hydrogeology and groundwater flow model, central catchment ... · a steady-state, sub-regional...

HYDROGEOLOGY AND GROUNDWATER FLOW MODEL,

CENTRAL CATCHMENT OF BRIBIE ISLAND, SOUTHEAST QUEENSLAND

by

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: ……………………………………..

i

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.

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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.

iii

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

v

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

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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



4.2 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



5.2 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

vii

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

1

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).

2

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.

3

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.

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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).

5

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).

6

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.

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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.

Shorncliffe

Redcliffe

Ningi

Caloundra

BribieIsland

MoretonIsland

NorthStradbroke

Island

UMICESTONEASSAGE

PP

ECEPTIONAY

DB

MORETONBAY

CabooltureRiver

Pine River

BrisbaneRiver

0 10 20

Kilometres

153°30′153°00′

27°30′

27°00′

Figure 1. Location map of Bribie Island

8

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.

9

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

10

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).

11

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).

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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).

13

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

14

Age Lithology

Holocene accretion ridges and swales

Holocene to Pleistocene undifferentiated sediments - mainly back barrier 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).

15

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)

17

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)

18

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;

19

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).

20

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)

21

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).

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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

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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.

24

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

25

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

26

(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).

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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.

28

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.

29

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

30

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)

31

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):

L

hhKAQ )( 21 −= Equation 1

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)

32

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

33

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

34

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.

35

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 unit

Model layer Aquifer type Model layer

type Model layer thickness

Surficial sand Layer 1 Unconfined 4 – 10 m

Indurated sand

Layers 2 and 3

Semi-confining layer

1.5 – 7 m

Basal sand Layer 4 Semi-confined

Confined / unconfined, variable S,T

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

36

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.

0123456789101112

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.

m

(AHD)

37

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.

D

KWLC *)*(= Equation 2

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.

38

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.

39

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)

40

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

41

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.

42

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

43

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)

44

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.

Caloundra

0

5

10

15

20

25

30

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

Tem

p o C

Redcliffe

0

5

10

15

20

25

30


Tem

p o C

Cape Moreton

0

5

10

15

20

25

30


Tem

p o C

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

45

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.

0

50

100

150

200

250


Mea

n M

onth

ly R

ainf

all (

mm

)

Bore 14100090Bongaree StationUniversity of Qld

Figure 20. Average monthly rainfall on southern Bribie Island

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

46

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

47

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

48

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)

51

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.

Monitoring Bores EC

µS/cm EC

µS/cm pH pH

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.

52

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.

53

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)

55

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).

56

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.

L

hhKAQ

)( 21 −=

Units Shallow Sands

Indurated Sand

Basal Sands

K mean m/day 6.4# 0.4# 13*

A mean m3 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

57

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.

58

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.

59

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.

60

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

b)

a)

61

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.

62

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

Figure 32. Mass balance for steady-state model

63

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.

64

Layer 1

National Park &

remainder Swale

Pine Plantation

Layer 2 & 3 Layer 4

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 = 31.4

Zone 1 to 2 = 51.5

Zone 1 to 3 = 182.2

Zone 1 to 4 = 3787.7

Zone 4 to 5 = 6953.0

Zone 3 to 1 = 182.4

Zone 3 to 2 = 136.2

Zone 2 to 3 = 5.6

Zone 2 to 4 = 968.0

Zone 4 to 1 = 54.2

Zone 4 to 2 = 0.0

Zone 4 to 3 = 0.0

Zone 3 to 4 = 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 = 51.5

Zone 2 to 1 = 31.4

Zone 3 to 1 = 182.4

Zone 4 to 1 = 54.2

Zone 5 to 4 = 21.4

Zone 1 to 3 = 182.2

Zone 2 to 3 = 5.6

Zone 3 to 2 = 136.2

Zone 4 to 2 = 0.0

Zone 1 to 4 = 3787.7

Zone 2 to 4 = 968.0

Zone 3 to 4 = 2308.3

Zone 4 to 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

65

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.

