The approach for assessing potential for () and is discussed in companion submethodology M10 (as listed in Table 1) for analysing impacts and risks (). The focuses the attention of the analysis on areas where there may be changes in and/or that are attributable to .
The principal focus of the BA’s impact analysis is on water-dependent assets that are nominated by the community, or are recognised as being significant at state- or national-level (e.g. listed as a matter of national environmental significance under the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999). These may have a variety of values, including ecological, sociocultural and economic values. The (companion product 1.3 for the Galilee subregion (); Bioregional Assessment Programme, ) provides a simple and authoritative listing of the assets within the . The register is a compilation of assets identified in databases compiled by several natural resource management groups in the , as well as Australian and Queensland government databases. Additional assets were also supplied during several Galilee subregion BA assets workshops with various experts and organisations with local knowledge, held in September 2014 (in Longreach and Richmond), and October 2014 (in Brisbane). The identified assets compiled from all sources were assessed by the Assessment team for fitness for BA purpose, location within the assessment extent and water dependency. Assets that satisfied the requirements were considered in the impact and analysis reported in this product.
Landscape classification is fundamental to the impact and risk analysis and was used to discretise the heterogeneous landscape across the Galilee assessment extent into a manageable number of landscape classes for the impact and risk analysis. For BA purposes, a landscape class is an ecosystem with characteristics that are expected to respond similarly to changes in groundwater and/or surface water due to coal resource development. Landscape classes were used to reduce the complexity of assessing potential impacts on a large number of water-dependent assets by focusing on the hydrological drivers and interactions relevant for regional-scale assessment. Although some degree of inherent heterogeneity invariably exists, individual landscape classes are nevertheless considered by the Assessment team to share a greater level of biophysical attributes (in comparison to different landscape classes), and hence are regarded as appropriate for the regional-scale focus of the BA for the Galilee subregion.
The landscape classes provide a meaningful scale for understanding potential ecosystem impacts and communicating them through their more aggregated system-level view. The landscape classification for the Galilee subregion is described in Section 2.3.3 of companion product 2.3 () and the methodology that underpins it is described in companion submethodology M05 (as listed in Table 1) for developing a conceptual model of causal pathways ().
Potential hydrological changes were assessed by overlaying the extent of a landscape class or asset on the zone of potential hydrological change due to additional coal resource development. For the landscape classes or assets that lie wholly outside the zone, hydrological changes (and hence any potential ecosystem or asset-level impacts) are , and are thus ruled out in terms of further analysis. Section 3.4.2 identifies landscape classes in the Galilee subregion that can be ruled out from potential impacts on this basis.
Where an asset or landscape class wholly or partially intersects the zone of potential hydrological change, there is the potential for impact. This does not necessarily mean there will be an impact, but rather, based on the magnitude of the hydrological change, the possibility of an impact cannot be ruled out and further investigation is required. The nature of the water dependency of the landscape class can also be important at this stage of the analysis. For example, if the water dependence of a landscape class relates to to support seedling establishment, but the significant hydrological changes in the nearby stream relate only to low-flow variables (i.e. flows that are contained within the streambanks), then it may be possible to rule the landscape class out of further consideration because it is unlikely to be impacted.
Four were built, representing three in the Galilee subregion (Table 8). These were used to quantify the potential impact of the predicted hydrological changes on a selected within the receptor impact model (companion product 2.7 for the Galilee subregion ()). Meaningful and receptor impact variables (Table 8) were elicited from experts (listed in Table 3 in companion product 2.7 for the Galilee subregion ()) during qualitative and receptor impact model workshops and subsequent correspondence. A full description of receptor impact modelling is described in companion submethodology M08 (as listed in Table 1) (), with its application to the Galilee subregion in companion product 2.7 (). This includes Table 4 in Section 220.127.116.11.6 of companion product 2.7 which summarises some of the assumptions made for the receptor impact modelling, the implications of those assumptions for the results, and how those implications are acknowledged through the BA workflow and ultimately within this product. Examples of the main assumptions include the simplification of complex ecological systems, the segregation of the system into discrete classes that are assumed to respond similarly to hydrological changes, and the assumption that areas of landscapes classes remain constant over time (see Table 4 in companion product 2.7 for the Galilee subregion () for the complete list of assumptions). The specific implications or flow-on effects of these assumptions are further explained in the respective sections for individual landscape classes in companion product 2.7 (). It is also important to note that the outputs from receptor impact modelling (which translate potential hydrological change into potential change in ecosystem indicators) are only one line of evidence used in this impact and risk analysis, and these outputs need to be considered in the of the assumptions made and the availability and quality of local data.
