A carefully designed and implemented receptor placement strategy is fundamental to the development of receptor impact models within a BA.
To assist in assigning receptors, the following guiding principles are articulated:
The assessment is a regional assessment and there are trade-offs between the number of receptors and hydrological response variables that can be analysed in the uncertainty analysis. Such trade-offs require the Assessment team to pay close attention to the spatial and temporal scale of the BA. Those choices must then guide the finalisation of the distribution of receptors.
A comprehensive distribution of receptors (points in the landscape) will be generated which are then the point locations at which impacts on assets are assessed. A subset of these locations will be selected as ‘model nodes’ and used as the receptors for detailed and specific hydrological modelling of hydrological response variables and associated uncertainty analysis. In some cases, the model nodesmight not coincide with receptor locations. In these cases, hydrological changes will be interpolated to receptor locations.
The selection and/or choice of these ‘model nodes’ from the full set of receptors must be made in consultation with BA surface water and groundwater modellers and incorporate information contained within the CRDP and hazard analysis and facilitate interpolation of hydrological responses and associated uncertainty to all receptors.
The selection and/or choice of receptors must be tested at each stage against the principles of being complete, efficient and representative:
A complete set of receptors adequately covers the range of potential impacts contained within the environmental space occupied by the water-dependent assets.
An efficient set of receptors adequately defines the potential impacts of coal resource development on water-dependent assets without the need for defining further receptors.
A representative receptor or set of receptors for a water-dependent asset is located so that relevant information is provided on the potential impacts of coal resource development on that water-dependent asset.
Receptors need only be assigned to landscape classes deemed to be water dependent for the purposes of the Assessment.
Receptors may be assigned directly to assets where landscape classes are not required or relevant. For example, to bores or subsurface features such as an aquifer.
Receptors must encompass the complete spatial extent of all water-dependent landscape classes within the preliminary assessment extent (PAE). This is necessary to identify areas potentially impacted by coal seam gas (CSG) and coal resource development and avoids bias or circular reasoning (i.e. the receptor locations should not be used to guide spatial prioritisation of hydrological and hydrogeological modelling). This submethodology (M03) recognises that:
Receptors may fall outside of model domains; in which case they will be noted as a knowledge gap in the Assessment.
Potentially large numbers of receptors may have no observable hydrological change; this is an important communication outcome from the Assessment and should be noted as ‘No modelled difference in hydrological changes for baseline and CRDP’.
Expert elicitation will be used extensively to guide selection of landscape classes, and the resultant finalised receptor distribution.