66

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.

67

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.

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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

69

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.

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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

71

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

72

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

73

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

74

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.

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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.

76

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.

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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.

78

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.

79

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.

80

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Brisbane.

Mercer, J.W. and Faust, C.R. (1981). Ground-Water Modeling. National Water

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1-17.

South East Queensland Regional Strategy Group (2000). Strategic Guide to

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85

Bribie Island, Queensland. ICHE 2004, 6th International Conference on Hydro-

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86

Zheng, C. and Bennett, G.D. (1995). Applied contaminant transport modeling:

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APPENDIX A

Climate Records

Rainfall Stations Bongaree Bowls Club

University of Queensland

Dept. of Natural Resources & Mines

Bore 14100090

Station Number 040027 040685 540055

Duration of Records 1931 - 1990 1978 - 1993 1993 - present

Years of Record 59 15 11

Minimum Rainfall (mm) 725.8 940.1 924.0

Maximum Rainfall (mm) 2471.2 1639.0 2344.0

Average Rainfall (mm) 1358.2 1287.3 1362.6

Stations Redcliffe Council

Cape Moreton Lighthouse

Caloundra Signal Station

Station Number 040697 040043 040040

Duration of Records 1981 - present 1869 - present 1899 - present

Years of Record 24 136 106

APPENDIX B

Mean Pan Evaporation

University of Qld (1970 – 1993)

Days Epan

(mm/day) Epan

(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

Bore Id. Easting Northing Natural Elevation

Relative Elevation

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Bottom of hole Source

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


Relative Elevation

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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


Relative Elevation

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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


Relative Elevation

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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


Relative Elevation

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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


Relative Elevation

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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


Relative Elevation

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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


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


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


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


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 HCO3mg/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 16.514100087 63.0 2.4 5.5 3.4 0.17 8.50 0.00 97.0 23.0 2.4 9.214100088 57.0 4.3 6.0 7.7 0.05 5.00 0.10 68.0 2.2 0.5 98.014100088 64.0 5.3 8.2 14.0 0.30 9.00 0.15 82.0 4.5 0.0 124.414100088 49.2 4.6 7.1 8.7 0.00 0.25 0.03 0.08 0.08 50.2 0.0 3.3 104.914100088 51.4 4.9 6.9 6.4 0.03 0.10 0.03 0.00 0.01 46.6 0.0 0.0 111.814100088 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 99.814100088 47.2 4.2 6.9 6.5 0.03 0.00 0.07 0.00 0.07 46.5 0.0 0.0 108.714100088 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 1.1 120.014100088 51.3 4.6 6.0 6.3 0.01 0.00 0.01 0.07 0.10 47.3 0.0 0.0 111.814100089 53.0 5.9 9.0 12.0 0.22 6.90 0.10 80.0 2.0 0.5 105.014100089 81.0 4.3 33.0 51.0 8.60 13.00 0.00 72.0 1.0 0.5 451.314100089 52.4 3.7 13.9 20.5 3.03 0.21 0.00 0.06 0.03 69.2 0.0 0.0 159.714100089 46.6 4.1 8.7 15.8 1.80 0.00 0.01 0.00 0.00 65.7 0.0 0.0 110.114100089 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 88.314100089 41.8 3.9 6.9 11.7 0.80 0.00 0.15 0.00 0.02 65.2 0.5 0.0 83.214100089 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 0.2 110.014100089 43.6 4.6 6.5 9.9 0.47 0.00 0.03 0.04 0.03 65.8 0.0 0.0 79.914100090 53.0 4.3 4.5 4.1 0.04 0.02 0.10 95.0 2.0 0.5 16.514100090 43.0 2.5 3.2 3.3 0.08 2.00 0.00 70.0 6.4 0.0 4.814100090 44.0 2.8 3.4 1.6 0.05 2.30 0.00 64.0 5.7 0.0 19.714100090 45.3 4.2 3.6 4.3 0.03 3.58 0.16 0.03 0.01 72.9 0.4 3.9 20.214100090 34.1 2.9 2.7 2.2 0.02 2.80 0.07 0.00 0.00 58.9 0.9 0.0 17.114100090 43.7 3.9 3.7 4.6 0.04 4.28 0.91 0.01 0.00 75.9 1.1 0.0 29.814100090 37.5 3.2 2.9 3.2 0.02 0.02 0.56 0.49 0.01 66.1 3.2 0.0 17.514100091 350.0 15.5 63.0 55.0 2.00 23.00 0.20 550.0 120.0 1.0 320.014100091 150.0 9.4 28.0 26.0 3.40 2.30 0.50 215.0 74.0 0.5 200.014100092 65.0 3.0 11.0 19.0 0.60 8.30 0.10 96.0 29.0 0.5 84.0