Table 8 Landscape groups, receptor impact variables and relevant hydrological response variables for receptor impact modelling for the Galilee subregion
LQD = the number of days per year with low flow (<10 ML/day), averaged over a 30-year period, LME = the maximum length of spells (in days per year) with low flow, averaged over a 30-year period, dmaxRef = maximum difference in drawdown under the baseline future or under the coal resource development pathway future relative to the reference period (1983 to 2012), tmaxRef = the year that the maximum difference in drawdown occurs, across all years. tmaxRef is negative if before the end of the relevant period or positive if after the end of the relevant period. The short-term period is 2013 to 2042 and the long-term period is 2073 to 2102, EventsR2.0 = the mean annual number of events with a peak daily flow exceeding the threshold (the peak daily flow in flood events with a return period of 2.0 years as defined from modelled baseline flow in the reference period (1983 to 2012)). This metric is designed to be approximately representative of the number of overbank flow events in future 30-year periods. Each hydrological response variable is typically reported as the maximum change due to additional coal resource development.
Potential impacts as determined from this BA are reported in Section 3.4 for landscape classes and Section 3.5 for assets. Given the large number of assets, the focus of Section 3.5 is on identifying those assets that are considered to be ‘more at risk of hydrological change’. These are the assets that overlap with areas in the zone of potential hydrological change that have at least a 50% chance of a hydrological change larger than the threshold hydrological response variable values used to define the zone. Local information is necessary to improve upon the regional-scale risk predictions made by this BA at any given site.
In addition to the analysis presented in this product, impact profiles for landscape classes and assets are available at www.bioregionalassessments.gov.au. Each profile summarises the hydrological changes and potential impacts that pertain to that landscape class or asset, for example, an increase in groundwater in the ‘Floodplain terrestrial groundwater-dependent ecosystems’ landscape group in the zone of potential hydrological change. Users of the BA products can aggregate and consider potential impacts for their own scale of interest.
The BA product suite can also be used to explore the results for landscape groups and assets using the map-based BA Explorer interface at www.bioregionalassessments.gov.au/explorer/GAL/.
A large number of multi-dimensional and multi-scaled were used in the and analysis for the , including hydrological model outputs, and ecological, economic and sociocultural data from a range of sources. To manage these datasets and produce meaningful results, a consistent spatial framework was needed that permitted rapid spatial and temporal analyses of impacts, without compromising the resolution of the results.
The datasets for this were organised into an impact and risk analysis database (Bioregional Assessment Programme, ) to enable efficient and effective data management. The purpose of the database is to produce result datasets that integrate the available modelling and other evidence across the Galilee . The database is required to support three types of analyses:
The results of these analyses are summarised in each of the following three main sections of this product (i.e. Sections 3.3, 3.4 and 3.5), with more detailed information available at www.bioregionalassessments.gov.au. The impact and risk analysis database is also available at data.gov.au (Bioregional Assessment Programme, ).
As previously mentioned, the main geographic focus of the and analysis for the is on the area termed the zone of potential hydrological change (see Section 3.3.1 for details regarding the development of this zone). This area is near the central-eastern boundary of the Galilee , around the seven coal mines evaluated by the numerical hydrological modelling. The area of the Galilee is about 14,000 km2, which represents less than 3% of the total area of the Galilee assessment extent (about 612,000 km2). One important of narrowing the spatial extent of this is that most of the maps presented in this product have been redesigned to zoom into the main area of interest, thereby excluding large parts of the Galilee assessment extent (Figure 17).
The Galilee zone of potential hydrological change is less than 3% of the area of the assessment extent, which represents the entire area investigated for this bioregional assessment. Consequently, most results presented on maps in the impact and risk analysis product are zoomed to this main area of interest, and exclude much of the broader Galilee assessment extent.
In addition to displaying results on various maps, this product uses two other main data and information presentation methods. The Assessment team considers these are the most appropriate means to communicate the impact and risk analysis results:
- Data tables
- Cumulative exceedance plots.
18.104.22.168.1.1 Data tables
The vast amount of data produced by the and analysis database are summarised in this product in tabular form (see Section 3.3 and Section 3.4 for specific examples). The probabilistic outputs for selected (output from either the or models) are categorised against specified thresholds and reported for the 5th, 50th and 95th results from relevant modelling runs. The thresholds are used consistently across all impact and risk products in the Bioregional Assessment Programme, and have been chosen with regard for existing impact thresholds under either Queensland or NSW legislation (such as groundwater thresholds of 0.2 m, 2 m and 5 m specified in Queensland’s Water Act 2000), or for clarity in reporting data ranges across the surface water impacts.
