Gosford City Council Historical Water Quality Review & Analysis

Gosford City Council 

Historical Water Quality 

Data Review and Analysis 

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R.N0754.002.01.doc 

Gosford City Council Historical Water 

Quality Data Review and Analysis 

Philip Haines 

Philip Haines 


Leah Wheatley 

This document presents the findings of an 

investigation of Council's historical water 

quality data. It provides a comparison of 

the data with ANZECC guidelines, and 

recommends a strategy for continued 

water quality monitoring in the future. 

REVISION/CHECKING HISTORY 

REVISION 

NUMBER 

REVISION 

DESCRIPTION 

DATE CHECKED BY ISSUED BY 

0 

Draft 

27/8/03 

DJW 

PEH 

1 

Final 

3/11/03 

DJW 

PEH 

DISTRIBUTION 

DESTINATION 

REVISION 

0 1 2 3 4 5 6 7 8 9 10 


WBM File 

WBM Library 

2 

1 

10 

1 

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CONTENTS 

I 

CONTENTS 

Contents 

List of Figures 

List of Tables 

i 

iii 

iv 

1 INTRODUCTION 1-1 

1.1 Background 1-1 

1.2 Water Quality Data Sources 1-1 

1.2.1 Past Reports 1-1 

1.2.2 Electronic Information 1-2 

1.3 Overview of the ANZECC Water Quality Guidelines 1-3 

1.3.1 Protection of Aquatic Ecosystem 1-3 

1.3.2 Biological Indicators 1-5 

1.3.3 Physical and Chemical Stressors 1-5 

1.3.4 Toxicant in Water 1-6 

1.3.5 Toxicants in Sediment 1-7 

1.3.6 Application 1-7 

2 GWQ: A DATA MANAGEMENT AND ASSESSMENT TOOL 2-1 

2.1 Overview 2-1 

2.2 General Philosophy of Data Flow and Database Structure 2-2 

2.3 Outputs from GWQ 2-5 

2.3.1 Historical Analysis 2-5 

2.3.2 Yearly Analysis 2-6 

2.3.3 Quarterly Analysis 2-7 

3 RESULTS OF WATER QUALITY DATA ANALYSIS 3-1 

3.1 Contemporary Water Quality Results 3-1 

3.1.1 Physical Parameters 3-2 

3.1.1.1 Temperature 3-2 

3.1.1.2 pH 3-3 

3.1.1.3 Turbidity 3-4 

3.1.1.4 Secchi Depth 3-5 

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CONTENTS 

II 

3.1.1.5 Salinity 3-6 

3.1.1.6 Dissolved Oxygen 3-7 

3.1.2 Chemical Parameters 3-8 

3.1.2.1 Ammonia 3-8 

3.1.2.2 Oxidised Nitrogen 3-9 

3.1.2.3 Total Nitrogen 3-10 

3.1.2.4 Orthophosphate 3-11 

3.1.2.5 Total Phosphorus 3-12 

3.1.3 Compound Water Quality Index 3-13 

3.2 Water Quality Datasondes 3-14 

3.2.1 Brisbane Water (Koolewong) 3-14 

3.2.2 Avoca Lagoon 3-16 

3.2.3 Cockrone Lagoon 3-17 

3.3 Historical Water Quality Results 3-18 

3.3.1 Chemical Parameters 3-18 

3.3.2 Bacteria 3-19 

3.3.3 Algae 3-19 

3.3.3.1 Algal counts 3-19 

3.3.3.2 Chlorophyll-a 3-20 

3.3.4 Metals 3-21 

4 FUTURE DIRECTIONS FOR WATER QUALITY / ENVIRONMENTAL HEALTH 

MONITORING 4-1 

4.1 Discussion of Previous Monitoring Programs 4-1 

4.2 The Notion of ‘Environmental Health’ 4-1 

4.2.1 Coastal CRC EHMP 4-1 

4.2.1.1 Water quality 4-2 

4.2.1.2 Seagrass 4-3 

4.2.1.3 Sewage 4-3 

4.2.1.4 Report cards 4-3 

4.3 Review of ANZECC Monitoring Guidelines 4-5 

4.3.1 Introduction 4-5 

4.3.2 Setting Objectives 4-5 

4.3.3 Study Design 4-7 

4.3.4 Field Sampling Program 4-8 

4.3.5 Laboratory Analysis 4-9 

4.3.6 Data Analysis and interpretation 4-10 

4.3.7 Reporting 4-11 

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LIST OF FIGURES 

III 

4.4 Outcomes from Community Workshops 4-12 

4.4.1 General Comments 4-12 

4.4.2 Possible Sites for Future Monitoring 4-12 

4.4.3 Possible Parameters for Future Monitoring 4-13 

4.4.4 Possible Frequency of Monitoring 4-13 

4.4.5 Possible Ways of Reporting the Data 4-13 

4.5 Options for Future Water Quality Monitoring 4-14 

4.5.1 Option 1: Routine Monthly Water Quality Monitoring 4-14 

4.5.2 Option 2: Catchment and Receiving Water Monitoring 4-15 

4.5.3 Option 3: Quarterly Seagrass Depth Monitoring 4-16 

4.5.4 Option 4: Quarterly Benthic Macroinvertebrate Monitoring 4-16 

4.5.5 Indicative Costs of Options 4-17 

4.5.5.1 Assumptions in Determining Costs 4-18 

4.6 Recommended Monitoring Program 4-18 

4.6.1 Recommendations for a Gosford Environmental Health Indicator 4-23 

5 REFERENCES 5-1 

APPENDIX A: MHL DATASONDE RESULTS: AVOCA LAGOON A-1 

APPENDIX B: MHL DATASONDE RESULTS: COCKRONE LAGOON B-1 

APPENDIX C: MHL DATASONDE RESULTS: KOOLEWONG C-1 

LIST OF FIGURES 

Figure 1.1 Classification of ecosystem type for each category 1-4 

Figure 1.2 Types of Physical and Chemical Stressors 1-5 

Figure 2.1 Water Quality Data Management System 2-1 

Figure 2.2 Data Flow 2-3 

Figure 2.3 Database Structure 2-4 

Figure 2.4 MapInfo Database Interface 2-4 

Figure 2.5 Sample Historical Data Chart 2-5 

Figure 2.6 Example of a Yearly Analysis Report 2-6 

Figure 2.7 Example of a Quarterly Analysis Report 2-7 

Figure 3.1 Sites for Most Recent (Cheng) Water Quality Monitoring Program 3-1 

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LIST OF TABLES 

IV 

Figure 4.1 

Figure 4.2 

Conceptual model of the current ecosystem health of Moreton Bay and its river 

estuaries (Coastal CRC) 4-2 

Seagrass depth range measures the distance between the upper tidal limit of 

seagrass distribution and the lower light-limited distribution 4-3 

Figure 4.3 Example of EHMP Report Card 4-4 

Figure 4.4 Spatial Distribution of Ecosystem Health Index values in Moreton Bay 4-4 

Figure 4.5 Framework for Setting Objectives (ANZECC/ARMCANZ, 2000) 4-5 

Figure 4.6 Framework for Study Design (ANZECC/ARMCANZ, 2000) 4-7 

Figure 4.7 Framework for Field Sampling Program (ANZECC/ARMCANZ, 2000) 4-8 

Figure 4.8 Framework for Laboratory Analysis (ANZECC/ARMCANZ, 2000) 4-9 

Figure 4.9 Framework for Data Analysis (ANZECC/ARMCANZ, 2000) 4-10 

Figure 4.10 General Locations of Future Monitoring Sites 4-21 

Figure 4.11 Detailed Locations of Monitoring Sites 4-22 


Table 1.1 

Default trigger values for Physical and Chemical Stressors as applicable to 

Gosford Waters 1-6 

Table 3.1 Annual Medians for Temperature 3-2 

Table 3.2 Quarterly Means for Temperature 3-2 

Table 3.3 Annual Medians for pH 3-3 

Table 3.4 Quarterly Means for pH 3-3 

Table 3.5 Annual Medians for Turbidity 3-4 

Table 3.6 Quarterly Means for Turbidity 3-4 

Table 3.7 Annual Medians for Secchi Depth 3-5 

Table 3.8 Annual Medians for Salinity 3-6 

Table 3.9 Quarterly Means for Salinity 3-6 

Table 3.10 Annual Medians for Dissolved Oxygen 3-7 

Table 3.11 Quarterly Means for Dissolved Oxygen 3-7 

Table 3.12 Annual Medians for Ammonia 3-8 

Table 3.13 Quarterly Means for Ammonia 3-8 

Table 3.14 Annual Medians for Oxidised Nitrogen 3-9 

Table 3.15 Quarterly Means for Oxidised Nitrogen 3-9 

Table 3.16 Annual Medians for Total Nitrogen 3-10 

Table 3.17 Quarterly Means for Total Nitrogen 3-10 

Table 3.18 Annual Medians for Orthophosphate 3-11 

Table 3.19 Quarterly Means for Orthophosphate 3-11 

Table 3.20 Annual Medians for Total Phosphorus 3-12 

Table 3.21 Quarterly Means for Total Phosphorus 3-12 

Table 3.22 Gosford Water Quality Index Range Definition Matrix 3-13 

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V 

Table 3.23 Water Quality Index for Gosford Waters, 1999 - 2002 3-15 

Table 3.24 Basic Scorecard Index 3-15 

Table 3.25 Scorecard for Gosford Waters, 1999 - 2002 3-15 

Table 3.26 Nutrients in the Coastal Lagoons (1993 – 2002) 3-18 

Table 3.27 Faecal Coliform Levels (no. per 100mL) 1996 – 1998 (from Laxton, 1999)3-19 

Table 3.28 Algal cell count results 2000 – 2002 (Ecoscience Technology, 2002) 3-19 

Table 3.29 Chlorophyll-a results (µg/L) 1996 – 1998 (Laxton, 1999) 3-21 

Table 4.1 Indicative Costs for Future Monitoring Options 4-17 

Table 4.2 Parameters to be monitored 4-20 

Table 4.3 

Recommended Water Quality Scores for different sections of the Gosford 

Waterways 4-23 

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INTRODUCTION 1-1 

1 INTRODUCTION 

1.1 Background 

Gosford City Council is the custodian of a significant amount of water quality data, which has been 

collected over the past 30 years. The effective management and use of this substantial dataset is an 

ongoing concern. Difficulties stem from the lack of integration between past monitoring programs, 

inconsistent monitoring locations, and a wide variety of constituents that have been analysed in the 

past. These issues meant that the information was retained as individual datasets only with little or no 

cross-referencing between them. 

This report documents the analysis of Gosford Council’s historical water quality data and formulates 

a future monitoring strategy, based on an appreciation of the historic results and Council’s allocated 

budget. As part of the study, a system for water quality management has been developed by 

customizing common desktop software packages for database management (MS Access), 

geographical interrogation (MapInfo) and data analysis and presentation (MS Excel). This system 

was subsequently used to integrate and analyse the historical data, and provide an understanding of 

water quality processes over the past 30 years. 

The water quality management system has also been designed to accept new data, and provide 

automated reporting on the data, with comparisons and references to the historical data and trends. 

The reporting has been designed to slot easily within Council’s standard State of the Environment 

report and give an overall indication of the environmental health of Gosford’s waterways. 

The following is a summary of the water quality data now held within the water quality database: 

• Water quality data spans from 1974 to June 2002; 

• There are about 200 different monitoring sites within Brisbane Water, its tributary creeks and the 

coastal lagoons within Gosford LGA; 

• Over 60 different water quality parameters have been monitored; 

• Over 30,000 individual records are stored on the database. 

1.2 Water Quality Data Sources 

1.2.1 Past Reports 

The following reports contained water quality information that was entered into the database: 

• Environmental Study of Brisbane Waters (Cheng, 1994) contains water quality results for the 

following parameters; dissolved oxygen, water temperature, salinity, turbidity, pH and 

phytoplankton. The samples were collected at seven locations in Brisbane Waters from April 

1993 to September 1994. 

• Water Quality Monitoring of Brisbane Water and Gosford Lagoons (Cheng, 2001) contains 

water quality results for the following parameters; water temperature, dissolved oxygen, salinity, 

temperature, secchi transparency, pH, turbidity, total phosphorus, ortho-phosphate, total nitrogen, 

total inorganic nitrogen, oxidised nitrogen and ammonia. The samples were collected at seven 

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locations in Brisbane Water, as well as Wamberal Lagoon, Terrigal Lagoon, Avoca Lagoon and 

Cockrone Lagoon. The samples were collected between August 2000 to September 2000 

• Water quality and biological monitoring of Brisbane Water and Gosford Lagoon (Ecoscience 

Technology, 2002) contains water quality results for the following parameters; dissolved oxygen, 

temperature, salinity, turbidity, pH, phosphorus (total phosphorus), nitrogen (total nitrogen, total 

inorganic nitrogen, oxidised nitrogen and ammonia) and phytoplankton. The samples were 

collected at seven locations around Brisbane Water, as well as Cockrone Lagoon, Avoca Lagoon, 

Terrigal Lagoon and Wamberal Lagoon. The samples were collected from October 2000 and 

June 2002 

• Phytoplankton Monitoring of Brisbane Water and Gosford Lagoons (Ecoscience Technology, 

2000b) contains phytoplankton results for the period between August 1999 and January 2000. 

Samples were collected at seven locations within Brisbane Water, and in Wamberal Lagoon, 

Terrigal Lagoon, Avoca Lagoon, and Cockrone Lagoon. 

• Phytoplankton Monitoring of Brisbane Waters and Gosford Lagoons (Ecoscience Technology, 

2000), contains phytoplankton results for the period between August 1999 and May 2000. 

Samples were collected at seven locations within Brisbane Water, and in Wamberal Lagoon, 

Terrigal Lagoon, Avoca Lagoon, and Cockrone Lagoon. Note that the above report dealt with 

some of this information, therefore the remaining information (January to May 2000) was 

extracted from this report. 

• Water Quality Monitoring of Brisbane Water and Gosford Lagoons (Insearch, 2000), contains 

water quality results for the following parameters; temperature, dissolved oxygen, salinity, pH, 

total phosphorus, total nitrogen, ortho-phosphate, total inorganic nitrogen, oxidised nitrogen and 

ammonia. The samples were collected at seven locations in Brisbane Water, as well as 

Wamberal Lagoon, Terrigal Lagoon, Avoca Lagoon, and Cockrone Lagoon. The samples were 

collected for a period between August 1999 and May 2000. 

• Water Quality of Gosford Lagoons, (JH & ES Laxton, 1994) contains water quality results for 

the following parameters; water temperature, salinity, pH, dissolved oxygen, ammonia, organic 

nitrogen, oxidised nitrogen, total nitrogen, orthophosphate and total phosphorus, turbidity, total 

suspended solids, and faecal coliforms. The samples were collected at a number of locations in 

Wamberal Lagoon, Terrigal Lagoon, Avoca Lagoon and Cockrone Lagoon. The samples were 

collected between September 1993 and October 1994. 

