Inland Waters Regional NRM Assessment | 2015 1 Prepared by: NRM Planning @ Northern Gulf Resource Management Group Ltd Lead author: Jim Tait, Econcern Consulting Contributors: Sarah Rizvi & Natalie Waller Reviewers & Advisors: Alf Hogan, Amanda Stone, Andrew Brooks, Brynn Matthews, Damien Burrows, Jon Brodie, Jeff Shellberg, Malcolm Pearce, Mark Kennard, Michaelie Pollard, Michele Burford, Rob Ryan, Sarah Connor, Stephen Mackay, Terry Valance, Timothy Jardine Design work: Clare Powell & Federico Vanni Editing: Nina Bailey Photography: Federico Vanni This project is supported by the Northern Gulf Resource Management Group Ltd through funding from the Australian Government. Inland Waters Regional NRM Assessment | 2015 2 CONTENTS 1.1. INTRODUCTION - NORTHERN GULF FRESHWATER ECOSYSTEM NRM ISSUES ............................................ 5 1.2. ASSETS AND STATUS .................................................................................................................................................. 8 1.2.1. Freshwater Environments .................................................................................................................................... 8 1.2.2. Freshwater Biodiversity .................................................................................................................................. 38 1.2.3. Freshwater Fishery Resources ........................................................................................................................ 51 1.2.4. Water Resources .............................................................................................................................................. 55 1.3. SUMMARY OF THREATS AND STRATEGIC MANAGEMENT RESPONSES ..................................................... 69 1.4.1. Catchment Land Use, Development and Management .................................................................................. 69 1.4.2. Water Resource Development ...................................................................................................................... 81 1.4.3. Exotic Species ................................................................................................................................................... 84 1.4.4. Instream Barriers .............................................................................................................................................. 90 1.4.5. Outdoor Recreation and Fishery Sustainability ......................................................................................... 91 1.4.6. Global Warming and Climate Change ....................................................................................................... 94 1.5. CLIMATE CHANGE RISK ASSESSMENT FOR INLAND WATERS ....................................................................... 98 1.4. REFERENCES ............................................................................................................................................................. 105 APPENDIX 1. RIVER BASIN NRM PLANNING CONTEXT .............................................................................................. 116 APPENDIX 2. NORTHERN GULF REGION FRESHWATER FISH SURVEYS ................................................................. 117 APPENDIX 3. NORTHERN GULF PROTECTED AREAS AND RESERVES ....................................................................... 119 APPENDIX 4. ECONOMIC, SOCIAL AND ECOLOGICAL OUTCOMES OF THE AMENDED (2014) GULF WATER RESOURCE PLAN 2007 ...................................................................................................................................................... 121 1. Economic outcomes ................................................................................................................................................ 121 2. Social outcomes ...................................................................................................................................................... 121 3. Ecological outcomes .............................................................................................................................................. 