22.214.171.124.1.2 Cumulative exceedance plots
Cumulative exceedance diagrams are another method of presenting the and analysis results in this product. Specific hydrological examples are provided in Section 3.3. Similar to the data tables, these results are also shown for the 5th, 50th and 95th to illustrate the range of predictions. The cumulative exceedance plots are particularly useful in summarising changes in various for different areas or stream lengths. For example, these plots can provide a clear summary of the total area within the that may be subject to a certain amount of across the range of the ). Likewise, the total length of stream network potentially subjected to increases or decreases in the number of days of low flow or high flow (respectively) is clearly summarised using cumulative exceedance plots, as reported in Section 3.3.3.
The used in the and analysis database (Bioregional Assessment Programme, ) include the , , numerical modelling results (, and receptor impact modelling), coal resource development 'footprints' and other relevant geographic information, such as the boundaries of the subregion, and . All data in the impact and risk analysis database (and the results derived from it) meet the overarching requirements for data and accessibility.
The data were structured to overcome the slow geoprocessing operations typical of complex queries of very large spatial datasets, such as those required for this BA. This structuring was achieved by:
An assessment unit is a geographic area represented by a square polygon with a unique identifier. Assessment units are non-overlapping and completely cover the Galilee zone of potential hydrological change. The spatial resolution of the assessment units is closely related to that of the BA groundwater modelling and is 1 km x 1 km for the (Figure 18). Assessment units were used to partition and landscape class spatial data for the impact analysis. The partitioned data can be combined and recombined into any aggregation supported by the conceptual modelling, and model data.
The interpolated modelled groundwater (see Section 126.96.36.199) are at the same resolution as the assessment units and contain a single value per assessment unit. However, the surface water modelling generated results at points (). These are then extrapolated to specific reaches of the surface water network (see Section 188.8.131.52), and are mapped to assessment units. For assessment units with only a single stream reach, the assessment unit stores the information associated with this stream segment. However, where the assessment unit contains multiple stream reaches (e.g. at the confluence of two streams), it was necessary to prioritise which stream reach was used to inform the value of the assessment unit for representing the surface water modelling results. This process applied expert hydrological judgement and reasoning, and followed a general set of rules for prioritising stream reaches, including:
- whether the modelled reaches show a hydrological change (i.e. a reach with a potential hydrological change takes priority over a reach predicted to have no significant change)
- whether the stream reach is represented in the model (i.e. modelled reaches take priority)
- the stream order of each reach (i.e. a higher order stream, such as a main channel, takes priority over a lower order stream, such as a tributary)
- reach length (i.e. where two streams in an assessment unit are of equally high stream order, priority is given to the longer of the two).
To manage issues of geospatial quality in and also technology integration, the impact and risk analysis database performed a series of geospatial operations on the source data geometry. These operations are PostGIS geometry validation, 1 m or less snap-to-grid, and (in some cases) 1 cm polygon buffering. The effect of these operations on area and length calculations is considered small. In general, the larger an individual geospatial feature, the smaller the relative impact and vice versa. For features with area greater than 10 km2 and length greater than 10 km, variation from source data calculations ranges between 0.0% and 0.5%. This variation may approach 40% for smaller geospatial features (e.g. features that may be up to several square metres in area). The geospatial operations necessary for the impact and risk analysis account for all differences in length and area that may be found when comparing data stored and used within a GIS environment, with that used in the impact and risk analysis database.
The inset box (a) provides an example of the interpolation approach used to allocate hydrological response variable data from surface water model nodes to adjacent surface water reaches. In this example, near the proposed Hyde Park Coal Mine, there are three surface water model nodes shown on the main stream (Bully Creek) that flows through the mining project. Surface water model interpolation upstream of node 19 was not possible due to proximity to the proposed mine site. Hence, these stream reaches are classed as ‘unquantified potential hydrological change’ for the purposes of the bioregional assessment for the Galilee subregion. Likewise, the network of smaller non-modelled streams that will be intersected by the mine pits and site infrastructure are also classed as streams with ‘unquantified potential hydrological change’. The other stream reaches shown on Bully Creek are coloured according to the model node used for the interpolation. This inset also depicts the regular 1 km x 1 km grid of assessment units for the zone.
Product Finalisation date
- 3.1 Overview
- 3.2 Methods
- 3.3 Potential hydrological changes
- 3.4 Impacts on and risks to landscape classes
- 3.4.1 Overview
- 3.4.2 Landscape classes that are unlikely to be impacted
- 3.4.3 'Springs' landscape group
- 3.4.4 'Streams, GDE' landscape group
- 3.4.5 'Streams, non-GDE' landscape group
- 3.4.6 'Floodplain, terrestrial GDE' landscape group
- 3.4.7 'Non-floodplain, terrestrial GDE' landscape group
- 3.5 Impacts on and risks to water-dependent assets
- 3.6 Commentary for coal resource developments that are not modelled
- 3.7 Conclusion
- Contributors to the Technical Programme
- About this technical product