• Gosford Coastal Lagoons Estuary Processes Study (Webb, McKeown & Associates Pty Ltd, 

1994) contains water quality information in an appendix obtained, from a number of sources. In 

total water quality sampling was undertaken in 35 locations, in Brisbane Water, Avoca Lagoon. 

Terrigal Lagoon, Cockrone Lagoon and Wamberal Lagoon. The information was collected from 

April 1974 to January 1993. 

1.2.2 Electronic Information 

Gosford City Council provided some water quality data in electronic form. The electronic data 

included the following: 

• Manly Hydraulics Laboratory undertook water quality sampling at three sites; Cockrone 

Lagoon, Avoca Lagoon and Brisbane Water (Koolewong). The sampling was continuous and 

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was collected for the period between January 1996 and June 2002. Monitoring included 

conductivity, salinity, pH, temperature, dissolved oxygen and turbidity. 

• Gosford Water Quality Study, contains water quality data collected by Laxton. Information was 

collected at 13 locations in Brisbane Waters, as well as Wamberal Lagoon, Terrigal Lagoon, 

Avoca Lagoon and Cockrone Lagoon. Data was collected between February 1996 and June 

1999. The water quality parameters include temperature, salinity, pH, dissolved oxygen, specific 

gravity, turbidity, ammonia, organic nitrogen, oxidised nitrogen, total nitrogen, orthophosphate, 

total phosphorus, inorganic suspended solids, volatile suspended solids, chlorophyll-a, and 

faecal coliforms. 

• Gosford Water Quality Survey Stage 2 Report – Major Tributary Water Quality Assessment 

information (AWT, 2001) contains water quality sampling at three tributaries Kincumber Creek 

(four sites), Narara Creek (six sites) and Erina Creek (seven sites). The water quality parameters 

that were collected included conductivity, dissolved oxygen, pH, turbidity, faecal coliforms, total 

phosphorus, total nitrogen, and ammonia. 

1.3 Overview of the ANZECC Water Quality Guidelines 

Water quality guidelines have been prepared for Australian and New Zealand waters by the Australia 

and New Zealand Environment Conservation Council (ANZECC). The most recent guidelines, as 

described below were released in 2000, superseding previous guidelines issued in 1992. 

The objective of the water quality guidelines for fresh and marine waters (ANZECC, 2000) is; 

‘to provide an authoritative guide for setting water quality objectives required 

to sustain current, or likely future, environmental values [uses] for natural 

and semi-natural water resources in Australia and New Zealand.’ 

These guidelines were prepared as part of Australia’s National Water Quality Management Strategy 

(NWQMS) and relate to New Zealand’s National Agenda for Sustainable Water Management. The 

guidelines provide the government and the community with a method for assessing and managing 

ambient water quality in natural and semi-natural water resources. These guidelines are not 

mandatory and have no legal status. 

The guidelines are specifically based on the philosophy of ecologically sustainable development 

(ESD). ESD has been defined by the Australian National Strategy for Ecologically Sustainable 

Development as; 

‘using, conserving and enhancing the community’s resources so that ecological processes 

on which life depends, as maintained and the total quality of life, now and in the future can 

be increased. Put more simply, ESD is development which aims to meet the needs of 

Australians today while conserving our ecosystem to benefit future generations.’ 

1.3.1 Protection of Aquatic Ecosystem 

The document provides guidance to determine whether the water quality of a water resource is 

suitable for a range of different uses, including maintenance of natural aquatic ecosystems. Of 

specific interest to the Gosford Water Quality Assessment is the suitability of water quality for 

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aquatic ecosystems. Aquatic systems include animals, plants and micro-organisms that live in the 

water as well as the physical and chemical environment and climatic regime that they interact with. 

The physical, chemical and biological components of an ecosystem determines what lives and breeds 

within the ecosystem. Aquatic ecosystem have suffered profound changes due to human impact, 

therefore the ecological objective of these guidelines is: 

‘to maintain and enhance the ‘ecological integrity’ of freshwater and marine 

ecosystems, including biological diversity, relative abundance and ecological 

processes.’ 

There are diverse ranges of ecosystem types, which have naturally variable physical and chemical 

water quality characteristics. In order to consider these varying ecosystems the guidelines classify the 

ecosystem into six categories (Figure 1.1). The classification of the ecosystems is quite broad. The 

figure shows that there are different classifications depending on the indicator in question (shown on 

the left of Figure 1.1). 

Figure 1.1 Classification of ecosystem type for each category 

In terms of the level of protection of the ecosystem the guidelines suggest three levels depending on 

the ecosystem condition. The three ecosystem levels are recognised as, high conservation/ecological 

value systems, slightly to moderately disturbed system, and highly disturbed systems. Site-specific 

protection levels can also be determined by considering the type and quantity of contaminant that will 

possibly enter the aquatic ecosystem. 

Indicators are used to determine the overall health of the aquatic ecosystems. These include, 

biological indicators, physical and chemical stressors, toxicants, and sediments. These indicators are 

described in the following Sections. 

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1.3.2 Biological Indicators 

Biological indicators are algae, macrophytes, macroinvertebrates and fish, which display the effects 

of the past and present exposure to contaminants or pressures. 

Biological assessment (bioassessment) is used to provide information on biological or ecological 

changes, which may be due to changes in water quality or physical habitats. Bioassessment and 

biological indicators are used because traditional physical and chemical guidelines can be too simple 

to provide a meaningful assessment of biological communities or processes. Bioassessment is also a 

useful tool to assess achievements of environmental values and attain water quality objectives. 

The ANZECC guidelines recommend stressors and biological indicators to be used for monitoring 

and assessment of water quality, for different ecosystem types. The indicators are selected depending 

on the object of the assessment i.e. broad scale assessment, early detection, or biodiversity or 

ecosystem-level response. The guidelines provide concepts and monitoring frameworks that are 

necessary to assess aquatic biological communities. 

1.3.3 Physical and Chemical Stressors 

Physical and chemical stressors include nutrients, biodegradable organic matter, dissolved oxygen, 

turbidity, suspended particulate matter (SPM), temperature, salinity, pH, change in flow regime, 

ammonia, cyanide, heavy metals, biocides and other toxic organic compounds. Physical and 

chemical stressors are classified into two types, depending on whether they have a direct or indirect 

impact on the ecosystem, as shown in Figure 1.2. 

Figure 1.2 Types of Physical and Chemical Stressors 

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Default trigger values were derived for the physical and chemical stressors using regional reference 

data for climatic/geographical regions across Australia and New Zealand. New Zealand and 

Australian state and territory representatives used percentile distributions of available data and 

professional judgement to derive trigger values for each of the ecosystems. Trigger values were then 

collated, discussed and agreed upon for each region. It is emphasised that these default trigger values 

should only be used until site-specific or ecosystem-specific values can be generated. Default trigger 

values for South-east Australia estuarine ecosystems are presented in Table 1.1. 

Table 1.1 

Default trigger values for Physical and Chemical Stressors as applicable 

to Gosford Waters 

Physical and Chemical Stressors 

Chlorophyll-a 

Total Phosphorus 

Filterable Reactive Phosphorus (Orthophosphate) 

Total Nitrogen 

Oxidised Nitrogen 

Ammonium 

Dissolved Oxygen 

pH 

Turbidity 

Trigger Values 

4 µg/L 

30 µg P/L 

5 µg/L 

300 µg N/L 

15 µg N/L 

15 µg N/L 

80% (lower limit) & 110% (upper limit); 

7.0 (lower limit) & 8.5 (upper limit); 

0.5 – 10 NTU 

Physical and chemical trigger values are to be used, in conjunction with professional judgement, to 

provide an initial assessment of the state of a water body regarding the issue in question. After 

determining the guideline trigger value the decision tree option should be used to obtain an 

appropriate trigger value. The trigger value is determined depending on response of the test site value 

to the guideline trigger value. If the test site value is less than the guideline trigger value, showing 

there is a low risk that a problem exist, monitoring should continue. In the case that the trigger value 

is exceeded, management/remedial action or further site-specific investigation is required, and a 

‘potential risk’ exists. Following continuous monitoring, if the indicator values at the site remain as 

‘low risk’ the guideline trigger value needs to be refined. In order to derive a low-risk trigger value 

(appropriate trigger value), biological and ecological effects data, reference system data, predictive 

modelling or professional judgement should be used. 

1.3.4 Toxicant in Water 

Toxicants are chemical contaminants such as metals, aromatic hydrocarbons, pesticides and 

herbicides that have the potential to exert toxic effects at concentrations, which might be encountered 

in the environment. In reference to toxicants the guidelines aim to protect waters from sustained 

exposure to toxicants. 

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The guidelines provide trigger values for freshwater and marine water. The guidelines recommended 

moving away from relying solely on chemical guideline values for managing water quality, to using 

an integrated approach which would involve chemical-specific guidelines coupled with water quality 

monitoring, direct toxicity assessment, and biological monitoring. This approach ensures that water 

management will focus on protecting the environment instead of focussing on meeting a number. 

The trigger values provided by the ANZECC (2000) guidelines are presented as three grades of 

trigger values; high, moderate or low reliability. These grades are dependent on the amount of data 

available and hence the confidence or reliability of the final figure. Trigger values have also been 

derived for four different protection levels; 99%, 95%, 90% and 80%. The protection level signifies 

the percentage of species expected to be protected by monitoring concentrations below the define 

values. These values were derived using the statistical distribution method. 

1.3.5 Toxicants in Sediment 

Sediment are important in aquatic ecosystems as they are a source and sink for dissolved 

contaminants, they influence surface water quality, and they are a source of bioavailable 

contaminants to benthic biota. Consequently it is important to identify areas were sediments present a 

likely threat to ecosystem health. Recommended guideline values are provided as interim sediment 

quality guideline (ISQG) values. Guidelines are not specified for some contaminants, which reflects 

the absence of an adequate data set for that contaminant. A value for this contaminant can be derived 

based on the natural background concentration multiplied by an appropriate factor (a value between 2 

and 3 is recommended). 

1.3.6 Application 

A framework is provided for the application of guidelines for the protection of aquatic ecosystems. 

The initial step involves two stages, which are common for the application of all of the indicator types 

(biological, physiochemical, chemical and sediment); 

1 determine the type of water body, the environmental values, the level of protection required, the 

environmental concerns, the factors that are affecting the ecosystem and the management goals; 

and 

2 select the indicator types depending on the first step and then determining the appropriate trigger 

values. 

For the remaining steps it is convenient to consider guidelines application separately for biological 

indicators and non-biological indicators (physical and chemical stressors and toxicants in water and 

sediments). For biological indicators decision trees are used to derive the water quality guidelines. 

Non-biological indicators are based on given water quality guidelines, however, there is the option to 

refine guidelines using a decision tree. The ANZECC (2000) guidelines detail the method to derive 

appropriate guidelines for a specific site, instead of using the trigger values provided within the 

guidelines. 

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GWQ: A DATA MANAGEMENT AND ASSESSMENT TOOL 2-1 

2 GWQ: A DATA MANAGEMENT AND ASSESSMENT TOOL 

2.1 Overview 

The ongoing management of the data in a digital form is an outcome of the review of historical water 

quality data, and the recommendation of future directions for water quality management within the 

Gosford City LGA. The objectives of such a management system are to: 

• Manage data within a single system that improves access to the data and efficiency in retrieval 

and distribution. 

• Set standards and specifications for all future data and for any reformatting of existing data, so 

that data relating to a common theme are managed in a consistent and compatible format. 

• Provide an efficient data management structure for GCC staff to query, view and analyse data. 

This section describes the design of the Gosford Water Quality Database (GWQ), the system 

developed by WBM to address the above objectives. 

Figure 2.1 Water Quality Data Management System 

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Development of the database involved a number of steps as follows: 

• Design the system. The findings from meetings with GCC and a review of the nature of existing 

water quality data allowed the identification of the data needs and requirements which provided 

the basis for the design; 

• Transfer existing water quality data, from both hard copy and existing digital formats, into a 

digital format that was compatible with the requirements and specifications of the GWQ system. 

This stage also assisted in finalising the standards and specifications for the data, and for testing 

and fine-tuning the design before further development of software to enter, access, manipulate 

and report on the data; 

• Develop software in Microsoft Access for the addition of water quality file records to the 

database, including vital quality checks of the data prior to addition to the database to ensure 

integrity of the data and consistency with the requirements of the GWQ system. In addition, 

applications have been developed in Map Info and Microsoft Excel to facilitate interrogation, 

analysis and reporting on the data. 

• Handover, installation and training. 

Protocols were also developed for the specification of data collection and the digital water quality file 

format (*.gwq files) that is used by the water quality data management system. 

2.2 General Philosophy of Data Flow and Database Structure 

Figure 2.2 illustrates the general process of data flow between GCC, water quality data providers, the 

GWQ Database, computer storage and outputs. 

Furthermore, the structure of the underlying database is shown in Figure 2.3. The database is centred 

around the “Data Items” table. Each entry in the data items table represents a single water quality file 

saved in secure storage on GCC’s server. The data set is uniquely identified by a “DataSetID” 

number and the name of the associated file in secure storage reflects that number, the site at which 

measurements were made, the water quality parameter measured, and the year and month of 

measurements. This means that a single file can exist for each unique combination of site, parameter, 

year and month combination, provided that the appropriate water quality data is available. Further 

information on data naming conventions is provided in the technical reference manual for the GWQ 

database (WBM, 2003). 

The sites, parameters, data sources and entry personnel tables are provided as ancillary tables to assist 

with the integrity checks undertaken on the data and to assist with presentation of results. The system 

defaults table contains information on the location of secure storage and a password enabling access 

to the database for administrative purposes. The functional groups table is provided to assist with the 

grouping of related sites for analysis. 

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Water Quality Data 

Suppliers 

Data Supply 

Data Specification 


Water Quality Database (Microsoft Access) 

- Checks integrity of incoming text file data 

- Copies text file to secure storage on server 

- Updates Database with details of saved files 

- Entry of raw data and saving in standard format 

Secure Storage of 

water quality text 

files (*.gwq) using 

standard naming 

protocols 

Database 

Updating 

Database 

Interrogation 

WQ Map (MapInfo Application) 

- Interrogates Database regarding data files in secure storage 

- Extracts required data from secure storage 

- Organises output of requested data 

Outputs 

Figure 2.2 Data Flow 

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Figure 2.3 Database Structure 

Figure 2.4 MapInfo Database Interface 

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2.3 Outputs from GWQ 

Three types of analyses can be undertaken using the database application. These are: 

o Historical Analysis; 

o Yearly Analysis; and 

o Quarterly Analysis. 

