An Investigation of the Potential Ecological Impacts of Freshwater Extraction from the Richmond River Tidal Pool
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AN INVESTIGATION OF THE POTENTIAL ECOLOGICAL IMPACTS OF FRESHWATER EXTRACTION FROM THE RICHMOND RIVER TIDAL POOL WRL Technical Report 99/51 November 1999 THE QUALITY OF THIS SCAN IS BASED ON THE ORIGNAL ITEM THE UNIVERSITY OF NEW SOUTH WALES WATER RESEARCH LABORATORY AN INVESTIGATION OF THE POTENTIAL ECOLOGICAL IMPACTS OF FRESHWATER EXTRACTION FROM THE RICHMOND RIVER TIDAL POOL WRL Technical Report 99/51 November 1999 by W L Peirson, K A Bishop, R Nittim and M J Chadwick https://doi.org/ 10.4225/53/58d49e7613006 Unisearch Ltd a c n ooo 263 025 Water Research Laboratory Technical Report No 99/51 University of New South Wales Report Status Final King Street Date of Issue November 1999 Manly Vale NSW 2093 Australia Telephone: +61 (2) 9949 4488 WRL Project No. 99069 Facsimile: +61 (2) 9949 4188 Project Manager W L Peirson Title An Investigation of the Potential Ecological Impacts of Freshwater Extraction from the Richmond River Tidal Pool Author(s) W L Peirson, K A Bishop, R Nittim and M J Chadwick Client Name Department of Land and Water Conservation, NSW. Client Address AMP Centre, 24 Gordon St, PO Box 582, Coffs Harbour NSW 2450. Client Contact Linden Bird Client Reference The work reported herein was carried out by Unisearch Ltd, the commercial company of the University of New South Wales, acting on behalf of the client. The work was undertaken at the University's Water Research Laboratory. Information published in this report is available for general release only by permission of the Water Research Laboratory and the client. WRL TECHNICAL REPORT 99/51 CONTENTS 1. INTRODUCTION 1 2. HYDROLOGICAL ANALYSIS 3 2.1 Approach 3 2.2 Hydrological Model Description 3 2.3 Hydrological Model Calibration 4 2.4 Hydrological Model Results 6 2.5 Estuary Model Description 7 2.6 Estuary Model Configuration 7 2.7 Estuary Model Calibration 8 2.7.1 RMA-2 Calibration 8 2.7.2 RMA-2 Verification 10 2.7.3 RMA-11 Calibration 10 2.8 Prediction of Salinity Structure 12 2.8.1 Empirical Calculations 12 2.8.2 Model Simulations and Management Scenarios 12 2.8.3 Discussion of Results 13 2.9 Simulation of 1901-1902 15 3. ANALYSIS OF HABITAT 17 3.1 Approach 17 3.2 Estuarine Vegetation 17 3.3 Fish Communities and Their Habitats 19 3.4 The Platypus 21 3.5 Indicative Salinity Limits and Their Use 22 3.6 Risk Analysis of Water Extraction Scenarios 23 3.6.1 Dimensions of the Analysis 23 3.6.2 Habitat-Availability Data Arising from Salinity Thresholds 25 3.6.3 Assumptions Regarding Risk 26 3.6.4 Measuring Habitat Contraction and Risk Categories 26 3.6.5 Percentile Condition Synthesis and Thresholds 27 3.6.6 Changes in Habitat Availability and Risk 28 3.6.7 Synthesis 34 4. CONCLUSIONS AND RECOMMENDATIONS 38 5. REFERENCES 41 LIST OF TABLES 2.1 Catchments Selected for AWBM Calibration 2.2 AWBM Catchment Models: Key Parameters Adopted for Calibration 2.3 Comparison of Measured and Modelled Tidal Prisms: Richmond River, 3 November, 1994 2.4 Comparison of Measured and Modelled Tidal Prisms: Wilsons River, 3 November, 1994 - i - WRL TECHNICAL REPORT 99/51 LIST OF FIGURES 1.1 General Plan of the Richmond Catchment 2.1 Schematic Representation of the AWBM Model 2.2 Catchment Plan Showing Major Rainfall and Stream Gauge Locations 2.3 AWBM Model Calibration: Richmond River at Casino 2.4 AWBM Model Calibration: Leycester River at Rock Valley 2.5 AWBM Model Calibration: Wilsons River at Eltham 2.6 AWBM Model Calibration: Myrtle Creek at Rappville 2.7 AWBM Model Verification: Richmond River at Casino 2.8 AWBM Model Verification: Leycester River at Rock Valley 2.9 AWBM Model Verification: Wilsons River at Eltham 2.10 AWBM Model Verification: Myrtle Creek at Rappville 2.11 Representative Rainfall and Streamflow hydrograph (1940-1997) 2.12 Channel Volume and Area Richmond River 2.13 Channel Volume and Area Wilsons River 2.14 Channel Volume and Area Bungawalbin Creek 2.15 The Finite Element Estuary Mesh 2.16 Locations of Calibration Data for RMA-2 Calibration: 3 November 1994 2.17 Comparison of Measured and Modelled Tide Levels - Richmond River: 3 Nov 1994 2.18 Comparison of Measured and Modelled Tide Levels - Wilsons River: 3 Nov 1994 2.19 Comparison of Measured and Modelled Tidal Lags - Richmond River: 3 No. 1994 2.20 Comparison of Measured and Modelled Tidal Lags - Wilsons River: 3 Nov 1994 2.21 Comparison of Measured and Modelled Salt Distributions: Richmond River, 1994 2.22 Existing Conditions: Modelled Salt Distributions in the Richmond River: 1940-1997 2.23 Existing Conditions: Modelled Salt Distributions in the Wilsons River: 1940-1997 2.24 Existing Conditions: Modelled Salt Distributions in Bungawalbin Creek: 1940-1997 2.25 Option A: Modelled Salt Distributions in the Richmond River: 1940-1997 2.26 Option A: Modelled Salt Distributions in the