0 46.7 14100101 11.4 0.6 3.2 0.9 0.01 0.64 0.20 0.06 0.00 22.3 1.5 0.0 9.2 14100101 13.9 0.5 2.5 1.9 0.02 0.49 0.04 0.01 0.00 28.2 3.0 0.0 5.2 14100101 22.6 1.2 2.7 0.8 0.01 0.01 1.75 0.01 0.00 0.00 37.4 0.11 0.7 0.5 9.0 14100101 15.8 0.2 2.9 0.6 0.01 0.01 3.42 0.04 0.02 0.05 31.5 0.10 0.3 1.0 10.0 14100101 16.1 1.1 2.2 0.9 0.00 0.31 0.09 0.21 0.00 28.5 0.5 0.0 5.9 14100110 24.6 2.9 3.6 4.2 0.47 0.16 0.13 0.03 0.00 27.3 8.0 32.4 0.0 14100110 37.7 2.1 4.9 5.7 0.04 0.61 0.02 0.01 0.00 45.7 0.4 0.0 59.2 14100111 84.2 6.5 13.6 26.2 0.43 0.09 0.04 0.04 0.00 192.1 1.4 15.5 35.0 14100111 68.9 1.0 7.9 1.3 0.06 8.85 0.06 0.00 0.00 115.2 3.3 0.0 14.0 14100112 23.1 0.9 3.5 1.0 0.05 5.54 0.18 0.01 0.00 37.7 3.3 0.0 11.0 14100112 26.5 1.0 3.9 1.0 0.08 1.24 0.17 0.14 0.00 43.8 8.1 0.0 5.5 14100114 17.5 0.5 3.1 1.9 0.00 0.30 0.03 0.01 0.00 29.5 0.4 0.0 6.7 Sample Id. CO3 PO4 Al SIO2 B Site Cond pH Date T(Wa) Depth colour HARD TURB mg/L mg/L mg/L mg/L mg/L µS/cm 14100092 0.0 22.0 deep 362 5.9 02 Mar 92 15 57 14100092 0.0 0.10 13.0 0.10 deep 274 5.6 04 Sep 95 57 33 271 14100092 0.0 0.26 14.0 0.00 deep 282 5.4 07 Aug 96 80 28 803 14100092 0.0 0.18 15.0 0.05 deep 297 5.9 15 May 01 15 109 35 85 14100092 0.0 0.13 14.0 0.07 deep 266 5.4 07 Aug 02 16 19 28 11 14100100 0.0 12.0 deep 400 4.7 06 Feb 92 20 53 14100100 0.0 12.0 deep 346 4.8 03 Mar 92 18 36 14100100 0.0 1.06 12.0 0.10 deep 328 5.2 06 Sep 95 209 30 1 14100100 0.0 1.62 12.0 0.00 deep 347 5.3 09 Aug 96 280 36 57 14100100 0.0 0.02 1.92 deep 389 4.5 14 Sep 00 22.8 14100100 0.0 1.78 12.0 0.05 deep 372 4.9 17 May 01 20 333 33 14 14100100 0.0 0.00 1.49 15.4 deep 351 4.9 19 Sep 01 20.9 14100100 0.0 0.00 1.78 16.9 deep 354 5.0 30 Jul 02 22.3 231 119 14100100 0.0 2.68 12.0 0.12 deep 367 4.8 07 Aug 02 20 482 35 17 14100101 0.0 6.0 deep 330 4.4 07 Feb 92 20 60 14100101 0.0 7.0 deep 170 4.6 03 Mar 92 15 34 14100101 0.0 1.08 4.0 0.10 deep 108 4.6 06 Sep 95 426 15 21 14100101 0.0 1.54 6.0 0.00 deep 111 5.1 08 Aug 96 265 15 23 14100101 0.0 0.00 1.55 deep 148 4.7 14 Sep 00 23.4 14100101 0.0 0.00 1.73 11.4 deep 118 4.5 19 Sep 01 21.6 14100101 0.0 1.05 8.0 0.07 deep 121 5.1 07 Aug 02 20 122 11 8 14100110 0.0 0.00 9.0 0.10 deep 209 6.1 07 Sep 95 20 25 355 14100110 0.0 0.06 16.0 0.00 deep 246 6.2 07 Aug 96 131 34 207 