2.3.1 Historical Analysis 

Historical analysis outputs the following data in excel spreadsheet format: 

• A chart showing data from all sites 

• A worksheet summarising all data for that period, for the sites chosen for analysis 

• Yearly worksheets summarising data in yearly groups within the selected period, for the sites 

chosen for analysis. 

A sample historical analysis chart is provided as Figure 2.5. 

Figure 2.5 Sample Historical Data Chart 

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2.3.2 Yearly Analysis 

When yearly analysis is undertaken, an Excel workbook is created with the following individual 

worksheets: 

For each parameter chosen for analysis: 



• A yearly report for each site summarising and charting statistics for the analysis year and the 

previous four years. 

A sample yearly analysis report is provided as Figure 2.6. 

Figure 2.6 Example of a Yearly Analysis Report 

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2.3.3 Quarterly Analysis 

When quarterly analysis is undertaken, an Excel workbook is created with the following individual 

worksheets: 

For each parameter chosen for analysis: 



• A quarterly report for each site summarising and charting statistics for the analysis quarter 

and the previous four quarters. 

Prior to completion of the macro, the user will be prompted to indicate whether a report is to be 

printed. If the answer is yes, all quarterly reports will be printed in standard format for inclusion in, 

for example, state of the environment reports. 

A sample quarterly analysis report is provided as Figure 2.7. 

Figure 2.7 Example of a Quarterly Analysis Report 

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RESULTS OF WATER QUALITY DATA ANALYSIS 3-1 

3 RESULTS OF WATER QUALITY DATA ANALYSIS 

3.1 Contemporary Water Quality Results 

The most recent water quality monitoring carried out in Gosford LGA was undertaken by Assoc. 

Prof. Dominic Cheng of Ecoscience Technology (University of Technology, Sydney). Monitoring 

was carried out at ten (10) sites within Brisbane Water and the coastal lagoons, as identified in Figure 

3.1. Monitoring was on a monthly basis between August 1999 and June 2002. Details of the 

monitoring results are found in Ecoscience Technology (2002). The general results of this 

monitoring program are described in the Sections below. The results have been obtained using the 

yearly and quarterly reporting tools of GWQ, as described in Section 2.3. Analysis is thus 

provided for annual comparisons for the entire dataset, and for quarterly comparisons over the last 12 

month period (2001 / 2002). Median values for annual results have been reported to reflect a more 

‘typical’ value within the waterways, whereas mean values are reported for the quarterly results given 

the lack of statistical data (i.e. generally only three records per quarter). 

The quarterly results are slighted skewed by the fact that the Jan – Mar 2002 period contained only 

one record (other quarters contained either three or four records). Therefore, care should be taken 

when interpreting the results. This problem highlights the importance of consistent data collection 

throughout the monitoring period. 

Figure 3.1 Sites for Most Recent (Cheng) Water Quality Monitoring Program 

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3.1.1 Physical Parameters 

3.1.1.1 Temperature 

Median annual temperatures for the Gosford waterways are presented in Table 3.1, while mean 

quarterly temperatures are presented in Table 3.2. 

The annual results show typically warmer temperatures in 1999/2000 compared to the other two 

years. This would be due to the summer biasing of the 9 records that were collected during that year. 

Given the natural variability in temperature, no definitive temporal trend was identified. 

On a quarterly basis, the results show a distinctive change associated with seasonal variations of 

ambient air temperature. However, there was not a significant difference in mean temperature 

between the Apr – Jun 2002 period and the previous Apr – Jun 2001 period, with most results within 

+/- 1°C. 

Table 3.1 

Annual Medians for Temperature 

Temperature (Degrees C) 

Site No. and Location 2001/ 2002 2000/ 2001 1999/ 2000 

n=11 n=12 n=9 Trend 

Site : 77 - Booker Bay 20.2 17.0 19.9 

Site : 78 - Narara Creek Entrance 19.6 18.0 22.0 

Site : 79 - Erina Creek Entrance 19.6 18.5 21.3 

Site : 80 - Kincumber Creek Entrance 18.3 18.4 22.0 

Site : 81 - Cockle Creek 19.3 18.5 22.0 

Site : 82 - Woy Woy Creek 20.0 18.0 23.0 

Site : 83 - Wamberal Lagoon 18.4 15.8 23.3 

Site : 84 - Terrigal Lagoon 18.6 15.1 23.3 

Site : 85 - Avoca Lagoon 19.1 16.1 23.8 

Site : 86 - Cockrone Lagoon 18.6 17.0 22.9 

Average Rainfall at Gosford 1248mm 1038mm 1228mm 

Table 3.2 

Quarterly Means for Temperature 

Temperature (Degrees C) 

Site No. and Location 

Apr - Jun Jan - Mar Oct - Dec Jul - Sep Apr - Jun 

2002 2002 2001 2001 2001 

n=4 n=1 n=3 n=3 n=3 Trend 

Site : 77 - Booker Bay 17.7 24.1 21.7 16.3 17.8 seasonal 

Site : 78 - Narara Creek Entrance 17.0 24.8 22.8 16.2 15.6 seasonal 

Site : 79 - Erina Creek Entrance 17.1 24.5 23.3 16.2 16.2 seasonal 

Site : 80 - Kincumber Creek Entrance 16.0 23.9 22.1 14.6 14.8 seasonal 

Site : 81 - Cockle Creek 17.6 24.0 22.2 16.3 19.2 seasonal 

Site : 82 - Woy Woy Creek 16.9 24.1 23.1 16.6 16.9 seasonal 

Site : 83 - Wamberal Lagoon 16.0 23.5 21.9 15.5 16.6 seasonal 

Site : 84 - Terrigal Lagoon 15.7 23.4 22.0 15.5 15.2 seasonal 

Site : 85 - Avoca Lagoon 16.2 23.9 22.8 15.4 16.3 seasonal 

Site : 86 - Cockrone Lagoon 15.7 24.6 22.5 15.4 14.8 seasonal 

Average Rainfall at Gosford 150mm 735mm 189mm 174mm 445mm 

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3.1.1.2 pH 

Median annual pH for the Gosford waterways is presented in Table 3.3, while mean quarterly pH is 

presented in Table 3.4. pH levels tend to be quite variable, although levels in the last year (2001 / 

2002) were generally slightly higher than previous years (with the obvious exception of Site 80: 

Kincumber Ck entrance). 

pH levels were generally higher in the coastal lagoons that the Brisbane Water sites, particularly 

Cockrone Lagoon. The elevated pH levels in these type of environments is generally attributed to 

high rates of photosynthesis by micro and macro algae. 

On a quarterly basis, pH levels varied considerably. The results suggest a quasi-seasonal variation, 

with typically higher concentrations in the summer months, and lower concentrations in the winter 

months. 

Table 3.3 

Annual Medians for pH 

pH 














Table 3.4 

Quarterly Means for pH 

pH 


Apr – Jun Jan – Mar Oct – Dec Jul – Sep Apr – Jun 

2002 2002 2001 2001 2001 

n=4 n=1 n=3 n=3 n=3 Trend 

Site : 77 – Booker Bay 7.81 8.21 8.73 8.57 8.37 Seasonal 

Site : 78 – Narara Creek Entrance 7.47 8.06 8.59 8.28 7.88 Seasonal 

Site : 79 – Erina Creek Entrance 7.16 8.34 8.58 8.21 8.07 Seasonal 

Site : 80 – Kincumber Creek Entrance 6.97 8.26 7.86 7.72 7.43 Seasonal 

Site : 81 – Cockle Creek 7.61 8.22 8.57 8.37 8.40 Seasonal 

Site : 82 – Woy Woy Creek 7.49 7.92 8.51 8.37 7.98 Seasonal 

Site : 83 – Wamberal Lagoon 7.45 7.97 9.11 8.90 8.24 Seasonal 

Site : 84 – Terrigal Lagoon 7.38 7.73 8.57 8.57 7.97 Seasonal 

Site : 85 – Avoca Lagoon 7.81 7.51 9.40 8.97 8.22 Seasonal 

Site : 86 – Cockrone Lagoon 8.59 7.23 10.13 8.98 8.16 Seasonal 


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3.1.1.3 Turbidity 

Median annual turbidity for the Gosford waterways is presented in Table 3.5, while mean quarterly 

turbidity is presented in Table 3.6. Turbidity is very much influenced by catchment runoff events, 

meaning that periods of higher rainfall generally result in higher turbidity levels within receiving 

waterways. Turbidity can also be influenced by the amount of algae growing within the water 

column. Trends in the annual medians for water quality would likely be attributed to the degree of 

catchment runoff experienced at those sites during the monitoring period. Sites experiencing the 

higher turbidity levels are generally near the outlets of creeks, and thus would be quite influenced by 

runoff flows. Turbidity can also be influenced by wind turbulence and resuspension of bed 

sediments. This is particularly the case in the coastal lagoons when water levels are low and depths 

around foreshore fringes are generally quite shallow. 

The quarterly analysis also highlights the variability in turbidity levels, with no consistent pattern 

over the preceding 12 months. Rainfall records for the relevant periods are also presented in the 

tables below. The most significant period of rainfall was Jan-Mar 2002, with over 700mm of rain. 

Unfortunately, only one water quality monitoring event coincided with this period, so wet-weather 

correlations are difficult to interpret. 

Table 3.5 

Annual Medians for Turbidity 

Turbidity (NTU) 














Table 3.6 

Quarterly Means for Turbidity 

Turbidity (NTU) 



2002 2002 2001 2001 2001 

n=4 n=1 n=3 n=3 n=3 Trend 

Site : 77 - Booker Bay 1.5 3.0 2.0 2.0 2.7 Rain dep 

Site : 78 - Narara Creek Entrance 20.3 6.0 4.3 11.0 14.3 Rain dep 

Site : 79 - Erina Creek Entrance 23.0 7.0 8.3 9.3 16.7 Rain dep 

Site : 80 - Kincumber Creek Entrance 39.8 13.0 14.0 46.0 9.3 Rain dep 

Site : 81 - Cockle Creek 3.5 1.0 2.7 3.7 8.3 Rain dep 

Site : 82 - Woy Woy Creek 15.0 6.0 8.3 4.7 18.7 Rain dep 

Site : 83 - Wamberal Lagoon 11.0 5.0 2.3 2.7 7.3 Rain dep 

Site : 84 - Terrigal Lagoon 9.3 5.0 4.3 8.0 14.7 Rain dep 

Site : 85 - Avoca Lagoon 7.8 18.0 3.3 2.7 7.0 Rain dep 

Site : 86 - Cockrone Lagoon 7.3 26.0 1.3 7.3 7.7 Rain dep 


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3.1.1.4 Secchi Depth 

Secchi depth is a measure of the amount of light penetration through the water column, and is similar 

to turbidity in this regard. The annual medians for secchi depth are shown in Table 3.7. Data 

collection of secchi depth was terminated in September 2000, after only 15 months of monitoring. 

Therefore, interpretation of the results is limited, and no recent quarterly values are available. 

The annual data shows that significant improvements in secchi depth occurred between 1999 / 2000 

and 2000/2001 at Erina Ck, Woy Woy Ck, Wamberal Lagoons and Terrigal Lagoon. The accuracy 

of this trend is questionable, however, due to the limited data set within the later period. 

Table 3.7 

Annual Medians for Secchi Depth 

Secchi Depth (metres) 



Site : 77 - Booker Bay - 2.02 2.02 

Site : 78 - Narara Creek Entrance - 1.45 1.44 

Site : 79 - Erina Creek Entrance - 1.50 0.90 

Site : 80 - Kincumber Creek Entrance - 0.90 0.70 

Site : 81 - Cockle Creek - 1.95 1.73 

Site : 82 - Woy Woy Creek - 2.00 1.00 

Site : 83 - Wamberal Lagoon - 2.00 1.25 

Site : 84 - Terrigal Lagoon - 1.80 0.66 

Site : 85 - Avoca Lagoon - 2.00 2.23 

Site : 86 - Cockrone Lagoon - 2.50 2.20 


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3.1.1.5 Salinity 

Median annual salinity for the Gosford waterways is presented in Table 3.8, while mean quarterly 

salinity is presented in Table 3.9. 

Salinity responds to freshwater catchment inflows, and is dependent on the ability of the tides to 

restore oceanic waters following fresh events. The influence of catchment runoff on salinity is 

particularly highlighted in the quarterly results. Low salinity levels (< 15ppt) at the sites near creek 

outlets occur following catchment runoff. Tidal flushing then restores oceanic salt levels (~35ppt) 

over the following months. Salinity was generally lowest in the period Apr – Jun 2002, following 

extensive rainfall in February, March and April 2002. 

Of particular interest in the data is the evidence of Cockle Creek behaving as a backwater area (with 

sustained higher salinity levels during general catchment runoff events). Also, the behaviour of 

salinity in the coastal lagoons is further complicated by the lagoon entrance conditions. When closed, 

water levels in the lagoons increase (reducing salinity) until the entrance berm is breached, the lagoon 

is drained, and oceanic waters are flushed into the lagoon (before the entrance closes once again). 

Table 3.8 

Annual Medians for Salinity 

Salinity (ppt) 














Table 3.9 

Quarterly Means for Salinity 

Salinity (ppt) 



2002 2002 2001 2001 2001 

n=4 n=1 n=3 n=3 n=3 Trend 

Site : 77 - Booker Bay 31.9 34.4 36.1 35.2 32.8 Rain dep. 

Site : 78 - Narara Creek Entrance 8.8 27.0 34.5 26.6 16.5 Rain dep 

Site : 79 - Erina Creek Entrance 6.0 25.7 34.1 24.5 13.4 Rain dep 

Site : 80 - Kincumber Creek Entrance 12.6 26.9 32.8 2.1 17.0 Rain dep 

Site : 81 - Cockle Creek 30.7 32.3 36.1 34.5 30.5 Rain dep 

Site : 82 - Woy Woy Creek 16.2 26.8 35.1 31.4 24.3 Rain dep 

Site : 83 - Wamberal Lagoon 11.8 34.3 18.2 14.2 15.5 Rain dep 

Site : 84 - Terrigal Lagoon 17.9 23.1 16.4 13.4 12.7 Rain dep 

Site : 85 - Avoca Lagoon 14.0 23.0 12.5 13.3 19.4 Rain dep 

Site : 86 - Cockrone Lagoon 16.2 24.4 14.8 16.5 14.5 Rain dep 


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3.1.1.6 Dissolved Oxygen 

Median annual dissolved oxygen for the Gosford waterways is presented in Table 3.10, while mean 

quarterly dissolved oxygen is presented in Table 3.11. Dissolved oxygen within the water is 

consumed by respiration of organic matter. Heterotrophic conditions within the waterways result in 

reducing oxygen levels. 

The quarterly analysis suggests that the dissolved oxygen levels are at least quasi-seasonal, with 

notable decreases over the summer months, only to return to high levels during the last quarter. 

