1.1.7.3 Aquatic species and communities

The Maranoa-Balonne-Condamine subregion is included in the Queensland Murray–Darling Freshwater Biogeographic Province (Marshall et al., 2006). This province was identified using the response of its biota, and shows a high degree of dependence on the majority of biophysical processes (e.g. climate, hydrology and habitat factors) used in the assessment (DEH, 2013c). The majority of the Maranoa-Balonne-Condamine subregion was assessed as part of the Aquatic Conservation Assessments in 2011, an analysis that used multiple criteria to determine conservation values of wetlands in the Queensland portion of the Murray–Darling Basin (including the Border Rivers river basin in NSW) (Fielder et al., 2011). The assessment provides baseline ecological and conservation information for the region based on aquatic naturalness, catchment naturalness, diversity and richness, threatened species, special features and representativeness (Fielder et al., 2011). The report found that approximately half of the area assessed received a ‘medium’ score across the assessment criteria and noted that the Maranoa-Balonne-Condamine river basins are relatively data rich in comparison to those further west (Fielder et al., 2011).

Based on 2009 wetland mapping for the Queensland portion of the Murray–Darling Basin, of the the 4000 km² of wetlands approximately one-third are palustrine – vegetated, non-riverine or non-channel systems; one-third are riverine – systems associated within a channel and the remaining third being either lacustrine – wetlands or lakes dominated by open water or artificial and highly modified systems (DEH, 2014a). From 2001 to 2009, the areal extent of riverine and palustrine wetland systems have been reduced by approximately 15% and 11% respectively. During the same period artificial and highly modified systems increased by around 50% (DEH, 2014a).

There are three nationally significant wetlands included in the Maranoa-Balonne-Condamine subregion listed under the Directory of Important Wetlands (Department of the Environment, 2013a). The Gums Lagoon is in the northern part of the Maranoa-Balonne-Condamine subregion (Figure 36) and is a relatively undisturbed wooded swamp in a small (340 ha) reserve of similarly undisturbed woodlands and open forest (Figure 36). The lagoon supports a low open forest of river red gum (Eucalyptus camaldulensis) over perennial tussock grasses (species such as Chloris spp. and Leptochloa digitata) (Department of the Environment, 2013a). Ephemeral semi-aquatic plants (e.g. Marsilea spp. and Cyperaceae spp.) occur during periods of inundation. Large numbers of waterbirds and fish are known to use the lagoon when it is full (Department of the Environment, 2013a).

The Balonne River floodplain is an aggregation of permanent and ephemeral freshwater billabongs and swamps on an inland floodplain in the western part of the Maranoa-Balonne-Condamine subregion (Figure 37). Coolibah (Eucalyptus coolibah) open woodland is the dominant community fringing billabongs and swamps, and on the floodplain (Department of the Environment, 2013a). Occasional black box (Eucalyptus largiflorens) and river red gum (Eucalyptus camaldulensis) also occur in this community (Department of the Environment, 2013a). Open water areas support a variety of aquatic vegetation, and large numbers of waterbirds are known to use the wetlands (Department of the Environment, 2013a). Despite major agricultural disturbance in recent years, the fringing and aquatic vegetation of the wetlands appears to be reasonably intact (Department of the Environment, 2013a).

Lake Broadwater is situated within a conservation park at the edge of the broad valley of the Condamine River and lies to the west of the associated Long Swamp (Figure 36; Department of the Environment, 2013a). The lake has been enhanced by minor levee construction to a height of approximately 0.75 m. Lake Broadwater is a good example of a semi-permanent freshwater lake in an area where these types of water bodies are rare. Four wetland communities are recognised as being associated with the lake:

There are various other wetland and instream environments scattered across the subregion. The ecological values of the Moonie River instream environments are not well described (CSIRO, 2008). The Thallon waterholes (along the Moonie River) have been identified as significant for waterbirds in the Murray–Darling Basin. The waterholes can support between 10,000 and 20,000 waterbirds (Kingsford et al., 1997).

The Morella Watercourse, Boobera Lagoon and Pungbougal Lagoon are located on the Macintyre River floodplain within the Border Rivers river basin. This area floods from the river approximately once in ten years on average (Environment Australia, 2001). Boobera Lagoon is considered to be one of the most important Indigenous places in eastern Australia. The floodplain between Goondiwindi and Mungindi contains large areas of anabranches and billabongs. When flooded, these provide large amounts of organic carbon, and a major energy input to the aquatic ecosystem. Downstream from Goondiwindi small effluent creeks such as Boomi, Callandoon, Dingo and Whalan creeks break off from the main channel and meander across the landscape forming a complex floodplain of billabongs and wetlands that rely on overbank flows (Kingsford, 1999). These wetlands support the breeding of waterbirds listed under the NSW Threatened Species Conservation Act 1995 including: brolgas (Grus rubicunda), black-necked storks (Ephippiorhynchus asiaticus) and magpie geese (Anseranas semipalmata).