Sample Id.

14100087141000871410008814100088141000881410008814100088141000881410008814100088141000891410008914100089141000891410008914100089141000891410008914100090141000901410009014100090141000901410009014100090141000911410009114100092

CO3 PO4 Al SIO2 B Site Cond pH Date T(Wa) Depth colour HARD TURBmg/L mg/L mg/L mg/L mg/L µS/cm

0.0 19.0 deep 280 4.8 11 Feb 92 30 220.0 90.0 deep 370 5.0 03 Mar 92 25 310.0 17.0 deep 385 6.6 07 Feb 92 40 440.0 20.0 deep 420 6.4 03 Mar 92 27 690.1 0.00 16.0 0.10 deep 320 7.1 06 Sep 95 17 51 130.0 0.00 16.0 0.10 deep 325 6.6 08 Aug 96 29 44 27

0.02 0.02 deep 374 6.6 14 Sep 00 23.40.0 0.01 17.0 0.07 deep 327 6.7 15 May 01 20 3 45 268

0.00 0.00 24.3 deep 326 5.6 19 Sep 01 21.60.0 0.01 18.0 0.09 deep 326 6.4 07 Aug 02 20 2 40 30.0 14.0 deep 410 5.1 06 Feb 92 41 670.1 24.0 deep 830 6.2 03 Mar 92 27 2630.4 0.00 21.0 0.10 deep 454 7.6 06 Sep 95 19 108 30.0 0.00 19.0 0.00 deep 384 6.4 09 Aug 96 20 75 66

0.03 0.00 deep 390 5.7 14 Sep 00 23.20.0 0.00 20.0 0.05 deep 347 6.3 17 May 01 20 6 58 108

0.00 0.14 27.7 deep 364 5.9 19 Sep 01 21.20.0 0.00 19.0 0.06 deep 340 6.1 07 Aug 02 30 1 51 360.0 10.0 deep 325 6.1 19 Feb 92 34 290.0 24.0 deep 236 5.2 03 Mar 92 19 210.0 21.0 deep 245 5.5 03 Mar 92 27 180.0 0.00 13.0 0.10 deep 324 5.7 06 Sep 95 93 26 30.0 0.08 15.0 0.00 deep 240 5.7 09 Aug 96 101 17 60.0 0.02 13.0 0.03 deep 315 5.8 17 May 01 20 118 27 130.0 0.00 15.0 0.04 deep 260 5.6 07 Aug 02 20 4 20 90.0 36.0 shallow 2350 6.0 07 Feb 92 7 3970.0 31.0 shallow 1100 6.2 02 Mar 92 5 1800.0 14.0 deep 510 4.9 07 Feb 92 16 93


