The approach detailed in Section 2.3.3.1 identified 34 landscape classes, which are aggregated into five landscape groups based on broad-scale distinctions in their water dependency and association with GAB or non-GAB GDEs, floodplain/non-floodplain or upland/lowland environments and remnant/human-modified habitat types (Table 7). Most of the PAE (72.2%) is classified in the ‘Human-modified’ landscape group, which includes agricultural, urban and other intensive land uses (Table 7).
The distribution of remnant vegetation in the five landscape groups is shown in Figure 18. Among those areas mapped under the Queensland regional ecosystems (classed as remnant vegetation) (Table 7), the largest proportion (19.8%) are classed as ‘Dryland remnant vegetation’ (Table 7). ‘Dryland remnant vegetation’ are not considered water dependent (i.e. solely dependent on incident rainfall) because they do not intersect floodplain, wetland or GDE features. The ‘Floodplain or lowland riverine (including non-GAB GDEs)’ landscape group covers approximately 5% of the PAE. Of the remaining non-floodplain landscapes, the ‘Non-floodplain or upland riverine (including non-GAB GDEs)’ landscape group covers 2.2% of the PAE and the ‘GAB GDEs (riverine, springs, floodplain or non-floodplain)’ landscape group covers 1.3% of the PAE (Table 7).
Table 7 Land area and percentage of total area in each landscape class in the Maranoa-Balonne-Condamine preliminary assessment extent (PAE)
GAB = Great Artesian Basin, GDE = groundwater-dependent ecosystem
Data: Bioregional Assessment Programme (Dataset 5)
GAB = Great Artesian Basin, GDE = groundwater-dependent ecosystem
Data: Bioregional Assessment Programme (Dataset 5)
‘Temporary lowland streams’ (47%) in the ‘Floodplain or lowland riverine (including non-GAB GDEs)’ landscape group and ‘Temporary upland streams’ (36%) in the ‘Non-floodplain or upland riverine (including non-GAB GDEs)’ landscape group are the most common landscape classes in the stream network. Figure 18 shows the distribution of streams in each landscape group in the Maranoa-Balonne-Condamine PAE. Streams that contain GDEs are less widespread, with streams that contain GAB GDEs covering 15% and streams that contain non-GAB GDEs covering 6% of the stream network in the PAE (Table 8). Figure 19 shows the distribution of catchments within the Maranoa-Balonne-Condamine PAE classed as either ‘upland’ or ‘lowland’. Those stream segments classified as ‘upland’ tend to be found along the eastern and northern portions of the PAE (particularly in the Fitzroy River and Burnett River basins) and are associated with the Main Range Volcanics and sandstone outcropping areas and other elevated portions of the Maranoa-Balonne-Condamine PAE (Figure 19). ‘Lowland’ streams are predominately in the Condamine-Culgoa, Moonie and Border river basins (Figure 19).
Table 8 Length of stream network in each landscape class in the Maranoa-Balonne-Condamine preliminary assessment extent (PAE)
GAB = Great Artesian Basin, GDE = groundwater-dependent ecosystem
Data: Bioregional Assessment Programme (Dataset 5)
Dataset: Bioregional Assessment Programme (Dataset 5)
Most springs and spring complexes in the Maranoa-Balonne-Condamine PAE (86%) are associated with GAB aquifers (Table 9). Figure 18 shows that most of the GAB springs are located in the north of the PAE. Non-GAB springs are associated with Cenozoic or Main Range Volcanics aquifers, which are located along the eastern boundary of the PAE (Figure 18).
Table 9 Springs in each landscape class in the Maranoa-Balonne-Condamine preliminary assessment extent
GAB = Great Artesian Basin, GDE = groundwater-dependent ecosystem
Floodplain or lowland riverine (including non-Great Artesian Basin groundwater-dependent ecosystems)
Floodplains can be broadly defined as a collection of landscape and ecological elements exposed to inundation or flooding along a river system (Rogers, 2011). The floodplain landscapes of the Maranoa-Balonne-Condamine PAE are predominantly lowland-dryland systems incorporating a range of wetland types such as riparian forests, marshes, billabongs, tree swamps, anabranches and overflows (Rogers, 2011). Floodplains are underlain by alluvial aquifers, which are formed from deposited sediments such as gravel, sand, silt and/or clay within river channels or on floodplains. Water is stored and transmitted to varying degrees through inter-granular voids meaning that alluvial aquifers are generally unconfined, shallow and have localised flow systems (DSITI, 2015). Groundwater expressed at the surface supports GDEs occupying drainage lines, riverine water bodies, and lacustrine and palustrine wetlands. Ecosystems associated with the subsurface expression of groundwater include fringing riverine communities and woodlands occupying the back plain environment.