Catchment runoff during the last quarter (as evidenced by monthly rainfall records and associated 

salinity levels) probably contributed to the sudden increase in dissolved oxygen at most sites, 

particularly Kincumber Creek, Avoca Lagoon and Cockrone Lagoon. 

Possible reasons for the seasonal variation in dissolved oxygen could be related to the boom and bust 

cycle of algae, where elevated temperatures in the summer make conditions ideal for algal growth, 

but when nutrients become limiting, the bloom dies off, and the organic matter decay (consuming 

oxygen in the process). 

Table 3.10 Annual Medians for Dissolved Oxygen 

Dissolved Oxygen (mg/L) 














Table 3.11 Quarterly Means for Dissolved Oxygen 

Dissolved Oxygen (mg/L) 



2002 2002 2001 2001 2001 

n=4 n=1 n=3 n=3 n=3 Trend 

Site : 77 - Booker Bay 6.87 5.84 6.72 6.92 6.93 Seasonal 

Site : 78 - Narara Creek Entrance 6.12 4.56 5.86 5.80 6.93 Seasonal 

Site : 79 - Erina Creek Entrance 6.16 4.80 5.65 6.22 6.84 Seasonal 

Site : 80 - Kincumber Creek Entrance 5.50 2.76 3.40 6.68 5.99 Seasonal 

Site : 81 - Cockle Creek 7.50 4.46 5.68 6.96 8.72 Seasonal 

Site : 82 - Woy Woy Creek 6.35 4.03 4.55 5.87 6.26 Seasonal 

Site : 83 - Wamberal Lagoon 7.22 4.71 5.91 7.34 9.48 Seasonal 

Site : 84 - Terrigal Lagoon 7.27 5.58 5.87 7.22 7.33 Seasonal 

Site : 85 - Avoca Lagoon 7.53 2.60 5.69 7.19 8.16 Seasonal 

Site : 86 - Cockrone Lagoon 8.86 2.02 6.96 7.70 7.54 Seasonal 


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3.1.2 Chemical Parameters 

3.1.2.1 Ammonia 

Annual median concentrations of ammonia in the Gosford waters is shown in Table 3.12, while the 

quarterly averages of ammonia for the past 15 months is shown in Table 3.13. The annual data 

suggests that there has not been any notable trends in ammonia concentrations, except possibly for 

Avoca Lagoon, where the median concentration essentially halved between 1999/2000 and 

2001/2002. The reason for this reduction is not known, and was not consistent with trends at other 

locations, or with overall rainfall / runoff patterns. 

The quarterly analysis shows that high concentrations were recorded in the Brisbane Water sites 

during the last quarter (Apr-Jun 2002), however, notably higher ammonia concentrations were 

recorded in the coastal lagoons during the preceding quarter (Jan-Mar 2002, although only one record 

was taken in this period, so caution is required in interpreting the results). It is likely that the variable 

nature of ammonia concentrations is closely linked with catchment runoff (given that significant 

runoff occurred between February and Apr 2002), however, the chemical processes within the 

waterways would obscure this connection to some degree. 

Table 3.12 Annual Medians for Ammonia 

Ammonia (mg/L) 














Table 3.13 Quarterly Means for Ammonia 

Ammonia (mg/L) 



2002 2002 2001 2001 2001 

n=4 n=1 n=3 n=3 n=3 Trend 

Site : 77 - Booker Bay 0.022 0.008 0.010 0.010 0.013 Variable 

Site : 78 - Narara Creek Entrance 0.046 0.017 0.017 0.018 0.024 Variable 

Site : 79 - Erina Creek Entrance 0.047 0.019 0.018 0.015 0.024 Variable 

Site : 80 - Kincumber Creek Entrance 0.067 0.028 0.022 0.021 0.034 Variable 

Site : 81 - Cockle Creek 0.034 0.013 0.012 0.011 0.015 Variable 

Site : 82 - Woy Woy Creek 0.048 0.027 0.027 0.015 0.024 Variable 

Site : 83 - Wamberal Lagoon 0.018 0.049 0.022 0.010 0.019 Variable 

Site : 84 - Terrigal Lagoon 0.019 0.044 0.012 0.011 0.015 Variable 

Site : 85 - Avoca Lagoon 0.023 0.116 0.012 0.009 0.021 Variable 

Site : 86 - Cockrone Lagoon 0.020 0.132 0.010 0.008 0.011 Variable 


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3.1.2.2 Oxidised Nitrogen 

Annual median concentrations of oxidised nitrogen (i.e. nitrates and nitrites) in the Gosford waters is 

shown in Table 3.14, while the quarterly averages of oxidised nitrogen for the past 15 months is 

shown in Table 3.15. The annual results show that the sites located at the creek entrances (i.e. 

Narara, Erina, Kincumber and Woy Woy Creeks) all have relatively elevated concentrations of 

oxidised nitrogen. 

The quarterly results show variable concentrations throughout the 15 month period, which may be a 

function of the amount of catchment runoff during preceding weeks or months. Highest 

concentrations were recorded during the last quarter (Apr – Jun 2002) following extensive rainfall 

during the February to April 2002 period. Oxidised nitrogen is generated through the nitrification of 

ammonia, and so its presence in the environment can be delayed somewhat due to the time taken for 

such chemical processes to occur. 

Table 3.14 Annual Medians for Oxidised Nitrogen 

Oxidised Nitrogen (mg/L) 














Table 3.15 Quarterly Means for Oxidised Nitrogen 

Oxidised Nitrogen (mg/L) 



2002 2002 2001 2001 2001 

n=4 n=1 n=3 n=3 n=3 Trend 


Site : 78 - Narara Creek Entrance 0.145 0.034 0.049 0.042 0.057 Variable 

Site : 79 - Erina Creek Entrance 0.091 0.024 0.049 0.031 0.047 Variable 

Site : 80 - Kincumber Creek Entrance 0.135 0.045 0.059 0.042 0.056 Variable 

Site : 81 - Cockle Creek 0.072 0.036 0.043 0.026 0.035 Variable 

Site : 82 - Woy Woy Creek 0.082 0.040 0.041 0.024 0.039 Variable 

Site : 83 - Wamberal Lagoon 0.049 0.028 0.025 0.025 0.040 Variable 

Site : 84 - Terrigal Lagoon 0.082 0.026 0.026 0.033 0.056 Variable 

Site : 85 - Avoca Lagoon 0.079 0.066 0.029 0.034 0.052 Variable 

Site : 86 - Cockrone Lagoon 0.069 0.070 0.025 0.026 0.032 Variable 


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3.1.2.3 Total Nitrogen 

Annual median Total Nitrogen (TN) concentrations in the Gosford waterways are presented in Table 

3.16, while quarterly average concentrations are shown in Table 3.17. Total nitrogen tends to be a 

parameter that can be highly variable, particularly in semi-enclosed estuaries like Brisbane Water, 

where the level is constantly being affected by oceanic inputs and catchment runoff. In general, the 

TN concentrations in Brisbane Water tend to be lower than in the coastal lagoons, due to the greater 

and permanent tidal flushing of the semi-enclosed estuary, compared to the intermittently closed 

coastal lagoons. 

The quarterly results highlight the highly variable nature of TN concentrations, particularly at the 

creek sites and in the coastal lagoons. The creek sites generally exhibited higher TN concentrations 

following rainfall. However, the coastal lagoons showed greater variability during dry weather times, 

possibly suggesting alternative nitrogen-based processes within the lagoons. Haines (in prep.) has 

found that many coastal lagoons, which are mostly closed to the ocean, exhibit highly variable 

nitrogen concentrations that are independent of catchment runoff events, and postulates sediment 

interactions as a significant nitrogen input to such lagoons. 

Table 3.16 Annual Medians for Total Nitrogen 

Total Nitrogen (mg/L) 














Table 3.17 Quarterly Means for Total Nitrogen 




2002 2002 2001 2001 2001 

n=4 n=1 n=3 n=3 n=3 Trend 

Site : 77 - Booker Bay 1.00 0.40 0.90 1.47 0.70 Highly var 

Site : 78 - Narara Creek Entrance 4.15 0.40 0.80 1.27 4.43 Highly var 

Site : 79 - Erina Creek Entrance 2.35 1.00 0.80 1.00 18.00* Highly var 

Site : 80 - Kincumber Creek Entrance 2.33 0.70 1.00 3.10 2.70 Highly var 

Site : 81 - Cockle Creek 0.83 0.50 1.03 1.50 1.00 Highly var 

Site : 82 - Woy Woy Creek 1.20 0.60 0.73 2.63 1.47 Highly var 

Site : 83 - Wamberal Lagoon 2.68 0.80 2.03 4.30 2.20 Highly var 

Site : 84 - Terrigal Lagoon 1.20 0.50 1.63 2.57 5.80 Highly var 

Site : 85 - Avoca Lagoon 1.60 0.30 0.97 3.80 0.97 Highly var 

Site : 86 - Cockrone Lagoon 1.73 0.80 0.37 1.53 4.30 Highly var 


* value distorted due to very high concentration (52.4mg/L) measured in May 2001. 

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3.1.2.4 Orthophosphate 

Annual median orthophosphate concentrations for sites located in the Gosford waterways are 

presented in Table 3.18, while quarterly mean concentrations for the last 15 months of monitoring are 

presented in Table 3.19. Annual data suggests that there has been no distinguishable overall trend in 

phosphate concentrations over the last 3 years of monitoring, with all concentrations generally quite 

low (and probably limiting primary productivity in most circumstances). 

The quarterly analysis shows appreciably higher phosphate concentrations following periods of 

significant rainfall (and runoff), with elevated concentrations at all sites during the April to June 2002 

quarter (when over 800mm of rain fell between February and April) and also the April to June 2001 

quarter (when 770mm of rain fell between February and May). Inorganic phosphorus (or 

orthophosphate) is a typical urban pollutant, generated by numerous anthropogenic activities 

including domestic gardening (i.e. fertilising). 

Table 3.18 Annual Medians for Orthophosphate 

Orthophosphate (mg/L) 














Table 3.19 Quarterly Means for Orthophosphate 

Orthophosphate (mg/L) 



2002 2002 2001 2001 2001 

n=4 n=1 n=3 n=3 n=3 Trend 


Site : 78 - Narara Creek Entrance 0.023 0.007 0.007 0.013 0.015 Rain dep. 

Site : 79 - Erina Creek Entrance 0.030 0.009 0.009 0.011 0.021 Rain dep. 

Site : 80 - Kincumber Creek Entrance 0.032 0.007 0.010 0.024 0.020 Rain dep. 

Site : 81 - Cockle Creek 0.027 0.006 0.007 0.013 0.019 Rain dep. 

Site : 82 - Woy Woy Creek 0.031 0.004 0.016 0.017 0.024 Rain dep. 

Site : 83 - Wamberal Lagoon 0.015 0.002 0.006 0.004 0.012 Rain dep. 

Site : 84 - Terrigal Lagoon 0.038 0.010 0.006 0.006 0.014 Rain dep. 

Site : 85 - Avoca Lagoon 0.020 0.003 0.006 0.004 0.014 Rain dep. 

Site : 86 - Cockrone Lagoon 0.018 0.004 0.005 0.004 0.010 Rain dep. 


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3.1.2.5 Total Phosphorus 

Median annual Total Phosphorus (TP) concentrations for the Gosford waterways is presented in 

Table 3.20, while mean quarterly TP is presented in Table 3.21. Like many other water quality 

parameters, TP concentrations are quite variable from one year to the next. Based on the quarterly TP 

results, concentrations appear to be quite dependent on rainfall and runoff, with notably higher TP 

concentrations recorded during the last quarter (April – June 2002), following substantial rainfall and 

runoff from the catchment. 

Phosphorus can be attached to sediment, and hence an increase in sediment within the water column 

can sometimes translate to an increase in total phosphorus. Phosphorus processes within the 

waterway are more simplistic than the nitrogen processes. Hence, the relationships between 

phosphorus and rainfall are generally more robust. 

Table 3.20 Annual Medians for Total Phosphorus 

Total Phosphorus (mg/L) 














Table 3.21 Quarterly Means for Total Phosphorus 




2002 2002 2001 2001 2001 

n=4 n=1 n=3 n=3 n=3 Trend 

Site : 77 - Booker Bay 0.038 0.010 0.053 0.043 0.050 variable 

Site : 78 - Narara Creek Entrance 0.078 0.010 0.037 0.050 0.057 Rain dep. 

Site : 79 - Erina Creek Entrance 0.123 0.030 0.050 0.043 0.077 Rain dep. 

Site : 80 - Kincumber Creek Entrance 0.143 0.010 0.053 0.137 0.073 Rain dep. 

Site : 81 - Cockle Creek 0.175 0.010 0.033 0.047 0.067 Rain dep. 

Site : 82 - Woy Woy Creek 0.128 0.020 0.038 0.170 0.097 Rain dep. 

Site : 83 - Wamberal Lagoon 0.085 0.020 0.047 0.020 0.060 Rain dep. 

Site : 84 - Terrigal Lagoon 0.230 0.040 0.027 0.027 0.073 Rain dep. 

Site : 85 - Avoca Lagoon 0.100 0.010 0.027 0.023 0.067 Rain dep. 

Site : 86 - Cockrone Lagoon 0.103 0.010 0.030 0.020 0.050 Rain dep. 


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3.1.3 Compound Water Quality Index 

Considerable insight to the water quality of the Gosford waterways can be obtained through 

investigation of the various water quality parameters, as discussed in the preceding Sections of this 

report. However, it is most useful to simplify the information into a single parameter, which can be 

reported to the community and Councillors to give an overall indication of the general water quality 

condition. 

In order to obtain a ‘Compound Water Quality Index’, the data from a range of water quality 

parameters needs to be synthesised and considered concurrently. For each major water quality 

parameter, the measured concentration is compared to a criteria set, and categorised into one of four 

different ranges. The overall water quality score can be determined by applying a value to each of the 

ranges (1 = good; 4 = highly degraded), summing the individual scores, and then dividing by the 

number of parameters included in the assessment. 

Table 3.22 presents the key water quality parameters and the interim relative ranges (and scores) for 

each as applicable to the Gosford waterways. Although Chlorophyll-a was not included in the most 

recent water quality monitoring program (as described in the previous Sections of this report), it has 

been included in the matrix below for future reference, as it is an extremely valuable water quality 

indicator that is likely to be included as part of any future monitoring program. 

