2.7.1 Methods


This section details the specific application to the Hunter subregion of methods described in companion submethodology M08 (as listed in Table 1) for receptor impact modelling (Hosack et al., 2018).

In bioregional assessments (BAs), receptor impact models are intended to characterise potential changes to specific components of an ecosystem that may result from hydrological changes predicted in response to coal resource development. A receptor impact model is constructed for one or more landscape classes. A landscape class represents ecosystems with similar water dependencies that are expected to respond similarly to changes in groundwater and/or surface water. Only landscape classes that intersect the zone of potential hydrological change are considered to be candidates for receptor impact models. Outside the zone, hydrological changes are considered too small to result in adverse impacts to water-dependent ecosystems.

The potential impacts of coal resource development on ecological assets are initially assessed using qualitative mathematical models. These models are elicited from independent experts and contain key components and processes of the landscape class ecosystems, and the hydrological variables that support them. They are then used to qualitatively predict (reported as increase, decrease or no change) how the landscape class ecosystem will respond to changes in hydrology that may occur as a result of coal resource development.

The receptor impact modelling process continues with selection of receptor impact variables from the ecological components identified in the qualitative mathematical model and hydrological response variables to represent the hydrological regimes that support these components. Thus, the landscape classification and qualitative mathematical models form the bases for carefully structured elicitations that use expert opinion to quantify the potential changes in receptor impact variables in response to (often simultaneous) changes in hydrological response variables. Importantly, the elicitations capture experts’ uncertainty in this response and allow for variability in the response within the landscape class.

The elicitation allows the BA team to construct a statistical model that predicts how changes in the hydrological response variables due to coal resource development will impact the receptor impact variables. The statistical model describes the conditional probability of the receptor impact variable taking specific values given specified values of the hydrological response variables. Within a landscape class, this statistical model enables the BA team to quantify the risk to ecological assets of coal resource development using predicted changes in hydrological response variables in a short-term (2013 to 2042) and long-term (2073 to 2102) period.

The receptor impact models predict the distribution function of the receptor impact variables for different futures (baseline and coal resource development pathway) and at specific assessment years (2042 and 2102). The distribution functions are summarised in BAs by a limited series of percentiles (or quantiles), nominally 5% increments between the 5th and 95th percentiles.

Last updated:
18 January 2019
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