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(PDF 1.75MB) | Report of the Broken River Scientific Panel on the environmental condition and flows of the Broken River and Broken Creek
Peter Cottingham Mike Stewardson Jane Roberts Leon Metzeling Paul Humphries Terry Hillman Graeme Hannan |
Contents
1 introduction 1
1.1 Project Objectives 1
1.2 Structure of this report 1
2 overview of the study area 3
3 scientific panel approach 5
3.1 Broken Scientific Panel assessment framework 5
3.2 Approach to developing environmental flow recommendations 6
3.2.1 The Flow Events Method 6
4 history of Flow regulation in the BROKEN River system 9
4.1 Overview of the system 9
4.2 Lake Nillahcootie and Lake Mokoan 9
4.2.1 Operation of Lake Nillahcootie 9
4.2.2 Operation of Lake Mokoan 10
4.3 Operation of Casey’s Weir and Gowangardie Weir 10
4.3.1 Casey’s Weir 10
4.3.2 Gowangardie Weir 10
4.4 Modifications to floodplain drainage 11
4.5 Potential developments in flow regulation 11
4.5.1 Tungamah pipeline 11
4.5.2 Future of Lake Mokoan 11
4.5.3 Potential long-term changes to stream flow 12
5 Hydrolgical impacts of flow regulation 14
5.1 System Operation 14
5.2 Impact of current regulation on the Broken River flow regime 16
5.3 Impact of future water management scenarios on the Broken River flow regime 21
5.4 Impact of current regulation and future water management scenarios on the Broken Creek flow regime 24
6 River geomorphology and Ecology 26
6.1 Geomorphology 26
6.2 Water Quality 26
6.3 Riparian and In-channel vegetation 30
6.3.1 Evaluating effects of flow modifications on riverine vegetation 31
6.4 Macroinvertebrates 36
6.4.1 Broken River 36
6.4.2 Broken Creek 39
6.4.3 Effects of regulation on invertebrates 39
6.5 Fish 40
6.5.1 Fish species across the study area 40
6.5.2 Habitat availability 43
6.5.3 Fish movement and fish passage 44
6.5.4 Stocking of fish 45
6.5.5 Relationship with flow 46
6.6 Threatened species 47
6.7 River channel – floodplain linkages 47
6.7.1 Impact of river regulation on floodplains 49
6.8 Summary of environmental values and threats 49
6.9 Summary of the environmental effects of flow regulation 49
7 management recommendations 53
7.1 Environmental flow recommendations for the Broken River 53
7.1.1 Potentially important flow events 53
7.1.2 Rapid flow reductions 56
7.1.3 Rapid flow increases 59
7.1.4 Slow water habitat 61
7.1.5 Drying of the stream bed 63
7.1.6 Inundation of channel benches 65
7.1.7 Shallow water habitat 65
7.1.8 Flow into anabranches and floodplain inundation 67
7.2 Summary of flow recommendations 68
7.2.1 Hypotheses linking flow recommendations to measurable outcomes 69
7.3 Implications of changes to the operation of Lake Mokoan 71
7.4 Management of Broken Creek 74
7.4.1 Proposed Tungamah pipeline 74
7.4.2 Management Recommendations 75
7.5 Other Management Recommendations 75
7.6 Key knowledge gaps 76
8 REFERENCES 78
APPENDIX 1 EXPERIENCE OF THE BROKEN SCIENTIFIC PANEL.……. 82
APPENDIX 2 DAILY FLOW AND HYDRAULIC MODELLING….…………. 85
APPENDIX 3 WATER QUALITY STATISTICS.………………………………. 88
APPENDIX 4 THREATENED SPECIES …...………………………………….... 95
APPENDIX 5 INDICATIVE FLOW REGIME OF BROKEN CREEK BETWEEN CASEY’S WEIR AND KATAMATITE……..……... 98
Acknowledgements
The Scientific Panel wishes to extend its thanks to the following people and organisations who assisted with their knowledge, data and opinions:
Paul Bennett Department of Natural Resources and Environment
Gary Howell Department of Natural Resources and Environment
Barry James Department of Natural Resources and Environment
Kes Kesari Department of Natural Resources and Environment
Joy Sloan Department of Natural Resources and Environment
Nelum Piyasena Department of Natural Resources and Environment
Gerry Quinn CRC Freshwater Ecology`
Thiess Environmental Services
Goulburn Valley Irrigation Services
This report was funded by the Department of Natural Resources and Environment on behalf of the Broken Bulk Entitlement Group.
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