Table 3.22 Gosford Water Quality Index Range Definition Matrix 

Parameter Range 1 

(value = 1) 

Range 2 

(value = 2) 

Range 3 

(value = 3) 

Range 4 

(value = 4) 

Turbidity 0 – 5 NTU 5 – 15 NTU 15 – 30 NTU > 30 NTU 

Dissolved Oxygen > 6.5 mg/L 4.0 – 6.5 mg/L 2.0 – 4.0 mg/L < 2.0 mg/L 

Ammonia 0 – 0.01 mg/L 0.01 – 0.03 mg/L 0.03 – 0.05 mg/L > 0.05 mg/L 

Oxidised Nitrogen 0 – 0.02 mg/L 0.02 – 0.05 mg/L 0.05 – 0.10 mg/L > 0.10 mg/L 

Total Nitrogen 0 – 1.0 mg/L 1.0 – 1.5 mg/L 1.5 – 2.0 mg/L > 2.0 mg/L 

Orthophosphate 0 –0.01 mg/L 0.01 – 0.03 mg/L 0.03 – 0.05 mg/L > 0.05 mg/L 

Total Phosphorus 0 – 0.05 mg/L 0.05 – 0.10 mg/L 0.10 – 0.20 mg/L > 0.20 mg/L 

Chlorophyll-a 0 – 2 µg/L 2 – 5 µg/L 5 – 10 µg/L > 10 µg/L 

Waterways that exhibit water quality concentrations within Range 1 can be considered to be in 

relatively good condition (with respect to water quality at least). If waterways start to exhibit a large 

number of Range 3 or Range 4 values, then it would tend to indicate a more degraded system (which 

is likely to have follow-on effects to the general aquatic ecosystem). The values provided in Table 

3.22 are intended to provide a more sites-specific assessment of water quality, as recommended by 

ANZECC (2000). In determining the values, consideration was given to the default trigger values for 

physical and chemical stressors (as defined in ANZECC, 2000), along with an appreciation of the 

historical water quality results. 

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From an objectives viewpoint, the primary goal would be to ensure that all water quality parameters 

remain within Range 1. However, it is recognised that this would not be achievable (in the short term 

at least) due to the considerable amount of urban development within the catchment. Therefore, from 

time to time, values within Range 2 would be acceptable (eg. 25% exceedance of the Range 1 upper 

bound). 

The resulting Water Quality Index for the Gosford waters over the last three years of monitoring is 

presented in Table 3.23. To simplify the Water Quality Index further, a Scorecard approach has been 

developed that provides an overall water quality score (out of 10). The Scorecard Index is presented 

in Table 3.24, while the final scores for the Gosford waterways are presented in Table 3.25. Intervals 

between scores in Table 3.24 are not even, with a narrower range at the more pristine end of the scale, 

and a wider range at the more degraded end. The reason for this is to expand the spread of expected 

water quality scores, and to ensure that a 10/10 score is truly representative of an exceptionally 

healthy waterway. 

The overall conclusion that can be drawn from the water quality scorecard is the fact that water 

quality appears to be naturally quite variable with time. There are a number of reasons for this 

variability, least of which is the influence of runoff from the surrounding catchment. While 

catchment runoff is inevitable and a natural response to rainfall on the watershed, the quantity and 

quality of the runoff have been modified by development and other activities within the catchment 

area. It is these anthropogenic factors that should be the focus of any water quality remediation 

programs for Brisbane Water and the Gosford coastal lagoons. 

3.2 Water Quality Datasondes 

Water quality datasondes (probes) have been installed at three locations in the Gosford Waters. One 

datasonde was located at Koolewong, in Brisbane Water, and the other two in Avoca Lagoon and 

Cockrone Lagoon. The datasondes were installed in March 1996, and have been collecting physical 

water quality parameter data every 15 minutes since that time. 

The results of the water quality datasondes are presented in Appendix A. 

3.2.1 Brisbane Water (Koolewong) 

Salinity was generally above 30ppt, and exhibited a behaviour whereby levels reduced suddenly (to 

generally between 20 and 30ppt) followed by a slow recovery up to approximately 35ppt (full 

oceanic salt concentrations). The sudden drops in salinity would correspond to catchment runoff 

events, while the recovery is the result of tidal flushing. 

Temperature showed a typical seasonal trend, with peak temperatures recorded in January / February 

(at levels of around 25 °C), and minimum temperatures recorded in July (at levels of around 13 °C). 

pH was generally between 7.5 and 8.5, although levels of up to 9 were recorded occasionally. There 

did not appear to be any correlation between pH and salinity, suggesting that pH was not strongly 

influenced by catchment runoff events. There was no distinguishable seasonal trend in pH levels 

either. 

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Table 3.23 Water Quality Index for Gosford Waters, 1999 - 2002 

Location 2001 / 2002 2000 / 2001 1999 / 2000 

Booker Bay 1.43 1.43 1.14 

Narara Ck entrance 1.71 1.86 1.57 

Erina Ck entrance 1.86 2.00 2.00 

Kincumber Ck entrance 2.14 1.71 1.57 

Cockle Broadwater 1.29 1.86 1.00 

Woy Woy Creek 1.71 2.43 1.86 

Wamberal Lagoon 1.57 2.00 1.57 

Terrigal Lagoon 1.43 2.14 1.86 

Avoca Lagoon 1.71 1.71 1.43 

Cockrone Lagoon 1.29 1.14 1.14 

Table 3.24 

Basic Scorecard Index 

1.00 – 1.09 10/10 

1.10 – 1.24 9/10 

1.25 – 1.49 8/10 

1.50 – 1.74 7/10 

1.75 – 1.99 6/10 

2.00 – 2.39 5/10 

2.40 – 2.79 4/10 

2.80 – 3.19 3/10 

3.20 – 3.59 2/10 

3.60 – 4.00 1/10 

Table 3.25 Scorecard for Gosford Waters, 1999 - 2002 

Location 2001 / 2002 2000 / 2001 1999 / 2000 

Booker Bay 8/10 8/10 9/10 

Narara Ck entrance 7/10 6/10 7/10 

Erina Ck entrance 6/10 6/10 6/10 

Kincumber Ck entrance 5/10 7/10 7/10 

Cockle Broadwater 8/10 6/10 10/10 

Woy Woy Creek 7/10 4/10 6/10 

Wamberal Lagoon 7/10 6/10 7/10 

Terrigal Lagoon 8/10 5/10 6/10 

Avoca Lagoon 7/10 7/10 8/10 

Cockrone Lagoon 8/10 9/10 9/10 

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The dissolved oxygen concentrations measured by the probe are difficult to interpret and are of 

limited value. The reason for this is the fact that the probe appears to have been affected by 

biological fouling. The results show a slow decline in dissolved oxygen concentrations between 

changeover periods. At changeover, the levels increase suddenly, indicating that prior to changeover, 

recorded levels were incorrect. 

Turbidity levels measured at Koolewong were highly variable, with values up to 160 NTU recorded 

regularly. A comparison of the turbidity and salinity plots indicated that higher turbidity levels were 

not always corresponding to catchment runoff events (as depicted by a reduction in salinity levels). 

Therefore, other factors also affect turbidity levels at the Koolewong datasonde. By way of example, 

it may be possible that wind waves cause resuspension of finer bottom sediments in the vicinity of the 

Koolewong probe. Also, the turbidity probe appears to be affected by biological fouling, with sudden 

reductions in turbidity occurring at instrument changeover (and coinciding with sudden changes in 

dissolved oxygen levels). 

3.2.2 Avoca Lagoon 

The results of the Avoca Lagoon datasonde show that the Avoca Lagoon entrance broke out 14 times 

between March 1996 and June 2002. On most occasions tides returned to the lagoon following 

breakout for a period of a few days before closing once again. When closed, water levels in the 

lagoon respond to periods of catchment runoff (with sudden increases in water levels) and 

evaporation from the water surface (with slow reductions in water level). 

In most cases, salinity follows a reverse trend to water level, with dramatic increases in salt 

concentration associated with entrance breakout, followed by a gradual reduction in salinity as the 

lagoon hydrology is subsequently dominated by freshwater catchment inputs. 

Temperature showed a strong seasonal trend, with temperatures peaking in January / February at 

about 25 – 30 °C, and reaching a minimum in June / July at about 10 – 12 °C. 

pH varied considerably within Avoca Lagoon, between about 7 and 9.5, although some values greater 

than 10 were also recorded. In general, higher pH levels appeared to occur during the early summer 

months (Oct – Dec) with levels generally about 9 or greater. Levels would then reduce to about 7.5 

during late spring / winter months. It is suggested that the pH levels within Avoca Lagoon are 

influenced by the seasonal cycles of phytoplankton and macroalgae growth. Although chlorophyll-a 

monitoring has not been conducted to measure the amount of primary productivity within the lagoon, 

it is likely that the increasing temperatures associated with the early summer months would initiate 

higher amounts of productivity in the waterway, resulting in increasing pH levels. When pH levels 

are elevated, entrance breakout can also have an impact on pH, as most of the phytoplankton and 

macroalgae would be removed or detrimentally affected by the sudden change in lagoon hydrology. 

Dissolved oxygen levels in Avoca Lagoon vary between 16 mg/L and zero. Oxygen levels can be 

influenced by several different factors in mostly closed lagoons, including phytoplankton and 

macroalgae growth (photosynthesis), organic decay (respiration), entrance breakout, and catchment 

runoff. The DO probe also shows some signs of biological fouling of the sensor, so all information 

derived from the data should be used with caution. 

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Turbidity in Avoca Lagoon is also highly variable, with measurements up to 160 NTU. As discussed 

for the Koolewong site, turbidity records can be influenced by fouling of the probe, and there appears 

to be some evidence of this at Avoca Lagoon. Also, given its relatively shallow water, stirring of fine 

bed sediments during periods of lower water levels would also be a notable cause of elevated 

turbidity levels in Avoca Lagoon. Higher turbidity concentrations are observed during and flowing 

entrance breakout events, and also periods of catchment runoff (which do not result in entrance 

breakout). 

3.2.3 Cockrone Lagoon 

The Cockrone Lagoon entrance also broke out 14 times during the period March 1996 to Jun 2002, 

which included a period of 20 months (Sept 1999 to May 2001) when no breakouts occurred. The 

hydrology of Cockrone Lagoon is very similar to that described for Avoca Lagoon, with sudden 

responses to catchment runoff, gradual evaporation effects, and small periods of tidal influence 

following entrance breakout. 

The salinity of Cockrone Lagoon is variable, falling to levels of about 6ppt when the lagoon is ‘full’, 

and peaking at levels well in excess of oceanic salt concentrations (i.e. Hypersaline conditions) 

following breakout, recharge with ocean waters, and subsequent evaporation of ocean waters from the 

closed waterway. 

Temperature within Cockrone Lagoon varied on a seasonal basis, from approximately 25 – 30 °C in 

the summer to about 10 – 15 °C in the winter. 

pH levels generally ranged between 7 and 10. Similar to Avoca Lagoon, the pH levels in Cockrone 

Lagoon generally followed a seasonal trend, with higher levels during the later Autumn / early 

Summer months, and lower levels during the Autumn / Winter months. This trend was somewhat 

disrupted by the predominantly dry period of 2000 / 2001, which resulted in higher than expected pH 

levels for the majority of the time. pH is likely to be affected by the amount of primary productivity 

(photosynthesis) occurring within the water. 

Dissolved Oxygen (DO) in Cockrone Lagoon is highly variable ranging between 16 mg/L and zero. 

Although not completely evident, there appears to be a trend in DO concentrations that is also 

seasonal. Higher DO concentrations are recorded during the late autumn / early summer period, 

coinciding with the increase in primary productivity (as suggested by the higher pH levels). Lower 

DO levels occur during mid to late summer, extending through autumn. It is possible that the higher 

primary production rates in early summer are unsustainable, resulting in a massive die-off of the algae 

colonies. The decay (reduction) of this organic matter would generate a significant oxygen demand 

on the water column, thus depleting DO levels. 

Turbidity in Cockrone Lagoon is mostly less than about 10 NTU, however, some periods of heighten 

hydrologic activity result in significantly elevated turbidity levels (up to 160 NTU). Higher turbidity 

is recorded coinciding with catchment runoff events and entrance breakouts. However, there remains 

a considerable amount of data with higher turbidity concentrations that cannot be explained by such 

mass hydrologic processes. 

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3.3 Historical Water Quality Results 

3.3.1 Chemical Parameters 

Chemical parameters, such as nitrogen and phosphorus have been measured within the Gosford 

waters at various times in the past. John Laxton (1994, 1999) completed two different monitoring 

programs in the 1990s, with monitoring carried out approximately monthly. The first period was 

from September 1993 to October 1994. The second period was from February 1996 to December 

1998. Monitoring sites for these previous programs were not the same as the most recent monitoring 

program by Cheng, and therefore, direct comparisons between the datasets is difficult. 

A summary of the water quality results for the coastal lagoons, taken from the previous Laxton 

datasets, is provided in Table 3.26. The most recent Cheng data is also shown in this table for 

comparative purposes. 

As can be seen in Table 3.26, the total nitrogen concentrations measured by Laxton are considerably 

lower than those taken by Cheng. There are a number of possible explanations for this significant 

different in results, including monitoring at different sites, and the use of different analytical 

approaches (both Laxton and Cheng use non-NATA accredited labs when determining water quality). 

Table 3.26 Nutrients in the Coastal Lagoons (1993 – 2002) 

1993/94 Mean 1996 – 98 Mean 1999 – 2002 Mean (Cheng) 




Avoca Lagoon 0.80 0.70 1.60 





Avoca Lagoon 0.079 0.066 0.070 


The total phosphorus concentrations were more similar between the Laxton and Cheng results. This 

may indicate that similar analytical techniques were adopted for both monitoring programs. 

Cheng also carried out a limited water quality monitoring program in Brisbane Water between April 

1993 and April 1994. Water quality at sites within Brisbane Water showed reasonably consistent 

results during this period, with a typical mean Total Phosphorus concentration of about 0.075 mg/L 

and a typical mean Total Inorganic Nitrogen concentration of about 0.135 mg/L. Cheng also noted 

that concentrations of phosphorus and inorganic nitrogen increased substantially following rainfall. 

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3.3.2 Bacteria 

Faecal coliforms, and to a lesser extent Total Coliforms, have been monitored in the Gosford waters 

as part of past water quality monitoring programs. Laxton has primarily been responsible for 

monitoring of bacteria at Gosford as part of environment monitoring programs. Bacterial results from 

Laxton’s 1996 – 1998 monitoring program are presented in Table 3.27. This table shows that the 

coastal lagoons and the tributary creeks are most susceptible to bacterial contamination, while sites 

within the broader Brisbane Water estuary are least affected by bacteria. 

Bacteria is also measured by Council as part of their routine Public Health Monitoring Program. 

Bacteria in the vicinity of the oyster leases within Brisbane Water are further monitoring under the 

Shellfish Quality Assurance Program (SQAP). 