122 Inland Waters Regional NRM Assessment | 2015 3 Lower Norman River Gilbert River Mid Basin Lower Staaten River main channel and floodplain Rifle Creek, upper Mitchell River Basin lagoons and Wyabba Creek confluence. FIGURE 1.1 RIVERSCAPES FROM THE FOUR RIVER BASINS COMPRISING THE NGRMG PLANNING AREA. Inland Waters Regional NRM Assessment | 2015 4 INTRODUCTION 1.1 INTRODUCTION- NORTHERN GULF FRESHWATER ECOSYSTEM NRM ISSUES The Northern Gulf planning region is comprised of four river basins, the Mitchell, Staaten, Gilbert and Norman. These four rivers collectively drain an area of over 190,000 km2 distributed across four biogeographic regions or ‘bioregions’ (Figure , Table 1.1) and 19 subregions (Sattler and Williams 1999). The four basins are biogeographically differentiated with the Staaten and Norman, lying almost entirely within the Gulf Plains, while the upper half of the Gilbert Basin and upper third of the Mitchell Basin drain the Einasleigh Uplands (Appendix 1). The eastern margin of the Mitchell Basin also extends into the Wet Tropics, while its northern extent includes the Cape York Peninsula Bioregion. These various bioregional settings support a diverse range of freshwater environments which include seasonal lowland rivers, coastal and floodplain wetlands, spring fed rocky gorges and perennial rainforest mountain streams. FIGURE 1.2 BIOREGIONAL COMPOSITION NORTHERN GULF RIVER BASINS TABLE 1.1 RIVER BASIN AREA AND MAJOR SUB-CATCHMENTS River Basin Area km2 Major Sub-catchments Norman 50,302 Clara, Yappar, Norman and Carron Rivers Gilbert 46,789 Smithburne, Etheridge, Einasleigh and Gilbert Rivers Staaten 25,665 Clark, Vanrook creeks, Red and Staaten Rivers Mitchell 75,426 Lynd, Tate, Walsh, Palmer, Alice and Mitchell Rivers Inland Waters Regional NRM Assessment | 2015 5 INTRODUCTION Rainfall across all river basins is highly seasonal and concentrated in the summer, monsoon-influenced wet season. There is a gradient in mean annual rainfall from the more northern Mitchell River basin which is dominated by a tropical savanna climate with >1200 mm rainfall, to the southern Norman River basin which is dominated by a hot grassland climate and receives <600 mm rainfall in its south (NLWRA 2002). Variability in climate creates variable hydrological conditions and flow regimes between and within Northern Gulf river basins. Within the more watered main stems of the Mitchell and upper Gilbert River basins, a stable summer flow regime occurs while in more western and southern basins, summer flow is predictable but intermittent. Smaller catchment systems have greater intermittency and less predictable summer flows (Kennard et al 2010). The limited development of water resources within Northern Gulf river basins and their retention of near natural flow regimes are recognised to underpin the health of their aquatic ecosystems and define them as ecological assets of global significance (Leigh and Sheldon 2008). Given the concentration or rainfall within the December to March wet season, flooding is common across the extensive river floodplains and low gradient coastal plains of the Northern Gulf region and all basins exhibit flow connectivity via distributary networks during major flood events (Hydrobiology 2005). Overbank flows associated with riverine systems creates extensive areas of vegetated swamps (palustrine wetlands) and also floodplain lagoon and lake (lacustrine) wetland systems. As for rivers, the majority of ‘off river’ wetlands are highly seasonal, with only a small but ecologically important proportion retaining water through the annual dry season (Burrows 2004a). In a seasonally dry environment like the Northern Gulf, groundwater plays an important role in the hydrology and ecology of freshwater ecosystems. It influences the flow regimes of streams, the availability of aquatic refugia during the dry season and the composition and structure of riparian vegetation communities (Hydrobiology 2005, Cook et al 2011). Groundwater aquifers within the Northern Gulf include shallow alluvial sand beds and beach ridge deposits, Tertiary sediments, fractured rock basements and sandstones within the Carpentaria and the Great Artesian Basin which underlies much of the region (CSIRO 2009). Rivers draining the Northern Gulf represent an eastern component of a contiguous band of relatively undeveloped tropical river systems that drain the entire northern margin of the Australian continent. These rivers collectively represent the greatest extent of high integrity natural rivers remaining in Australia, and one of the main remaining extents of natural tropical rivers globally (Pusey 2011, Arthington 2012). As such they have globally significant ecological values and nationally important cultural, social and economic values (Pusey and Kennard 2009, Pusey 2011). The values associated with Northern Gulf freshwaters are described more fully in the description of assets (following section) but include: • Wetland aggregations listed in the directory of nationally important wetlands in Australia (described below in section 1.2.2.4); • Australia’s largest distributary delta and greatest density of ox-bow lagoons, both in the Mitchel Basin (Blackman et al 1999, Cook et al 2011); • The second highest levels nationally of river basin (Mitchell) freshwater fish species richness and endemism (Pusey 2011); • Population