Figure 20 is an example of the distribution of landscape classes along a typical floodplain area, showing part of the Condamine Alluvium near Dalby. The river channel is fringed by the riparian zone, which is predominantly classed as ‘Floodplain, non-GAB GDE’ with smaller areas of the ‘Floodplain, non-GAB GDE, near-permanent wetland’, ‘Floodplain, non-GAB GDE, temporary wetland’, ‘Floodplain, near-permanent wetland’ and ‘Floodplain, temporary wetland’ landscape classes. Adjacent to the riparian zone is the back plain environment, representing the transition between the frequently flooded river channel and the upland environment. The back plain environment contains floodplain woodlands and various types of wetlands with varying degrees of groundwater dependency (Holloway et al., 2013). The back plain environment of the Condamine Alluvium is predominantly classed as ‘Floodplain remnant vegetation’. Important woodland species in the back plain environment include black box (Eucalyptus largiflorens), coolibah (Eucalyptus coolabah), river coobah (Acacia stenophylla) and other Eucalyptus spp., shrubs and grasses.
Figure 20 Distribution of landscape classes in the Condamine Alluvium near Dalby
GAB = Great Artesian Basin, GDE = groundwater-dependent ecosystem
Data: Bioregional Assessment Programme (Dataset 5)
Another typical floodplain environment is along the Balonne River in the western portion of the PAE, which is shown conceptually in Figure 21 and spatially in Figure 22. The conceptual model shows that inundation from flooding defines the riparian zone, with groundwater movement being predominantly downward from the surface to the alluvial aquifers. Floodplain trees are able to access groundwater in the alluvial aquifers. Figure 22 shows that the ‘Floodplain near-permanent wetland’ and ‘Floodplain near-permanent wetland, non-GAB GDE’ landscape classes are located adjacent to major river channels and are analogous to riparian forests. River red gum (Eucalyptus camaldulensis), co-occurring Eucalyptus and she-oak (Casuarina cunninghamiana) species and, in some cases, Gallery rainforest communities, are the dominant vegetation communities in ‘Floodplain, near-permanent wetland’ landscape class areas (Figure 22). The back plain environment of the Balonne River contains the ‘Floodplain remnant vegetation’, ‘Floodplain non-GAB GDEs’ and ‘Floodplain, temporary wetland’ classes that have a temporary water regime and reduced flooding frequency, duration and depth in comparison to the riparian zone (Figure 22). The ‘Floodplain, non-GAB GDEs’ landscape class tends to be interspersed along the riparian and back plain environments and groundwater use is influenced by groundwater depth and salinity (Holloway et al., 2013; Roberts and Marston, 2011). Several listed ecological communities are associated with the ‘Floodplain or lowland riverine (including non-GAB GDEs)’ landscape group. This includes the ‘Coolibah - Black Box Woodlands of the Darling Riverine Plains and the Brigalow Belt South Bioregions Threatened Ecological Community’ listed under the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) and threatened regional ecosystems listed under Queensland’s Vegetation Management Act 1999; ‘Gallery rainforest (notophyll vine forest) on alluvial plains Endangered Regional Ecosystem’ (as dominant component) and ‘Eucalyptus camaldulensis fringing open forest Endangered Regional Ecosystem’ (as dominant component) (Table 10).
The light blue and brown areas on the land surface delineate the frequently inundated riparian zone and the less frequently flooded back plain environment. The arrows indicate the direction of water movement, with the dashed arrow line indicating variable groundwater leakage and the crossed (red) arrow line, indicating negligible groundwater movement. The blue dashed horizontal line indicates the position of the water table within the cross-section.
