Ecological Consequences of Managing Water Levels to Prevent Acidification in Lakes Alexandrina and Albert: Technical Report
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E c For further information please contact: Email: [email protected] Phone: (08) 8204 1910 Post: Coorong, Lower Lakes and Murray Mouth Program Department of Environment and Natural Resources Reply paid 1047 ADELAIDE SA 5001 Website: www.environment.sa.gov.au Permissive licence © State of South Australia through the Department of Environment and Natural Resources. Apart from fair dealings and other uses permitted by the Copyright Act 1968 (Cth), no part of this publication may be reproduced, published, communicated, transmitted, modified or commercialised without the prior written approval of the Department of Environment and Natural Resources. Written requests for permission should be addressed to: Coorong, Lower Lakes and Murray Mouth Program Department of Environment and Natural Resources GPO Box 1047 Adelaide SA 5001 Disclaimer While reasonable efforts have been made to ensure the contents of this publication are factually correct, the Department of Environment and Natural Resources makes no representations and accepts no responsibility for the accuracy, completeness or fitness for any particular purpose of the contents and shall not be liable for any loss or damage that may be occasioned directly or indirectly through the use of or reliance on the contents of this publication. Printed on recycled paper December 2011 ISBN: 978-1-921800-47-4 Citation This report should be cited as: Muller K.L. (2011). Ecological consequences of managing water levels to prevent acidification in Lakes Alexandrina and Albert: Technical Report. Prepared for Department for Environment and Natural Resources, Adelaide, South Australia. A short summary of this Technical Report is also available: Muller K.L. (2011). Ecological consequences of managing water levels to prevent acidification in Lakes Alexandrina and Albert: Summary Report. Prepared for Department for Environment and Natural Resources, Adelaide, South Australia. December 2011. Ecological consequences of managing water levels to prevent acidification in Lakes Alexandrina and Albert: Technical Report. Prepared by Dr. Kerri L. Muller, Principal, Kerri Muller NRM. for the SA Department of Environment and Natural Resources, as part of the South Australian Government’s $610 million Murray Futures program funded by the Australian Government’s Water for the Future initiative, and the Murray-Darling Basin Authority. December 2011 i Table of Contents ii 1 Acknowledgements 1 Executive Summary 2 1. Introduction 4 1.1. Study Approach 4 1.2. Acid Sulfate Soils 7 1.3. ASS Management scenarios being assessed. 12 2. Methods and Assumptions 14 2.1. Key for consolidated diagrams 19 2.1.1. Action period 19 2.1.2. Recovery period 20 3. Receptor characteristics, selection rationale and baseline condition 22 3.1. Plankton Receptors 22 3.2. Vegetation receptors 24 3.3. Lacustrine macroinvertebrates 25 3.4. Estuarine macroinvertebrates 26 3.5. Fish Receptors 29 3.6. Frog receptors 30 3.7. Bird receptors 30 3.8. Summary of baseline condition 31 3.9. Probable receptor responses to changes in salinity, water level and pH. 33 4. Do-nothing scenario in Lakes Alexandrina and Albert: primary stressor trends and receptor effects 40 4.1. Lake Alexandrina under the Do-nothing scenario 40 4.1.1. Primary stressor trends when pumping to Lake Albert 40 4.1.2. Primary stressor trends when pumping to Lake Albert ceases 42 4.1.3. Ecological receptor responses in Lake Alexandrina 44 4.2. Lake Albert under the Do-nothing scenario 48 4.2.1. Primary stressor trends when pumping 48 4.2.2. Primary stressor trends when pumping ceases 49 4.2.3. Ecological receptor responses in Lake Albert 51 4.3. Conclusions for the Do-nothing scenario 54 5. Seawater scenario in Lakes Alexandrina and Albert, Murray Mouth and Coorong: primary stressor trends and receptor effects. 55 5.1. Lake Alexandrina under the Seawater scenario 55 5.1.1. Primary stressor trends when pumping 55 5.1.2. Primary stressor trends when pumping ceases 57 5.1.3. Ecological receptor responses in Lake Alexandrina 59 5.2. Lake Albert under the Seawater scenario 64 5.2.1. Primary stressor trends when pumping 64 5.2.2. Primary stressor trends when pumping ceases 65 5.2.3. Ecological receptor responses in Lake Albert 66 5.3. Murray Mouth and Coorong under the Seawater scenario 67 5.3.1. Primary stressor trends 67 5.3.2. Ecological receptor responses 70 5.4. Conclusions for the seawater-pumping scenario 71 6. Freshwater scenario in Lakes Alexandrina and Albert: primary stressor trends and receptor effects. 