14100092 49.0 2.3 6.7 12.0 1.20 12.00 0.00 75.0 5.4 0.0 84.314100092 41.2 1.7 5.4 4.2 0.12 0.27 0.16 0.05 0.00 66.9 2.1 0.0 13.314100092 42.7 2.0 5.1 3.0 0.11 0.34 0.12 0.01 0.00 70.7 1.1 0.0 15.814100092 39.8 1.7 5.5 4.9 0.07 2.42 0.13 0.00 0.00 69.2 2.0 0.0 33.114100092 38.4 1.8 5.0 3.0 0.02 0.27 0.08 0.06 0.00 69.0 0.6 0.0 16.014100100 57.0 2.5 9.0 6.4 0.08 0.15 0.10 105.0 2.0 0.5 29.514100100 53.0 1.2 6.9 2.9 0.10 2.70 0.00 89.0 0.0 0.0 21.714100100 52.2 1.6 5.8 2.3 0.03 0.34 0.12 0.04 0.00 89.9 2.9 0.0 7.014100100 52.6 1.3 7.0 2.9 0.04 0.54 0.10 0.00 0.00 92.2 0.9 0.0 14.914100100 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 18.014100100 54.3 1.3 7.2 1.2 0.02 0.46 0.06 0.00 0.00 99.7 2.1 0.0 0.014100100 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 10.014100100 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 7.514100100 55.7 1.5 7.7 1.5 0.01 0.39 0.20 0.18 0.00 97.6 2.2 0.0 0.014100101 41.0 2.4 8.2 10.5 0.05 0.70 0.10 77.0 2.0 0.5 26.014100101 24.0 1.3 5.3 5.0 0.10 3.50 0.00 30.0 0.0 0.0 46.714100101 11.4 0.6 3.2 0.9 0.01 0.64 0.20 0.06 0.00 22.3 1.5 0.0 9.214100101 13.9 0.5 2.5 1.9 0.02 0.49 0.04 0.01 0.00 28.2 3.0 0.0 5.214100101 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 9.014100101 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 10.014100101 16.1 1.1 2.2 0.9 0.00 0.31 0.09 0.21 0.00 28.5 0.5 0.0 5.914100110 24.6 2.9 3.6 4.2 0.47 0.16 0.13 0.03 0.00 27.3 8.0 32.4 0.014100110 37.7 2.1 4.9 5.7 0.04 0.61 0.02 0.01 0.00 45.7 0.4 0.0 59.214100111 84.2 6.5 13.6 26.2 0.43 0.09 0.04 0.04 0.00 192.1 1.4 15.5 35.014100111 68.9 1.0 7.9 1.3 0.06 8.85 0.06 0.00 0.00 115.2 3.3 0.0 14.014100112 23.1 0.9 3.5 1.0 0.05 5.54 0.18 0.01 0.00 37.7 3.3 0.0 11.014100112 26.5 1.0 3.9 1.0 0.08 1.24 0.17 0.14 0.00 43.8 8.1 0.0 5.514100114 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.

14100092141000921410009214100092141000921410010014100100141001001410010014100100141001001410010014100100141001001410010114100101141001011410010114100101141001011410010114100110141001101410011114100111141001121410011214100114