Source: DEHP (2015a)
Figure 22 Location of floodplain landscape classes along a reach of the Balonne River
GAB = Great Artesian Basin, GDE = groundwater-dependent ecosystem
Data: Bioregional Assessment Programme (Dataset 5)
Table 10 Location, associated communities, threatened ecological communities, water dependency and nature of water dependency for each landscape group
|
Landscape group |
Location |
Associated communities |
Listed ecological communities |
Nature of dependency |
Water sources and water regime (spatiala, temporalb) |
|
Floodplain or lowland riverine (including non-GAB GDEs) |
Land zone 3 – Quaternary alluvial systems |
|
|
|
Surface water (regional, episodic) and groundwater (landscape, aseasonal/intermittent) |
|
GAB GDEs (riverine, springs, floodplain, non-floodplain) |
|
|
|
|
|
|
Non-floodplain or upland riverine (including non-GAB GDEs) |
|
|
|
|
|
|
Dryland remnant vegetation |
Upland areas (excluding floodplain; Land Zone 3) |
Various woodland, shrubland and grassland communities not associated with floodplain, GDE or wetlands |
Brigalow (Acacia harpophylla dominant and co-dominant) Threatened Ecological Community and several of the associated Queensland regional ecosystemsc |
Reliant on locally stored soil water |
Rainfall and runoff, (localised, temporary) |
|
Human-modified |
Irrigated agriculture concentrated around Condamine Alluvium and other floodplain systems |
Herbaceous pasture and crop species. Plantation tree species. Some small areas of remnant native vegetation. |
Listed ecological communities are not associated with the human-modified landscape group. |
|
Rainfall (local, intermittent); surface water (local-regional, temporary-near-permanent); groundwater (local-regional, temporary-near-permanent) |
aSpatial scale of the flow system and its predominant pattern, refers to local (100 to 104 m2), landscape (104 to 108 m2) or regional (108 to 1010 m2) scales.
bTemporal scale of the water regime, refers to the timing and frequency of the reliance on a particular water source.
cThis EPBC-listed community and the Queensland regional ecosystems associated with Brigalow are common.
GDE = groundwater-dependent ecosystem, GAB = Great Artesian Basin
Great Artesian Basin groundwater-dependent ecosystems (riverine, springs, floodplain, non-floodplain)
This landscape group represents landscape classes that are hydrologically connected to GAB aquifers. GAB springs are surface expressions of groundwater sourced from aquifers contained in the Triassic, Jurassic and Cretaceous sedimentary sequences associated with the GAB (Habermehl, 1982). Spring ecosystems contain many locally endemic species and plant communities and have significant ecological, economic and cultural values (Fensham and Fairfax, 2003). Of the 94 GAB spring wetlands surveyed in a recent assessment of the Surat cumulative management area (Fensham et al., 2012), most (58) were listed under the EPBC Act as a threatened ecological community, while 34 springs were listed both as a threatened ecological community and for individual species found in the springs (Table 10). Three springs were listed for individual species found in the springs (Fensham et al., 2012).
Source: DEHP (2013a)
Apart from ecosystems associated with spring vents, other GDEs associated with GAB aquifers are located in areas where GAB sedimentary layers outcrop at or near the surface in the eastern and northern parts of the PAE. The GAB aquifer outcrop areas are predominantly GAB recharge areas, where rainwater percolates into the GAB aquifers between confining layers (Figure 23). However, fractures, inter-granular pores and weathered zones can cause groundwater to discharge locally at or near the surface in these areas (DSITIA, 2015). This is referred to as ‘rejected recharge’. These features describe the ‘Non-floodplain GAB GDE’ landscape class, which can also include near-permanent and temporary wetlands where groundwater is expressed at the surface (Figure 22). The plant communities of these GDEs tend to be dominated by Eucalyptus, Corymbia and Angophora spp. (Table 10).
Non-floodplain or upland riverine (including non-GAB GDEs)
The landscape classes in the ‘Non-floodplain or upland riverine (including non-GAB GDEs)’ landscape group include upland streams and wetlands that are not associated with floodplains or GAB GDEs. Non-floodplain, temporary wetlands on low permeability, shrink-swell cracking clays sometimes form gilgai (meaning ‘small waterhole’ wetlands) (DEHP, 2013b). These temporary wetlands are essentially small depressions within the Cenozoic clay deposits that are interspersed with mounds and depressions over relatively small distances (approximately 2 m; Chertkov, 2005). Spatial variation in infiltration occurs as these clays swell when wet, causing cracks to close and water to pool on the surface (Chertkov, 2005).