Table 3.27 Faecal Coliform Levels (no. per 100mL) 1996 – 1998 (from Laxton, 1999) 

Location Median (50%ile) Mean Maximum 

Wamberal Lagoon 22 319 7500 

Terrigal Lagoon 114 341 2500 

Avoca Lagoon 19 173 2250 

Cockrone Lagoon 31 172 2000 

Narara Creek 95 669 10000 

Erina Creek 132 507 5000 

Kincumber Creek 410 2671 20000 

Cockle Broadwater 8 112 1000 

Koolewong 3 20 355 

Woy Woy 6 29 300 

Booker Bay 16 43 250 

3.3.3 Algae 

3.3.3.1 Algal counts 

Biological monitoring of Brisbane Water and the coastal lagoons was carried out by Cheng between 

August 1999 and June 2002 (Ecoscience Technology, 2002). Algal cell count results for the later half 

of this monitoring period (i.e. Oct 2000 – June 2002) are summarised in Table 3.28. 

Table 3.28 Algal cell count results 2000 – 2002 (Ecoscience Technology, 2002) 

Location Minimum Maximum %age over 1000 cells/ml 

Narara Ck 7 475 0 

Erina Ck 6 1021 2 

Kincumber Ck 6 13634 40 

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Cockle Ck 9 212 0 

Woy Woy Ck 9 10760 29 

Brisbane Water 9 4532 9 

Booker Bay 7 6055 7 

Wamberal Lagoon 14 803 0 

Terrigal Lagoon 11 320 0 

Avoca Lagoon 7 1679 2 

Cockrone Lagoon 12 500000+ 9 

Of particular interest are the results for Cockrone Lagoon. As reported in Ecoscience Technology 

(2002), Cockrone Lagoon was opened and drained in February 2002 (refer Appendix A for MHL 

gauging of water levels in Cockrone Lagoon). Following drainage of the lagoon, filamentous bluegreen 

alga Oscillatoria (and other related species) grew rapidly on the exposed lagoon sediments. 

The algae remained in high numbers for a week or so until the water level increased following heavy 

rainfall. Comparisons with the MHL data indicate that dissolved oxygen in the lagoon (or at least at 

the datasonde location) was very low during the algal bloom (< 2 mg/L), while turbidity levels were 

high (up to 160 NTU), due to the fragmentation and resuspension of the benthic algae into the water 

column. 

Cheng indicates that the entrance openings of the coastal lagoons seem to cause a number of 

ecological problems, such as massive algal growth (and reduced dissolved oxygen levels), and that 

the lagoons need to be actively management and monitored to prevent degradation. In particular, 

Cheng points to better management of entrance openings, to be more sympathetic to lagoon ecology, 

as a means of minimising future degradation of the coastal lagoons. 

Further details on biological monitoring of the Gosford Waters are available in Ecoscience 

Technology (2000, 2002). 

3.3.3.2 Chlorophyll-a 

Chlorophyll-a can be considered as an indicator of algal growth, as it is a measure of the amount of 

green pigment within the water. Recent research by the University of Newcastle suggests that 

chlorophyll-a is a good surrogate of the amount of primary productivity within an estuarine waterway 

(pers comm. Dr A Redden, Uni. of Newcastle). 

Chlorophyll-a has been monitored within the Gosford waters as part of Laxton’s previous water 

quality monitoring programs (1993/94, 1996 – 1998). A summary of Laxton’s chlorophyll-a results 

for the latter of these two programs is shown in Table 3.29. 

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Table 3.29 Chlorophyll-a results (µg/L) 1996 – 1998 (Laxton, 1999) 

Location Median (50%ile) Mean Maximum 



Avoca Lagoon 4.2 5.0 19.6 


Narara Creek 3.9 5.0 29.0 

Erina Creek 4.1 5.4 20.0 

Kincumber Creek 8.5 12.1 65.9 

Cockle Broadwater 2.3 2.5 5.2 

Koolewong 2.7 2.7 5.7 

Woy Woy 1.9 2.4 6.1 

Booker Bay 2.5 3.0 8.9 

Once again Cockrone Lagoon showed a period of excessive algal growth, as indicated by the very 

high chlorophyll-a recording (193.5 µg/L on 1 July 1997). A closer examination of this event has 

revealed that the high levels were recorded the day before the entrance broke out. Thus, the algae 

bloom was not the result of an entrance breakout as was the case in February 2002 (as described in 

Section 3.3.3.1 above). 

Overall, Cockrone Lagoon had relatively high levels of chlorophyll-a. Likewise, Kincumber Creek 

also had high levels of chlorophyll-a, although the amount of chlorophyll-a in all of the coastal 

lagoons and the tributary creeks was higher than what would be expected under more natural 

conditions. Typical chlorophyll-a concentrations in the broader, more flushed, sections of Brisbane 

Water, were generally lower than the lagoons and tributary sites. 

3.3.4 Metals 

Very little water quality data regarding soluble metals is available. The only information in the 

database is from 1974, when concentrations of some basic metals (Calcium, Copper, Lead, Mercury, 

Zinc) were measured at a number of locations in the four coastal lagoons by R.A. Creelman, as noted 

in the Gosford Coastal Lagoons Estuary Processes Study (Webb McKeown & Associates, 1995). 

The results of the monitoring generally indicated low metal concentrations (mostly below the 

detection limits for the analysis). 

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FUTURE DIRECTIONS FOR WATER QUALITY / ENVIRONMENTAL HEALTH MONITORING 4-1 

4 FUTURE DIRECTIONS FOR WATER QUALITY / ENVIRONMENTAL 

HEALTH MONITORING 

4.1 Discussion of Previous Monitoring Programs 

Water quality has been collected within Gosford City Council’s waterways since 1974. The most 

recent monitoring program was carried out by Dominic Cheng of Ecoscience Technology, and 

concluded in June 2002 (following nearly 3 years of data collection at 10 sites within Brisbane Water 

and the coastal lagoons). 

In total, water quality data has been collected from over 200 different sites within the Gosford 

waterways, with over 60 different parameters monitored. Generally, it can be said that water quality 

monitoring in the past has not been carried out in a consistent or integrated manner. New programs 

have generally targeted new sites and sometimes new parameters. Programs have also been carried 

out for specific purposes, such as the water quality monitoring of the tributary creeks (AWT, 2001) 

and the periodic algae monitoring (Ecoscience Technology, 2000, 2002). 

The result of the generally uncoordinated and inconsistent monitoring programs of the past is the fact 

that the data provides little opportunity for interpretation of long-term trends and spatial distribution 

patterns. At best the data provides a ‘snap shot’ of conditions at a particular place and time. This 

conclusion is supported by Umwelt and SMEC (2002) as part of the Brisbane Water Data 

Compilation Study. 

4.2 The Notion of ‘Environmental Health’ 

The term ‘environmental health’, or sometimes more specifically ‘ecosystem health’, has been used 

for at least the last 10 years. The idea of quantifying the health of the environment has great appeal to 

managers, as it can provide an indication of how a system is improving, or degrading. Quantification 

of environmental health can help prioritise works for rehabilitation, and can provide a measure of the 

effectiveness of the works, once implemented. 

While the notion of environmental health is attractive to managers, it proves to be problematic for 

scientists. Coates at al (2002) points out the difficulties in defining ecosystem health given the large 

variability that natural ecosystems experience (as highlighted by the data presented in this document). 

He also highlights the difficulties in selecting an appropriate range of biotic and abiotic indicators to 

represent the ecosystem. It is generally agreed that an ecosystem measure based on single indicators 

is unreliable and possibly unrepresentative. 

4.2.1 Coastal CRC EHMP 

The most comprehensive environmental health assessment currently underway is likely to be that by 

the CRC for Coastal Zone, Estuary and Waterway Management (Coastal CRC) in South – East 

Queensland. The CRC’s Ecosystem Health Monitoring Program (EHMP) monitors estuarine 

waterways to determine if: 

• Key environmental processes operate to maintain stable ecosystems 

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• Human impacted zones do not deteriorate further 

• Critical habitats such as seagrass beds do not deteriorate. 

The CRC EHMP is based on a conceptual model of ecosystem processes. The model focuses on 

assessing the responses of the ecosystem to natural and human impacts, as shown in the figure below. 

The EHMP uses a range of biological indicators and water quality parameters to assess the 

ecosystem, and gauge the effectiveness of management practices being implemented within the 

catchments and around the foreshores. 

Figure 4.1 Conceptual model of the current ecosystem health of Moreton Bay and its 

river estuaries (Coastal CRC) 

Information collected by the CRC that contributes to the assessment of ecosystem health includes: 

• water quality 

• extent of sewage plumes 

• seagrass loss and recovery 

• toxic algal blooms 

• occurrence of nuisance algae 

• phytoplankton growth responses 

• turtle and dugong populations 

A few of these are described further below. 

4.2.1.1 Water quality 

Water quality monitoring is carried out monthly, and includes physical and chemical parameters. 

Physical indicators comprise Dissolved Oxygen, Turbidity, Salinity, Temperature and pH, while 

chemical indicators include Total Nitrogen; Ammonia; Oxides of Nitrogen; Total Phosphorus, 

Filterable Reactive Phosphorus; and chlorophyll-a. 

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4.2.1.2 Seagrass 

The depth range of the seagrass Zostera capricorni is monitored twice yearly at 18 locations 

throughout Moreton Bay. In the bay, the depth at which this seagrass can grow depends on water 

quality, particularly light availability (refer Figure 4.2). Detection of changes to the seagrass depth 

range therefore provides an indication of long term integrated water quality throughout the bay and if 

it is impacting on the integrity of these critical habitats. 

Figure 4.2 Seagrass depth range measures the distance between the upper tidal 

limit of seagrass distribution and the lower light-limited distribution 

4.2.1.3 Sewage 

Sewage effluent can contribute to the eutrophication of receiving estuarine and coastal waterways. It 

is important to be able to trace the source and extent of sewage effluent in receiving waters in order to 

evaluate the extent of its impact on the ecosystem. The use of nitrogen stable isotopes enables the 

detection and delineation of sewage-derived nitrogen from other nitrogen sources entering the 

waterways and its potential influence on the ecosystem. The most abundant form of naturally 

occurring nitrogen is 14 N. Sewage is generally enriched in 15 N compared to 14 N and therefore the 

relative proportion of 15 N to 14 N, referred to as d 15 N, is elevated in receiving waters of sewage 

treatment plants. 

4.2.1.4 Report cards 

Report cards are provided annually outlining the overall condition of the South-East Queensland 

waterways, based on the EHMP results. An example of an EHMP report card is provided in Figure 

4.3, while an example plot of the spatial representation of the Ecosystem Health Index is presented in 

Figure 4.4. 

The report cards provide a clear picture of the overall health of the waterways, and more importantly, 

how they relate to previous years. By comparing the waterway health with past results, managers and 

decision-makers can obtain quantitative feedback on the relative success of various management 

measures implemented within the catchments. The report cards are released each year amid the 

Annual Riverfestival, which is designed to maximise community awareness and ownership of the 

waterways and their issues. 

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Figure 4.3 Example of EHMP Report Card 

Figure 4.4 Spatial Distribution of Ecosystem Health Index values in Moreton Bay 

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4.3 Review of ANZECC Monitoring Guidelines 

4.3.1 Introduction 

The following sections are essentially a summary of the Water Quality Monitoring approach outlined 

in the joint Australian and New Zealand Environment Conservation Council (ANZECC) and 

Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ) 

guideline document Australian Guidelines for Water Quality Monitoring and Reporting. 

4.3.2 Setting Objectives 

The first step in undertaking any water quality monitoring exercise is to set clear objectives. 

Objectives are recommended to be set utilising the process outlined in Figure 4.5. 

Figure 4.5 Framework for Setting Objectives (ANZECC/ARMCANZ, 2000) 

The first step in the process is to define the issue that has resulted in planning of the monitoring 

program. The issues in Australia generally fall into one of four categories-: 

• long term management, protection and restoration of aquatic ecosystems so they can fulfil their 

environmental values; 

• contaminants, their sources and fates in aquatic ecosystems, the magnitude of the problem and 

actions required to protect the environmental values; 

• performance of management strategies; 

• conformity with water quality guidelines. 

The information requirements are defined from discussions with the stakeholders of the water body of 

interest, or whom are involved in the monitoring programme. The information requirements 

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essentially enable identification of issues that the stakeholders need addressed to narrow down the 

scope for the monitoring programme. 

The information requirements are then used as a base to compile and review relevant data. The 

information may be gathered from sources including previous monitoring, literature reviews, and 

community consultation. Data gaps should be identified at this stage and attempts made to fill these 

gaps and/or assess the limitations of not having the information. 

A conceptual process model is then developed to identify the key processes in the system that require 

monitoring. The conceptual process model outlines the understanding of how the system functions, 

and what are considered to be the dominant processes. The model only needs to be a simple box 

diagram that shows components and linkage in the system to be monitored. During the formulation 

of the model, a number of key decision need to be made to limit the complexity of the model. These 

include-: 

• What is the issue? (e.g. nutrients, metals). 

• What subsystem should the model describe? (e.g. freshwater, marine, wetland, mangroves). 

• What state of flow should the model describe? (e.g. base flow, flood). 

The key processes that define the ‘cause and effect’ and ‘how the system works’ need to be defined. 

The key processes that affect water quality include-: 

• transport, flow, turbulence, flushing, mixing and stratification; 

• precipitation, evaporation, wet and dry deposition; 

• contaminant transport, sedimentation, burial, resuspension and diffusion; 

• contaminant transformation, degradation, adsorption, desorption, precipitation, dissolution; 

• sulfate reduction, methanogenesis, organic diagenesis; 

• bioturbation, bioirrigation; 

• organism growth, primary productivity, grazing, succession; and 

• nutrient recycling, loss, transformation, recycling, ammonification, nitrification, denitrification. 

Following development of a conceptual process model, the understanding of information required to 

be collected is more clear, and the objectives for the monitoring programme can be defined. The 

objectives need to be specific, measurable, result orientated, realistic, and concise. Examples of 

typical objectives include-: 

• to determine annual nutrient loads from a specific catchment in a specific system; 

• to determine if specific contaminant concentrations from urban development exceed ANZECC 

water quality guideline trigger values for the protection of aquatic ecosystems in the receiving 

waters beyond the mixing zone. 

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4.3.3 Study Design 

The study design outlines a set of steps to take to ensure that a sampling and analysis program is cost 

effective. The study design also specifies the data requirements. The study design process is outlined 

in Figure 4.6. 

Figure 4.6 Framework for Study Design (ANZECC/ARMCANZ, 2000) 

Initially the study type needs to be defined. There are three distinct study types: 

• descriptive studies (e.g. monitoring for testing against water quality guidelines); 

• change measuring studies (e.g. studies repeated at the same location before and after a change); 

• studies that improve system understanding (e.g. study to understand biological processes in a 

particular aquatic ecosystem). 

