Within the BAs, all modelling of the potential ecological impacts of coal resource development is organised by, and conditioned upon, landscape classes. This classification provides a structure that enables qualitative and quantitative modelling at a scale and resolution that is appropriate to the objectives and scale of the BA. Each bioregion or subregion has multiple landscape classes grouped into terrestrial and aquatic landscape groups. Examples of landscape classes are found in product 2.7 (receptor impact modelling) (Figure 3).
The purpose of the landscape classification is to partition the landscape into ecologically similar subunits. The ecological similarities mainly manifest as similar vegetation types (terrestrial landscape group) and similar stream classes (aquatic landscape group) resulting from common geological, geomorphological and/or hydrological characteristics. Importantly, the ecosystems within each landscape class are assumed to respond in a similar way to any alterations in groundwater and/or surface water regimes.
In most instances, the BA landscape classification capitalises on existing aquatic and terrestrial classification schemes and hence links to existing conceptual models of these ecosystems and their water dependency. These models provide a conceptual understanding of how key ecosystem components and processes are shaped and maintained by surface water and groundwater regimes. The criteria that delineate the landscape classes and the methods used to identify landscape classes within each bioregion or subregion, are summarised by companion submethodology M03 (as listed in Table 1) for assigning receptors to water-dependent assets (O’Grady et al., 2016).
The surface water zone of potential hydrological change is defined in a similarly conservative manner (companion submethodology M06 (as listed in Table 1) for surface water modelling (Viney, 2016)). For flux-based variables (e.g. the annual flow volume or daily flow rate at the 1st percentile) it is defined by the surface water model nodes that exhibit at least a 1% change in the variable, relative to the baseline value, in at least 5% of the model simulations (replicates). For most of the frequency-based variables (e.g. the number of zero-flow days per year or the number of low-flow days per year), the zone is defined by model nodes that exhibit at least a 5% chance of the same relative magnitude of change (at least 1% compared to baseline) for at least 3 days in any simulated year. For one of the frequency-based metrics (the number of low-flow spells per year in perennial streams), it is defined by a greater than 5% chance of a change in the variable for at least two spells in any year (see companion submethodology M06 (as listed in Table 1) for surface water modelling (Viney, 2016)).
It is important to recognise that the zone of potential hydrological change represents an estimate of those parts of the landscape that are likely to experience at least some level of hydrological change attributable to coal resource development. The zone serves only to distinguish those landscape classes that should be taken into the next step of the receptor impact methodology from those landscape classes that should not, on the grounds that the latter are predicted to experience negligible (or insignificant) exposure to hydrological change due to coal resource development.