14100111 0.0 0.00 19.0 0.00 deep 716 6.2 07 Sep 95 47 121 45 14100111 0.0 0.80 12.0 0.00 deep 426 5.4 07 Aug 96 351 36 11 14100112 0.0 2.20 9.0 0.09 shallow 166 5.3 15 May 01 8 778 17 8 14100112 0.0 0.44 9.0 0.10 shallow 188 5.0 07 Aug 02 9 112 19 13 14100114 0.0 0.35 5.0 0.00 shallow 155 4.2 07 Aug 96 550 17 122 Sample Id. Na K Mg Ca Sr Mn Fe Zn Cu F Cl Br SO4 NO3 NO2 HCO3 mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L 14100114 24.1 0.8 5.8 0.6 0.00 0.34 0.05 0.00 0.00 49.6 1.5 0.0 0.0 14100114 29.5 1.3 6.3 0.6 0.02 0.05 0.39 0.01 0.01 0.02 50.9 0.16 4.4 0.2 4.6 14100114 21.4 0.5 3.9 0.4 0.00 0.26 0.09 0.09 0.00 39.6 0.7 0.0 0.0 14100114 18.7 0.1 3.6 0.4 0.01 0.00 0.20 0.15 0.01 0.02 39.4 9.8 1.0 0.0 14100115 39.9 2.6 7.0 0.8 0.01 0.01 0.51 0.10 0.00 0.02 76.3 0.24 2.1 2.8 0.0 14100115 39.7 0.8 6.4 0.7 1.49 0.01 0.73 0.01 0.00 0.00 77.8 0.25 1.2 3.9 0.0 14100115 35.5 0.6 6.1 0.7 0.01 0.41 0.11 0.01 0.00 74.2 2.1 0.0 0.0 14100115 35.7 1.7 5.9 0.4 0.01 0.01 0.29 0.05 0.01 0.14 69.9 0.21 1.4 0.3 0.0 14100115 34.0 0.8 5.3 0.6 0.01 0.01 0.41 0.03 0.01 0.15 64.5 0.26 2.1 0.2 0.0 14100115 34.4 0.8 5.4 0.8 0.00 0.27 0.12 0.20 0.00 71.2 2.6 0.0 0.0 14100116 1181.5 41.6 147.0 120.6 0.40 0.01 0.03 0.03 0.61 1851.0 658.5 4.5 235.8 14100116 1113.9 40.4 128.1 104.7 0.42 0.01 0.04 0.00 0.60 1624.0 718.9 0.0 189.9 14100116 1471.0 58.7 202.7 153.3 0.55 0.00 0.11 0.04 0.61 2478.8 792.0 0.0 204.0 14100116 4965.0 128.0 778.0 450.0 2.97 32.30 0.08 0.08 0.11 9933.0 1584.4 0.0 0.0 14100116 3558.0 94.0 634.5 304.3 3.99 2.04 136.40 <0.50 <0.05 1.80 6107.4 19.80 4831.2 173.9 14100116 2719.2 71.5 460.5 226.4 2.75 1.42 99.24 0.23 0.05 3.00 4932.0 16.50 1060.5 353.2 14100119 40.4 3.1 2.3 3.7 0.19 3.83 0.08 0.00 0.00 61.5 0.6 0.3 25.4 14100122 12.9 1.3 1.4 1.4 0.00 0.23 0.08 0.00 0.00 22.7 0.0 0.0 7.4 MW 2S 53.3 0.3 9.4 4.8 0.04 0.09 9.51 0.02 0.01 0.04 105.8 0.47 11.2 0.2 0.0 MW 3D 50.0 2.0 4.0 2.0 0.09 5.93 0.00 85.0 0.5 0.0 20.0 MW 3D 48.0 3.0 4.0 3.0 0.03 9.78 0.00 83.0 1.0 0.6 10.0 MW 3S 23.0 0.5 6.0 2.0 0.02 2.70 0.00 52.0 0.5 4.8 0.5 MW 3S 21.0 0.3 4.0 1.0 0.01 0.80 0.00 40.0 4.0 1.7 0.2 MW 3S 15.0 1.2 3.6 1.4 0.02 0.01 1.13 0.09 0.02 0.00 44.0 0.17 0.7 0.8 0.4 MW 4D 52.0 3.0 4.0 3.0 0.04 9.25 0.00 88.0 0.5 0.7 20.0 MW 4D 49.0 4.0 5.0 5.0 0.04 