0.0 22.0 deep 362 5.9 02 Mar 92 15 570.0 0.10 13.0 0.10 deep 274 5.6 04 Sep 95 57 33 2710.0 0.26 14.0 0.00 deep 282 5.4 07 Aug 96 80 28 8030.0 0.18 15.0 0.05 deep 297 5.9 15 May 01 15 109 35 850.0 0.13 14.0 0.07 deep 266 5.4 07 Aug 02 16 19 28 110.0 12.0 deep 400 4.7 06 Feb 92 20 530.0 12.0 deep 346 4.8 03 Mar 92 18 360.0 1.06 12.0 0.10 deep 328 5.2 06 Sep 95 209 30 10.0 1.62 12.0 0.00 deep 347 5.3 09 Aug 96 280 36 570.0 0.02 1.92 deep 389 4.5 14 Sep 00 22.80.0 1.78 12.0 0.05 deep 372 4.9 17 May 01 20 333 33 140.0 0.00 1.49 15.4 deep 351 4.9 19 Sep 01 20.90.0 0.00 1.78 16.9 deep 354 5.0 30 Jul 02 22.3 231 1190.0 2.68 12.0 0.12 deep 367 4.8 07 Aug 02 20 482 35 170.0 6.0 deep 330 4.4 07 Feb 92 20 600.0 7.0 deep 170 4.6 03 Mar 92 15 340.0 1.08 4.0 0.10 deep 108 4.6 06 Sep 95 426 15 210.0 1.54 6.0 0.00 deep 111 5.1 08 Aug 96 265 15 230.0 0.00 1.55 deep 148 4.7 14 Sep 00 23.40.0 0.00 1.73 11.4 deep 118 4.5 19 Sep 01 21.60.0 1.05 8.0 0.07 deep 121 5.1 07 Aug 02 20 122 11 80.0 0.00 9.0 0.10 deep 209 6.1 07 Sep 95 20 25 3550.0 0.06 16.0 0.00 deep 246 6.2 07 Aug 96 131 34 2070.0 0.00 19.0 0.00 deep 716 6.2 07 Sep 95 47 121 450.0 0.80 12.0 0.00 deep 426 5.4 07 Aug 96 351 36 110.0 2.20 9.0 0.09 shallow 166 5.3 15 May 01 8 778 17 80.0 0.44 9.0 0.10 shallow 188 5.0 07 Aug 02 9 112 19 130.0 0.35 5.0 0.00 shallow 155 4.2 07 Aug 96 550 17 122


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 0.014100114 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 4.614100114 21.4 0.5 3.9 0.4 0.00 0.26 0.09 0.09 0.00 39.6 0.7 0.0 0.014100114 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 0.014100115 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 0.014100115 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 0.014100115 35.5 0.6 6.1 0.7 0.01 0.41 0.11 0.01 0.00 74.2 2.1 0.0 0.014100115 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 0.014100115 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 0.014100115 34.4 0.8 5.4 0.8 0.00 0.27 0.12 0.20 0.00 71.2 2.6 0.0 0.014100116 1181.5 41.6 147.0 120.6 0.40 0.01 0.03 0.03 0.61 1851.0 658.5 4.5 235.814100116 1113.9 40.4 128.1 104.7 0.42 0.01 0.04 0.00 0.60 1624.0 718.9 0.0 189.914100116 1471.0 58.7 202.7 153.3 0.55 0.00 0.11 0.04 0.61 2478.8 792.0 0.0 204.014100116 4965.0 128.0 778.0 450.0 2.97 32.30 0.08 0.08 0.11 9933.0 1584.4 0.0 0.014100116 3558.0 94.0 634.5 304.3 3.99 2.04 136.40 <0.50 <0.05 1.80 6107.4 19.80 4831.2 173.914100116 2719.2 71.5 460.5 226.4 2.75 1.42 99.24 0.23 0.05 3.00 4932.0 16.50 1060.5 353.214100119 40.4 3.1 2.3 3.7 0.19 3.83 0.08 0.00 0.00 61.5 0.6 0.3 25.414100122 12.9 1.3 1.4 1.4 0.00 0.23 0.08 0.00 0.00 22.7 0.0 0.0 7.4MW 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 0.0MW 3D 50.0 2.0 4.0 2.0 0.09 5.93 0.00 85.0 0.5 0.0 20.0MW 3D 48.0 3.0 4.0 3.0 0.03 9.78 0.00 83.0 1.0 0.6 10.0MW 3S 23.0 0.5 6.0 2.0 0.02 2.70 0.00 52.0 0.5 4.8 0.5MW 3S 21.0 0.3 4.0 1.0 0.01 0.80 0.00 40.0 4.0 1.7 0.2MW 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 0.4MW 4D 52.0 3.0 4.0 3.0 0.04 9.25 0.00 88.0 0.5 0.7 20.0MW 4D 49.0 4.0 5.0 5.0 0.04 2.16 0.00 88.0 7.0 0.3 9.0MW 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 19.0MW 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.