The most common vegetation associated with non-floodplain wetlands is Brigalow (Acacia harpophylla) and belah (Casuarina cristata) (Table 10). Flora associated with the wet areas include grasses, aquatic herbs, sedges and rushes (DEHP, 2013b). These wetlands are ecologically important components of the Brigalow Belt in southern Queensland and support threatened EPBC Act-listed species such as the yakka skink (Egernia rugosa). The Brigalow threatened ecological community listed under the EPBC Act ('Brigalow (Acacia harpophylla dominant and co-dominant)') occurs in areas classified as dryland remnant vegetation as well as areas thought to be water dependent (e.g. ‘Floodplain remnant’ landscape class).The nature of wet and dry phases within these wetlands is determined by localised runoff from rainfall, which means that their dependency on flow systems at larger scales is likely to be negligible (Table 10).
Non-GAB GDEs includes the GDEs associated with inland sand ridges (Figure 24) and permeable rock or basalt aquifers (Figure 25). Inland sand ridges occur outside the most elevated portion of the floodplain or alluvial land zones and are classed as ‘Non-floodplain, non-GAB GDEs’. They are more common in the western region of the PAE (Figure 22). Inland sand ridges support Corymbia and Eucalyptus species with varying reliance on perched aquifers within the sandy profile (Holloway et al., 2013).
In permeable rocks, groundwater is transmitted and stored through fractures, inter-granular spaces or weathered zones and is typically discharged to the surface at contact zones between two rock types (Figure 25) (DSITI, 2015). Associated plant communities tend to be open woodlands, dominated by Eucalyptus spp. and often contain shrub and grass (Pennisetum spp.) layers (Table 10). Aquifers in permeable rocks may also support ecosystems within the aquifer itself, which is sometimes indicated by the presence of stygofauna (DEHP, 2015c). These basalt aquifer landscape features are located in the eastern portion of the PAE, in the more elevated areas of the Main Range Volcanics of the Condamine-Balonne river basin. These GDEs are characterised by localised flow systems that have intermittent/aseasonal connectivity (Figure 25 and Table 10) (DSITI, 2015).
Source: DEHP (2015b)
Source: DEHP (2015c)
Dryland remnant vegetation
This landscape group represents a large component of those landscapes classified as ‘remnant’ in the Queensland regional ecosystem mapping (Queensland Herbarium, Dataset 1). The term ‘dryland’ implies that this landscape class is reliant on incident rainfall and local runoff and does not include features in the landscape identified as wetlands, GDEs or springs. The associated communities are highly variable and cover many different types of woodland, shrubland and grassland (Table 10). The Brigalow threatened ecological community listed under the EPBC Act ('Brigalow (Acacia harpophylla dominant and co-dominant)') occurs across some areas classified as ‘Dryland remnant vegetation’ as well as being distributed across those landscape classes thought to be water dependent (e.g. ‘Floodplain remnant’ landscape class).
Human-modified landscapes
Most of the PAE (72.2%) is dominated by human-modified landscapes used for agricultural production, mining and urban development (Table 7). The water dependency of the landscape classes derived from this landscape group ranges from a heavy dependence on groundwater and surface water extracted from nearby aquifers and streams (e.g. intensive uses and production from irrigated agriculture and plantations), through to dryland cropping and grazing reliant on incident rainfall and local surface water runoff (e.g. production from dryland agriculture and plantations). The distribution of landscape classes on the Condamine Alluvium near Dalby shows that most of the landscape classes are in the ‘Human-modified’ landscape group (Figure 20). Deeper-rooted vegetation, including remnant vegetation and plantations may tap into groundwater within certain landscapes. Intensive areas, such as townships, often have a strong reliance on groundwater and surface water via bores and river offtakes. Figure 26 shows the location of human-modified land uses around a natural wetland conceptually, including dryland cropping, grazing, irrigated agriculture and mining.
Source: Adapted from DEHP (2012)