2.16 0.00 88.0 7.0 0.3 9.0 MW 4D 50.1 4.3 4.3 3.6 0.04 0.04 9.99 0.03 0.01 0.01 92.5 0.22 0.4 0.5 19.0 MW 4D 46.9 3.0 4.8 3.0 0.04 0.10 11.37 0.19 0.11 0.12 77.9 0.3 0.0 19.5 Sample Id. CO3 PO4 Al SIO2 B Site Cond pH Date T(Wa) Depth colour HARD TURB mg/L mg/L mg/L mg/L mg/L µS/cm 14100114 0.0 0.58 4.0 0.03 shallow 258 3.8 18 May 01 5 999 25 20 14100114 0.0 0.03 0.51 4.5 shallow 245 3.7 19 Sep 01 19.6 14100114 0.0 0.39 4.0 0.06 shallow 202 3.9 08 Aug 02 4 999 17 29 14100114 0.0 0.25 shallow 180 4.1 11 Nov 03 22.4 0 14100115 0.22 0.93 shallow 372 3.1 14 Sep 00 20.7 14100115 0.00 0.76 6.8 shallow 3.3 15 Nov 00 14100115 0.0 0.96 6.0 0.04 shallow 372 3.6 15 May 01 4 999 27 6 14100115 0.00 0.66 6.9 shallow 336 3.6 19 Sep 01 19.6 14100115 0.00 0.73 8.8 shallow 338 3.4 30 Jul 02 20.9 1380 203 14100115 0.0 0.71 7.0 0.09 shallow 341 3.6 07 Aug 02 4 999 24 158 14100116 0.2 0.00 44.0 0.80 Brackish Ck 7021 6.8 04 Sep 95 11 905 316 14100116 1.3 0.01 46.0 0.80 Brackish Ck 6040 7.8 07 Aug 96 16 788 226 14100116 0.1 0.00 40.0 0.94 Brackish Ck 8460 6.7 15 May 01 6 7 1216 605 14100116 0.0 0.71 53.0 1.69 Brackish Ck 25700 3.4 08 Aug 02 6 12 4322 217 14100116 1.70 Brackish Ck 0 6.5 15 May 03 21.3 0 14100116 0.82 Brackish Ck 17720 5.6 11 Nov 03 21.5 0 14100119 0.0 0.12 13.0 0.00 254 5.9 08 Aug 96 133 19 265 14100122 0.0 0.39 10.0 0.00 96 5.4 08 Aug 96 103 9 61 MW 2S 0.17 2.54 6.5 shallow 248 4.2 19 Sep 01 18.5 MW 3D 0.08 5.10 deep 344 5.4 26 Apr 00 MW 3D 0.01 1.00 deep 17 Jul 00 25 MW 3S 0.11 8.35 shallow 239 4.7 26 Apr 00 MW 3S 0.03 1.44 shallow 17 Jul 00 MW 3S 0.07 1.13 5.5 shallow 174 4.8 19 Sep 01 18.6 MW 4D 0.06 0.70 deep 351 5.4 26 Apr 00 MW 4D 0.02 0.13 deep 17 Jul 00 40 MW 4D 0.00 0.10 18.1 deep 341 5.3 19 Sep 01 20.8 MW 4D 0.20 deep 393 5.3 14 May 03 19.6 0 Sample Id. Na K Mg Ca Sr Mn Fe Zn Cu F Cl Br SO4 NO3 NO2 HCO3 mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L MW 4D 46.4 3.3 4.9 3.3 0.04 0.03 9.86 0.15 0.01 0.63 91.7 2.3 1.4 43.9 MW 4S 21.0 0.7 4.0 1.0 0.01 0.87 0.00 34.0 11.0 2.5 0.6 MW 5D 40.9 3.6 3.2 1.8 0.03 0.03 3.53 0.02 0.00 0.00 67.4 0.15 0.6 0.3 18.0 MW 6D 45.2 5.2 5.4 5.4 0.06 0.09 7.27 0.03 0.00 0.00 76.3 0.16 0.2 0.6 27.0 MW 7D 51.1 0.0 4.4 3.3 0.04 0.04 10.06 0.03 0.02 0.00 77.6 0.17 0.4 0.4 32.0 MW 8D 53.1 3.2 5.1 1.7 