Managing environmental flows in an agricultural landscape: the Lower Gwydir floodplain Final Report to the Commonwealth Department of Environment, Water, Heritage and the Arts September 2009 G. Glenn Wilson Tobias O. Bickel Peter J. Berney Julia L. Sisson Cover photos Top: Copeton Dam (Photo: N. Foster); second: Gingham Watercourse at “Willowlee” (Photo: G. Wilson); third: Gingham Watercourse at “ Boyanga Waterhole” (Photo: G. Wilson); bottom: Gingham floodplain at “Crinolyn” (Photo: P. Berney). Managing environmental flows in an agricultural landscape: the Lower Gwydir floodplain Final Report to the Commonwealth Department of Environment, Water, Heritage and the Arts September 2009 G. Glenn Wilson Tobias O. Bickel Peter J. Berney Julia L. Sisson Ecosystem Management School of Environmental and Rural Science University of New England Armidale This report should be cited as: Wilson, G.G., Bickel, T.O., Berney, P.J. & Sisson, J.L. 2009. Managing environmental flows in an agricultural landscape: the Lower Gwydir floodplain. Final Report to the Commonwealth Department of Environment, Water, Heritage and the Arts. University of New England and Cotton Catchment Communities Cooperative Research Centre, Armidale, New South Wales. 181pp © University of New England All rights reserved. This publication is copyright and may not be resold or reproduced in any manner (except parts thereof for bona fide study purposes in accordance with the Copyright Act) without prior consent of the publisher. Dr Glenn Wilson Ecosystem Management School of Environmental and Rural Science University of New England Ph: 02 6773 3078 Fax: 02 6773 2769 Email: [email protected] Inundated wetland on “Bunnor” in December 2007, Gingham Watercourse floodplain. Photo: P. Berney. i Contents Table of Contents Acknowledgements vi Executive summary vii Part 1 Introduction, scoping review, conceptual model and field 1 program design Chapter 1 General Introduction 2 Chapter 2. Review of existing ecological knowledge of the Lower 4 Gwydir aquatic ecology 2.1 Introduction 4 2.2 Hydrology and water quality 4 Rainfall seasonality and hydrology 4 Water quality 5 Water chemistry 6 Turbidity and sediments 7 Nutrients 7 Pesticides 8 2.3 Algae and in-stream vegetation 8 2.4 Floodplain vegetation 9 Vegetation patterns 9 Impacts of flooding and altered flow regime on 10 wetland vegetation Impacts of grazing 12 2.5 Zooplankton and microinvertebrates 13 2.6 Macroinvertebrates 14 2.7 Fish, amphibians and aquatic reptiles 14 Fish 14 Fish barriers and passage 16 Amphibians 17 Aquatic reptiles 18 Chapter 3. Conceptual models of ecological response to flow 20 variability in Lower Gwydir floodplain aquatic habitats 3.1 Introduction 20 3.2 In-stream responses 21 Channel structure 21 Macrophytes 22 Invertebrates 23 Fish 25 3.3 Floodplain responses 25 Physical patch structure 25 Floodplain vegetation 25 Managing Lower Gwydir environmental flows ii Contents Chapter 3 continued Macrophytes 25 Invertebrates 26 Fish 26 Chapter 4. Design of field sampling program 27 4.1 Introduction 27 4.2 Choice of study watercourses and spatial sampling design 28 4.3 Temporal sampling design – sampling specific flow events 30 4.4 Choice of response variables 31 Water chemistry, water quality, algae 34 Invertebrates 34 Fish 34 Wetland plants 34 Part 2 Responses of Lower Gwydir wetland and in-stream 36 environments to flow variability Chapter 5 Long-term analysis of the effects of inundation and 37 grazing on vegetation communities in the Gwydir wetlands 5.1 Introduction 37 5.2 Materials and methods 38 Study sites and inundation history 38 Vegetation monitoring 40 Data analyses 41 5.3 Results 43 5.4 Discussion 51 Chapter 6 Wetland vegetation responses to recent Environmental 54 Contingency Allowance releases 6.1 Introduction 54 6.2 Materials and methods 55 ECA hydrology and study sites 55 Vegetation monitoring 56 Data analyses 57 6.3 Results 59 April 2007 ECA release 59 Inundation levels 59 Species richness 60 Lippia responses to inundation 61 Water couch responses to inundation 61 Functional group responses at each site 63 November 2007 ECA release 68 Inundation levels 68 Vegetation response 68 6.4 Discussion 71 Managing Lower Gwydir environmental flows iii Contents Chapter 7 Responses of water chemistry, fish and aquatic 74 invertebrates to flow variability in Lower Gwydir channels and floodplain waterholes 7.1 Introduction 75 7.2 Materials and methods 76 Sampling sites and timing 76 Water chemistry 76 Fish assemblages 76 Invertebrate assemblages 79 7.3 Results 79 Hydrology 79 Water chemistry – general and spatial patterns 79 Water chemistry – temporal patterns 82 Fish – assemblage composition 87 Fish – temporal variation in abundances 87 Fish – spatio-temporal patterns in assemblage 93 structure