141001141410011414100114141001141410011514100115141001151410011514100115141001151410011614100116141001161410011614100116141001161410011914100122MW 2SMW 3DMW 3DMW 3SMW 3SMW 3SMW 4DMW 4DMW 4DMW 4D


0.0 0.58 4.0 0.03 shallow 258 3.8 18 May 01 5 999 25 200.0 0.03 0.51 4.5 shallow 245 3.7 19 Sep 01 19.60.0 0.39 4.0 0.06 shallow 202 3.9 08 Aug 02 4 999 17 290.0 0.25 shallow 180 4.1 11 Nov 03 22.4 0

0.22 0.93 shallow 372 3.1 14 Sep 00 20.70.00 0.76 6.8 shallow 3.3 15 Nov 00

0.0 0.96 6.0 0.04 shallow 372 3.6 15 May 01 4 999 27 60.00 0.66 6.9 shallow 336 3.6 19 Sep 01 19.60.00 0.73 8.8 shallow 338 3.4 30 Jul 02 20.9 1380 203

0.0 0.71 7.0 0.09 shallow 341 3.6 07 Aug 02 4 999 24 1580.2 0.00 44.0 0.80 Brackish Ck 7021 6.8 04 Sep 95 11 905 3161.3 0.01 46.0 0.80 Brackish Ck 6040 7.8 07 Aug 96 16 788 2260.1 0.00 40.0 0.94 Brackish Ck 8460 6.7 15 May 01 6 7 1216 6050.0 0.71 53.0 1.69 Brackish Ck 25700 3.4 08 Aug 02 6 12 4322 217

1.70 Brackish Ck 0 6.5 15 May 03 21.3 00.82 Brackish Ck 17720 5.6 11 Nov 03 21.5 0

0.0 0.12 13.0 0.00 254 5.9 08 Aug 96 133 19 2650.0 0.39 10.0 0.00 96 5.4 08 Aug 96 103 9 61

0.17 2.54 6.5 shallow 248 4.2 19 Sep 01 18.50.08 5.10 deep 344 5.4 26 Apr 000.01 1.00 deep 17 Jul 00 250.11 8.35 shallow 239 4.7 26 Apr 000.03 1.44 shallow 17 Jul 000.07 1.13 5.5 shallow 174 4.8 19 Sep 01 18.60.06 0.70 deep 351 5.4 26 Apr 000.02 0.13 deep 17 Jul 00 400.00 0.10 18.1 deep 341 5.3 19 Sep 01 20.8

0.20 deep 393 5.3 14 May 03 19.6 0


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 43.9MW 4S 21.0 0.7 4.0 1.0 0.01 0.87 0.00 34.0 11.0 2.5 0.6MW 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 18.0MW 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 27.0MW 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 32.0MW 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 20.0MW 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 9.8MW 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 15.9MW 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 0.8MW 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 0.0MW11-1D 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 5.2 490.4MW11-1D 4257.0 167.6 467.6 176.7 2.28 1.11 129.33 1.18 0.16 2.25 6457.5 29.25 1451.3 760.1MW11-1S 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 0.0MW11-1S 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 0.014100131 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 0.014100131 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 0.014100132 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 0.014100133 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 0.014100135 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 0.014100135 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 0.914100135 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 0.014100136 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 20.014100136 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 10.514100139 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 0.414100140 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 27.014100140 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 23.014100142 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 0.514100144 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.