0.02 0.05 6.06 0.02 0.00 0.00 96.2 0.24 2.2 1.0 20.0 MW 8D 51.3 1.9 6.1 0.7 0.01 0.15 2.16 0.11 0.07 0.12 82.8 0.15 0.0 9.8 MW 8D 49.2 2.1 5.6 1.0 0.01 0.02 4.81 0.12 0.02 0.03 98.6 0.24 4.4 1.1 15.9 MW 8S 8.9 1.2 1.1 0.6 0.01 0.01 0.64 0.02 0.00 0.01 13.4 0.04 3.6 1.4 0.8 MW 8S 8.7 1.7 1.8 0.7 0.01 0.01 0.73 0.14 0.02 0.09 17.4 0.07 5.2 1.6 0.0 MW11-1D 6258.0 231.3 895.3 364.3 5.44 1.77 131.31 0.95 <0.30 2.60 9594.0 26.00 1645.8 5.2 490.4 MW11-1D 4257.0 167.6 467.6 176.7 2.28 1.11 129.33 1.18 0.16 2.25 6457.5 29.25 1451.3 760.1 MW11-1S 2359.8 65.9 265.5 183.8 1.50 3.97 68.22 0.02 <0.10 4.80 3524.4 6.00 1078.8 0.0 MW11-1S 1953.5 71.8 262.3 179.0 1.50 2.57 280.00 0.63 0.09 2.00 3858.0 17.00 1443.0 0.0 14100131 8.8 0.0 1.2 1.0 0.02 0.02 0.78 0.02 0.00 0.34 19.5 0.08 1.6 0.4 0.0 14100131 7.9 1.3 1.7 1.1 0.02 0.01 0.49 0.17 0.01 0.11 14.1 0.07 5.3 1.2 0.0 14100132 19.2 0.4 4.9 0.3 0.01 0.00 0.43 0.03 0.01 0.04 52.3 0.31 1.1 0.2 0.0 14100133 43.7 0.7 8.7 1.9 0.04 0.00 1.89 0.21 0.01 0.16 82.3 0.26 6.9 1.5 0.0 14100135 66.4 0.6 9.9 0.6 0.03 0.00 1.08 0.03 0.00 0.03 124.3 0.28 19.8 2.6 0.0 14100135 34.1 0.4 4.5 0.6 0.01 0.01 1.36 0.02 0.00 0.16 63.4 0.24 5.6 0.4 0.9 14100135 72.3 1.6 7.4 0.6 0.02 0.00 0.79 0.03 0.02 0.14 135.0 0.33 24.3 0.5 0.0 14100136 61.9 2.9 5.1 1.6 0.02 0.02 1.95 0.04 0.01 0.04 83.9 0.24 2.4 0.3 20.0 14100136 42.9 3.4 4.3 2.5 0.03 0.02 2.98 0.06 0.01 77.8 0.12 0.0 0.0 10.5 14100139 35.6 0.6 6.0 0.4 0.02 0.00 0.58 0.03 0.01 0.00 68.9 0.32 0.8 0.4 0.4 14100140 44.5 3.2 5.1 2.8 0.04 0.03 5.80 0.03 0.00 0.00 77.1 0.15 2.2 0.8 27.0 14100140 43.8 3.7 4.0 2.8 0.03 0.02 4.94 0.02 0.01 0.11 73.2 0.20 2.2 21.8 23.0 14100142 6.8 2.6 1.5 0.8 0.01 0.04 0.37 0.02 0.02 0.01 9.9 0.07 2.8 0.6 0.5 14100144 165.5 10.1 20.4 12.4 0.16 0.12 7.78 0.02 0.00 0.09 256.6 0.67 79.8 0.8 2.4 Sample Id. CO3 PO4 Al SIO2 B Site Cond pH Date T(Wa) Depth colour HARD TURB mg/L mg/L mg/L mg/L mg/L µS/cm MW 4D 0.35 deep 392 4.9 12 Nov 03 22.4 0 MW 4S 0.12 0.99 shallow 17 Jul 00 2200 MW 5D 0.00 0.20 17.8 deep 251 5.1 19 Sep 01 20.8 MW 6D 0.00 0.06 21.6 deep 316 5.5 19 Sep 01 20.5 MW 7D 0.00 0.14 17.8 deep 287 5.3 19 Sep 01 208.0 MW 8D 0.00 0.29 19.4 deep 338 5.0 19 Sep 01 20.8 MW 8D 1.01 deep 343 5.1 14 May 03 0 MW 8D 0.63 deep 379 4.5 12 Nov 03 22.7 0 MW 