The study scope is then set to define-: 

• specific geographic boundaries (e.g. will the study monitor tributaries of a major river, or just the 

major river); 

• scale of monitoring to suit the phenomenon being monitored (both on spatial and temporal 

scales); 

• study duration ( to satisfy the requirement to better understand the system). 

The sampling design is then undertaken considering a number of issues including-: 

• variability – spatial, temporal, seasonal, contaminant loads, land uses; 

• sampling locations – number required, safe access, easily located, minimise intervention of 

humans (i.e. away from bridges), appropriate spacing of sites; 

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• sampling frequency – dictated by objectives and characteristics of the parameter being measured; 

• sampling numbers and precision – selected to detect changes, differences or effects based on the 

parameter being measured; 

• selection of measurement parameter – linked to the objective of the study and typically depends 

on the environmental values of the water body. The parameters used to assess the water quality 

can be either physical, chemical or biological; 

• cost effectiveness – requires optimisation of the cost of the data acquisition with the statistical 

power of the gathered data. 

4.3.4 Field Sampling Program 

The field sampling program identifies what the specific data requirements are, and outlines whether 

the parameters are to be measured in the field or in the laboratory. Planning is required to ensure that 

the sampling falls within the budget, without compromising to a detrimental extent on the statistical 

power of the findings. The field sampling program also outlines the protocol to be followed in 

sample collection, preservation, storage and transportation. The considerations for the field sampling 

program are outlined in Figure 4.7. 

Figure 4.7 Framework for Field Sampling Program (ANZECC/ARMCANZ, 2000) 

The specific data requirements for the field sampling program are determined during the sampling 

design phase. 

The sample collection methods are determined based on the parameters identified during the 

sampling design. The methods include hand sampling, autosampling, integrated sampling, real time 

sampling (automated), field measurements, remote sensing and field observation. The equipment 

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used for sampling of surface waters include bottle samplers, pumping systems, depth samplers, 

automatic samplers and integrated samplers. Groundwater sampling utilisers a number of pumping 

methods. Sediments are often sampled to determine the composition and concentration of 

contaminants, as well as the number of organisms. Sediments are typically sampled using a range of 

dredge, grab and coring methods. The choice of sampling method will depend on the parameter and 

conditions being measured. All methods and equipments are required to meet relevant Australian or 

ISO standards. 

A number of parameters can only be accurately measured in the field (eg temperature, flow), whilst 

others are susceptible to change in the sample after collection (eg dissolved oxygen, pH). 

Consideration should be given at this stage to utilising highly reliable sensors that are capable of 

accurately recording these types of parameters in the field. 

The sample containers are selected to minimise the potential for adsorption or contamination of the 

sample. Glass and plastic containers each have potential limitations and methods to consider for 

preparing the containers for sampling. 

Particular care is required with sampling protocols to prevent contamination of the samples by dust, 

powder, skin and hair. Care is particularly required when boats and helicopters are used to assist with 

sampling to ensure that these forms of transport do not lead to contamination of the samples. 

Observations and characteristics of the site should also be recorded at the time of sampling, and 

recorded on a standardised field sheet. A quality assurance/control system is required for field 

sampling to control sampling errors and manage the samples following collection. Field staff will 

need to be trained and be competent at undertaking the sampling tasks. The hazards likely to be 

encountered by the sampling staff will need to be identified and addressed to ensure that these 

hazards are minimised. 

4.3.5 Laboratory Analysis 

The objective of the laboratory analysis is to obtain accurate and precise data in a safe environment. 

The recommended methodology for laboratory analysis is summarised in Figure 4.8. 

Figure 4.8 Framework for Laboratory Analysis (ANZECC/ARMCANZ, 2000) 

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The selection of appropriate methods for analysing the physical, chemical or biological analytes will 

be dependent on the objectives of the monitoring programme, available budget, laboratory resources, 

speed on analysis, matrix type and contamination potential. The choice of an appropriate method is 

based on four primary considerations-: 

• The range of concentrations of the analytes that need to be detected (detection limits are method 

specific); 

• The accuracy and precision required (all results are only estimates, higher accuracy and precision 

increases the costs); 

• The period between sampling and analysis (some analysis may be required on-site); and 

• Familiarity with a particular method when more than one suitable method is available. 

Laboratory analyses also need to consider a range of issues including-: 

• Data management ( data storage and reporting); 

• Quality assurance/control; and 

• OH&S ( identification of hazards, risk minimisation plans, education). 

4.3.6 Data Analysis and interpretation 

A number of common statistical methods are used for the analysis of water quality data. A 

methodology for undertaking data analysis is shown in Figure 4.9. 

Figure 4.9 Framework for Data Analysis (ANZECC/ARMCANZ, 2000) 

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The data initially needs to be summarised from the laboratory into a form that is suitable for analysis, 

and preliminary checks made for erroneous, missing or below detection data. Suitable approaches for 

dealing with these types of data will need to be considered. 

The checked data is then reduced and summarised using a combination of commonly used statistical 

tools, including graphs, tables, statistical measures (e.g. mean, standard deviation). The objective of 

the summarised data is to present essential information contained in the data set concisely, and to 

assist in clearly identifying outliers. Advances in computer software have enabled highly 

sophisticated graphics to be readily accessible. 

A number of more advanced statistical methods are then typically used to assess data relationships. 

Methods including transformations, checking distributional assumptions, trend detection and 

smoothing can be undertaken. 

It is then important to subject the data to a process of statistical inference to assist with determining 

characteristics of the data set, enabling testing of hypothesis and comparison of the data with water 

quality guideline or trigger values. 

The relationship between pairs of water quality variables can be evaluated using correlation and 

regression analysis. 

Following the data analysis, the results should be summarised concisely, and compared with the 

monitoring programme objectives to determine if the original questions are answered by the results. 

4.3.7 Reporting 

The reporting of data from the water quality monitoring requires careful consideration of the end user 

to ensure that the technical nature of the topic is presented to the intended audience in an appropriate 

format. 

• Executive summary – summarises technical findings for managers; 

• Introduction – Outlining study objectives, study location and review of previous/related studies; 

• Methodology – Outline of study design, sampling and analysis methods; 

• Results – Summarised results; 

• Discussion – Data interpretation and implications for management; 

• Conclusions 

• Recommendations 

• References 

• Appendices – laboratory reports, data tables 

The report findings can be disseminated in a number of ways depending on the intended audience. 

Methods for disseminating the data include publications, meetings, internet web pages, film and 

video presentations, and media reporting. 

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4.4 Outcomes from Community Workshops 

A series of workshops were held (on 23 June 2003) with the Gosford community to discuss the future 

directions for Council-operated water quality monitoring of Brisbane Water and the coastal lagoons. 

Presented below is a summary of the key issues raised by community members during these 

workshops. 

4.4.1 General Comments 

The following general comments were made by the community: 

• Want water to be safe to swim in and safe for aquatic life, including coastal lagoons 

• Better integration of monitoring by CCCEN, Waterwatch and oyster farms, as well as Council 

monitoring, is required 

• Need to use the data once it is collected 

• Is there a need for more extensive biomonitoring, including pests? 

• Water quality in coastal lagoons needs to be considered in light of their hydrologic cycles 

• Water quality of coastal lagoons is different from Brisbane Waters 

• Need to monitor for environmental health 

• Can’t rely on tidal flushing to keep water quality good, therefore need to focus on remediation of 

catchment activities 

• Hawkesbury catchment has generally been overlooked in the past 

4.4.2 Possible Sites for Future Monitoring 

The following locations were suggested by the community members, as possible sites for future 

monitoring; 

• Green Point Creek, Pearl Beach 

• Siltation at Killcare and Hardys Bay 

• More offshore sites needed to provide picture of broader waterway 

• Erina Creek, particularly given all the development 

• GPTs 

• Target worst sites from past data, including industrial areas 

• Top of the catchment 

• Wamberal Lagoon – housing development upstream 

• Stormwater outfall and at marinas 

• Areas of landfill 

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4.4.3 Possible Parameters for Future Monitoring 

The following comments regarding what to monitor, were made by community members: 

• More public health parameters 

• Turbidity, particularly in the Hawkesbury catchment 

• Different sites may require different tests 

• Biological parameters, eg plankton 

• Chemical parameters 

• Physical parameters 

• Bacterial parameters, eg E. coli in areas of septic tank usage 

• Flow, eg in Erina Creek 

• Urban contaminants, as measured in GPTs 

4.4.4 Possible Frequency of Monitoring 

The community provided the following comments regarding when to monitor in the future: 

• Monitor storm events, using automatic samplers 

• Pre-development to get baseline conditions 

4.4.5 Possible Ways of Reporting the Data 

The community expressed a number of concerns regarding dissemination of the data collected. The 

following are comments provided by the community in this regard: 

• Information needs to be reported back to people doing the monitoring (Waterwatch specifically) 

and a formal network is needed 

• Need a common database for all water quality data and a website to access the data 

• Establish an e-mail forum 

• State of Environment reports, with specific community profiles and feedback on success of what 

has been done 

• Once a year formally, with quarterly updates on website and in local paper, and possibly rates 

notices 

• Star rating is a concern as it is subjective 

• Need to see actual data on website if want to 

• Differentiate community feedback based on regional locality and relevance to waterways (eg. 

Woy Woy residents not interested in coastal lagoons data) 

• Use the media wherever possible and maximise education opportunities 

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4.5 Options for Future Water Quality Monitoring 

A range of options for the future water quality / environmental health monitoring of Gosford waters 

have been considered. The options have been developed in light of Council’s expected financial 

restrictions (i.e. currently in the order of $40,000 per annum and possibly increasing to $50,000 - 

$60,000 in the future). 

Four different options have been formulated, targeting different aspects of the water environment. 

Therefore, the options can be adopted individually or in combination, in order to achieve Council’s 

objectives regarding future water quality / environmental health monitoring. The options are 

discussed in detail below. 

4.5.1 Option 1: Routine Monthly Water Quality Monitoring 

This option involves continuing the basic program of monitoring that was being carried out by Cheng 

(on behalf of Council) prior to July 2002. It would involve a minimum of 10 sites around the coastal 

lagoons and within Brisbane Water, and would be monitored on a regular monthly basis. 

In-situ water quality would be measured by hand-held probe at the time of sampling. The probe 

would measure pH, dissolved oxygen, salinity, temperature and turbidity. Collected water samples 

would be tested for BOD, ammonia, oxidised nitrogen, TKN, total nitrogen, orthophosphate, total 

phosphorus, suspended solids, chlorophyll-a and enterococci. In addition, it is suggested that three 

sites also be analysed for algal counts and composition. Experimental data from the University of 

Newcastle suggests that chlorophyll-a concentrations is a good surrogate for primary productivity (i.e. 

algae) within the water column. Therefore, monitoring chlorophyll-a at all sites provide an indication 

of primary productivity, while concurrent monitoring of algal counts and composition at three sites 

will provide additional data for identifying correlations between chlorophyll-a and primary 

production. 

The sites would include, as a minimum, Wamberal Lagoon, Terrigal Lagoon, Avoca Lagoon, 

Cockrone Lagoon, Woy Woy Creek, Narara Creek, Erina Creek, Kincumber Creek, Cockle Creek, 

and Booker Bay. The sites for the additional algae monitoring would likely include two coastal 

lagoons (one being Cockrone Lagoon) and one site in Brisbane Water. Further consideration to the 

locations of sampling should be given in light of the SQAP monitoring being carried out within 

Brisbane Water, and the CCCEN Streamwatch monitoring sites within the catchment. 

Although it is not intended to target public health, we consider that monitoring a relatively longlasting 

bacteria, such as enterococci, would provide a sound basic indicator for sewage inputs to the 

waterway associated with overflows and general urban runoff. An alternative to bacteria is faecal 

sterols. These compounds, found in the gut of animals (including humans) are a very good indicator 

of faecal contamination, as they do not readily break down in the natural environment. Also, 

composition of the sterols allows us to identify the source of the contaminant (eg humans, other 

omnivores, herbivores, etc). Another alternative, which is used as part of the South-East Queensland 

EHMP (refer Section 4.2.1) is d 15 N (delta 15 nitrogen). This is the difference between the 15 N and 

14 N isotopes, with 15 N generally associated with sewage discharges. Unfortunately, delta-N and 

faecal sterols assessments are both quite expensive at present, although it is understood that the 

University of Newcastle has recently developed techniques for rapid assessment of faecal sterols 

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using mass spectrometers, and is carrying out regular analysis for Lake Macquarie City Council (pers. 

comm. Assoc. Prof. Hugh Dunstan, Uni of Newcastle). 

To maximise the value of the water quality data, it is suggested that a few other environmental 

parameters be collected at the time of sampling. This would include the water level, and antecedent 

rainfall. For the coastal lagoons, it is suggested that tideboards are installed at the water quality 

monitoring sites, so that water levels can be easily read and documented at the time of sampling. 

Also, it should be noted whether the entrance of each lagoon is open or closed. For the Brisbane 

Water sites, monitoring should be carried out at the same stage of the tide (preferably high water 

slack +/- 1 hour). 

To determine antecedent rainfall, Council should operate and maintain at least two rainfall gauges, 

one located on the coast, and the other located around Brisbane Water (possibly on top of the Council 

building). Rainfall during the preceding 48 hours, and 7 day periods should be recorded as part of the 

water quality monitoring data. 

4.5.2 Option 2: Catchment and Receiving Water Monitoring 

This option involves monitoring the catchment-based inputs to the waterways, and the response of the 

waterways to these inputs. The inputs would be determined by monitoring water quality during high 

flow periods only. Given that it is the high flows that provide the vast majority of pollutants to the 

waterways, only high flows will be targeted. Actual pollutant loads will be calculated based on 

measured concentrations and flow rates. To enable effective monitoring of high flows, it is suggested 

that automatic samplers are installed within the catchment. These devices automatically extract a 

sample from the tributary when triggered, and store the sample (refrigerated if necessary) until 

collection. A flow measuring device would also be required in order to quantify the pollutant loads 

within the tributary, and possibly to trigger the auto-sampling (when flows exceed a given level). 

As a pilot study, it is recommended that monitoring be triggered during a 1 in 1 month high flow 

event, with approximately 3 samples taken during the course of the event. 

The response monitoring would involve hand collection of samples. It is suggested that sampling be 

done at various times after the triggered event (1 in 1 month as a pilot study), for example 24 hours, 

48 hours, and 7 days after the event. The response monitoring sites would be downstream of the 

catchment input site, and would represent the wider receiving water body of the catchment waterway. 

Where possible, one of the response sites should be consistent with the historical water quality 

monitoring sites, so that comparisons can be made with past results (eg previous sites in Narara 

Creek, Erina Creek and Kincumber Creek). 

Parameters analysed for both the input and response sites would be comparable to those outlined in 

Option 1, including both the physical and chemical constituents, as well as chlorophyll-a and bacteria. 