MW 4DMW 4SMW 5DMW 6DMW 7DMW 8DMW 8DMW 8DMW 8SMW 8SMW11-1DMW11-1DMW11-1SMW11-1S1410013114100131141001321410013314100135141001351410013514100136141001361410013914100140141001401410014214100144


0.35 deep 392 4.9 12 Nov 03 22.4 00.12 0.99 shallow 17 Jul 00 22000.00 0.20 17.8 deep 251 5.1 19 Sep 01 20.80.00 0.06 21.6 deep 316 5.5 19 Sep 01 20.50.00 0.14 17.8 deep 287 5.3 19 Sep 01 208.00.00 0.29 19.4 deep 338 5.0 19 Sep 01 20.8

1.01 deep 343 5.1 14 May 03 00.63 deep 379 4.5 12 Nov 03 22.7 0

0.06 0.47 4.2 shallow 102 3.9 19 Sep 01 20.63.72 0.47 shallow 120 3.8 12 Nov 03 23.4 0

120.12 near canal 0 6.1 15 May 03 22.9 058.30 near canal 26400 5.2 12 Nov 03 23.9 0

108.90 near canal 0 3.6 15 May 03 21.9 0114.00 near canal 13650 3.3 12 Nov 03 24.6 0

0.10 0.68 4.7 shallow 53 4.2 19 Sep 01 19.90.42 shallow 62 4.3 12 Nov 03 23.2 0

0.68 1.75 9.1 shallow 252 3.8 19 Sep 01 18.50.00 2.69 4.3 shallow 417 3.4 30 Jul 02 17.5 800 26800.07 3.21 2.4 shallow 577 3.4 05 Jun 01 21.70.00 2.66 6.7 shallow 295 3.8 19 Sep 01 19.00.00 5.95 7.6 shallow 568 3.6 30 Jul 02 19.4 203 55400.00 0.41 16.5 deep 270 4.7 19 Sep 01 21.30.00 0.26 18.3 deep 306 5.0 30 Jul 02 22.7 289 76000.00 1.89 8.6 shallow 291 4.3 19 Sep 01 19.80.00 0.35 19.8 deep 289 5.0 19 Sep 01 20.90.00 0.16 20.2 deep 328 5.3 30 Jul 02 22.9 146 266.41 0.24 16.3 shallow 71 3.9 19 Sep 01 19.30.00 0.15 20.3 deep 1119 5.7 05 Jun 01 21.2


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 1.1 180.014100144 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 89.714100145 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 0.014100145 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 0.014100146 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 0.614100147 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 4.114100147 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 0.014100147 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 0.614100148 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 5.314100151 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 0.0Bell nth 993.4 38.4 127.1 40.8 0.68 0.18 23.38 <0.09 <0.06 0.60 1473.0 363.6 138.5Bell 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 21.0 158.0Bell 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 74.4Bell 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 0.7 190.9Sland 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 0.0TCLP 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.

14100144141001441410014514100145141001461410014714100147141001471410014814100151Bell nthBell nthBell pubBell pubSland DrTCLP nth


19.46 0.20 20.0 deep 1109 5.5 19 Sep 01 20.50.25 deep 941 5.2 13 Nov 03 21.1 0

0.19 1.57 3.0 shallow 185 3.5 05 Jun 01 23.23.84 2.18 5.3 shallow 198 3.5 30 Jul 02 18.1 9800.03 2.60 6.8 shallow 57 4.3 19 Sep 01 22.50.00 1.33 9.3 deep 50 4.8 19 Sep 01 21.30.00 0.86 9.4 deep 91 4.8 30 Jul 02 18.6 302 43

0.82 deep 78 4.5 13 Nov 03 22.0 00.00 0.38 13.0 deep 65 4.5 19 Sep 01 21.20.28 0.58 14.5 deep 251 4.4 30 Jul 02 21.8 2870

0.72 near Dux Ck 6.2 15 May 03 00.51 near Dux Ck 10060 5.9 11 Nov 03 23.7 00.12 near shore 532 6.8 15 May 03 10.1 00.02 near shore 772 6.3 11 Nov 03 23.8 00.57 near canal 330 4.0 11 Nov 03 23.2 02.88 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

hydrogeology and groundwater flow model, central catchment ... · a steady-state, sub-regional...

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