8S 0.06 0.47 4.2 shallow 102 3.9 19 Sep 01 20.6 MW 8S 3.72 0.47 shallow 120 3.8 12 Nov 03 23.4 0 MW11-1D 120.12 near canal 0 6.1 15 May 03 22.9 0 MW11-1D 58.30 near canal 26400 5.2 12 Nov 03 23.9 0 MW11-1S 108.90 near canal 0 3.6 15 May 03 21.9 0 MW11-1S 114.00 near canal 13650 3.3 12 Nov 03 24.6 0 14100131 0.10 0.68 4.7 shallow 53 4.2 19 Sep 01 19.9 14100131 0.42 shallow 62 4.3 12 Nov 03 23.2 0 14100132 0.68 1.75 9.1 shallow 252 3.8 19 Sep 01 18.5 14100133 0.00 2.69 4.3 shallow 417 3.4 30 Jul 02 17.5 800 2680 14100135 0.07 3.21 2.4 shallow 577 3.4 05 Jun 01 21.7 14100135 0.00 2.66 6.7 shallow 295 3.8 19 Sep 01 19.0 14100135 0.00 5.95 7.6 shallow 568 3.6 30 Jul 02 19.4 203 5540 14100136 0.00 0.41 16.5 deep 270 4.7 19 Sep 01 21.3 14100136 0.00 0.26 18.3 deep 306 5.0 30 Jul 02 22.7 289 7600 14100139 0.00 1.89 8.6 shallow 291 4.3 19 Sep 01 19.8 14100140 0.00 0.35 19.8 deep 289 5.0 19 Sep 01 20.9 14100140 0.00 0.16 20.2 deep 328 5.3 30 Jul 02 22.9 146 26 14100142 6.41 0.24 16.3 shallow 71 3.9 19 Sep 01 19.3 14100144 0.00 0.15 20.3 deep 1119 5.7 05 Jun 01 21.2 Sample Id. Na K Mg Ca Sr Mn Fe Zn Cu F Cl Br SO4 NO3 NO2 HCO3 mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L 14100144 92.9 9.7 13.3 7.9 0.09 0.08 5.42 0.00 0.00 0.00 54.4 0.14 17.6 1.1 180.0 14100144 123.2 6.3 16.7 7.6 0.10 0.07 5.72 0.12 0.01 0.10 153.4 0.30 59.3 89.7 14100145 14.7 0.6 2.2 0.4 0.00 0.00 0.34 0.10 0.00 0.02 17.9 0.07 0.5 14.1 0.0 14100145 13.2 2.0 4.5 0.2 0.00 0.00 0.69 0.12 0.00 0.16 24.3 0.10 3.9 1.3 0.0 14100146 31.1 0.4 2.6 1.4 0.03 0.04 3.24 0.03 0.01 0.00 55.6 0.19 1.8 0.2 0.6 14100147 5.2 1.6 0.9 0.5 0.01 0.00 0.42 0.02 0.01 0.11 11.5 0.06 0.7 0.3 4.1 14100147 11.2 1.2 2.0 1.4 0.01 0.01 0.92 0.04 0.01 0.24 24.0 0.12 3.1 0.4 0.0 14100147 10.2 <0.4 1.8 1.2 0.01 0.01 2.88 0.28 0.02 0.09 30.3 0.13 2.7 0.6 14100148 13.7 0.2 1.5 0.3 0.01 0.00 0.29 0.00 0.01 0.00 22.4 0.09 0.8 0.2 5.3 14100151 36.0 1.3 2.8 1.8 0.03 0.01 1.63 0.03 0.01 0.29 59.2 0.18 6.5 0.5 0.0 Bell nth 993.4 38.4 127.1 40.8 0.68 0.18 23.38 <0.09 <0.06 0.60 1473.0 363.6 138.5 Bell nth 1399.6 45.0 266.2 93.4 1.51 0.41 49.44 0.10 0.09 1.00 2803.0 409.0 21.0 158.0 Bell pub 50.9 2.1 9.7 28.3 0.20 0.03 0.28 0.00 <0.03 0.10 73.9 40.5 0.6 74.4 Bell pub 57.0 4.6 15.4 40.5 0.28 0.05 0.54 0.14 0.03 