Algal monitoring could also be considered as part of the response monitoring, but not the input 

monitoring. 

Given that this approach would focus on water quality monitoring of specific sections of the Gosford 

catchment only, with the remainder left largely unmonitored, this option should target the worst 

effected sections of the waterways (i.e. greatest potential catchment input, most susceptible area to 

inputs, etc). Also, given the relatively high capital costs of installing the auto-samplers, it is 

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suggested that a pilot study be initiated in one subcatchment. Funds for future years could then be put 

towards the capital costs of installing additional auto-samplers. Alternatively, funds for the capital 

costs could be sourced separately, as the auto-samplers would represent assets of Council. 

4.5.3 Option 3: Quarterly Seagrass Depth Monitoring 

This option follows that carried out as part of the Coastal CRC 

EHMP, and involves surveying the seaward extent of seagrass 

growth at numerous locations around the waterways. The depth to 

which seagrasses grow is essentially limited by the penetration of 

light through the water. Areas of higher turbidity and pelagic algae 

tend to have shallower seagrass depth limits than more pristine areas. 

Seagrass depth limits tend to vary on a seasonal basis, hence the need 

for monitoring every 3 months or so. Comparisons should be made 

with the same period in previous years. 

The locations should include at least two control sites, in addition to 

the impact sites. Locations should be chosen to try and avoid areas 

where seagrass growth may be inhibited by physical factors, such as 

propeller boat wash or high tributary flows. 

Monitoring would involve establishing temporary shore-based benchmarks for three transects at each 

location. Transects would be surveyed as shoreline cross-sections, noting the variation in seagrass 

along each transect to the point where seagrass is no longer present. 

Seagrass depth monitoring would be best done to supplement another monitoring program, be it 

water quality, sediment quality or biological monitoring. 

4.5.4 Option 4: Quarterly Benthic Macroinvertebrate Monitoring 

This option involves monitoring of benthic macroinvertebrates from a number of locations around the 

waterways. A very carefully designed program would be necessary to address the natural variability 

in benthic population. This would involve having multiple control sites, and nesting both control and 

impact sites together, with four replicates at each site. 

Monitoring would be done either in the intertidal zone using cores, or in the subaqueous zone using 

grabs. Monitoring would need to be carried out on a quarterly basis to take into account the seasonal 

variability in benthic community abundance and diversity. 

In addition to benthic macroinvertebrates, sediment samples should be collected and analysed for TP, 

TN and TOC, with at least three replicates of sediment quality at each location. Correlations could 

then be performed between the sediment quality and the benthic macroinvertebrate population. 

Particle size distribution analysis of the sediment would also be required in order to characterise the 

benthic sedimentary environment. 

Comparisons would be drawn between the control and impact sites, with conclusions stating that the 

results from the impact sites fall either within or outside the natural variability experienced by the 

control sites. Care would be required when interpreting the results, as the results may only provide an 

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indication of the health of the waterway sediments, rather than the overlying water quality and 

general environmental health. 

4.5.5 Indicative Costs of Options 

The indicative costs for the various options are presented in Table 4.1 for Council’s consideration. 

Table 4.1 

Indicative Costs for Future Monitoring Options 

Option Description 

Annual cost 

Option 1: Routine Monthly Water Quality Monitoring 

WQ analysis for 10 sites................................................................ 

Additional sites .............................................................................. 

Collection of samples from the field............................................. 

Interpretation and reporting of results........................................... 

Set-up and survey of tideboards in lagoons .................................. 

Set-up of rainfall gauge ................................................................. 

Faecal sterols assessment (optional) ............................................. 

Option 2: Catchment and Receiving Water Monitoring 

Auto-sampler ................................................................................. 

WQ analysis for 1 input and 2 response sites (based on 3 

samples per month for each, capturing the 1 in 1 month event)... 

Collection of samples from the field............................................. 


$31,200 

$2,600 each 

$7,200 

$7,200 

$2,000 (one-off cost) 

$1,000 each (one-off cost) 

$150 per sample 

$20,000 each (one-off cost) 

$24,800 per sampler 

$7,200 

$7,200 

Option 3: Quarterly Seagrass Depth Monitoring 

8 – 10 sites (incl. at least 2 control sites), with three transects at 

each site.......................................................................................... 


Establish temporary survey marks for each transect .................... 

$12,000 

$3,000 

$3,000 (one-off cost) 

Option 4: Quarterly Benthic Macroinvertebrate Monitoring 

8 sites (4 nested pairs), incl. 4 control sites, with 4 replicates at 

each site.......................................................................................... 

Interpretation (stats) and reporting ................................................ 

Additional nested pair sites (incl. additional interpret & 

reporting)........................................................................................ 

Sediment quality analysis .............................................................. 

Sediment particle size distribution (PSD) analysis....................... 

$25,600 

$12,800 

$12,000 each 

$6,800 

$3,200 

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4.5.5.1 Assumptions in Determining Costs 

Please note that there were a few assumptions made when determining the indicative costs. 

• Costs for water quality and sediment quality analyses were based on commercial analytical 

laboratory rates. The use of Council’s public health laboratory may reduce costs, however, this 

would mean the analysis would not be carried out by a NATA accredited laboratory. It is 

expected that Council’s laboratory would not be able to carry out all of the analyses (especially 

sediment quality, chlorophyll-a, and algal counts and composition). An external lab would need 

to be sub-consulted for these components at least. 

• Water quality monitoring costs assume both algal counts and composition would be required. If 

only algal counts were to be carried out (with no composition / speciation), costs could be 

reduced by at least $2,700pa. If no algal counts or composition data are required, costs could be 

reduced by $5,400pa. Conversely, if algal data are required for more than 3 sites, costs would 

increase by $1,800pa per site. 

• Collection, interpretation and reporting costs were based on an external consultant undertaking 

the works. Costs may be reduced if Council staff could perform one or more of these costs. It is 

understood that staff from the public health laboratory may be available for collection of water 

quality samples. 

• Costs for routine water quality monitoring could be reduced if the number of sites to be 

monitored is reduced. Given the community pressure for broadscale monitoring throughout the 

City, it is likely that only a couple of sites could be removed without significantly compromising 

the program, these being Booker Bay and possibly Cockle Broadwater. Savings would be 

approximately $2,600pa per site. 

• No allowance was made for incorporation of monitoring that will be carried out as part of future 

Council projects, such as that Brisbane Water Biodiversity Study and the Brisbane Water Estuary 

Processes Study. 

4.6 Recommended Monitoring Program 

One of the primary objectives of this document is the recommendation of a future monitoring 

program to be implemented by Council. The purpose of the future program would be to: 

• provide information to the community on the health of the waterways; and 

• assist Council in their sustainable natural resource management role.With regards to the second 

point, monitoring provides a justifiable basis for prioritisation of future remediation works (given 

limited funds for works implementation) and also provides a measure of the effectiveness of the 

works once implemented. 

Council’s current water quality budget ($40,000) is an obvious limitation to the option(s) that can be 

implemented immediately. The continuous water quality probes at Avoca Lagoon, Cockrone Lagoon 

and Koolewong that were utilised in the past provided limited information on overall environmental 

health of the waterways, and are not recommended to be continued. This does not preclude their 

value in providing useful scientific data regarding the environmental processes occurring within the 

waterways. However, given the costs to maintain the probes (~$16,000 pa), their benefit cost is 

limited. 

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With regard to water quality monitoring, it is recommended that Option 1 be implemented utilising 

the same 10 sites as was adopted by Cheng. This would maximise the value of the historical data in 

assessing water quality retrospectively. Providing additional information regarding the water levels 

and rainfall, whilst also being consistent with the stage of the tide (preferably high water slack), will 

ensure that the information gathered can be readily interpreted. 

It is also recommended that Council move towards carrying out seagrass depth monitoring. Whilst 

this may not be completely implementable within the first 12 months, it is strongly recommended that 

Council seek additional funds to carry out seagrass depth monitoring in the future. Once the transects 

and monitoring protocols are established, Council could consider the possibility of the works being 

done by Council staff (possibly a survey team). Alternatively, seagrass depth monitoring could be 

carried out periodically by students from a university or other tertiary institution, as part of an 

environmental science program. 

It is not recommended that Council undertake benthic macroinvertebrate monitoring (Option 4) as a 

sole indicator for environmental health in the Gosford waterways. Firstly, it would be difficult to 

monitor all of the different waterways in question within the designated budget, and indeed find 

relevant control sites for the different types of waterways, especially the coastal lagoons. Secondly, 

considerable effort will be needed to appreciate the natural variability in benthic communities. 

Nonetheless, Council should explore possibilities of utilising Universities and other research 

organisations to carry out periodic benthic community assessments. The information gained from 

these assessments could be fed into Council’s broader assessment of environmental health using other 

indicators, such as water quality (and possibly seagrass depth limits). It is understood that the 

University of Newcastle is currently undertaking ecological research in Brisbane Water as part of a 

Biodiversity Study. Continuation of this program in the future, and other similar programs, should be 

encouraged. 

Option 2 is also not recommended, as it would focus on only very limited sections of the LGA. It 

would be difficult for Council to extrapolate the results and make comment regarding the overall 

environmental health of the Gosford waterways, unless numerous catchment and receiving water 

monitoring programs were set-up throughout the City. Option 2 represents an expensive ‘rolls royce’ 

solution to water quality monitoring in the Gosford LGA. 

A summary of the parameters that need to be included in the future monitoring program is provided 

in Table 4.2, while the locations of the sampling sites are provided in Figure 4.10 and Figure 4.11. 

Note that the monitoring program should be carried out on the same day of each month to ensure 

consistency. For simplicity, it is recommended that this be the first day of the month (or closest 

following working day). 

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Table 4.2 

Parameters to be monitored 

In-situ monitoring 

(monthly at high water slack) 

Sample & lab analysis 


Additional site information 


• Dissolved oxygen 

• pH 

• Turbidity 

• Temperature 

• Salinity / conductivity 

• Biochemical Oxygen Demand (BOD) 

• Ammonia 

• Oxidised nitrogen 

• Total Kjeldahl Nitrogen (TKN) 

• Total nitrogen 

• Orthophosphate 

• Total phosphorus 

• Suspended solids 

• Chlorophyll-a 

• Algal counts (3 sites only) (1) 

• Enterococci (or Faecal sterols) (2) 

• Water level (relative to surveyed tide board) (3) 

• Rainfall during preceding 48 hours (4) 

• Rainfall during preceding 7 days (4) 

• Entrance condition (lagoons only) 

1) Algal counts are recommended to be measured at the Cockrone Lagoon, Terrigal Lagoon and 

Woy Woy Creek sites. 

2) Faecal sterols should be substituted for Enterococci is there are sufficient funds available. 

Commercial faecal sterols analysis can be carried out locally at the University of Newcastle for 

less than $150 per sample (compared to approximately $30 per sample for enterococci, i.e. an 

extra $14,400 is required) 

3) Tide boards will need to be installed and surveyed to a standard datum prior to the 

commencement of water quality monitoring. 

4) Rainfall to be measured by automated local rain gauges, one located near the coastal lagoons 

(eg on the roof of a Council owned childcare centre), and one located closer to Brisbane Water 

(eg on the roof of Mann Street Council building). 

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Figure 4.10 General Locations of Future Monitoring Sites 

Figure 4.11 continued over page 

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Figure 4.11 Detailed Locations of Monitoring Sites 

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4.6.1 Recommendations for a Gosford Environmental Health Indicator 

Based on the Coastal CRC EHMP template, an appropriate Environmental Health Indicator for the 

Gosford water would incorporate the results of both biotic and abiotic assessments. As a minimum, it 

is recommended that the following be integrated into an Environmental Health Indicator: 

• Water Quality (as defined by Compound Water Quality Index or associated scorecards); 

• Seagrass depth assessment (as and when the opportunity arises to incorporate seagrass 

monitoring into routine Council environmental assessment programs); and 

• Benthic macroinvertebrate assessment (based on the initial Biodiversity Study by University of 

Newcastle [Dr Bill Gladstone], and assuming that repeatable assessments could be carried out at 

least annually as part of Council’s future environmental monitoring programs). 

In the first instance, however, it is likely that the only measure of Environmental Health will be the 

Compound Water Quality Index, as described in Section 3.1.3. The limitation of assessing only 

abiotic parameters, needs to be recognised though. 

With regard to the Compound Water Quality Index, or more specifically the Water Quality 

Scorecard, objectives can be set for different locations based on an understanding of the estuarine 

processes throughout the Gosford waterways. Recommended targets for future water quality scores 

are shown in Table 4.3. 

Table 4.3 

Recommended Water Quality Scores for different sections of the 

Gosford Waterways 

Location 

Water Quality 

Score 

Additional Objectives 

Lower Brisbane Water (e.g. Booker Bay) 10/10 

Upper Brisbane Water (e.g. Koolewong) 9/10 

Brisbane Water tributaries 8/10 Ammonia < 0/01 mg/L 

NO x < 0.02 mg/L 

Coastal Lagoons 8/10 Chlorophyll < 2 µg/L 

Recommendations regarding seagrasses and benthic macroinvertebrates, along with guidelines for 

amalgamating results into one ‘Environmental Health Index’ would be determined following baseline 

monitoring of the biological components. 

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REFERENCES 5-1 

5 REFERENCES 

AWT (2001) Gosford Water Quality Survey Stage 2 Report – Major Tributary Water Quality 

Assessment Information, Australian Water Technology, December 2001 

Coates B, Junes AR, Williams RJ (2002) Is ‘Ecosystem Health’ a Useful Concept for Coastal 

Managers? Coast to Coast 2002, pp 55 - 58 

Cheng D (1994), Environmental Study of Brisbane Waters, University of Technology Sydney, 

September 1994. 

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Coastal CRC web-site www.coastal.crc.org.au 

Ecoscience Technology (2002), Water Quality and Biological Monitoring of Brisbane Water and 

Gosford Lagoon, prepared for Gosford City Council. 

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prepared for Gosford City Council, May 2000. 

Ecoscience Technology (2000b) Phytoplankton Monitoring of Brisbane Water and Gosford Lagoons, 

prepared for Gosford City Council. 

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Gosford City Council, Insearch Ltd. 

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Consultants Pty Ltd, October 1994. 

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Prepared for Gosford City Council. 

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MHL DATASONDE RESULTS: AVOCA LAGOON A-1 

APPENDIX A: MHL DATASONDE RESULTS: AVOCA LAGOON 

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MHL DATASONDE RESULTS: COCKRONE LAGOON B-1 

APPENDIX B: MHL DATASONDE RESULTS: COCKRONE LAGOON 

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MHL DATASONDE RESULTS: KOOLEWONG C-1 

APPENDIX C: MHL DATASONDE RESULTS: KOOLEWONG 

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Gosford City Council Historical Water Quality Review & Analysis

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