72 6.1. Lake Alexandrina under the Freshwater scenario 72 6.1.1. Primary stressor trends when pumping to Lake Albert 72 6.1.2. Primary stressor trends when pumping ceases 72 6.1.3. Ecological receptor responses in Lake Alexandrina 74 6.2. Lake Albert under the Freshwater scenario 77 6.2.1. Primary stressor trends when pumping 77 6.2.2. Primary stressor trends when pumping ceases 78 6.2.3. Ecological responses in Lake Albert 79 iii 6.3. Conclusions for the Freshwater pumping scenario 82 7. Evaluation of capacity to recover 83 7.1. Introduction 83 7.2. Receptor strategies and conditions required for recovery 84 7.2.1. Plankton 84 7.2.2. Vegetation 85 7.2.3. Lacustrine Macroinvertebrates 91 7.2.4. Fish 93 7.2.5. Southern bell frog 96 7.2.6. Birds 96 7.2.7. General requirements for recovery 97 7.3. Observations from 2010/11 recovery 98 7.3.1 Vegetation 99 7.3.2. Lacustrine Macroinvertebrates 99 7.3.3. Estuarine macroinvertebrates 100 7.3.4. Fish 100 7.3.5. Southern bell frog 101 7.3.6. Birds 101 7.4. Hydrological modelling outputs: Water levels and salinity during the entitlement and average flow recovery periods. 101 7.4.1. Salinity and water level recovery under Entitlement flows 102 7.4.2. Salinity and water level recovery Average flows 102 7.5. Assessment of Ecological capacity to recover 103 7.5.1. Ecological recovery in Lake Alexandrina 104 7.5.2. Ecological recovery in Lake Albert 112 7.6. Conclusions 118 8. Ecosystem states and transitions during the action and recovery periods compared with the Ramsar and baseline states. 124 8.1. The Ramsar and Baseline ecosystem states 126 8.2. Descriptions of the predicted alternate ecosystem states 128 8.2.1. Disconnected Freshwater-derived: Brackish 128 8.2.2. Disconnected Freshwater-derived: Saline 129 8.2.3. Disconnected Freshwater-derived: Marine 130 8.2.4. Disconnected Freshwater-derived: Hypersaline 130 8.2.5. Disconnected Freshwater-derived or Seawater-derived: Ultrasaline 131 8.2.6. Disconnected Freshwater-derived: Acidified and Highly acidified 132 8.2.7. Disconnected Freshwater-derived: Post-Hypersaline 132 8.2.8. Disconnected Freshwater-derived: Post-Acidified or Post-Highly-acidified 133 8.2.9. Connected Freshwater-derived: Post-Hypersaline 134 8.2.10. Connected Freshwater-derived: Post-Acidified or Post-Highly acidified 134 8.2.11. Disconnected Seawater-derived: Hypersaline 135 8.2.12. Disconnected Seawater-derived: Post-Hypersaline 136 8.2.13. Connected Seawater-derived: Post-Hypersaline 137 8.2.14. Connected Freshwater-derived: Fresh 138 8.3. Do-Nothing ecosystem states and transitions 138 8.3.1. Lake Alexandrina 138 8.3.2. Lake Albert 141 8.4. Seawater ecosystem states and transitions 141 8.4.1. Lake Alexandrina 141 8.4.2. Lake Albert 143 8.4.3. Murray Mouth and Coorong 143 8.5. Freshwater ecosystem states and transitions 143 8.5.1. Lake Alexandrina 143 8.5.2. Lake Albert 145 iv 8.6. Conclusions 145 9. Conclusions and Future works recommendations 146 10. References 149 Attachments 156 Attachment A: Description of the Ramsar and baseline ecosystem states for Lakes Alexandrina and Albert, including the key to the receptor icons used in the conceptual diagrams. 157 Attachment B: Baseline condition of receptors in October 2009. 169 Attachment C: Level of stressor effect on the receptors 190 Attachment D: Salinity and pH consequence assessments at receptor level for all scenarios 209 Attachment E: Hydrological Modelling Sites for Lakes Alexandrina and Albert, Murray Mouth and Coorong 328 Attachment F: Assessment of alternative acidification control treatments 329 Attachment G: Receptor responses to Entitlement and Average flow during the recovery period 340 References 346 Glossary of Terms 347 v List of Tables Table 3.1: Phytoplankton receptors showing salinity or pH ranges used to determine receptor groupings and considerations for the consequences assessment provided by the experts. 23 Table 3.2: Zooplankton receptors showing salinity or pH ranges that determined the receptor groupings and considerations for the consequences assessment provided by the experts. 23 Table 3.3: Vegetation receptors present at baseline (October 2009) and considerations for the consequences assessment provided by the experts. 24 Table 3.4: Lacustrine macroinvertebrate receptors present at baseline (October 2009) showing salinity ranges used to determine groupings where relevant and considerations for the consequences assessment provided by the experts. 26 Table 3.5: Estuarine macroinvertebrate receptors present at baseline (October 2009) and considerations for the consequences assessment provided by the experts. 28 Table 3.6: Fish receptors present at baseline (October 2009) and considerations for the consequences assessment provided by the experts. 29 Table 3.7: Frog receptor present at baseline (October 2009) and considerations for the consequences assessment sourced from Mason (2011). 30 Table 3.8: Bird receptor present at baseline (October 2009) and considerations for the consequences assessment provided by the experts. 31 Table 3.9: Summary of baseline conditions for receptors (October 2009). Invasive receptors are indicated by the delta symbol (Δ). 32 Table 3.10: Receptor ranges or thresholds associated with the three primary stressors: salinity, water level (lake area) and pH used for scoring ecological consequences. 34 Table 7.4: Typical habitats and recovery strategies for Lakes’ receptors.