1 introduction 1

1.1 Project Objectives 1
1.2 Structure of this report 1

2 overview of the study area 2

3 scientific panel approach 4

3.1 Ovens Scientific Panel Approach 4
3.2 Reach Assessment Methodology 5

4 Flow regulation in the Ovens River system 7

4.1 Operation of Lake Buffalo 7
4.1.1 Extraction of water from the Buffalo River 8
4.2 Operation of Lake William Hovell 9
4.2.1 Extraction from the King River 10
4.3 Ovens River REALM model 10
4.4 The effects of regulation on river flow regimes 11
4.5 Potential long-term changes to stream flow 16
4.5.1 Ovens streamflow management plan 16
4.5.2 Representativeness of the modeled flow period 17
4.5.3 Climate and landuse change and streamflow 18
4.6 Groundwater 19

5 River geomorphology and Ecology 20

5.1 Geomorphic character of the Ovens and its tributaries 20
5.1.1 History of human impacts on the geomorphology of the Ovens and King Rivers 21
5.1.2 Anthropogenically Induced Sediment loads 24
5.1.3 Anabranch development 24
5.1.4 River management works 24
5.1.5 Likely geomorphic effects of flow regulation 25
5.1.6 Geomorphic features of the Ovens and King Rivers 25
5.2 Water Quality 25
5.2.1 Physico-chemical water quality 25
5.2.2 Other Water Quality Factors 28
5.2.3 Effect of river regulation on water quality 29
5.3 Macroinvertebrates 29
5.3.1 Impact of river regulation on macroinvertebrates 31
5.4 Aquatic and Riparian Vegetation 32
5.4.1 Riparian Vegetation 32
5.4.2 In-channel macrophytes. 33
5.4.3 Macrophytes in billabongs 34
5.4.4 Weeds. 34
5.4.5 Aquatic vegetation of the Ovens River in a broader context. 35
5.4.6 Impact of river regulation on aquatic vegetation 35
5.5 Fish Populations in the Ovens and its tributaries 36
5.5.1 Previous investigations 36
5.5.2 Fish of the Ovens river 37
5.5.3 Connectivity of the Ovens River 39
5.5.4 Fish stockings 39
5.5.5 Fish Kills 40
5.5.6 Cold Water Releases 40
5.5.7 Fish habitat 40
5.5.8 Fish recruitment 41
5.5.9 Impact of river regulation on fish populations 41
5.6 Threatened Species 42
5.6.1 Impact of river regulation on threatened species 42
5.7 Floodplains in the Ovens System 44
5.7.1 Background 44
5.7.2 Reaches 2 and 4. 45
5.7.3 Reach 5. 46
5.7.4 Impact of river regulation on floodplains 46
5.8 Summary of environmental values and threats 46
5.8.1 Ovens in the Murray Darling Basin Context 46
5.8.2 Summary of environmental values associated with the Ovens River system 47
5.9 Summary of threats to environmental values 48
5.10 Summary of the environmental effects of flow regulation 49

6 flow and associated management recommendations 51

6.1 Approach to setting flow recommendations 51
6.2 Flow recommendations for representative reaches 52
6.2.1 Buffalo River below Lake Buffalo 53
6.2.2 King River below Lake William Hovell 53
6.2.3 Ovens River below the Buffalo River confluence 54
6.2.4 Priority reaches for maintaining environmental flows 55
6.3 Other Management Recommendations 55
6.4 Winter Diversions 56
6.5 Key knowledge gaps 57

7 REFERENCES 58