Fish – small-scale assemblage variability 93 Fish – population size structure 98 Invertebrates 104 Temporal variation in macrocrustacean abundances 106 Spatial variation in macrocrustacean abundances 106 Benthic microinvertebrates – community composition 106 Benthic microinvertebrates – spatial and temporal 106 variation in abundances 7.4 Discussion 111 Part 3 Communication, and Management implications 117 Chapter 8 Communication of project findings 118 8.1 Introduction 118 8.2 Industry and community stakeholders 118 8.3 Scientific and management audiences 119 8.4 Lower Gwydir Community Forum 120 Chapter 9 Environmental flow management and monitoring 121 in the Lower Gwydir floodplain 9.1 Introduction 122 9.2 Environmental flow design and management 122 Management tools 125 9.3 Monitoring 126 Spatial and temporal design 126 Variables 127 Institutional arrangements 128 9.4 Key areas for future research 129 Soil ecology 129 Fish population ecology 129 Effect of in-stream barriers 130 Effect of habitat structure on fish assemblages 130 References 131 Managing Lower Gwydir environmental flows iv Contents Appendices 139 Appendix 1 Project presentations 140 Appendix 2 Project outputs and conference abstracts 144 Managing Lower Gwydir environmental flows v Acknowledgements Acknowledgements The present study was funded by the Australian Government, with additional support provided by the Cotton Catchment Communities Cooperative Research Centre and the University of New England. The authors particularly thank Gayle Stewart, Bruce Gray and Ian Krebs from the Commonwealth Department of the Environment, Water, Heritage and the Arts, and Lynda George and Kym Orman from the Cotton CRC, for their assistance with project administration and reporting. No project of this nature can function successfully without the support of landholders on whose property the field sites are located. We were strongly encouraged by the cheerful willingness of Lower Gwydir landholders to allow site access, the occasional quad bike loan, assistance with use of the grazing exclosure sites, accommodation and even the occasional assistance with processing fish catches: Bruce and Jen Southeron, “Old Dromana”; Lloyd and Bryce Wood, “Bullarah”; Sam Kirby, “Westholme” ; Howard Blackburn, “Crinolyn”; Jon Greer, ‘Birrah”; Shane Murphy, “Munwonga”; Guy Murphy, Baroona Waterhole; Rod Fulton-Kennedy, “Willowlee”; Vourn Houlahan, “Talmoi”; Joe Robinson, “Telleraga”; Stuart Boydell, “Weematong”; Fred Barlow, “Currigundi”; Gerry and John Carrigan, “Allambie”; and Phil Flemming and the Murphy family, “Old Boyanga”. Numerous colleagues provided invaluable assistance with fieldwork, including Liz Savage and Jane Humphries (Border Rivers – Gwydir Catchment Management Authority), Jeff Kelleway, Yoshi Kobayashi and Jennifer Spencer (NSW Department of Environment, Climate Change and Water). Rob McCosker and John Duggin from Ecosystem Management at the University of New England, allowed access to past data and information about their wetland vegetation study sites, and Ian Telford from the Beadle Herbarium at the University of New England provided herbarium space and materials and assistance with plant identification. Daryl Albertson, NSW Department of Environment, Climate Change and Water, provided advice on sites, ECA flows and numerous aerial photos. Members of the Gwydir ECA Operations Advisory Committee also provided useful advice and helped frame the study in the critical management context. We also received strong support from colleagues and their organisations with funding and organising the July 2008 Lower Gwydir Community Forum, particularly Janelle Montgomery and Lauryn Hanna (NSW Department of Primary Industries), Sara Foot, Ian Schwartz, Tariful Islam, Louise McMahon and Liz Savage (Border Rivers – Gwydir Catchment Management Authority), Neil Saintilan (NSW Department of Environment, Climate Change and Water) , Richard Moxham and Donna Ironfield (Murray-Darling Basin Authority), David Aber and Mike Montgomery (Moree Plains Shire Council), Paula Jones (Cotton Catchment Communities CRC), and James Houlahan and Michael Murray (Gwydir Valley Irrigators Association). The various steering committee members and their organisations are also thanked for their support of the study, attendance at committee meetings, and feedback on project progress and outputs: Gayle Stewart, Bruce Gray and Ian Krebs, Commonwealth Department of Environment, Water, Heritage and the Arts; Michael Murray, Gwydir Valley Irrigators Association; Jim Southeron, Lower Gwydir Water Users; Paula Jones, Cotton Catchment Communities Cooperative Research Centre; Liz Savage, Border Rivers – Gwydir Catchment Management Authority; David Ward, NSW Department of Primary Industries; Yoshi Kobayashi,