Wilsons River: 1940-1997 2.27 Option A: Modelled Salt Distributions in Bungawalbin Creek: 1940-1997 2.28 Option B: Modelled Salt Distributions in the Richmond River: 1940-1997 2.29 Option B: Modelled Salt Distributions in the Wilsons River: 1940-1997 2.30 Option B: Modelled Salt Distributions in Bungawalbin Creek: 1940-1997 2.31 Option C: Modelled Salt Distributions in the Richmond River: 1940-1997 2.32 Option C: Modelled Salt Distributions in the Wilsons River: 1940-1997 2.33 Option C: Modelled Salt Distributions in Bungawalbin Creek: 1940-1997 2.34 Option D: Modelled Salt Distributions in the Richmond River: 1940-1997 - n - WRL TECHNICAL REPORT 99/51 List of Figures (Contd) 2.35 Option D: Modelled Salt Distributions in the Wilsons River: 1940-1997 2.36 Option D: Modelled Salt Distributions in Bungawalbin Creek: 1940-1997 2.37 Option E: Modelled Salt Distributions in the Richmond River: 1940-1997 2.38 Option E: Modelled Salt Distributions in the Wilsons River: 1940-1997 2.39 Option E: Modelled Salt Distributions in Bungawalbin Creek: 1940-1997 2.40 Option F: Modelled Salt Distributions in the Richmond River: 1940-1997 2.41 Option F: Modelled Salt Distributions in the Wilsons River: 1940-1997 2.42 Option F: Modelled Salt Distributions in Bungawalbin Creek: 1940-1997 2.43 Modelled Salt Distributions in the Richmond River, 1902 3.1 Changes in Salinity Percentiles Along the Main Arm of the Richmond River Estuary: Existing Condition 3.2A Length of Habitat Remaining for Oxleyan Pygmy Perch (Thresh. =0.12 ppt) under Existing Conditions and 6 Options : Richmond River (middle) Arm 3.2B Length of Habitat Remaining for Oxleyan Pygmy Perch (Thresh. = 0.12 ppt) under Existing Conditions and 6 Options : Wilsons River Arm 3.2C Length of Habitat Remaining for Oxleyan Pygmy Perch (Thresh. = 0.12 ppt) under Existing Conditions and 6 Options : Bungawalbin Creek Arm 3.3A Length of Habitat Remaining for the Platypus (Thresh. = 0.5 ppt) under Existing Conditions and 6 Options : Richmond River (middle) Arm 3.3B Length of Habitat Remaining for the Platypus (Thresh. = 0.5 ppt) under Existing Conditions and 6 Options : Wilsons River Arm 3.3C Length of Habitat Remaining for the Platypus (Thresh. = 0.5 ppt) under Existing Conditions and 6 Options : Bungawalbin Creek Arm 3.4A Area of FE+ETC+Macrophytes Remaining (Thresh. = lppt) under Existing Conditions and 6 Options : Richmond River (middle) Arm 3.4B Area of FE+ETC+Macrophytes Remaining (Thresh. = lppt) under Existing Conditions and 6 Options : Wilsons River Arm 3.4C Area of FE+ETC+Macrophytes Remaining (Thresh. = lppt) under Existing Conditions and 6 Options : Bungawalbin Creek Arm 3.5 A Area of Habitat Remaining for Adult Bass NS & RG (Thresh. = 5 ppt) under Existing Conditions and 6 Options : Richmond River (middle) Arm 3.5B Area of Habitat Remaining for Adult Bass NS & RG (Thresh. = 5 ppt) under Existing Conditions and 6 Options : Bungawalbin Creek Arm 3.6 Area of Habitat Remaining for Bass Spawning (Thresh. = BT. 8-13 ppt) under Existing Conditions and 6 Options : Richmond River (middle) Arm 3.7 Length of Habitat Remaining for SR Oysters with LMF (Thresh. = <20 ppt) under Existing Conditions and 6 Options : Richmond River (middle) Arm 3.8 Summary of Percentage Change in the Length/Area of Estuary with Salinites Suitable for Six Ecosystem Facets 3.9 Relationships between the Risk Index and the Extraction Rate Surrogate (Ml/Ha/yr) for Four Freshwater-Content Percentile Conditions of the Richmond River Estuary - in - WRL TECHNICAL REPORT 99/51 1 . 1. INTRODUCTION This is a detailed assessment of the impacts of extracting fresh water from below the tidal limit on the saline structure of the Richmond River estuary. This investigation has been undertaken for the North Coast office of the Department of Land and Water Conservation by the Water Research Laboratory in conjunction with a team of aquatic ecologists. This study is a component of a wider program currently being undertaken by the New South Wales Government. Through the Council of Australian Governments, it has been agreed that action is needed Australia-wide to minimise unsustainable use of water resources. As a consequence, the State government is setting interim environmental objectives for water quality and quantity which all planning processes will aim to achieve. The 'stress' of a given stream is assessed in terms of these objectives so that independent and transparent management decisions are made. In rivers, the use of water is quantified simply as the proportion diverted for water supply, irrigation or industrial uses of the total flow down the river. This focus of this investigation is the Richmond River estuarine system in northern New South Wales (Figure 1.1). The issue that is to be determined from this investigation is whether irrigators below the tidal limits of estuaries should be treated differently from their counterparts extracting water from the rivers upstream.