0.08 43.0 0.48 30.2 0.7 190.9 Sland Dr 32.5 0.4 5.0 1.8 0.02 0.00 0.36 0.18 0.02 0.36 53.9 0.21 15.8 0.0 TCLP nth 39.7 1.3 8.3 7.7 0.06 0.04 1.69 0.72 0.02 0.36 73.6 0.30 19.7 2.5 0.0 Sample Id. CO3 PO4 Al SIO2 B Site Cond pH Date T(Wa) Depth colour HARD TURB mg/L mg/L mg/L mg/L mg/L µS/cm 14100144 19.46 0.20 20.0 deep 1109 5.5 19 Sep 01 20.5 14100144 0.25 deep 941 5.2 13 Nov 03 21.1 0 14100145 0.19 1.57 3.0 shallow 185 3.5 05 Jun 01 23.2 14100145 3.84 2.18 5.3 shallow 198 3.5 30 Jul 02 18.1 980 14100146 0.03 2.60 6.8 shallow 57 4.3 19 Sep 01 22.5 14100147 0.00 1.33 9.3 deep 50 4.8 19 Sep 01 21.3 14100147 0.00 0.86 9.4 deep 91 4.8 30 Jul 02 18.6 302 43 14100147 0.82 deep 78 4.5 13 Nov 03 22.0 0 14100148 0.00 0.38 13.0 deep 65 4.5 19 Sep 01 21.2 14100151 0.28 0.58 14.5 deep 251 4.4 30 Jul 02 21.8 2870 Bell nth 0.72 near Dux Ck 6.2 15 May 03 0 Bell nth 0.51 near Dux Ck 10060 5.9 11 Nov 03 23.7 0 Bell pub 0.12 near shore 532 6.8 15 May 03 10.1 0 Bell pub 0.02 near shore 772 6.3 11 Nov 03 23.8 0 Sland Dr 0.57 near canal 330 4.0 11 Nov 03 23.2 0 TCLP nth 2.88 near canal 384 4.1 11 Nov 03 23.7 0

APPENDIX F

Steady-state Groundwater Flow Model

(see attached CD)

APPENDIX G

Observed and Calculated Water Levels - Steady-state Model

Layer 1 Layer 4 Bore Id. Obs. Head Calc. Head Calc.-Obs. Bore Id. Obs. Head Calc. Head Calc.-Obs. 091 0.99 0.83 -0.16 087 1.89 1.68 -0.21 112 2.42 2.88 0.46 088 2.32 2.35 0.03 114 5.01 5.05 0.04 089 2.25 2.29 0.04 115 5.82 6.12 0.30 090/1* 2.24 1.87 -0.37 126 3.49 3.41 -0.08 090/2# 2.24 1.87 -0.37 131 5.16 5.55 0.39 092 1.46 1.45 -0.01 132 4.91 4.63 -0.28 110 2.16 1.88 -0.28 133 2.78 3.26 0.48 111 1.74 1.83 0.09 134 3.28 3.15 -0.13 119 2.95 2.92 -0.03 135 1.26 2.20 0.94 136 1.55 2.15 0.60 137 3.34 3.51 0.17 140 2.3 2.54 0.24 138 4.93 4.92 -0.01 144 1.56 1.74 0.18 139 5.83 5.89 0.06 147 1.51 1.65 0.14 141 6.87 6.70 -0.17 148 2.01 2.06 0.05 142 7.32 7.20 -0.12 151 1.34 1.36 0.02 145 2.99 3.10 0.11 3D 2.08 2.13 0.05 146 2.03 2.22 0.19 4D 1.32 1.23 -0.09 149 3.87 3.64 -0.23 5D 1.66 1.63 -0.03 1S 7.10 6.70 -0.40 6D 1.89 2.08 0.19 3S 6.33 6.08 -0.25 7D 1.86 1.68 -0.18 4S 2.39 2.45 0.06 8D 2.55 2.40 -0.15 5S 4.42 4.34 -0.08 6S 6.80 6.17 -0.63 7S 6.77 6.39 -0.38 8S 6.85 6.53 -0.32

Note: * First screen

# Second screen