Assessing water dependence

Following the compilation of assets into a database, water dependency of assets was assessed in a two-step procedure:

  1. Only assets that intersect with the subregion were retained for a further assessment of water dependence (M1 decision).
  2. For assets that intersected with the subregion, a preliminary assessment of water dependency was conducted (M2 decision).

Decisions on the preliminary water dependency (M2) were made using the following guiding principles:

  1. Efficiency. Methods developed to assess water dependency were suitable to application to large numbers of assets and where possible used automated procedures.
  2. Transparency. All decisions could be justified and included the rationale for inclusion, data sources, dates and responsible persons.
  3. Rigour. Decision making was based on sound ecological, economic and sociocultural principles and clear logic.
  4. Multiple lines of evidence. Wherever possible, multiple lines of evidence were simultaneously used to underpin decision making. Three broad groups of evidence were used including (i) naming conventions, (ii) documents describing asset profiles or management (where available) and (iii) simple spatial analysis.
  5. Precaution. Where only part of an asset was shown to be water dependent, the entire asset was deemed to be water dependent. For example, if it was demonstrated that a nature reserve contained water-dependent assets, such as watercourses, the entire nature reserve was deemed to be water dependent. Where evidence for definitive determinations of water dependence was lacking (for example descriptions of species habitat were incomplete or unclear), assets were assumed to be water dependent.

The associated ‘Water-dependent asset register and asset list for the Gwydir subregion on 24 August’ (Bruce and O’Grady, 2016) provides the details of these water-dependency decisions.

Assets classed in the ecological subgroups ‘Surface water features’ or ‘Groundwater features’, or assets with names that include the terms ‘waterhole’, ‘lake’, ‘lagoon’, ‘soak’, etc., were deemed ‘Assumed to be water dependent‘. Similarly, assets sourced from the National atlas of groundwater dependent ecosystems (GDE Atlas; Bureau of Meteorology, Dataset 7) with a known groundwater dependency (derived from previous field work or possessing a high or moderate potential for groundwater dependency) were assumed to be water dependent (attributed as ‘likely’). Assets with a moderate potential for groundwater dependency were attributed as ‘possible’ and also included in the register. Where assets were identified as having a low probability for groundwater dependence, it was assumed that these assets were unlikely to be groundwater dependent and were not included in the water-dependent asset register.

For many of the remaining assets, water dependency was not obvious. Such assets might include threatened ecological communities listed under the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act; Australian Government Department of the Environment, Dataset 8) (e.g. ‘Weeping Myall Woodlands’ Threatened Ecological Community) or assets derived from the Collaborative Australian Protective Areas Database (CAPAD; Australian Government Department of the Environment, Dataset 3) such as the Mount Kaputar National Park.

The water dependency of threatened species’ habitat including threatened ecological communities listed under the EPBC Act were assessed by a review of the habitat requirements for each species or community. An important caveat is that the Assessment considers the potential impact of coal resource development on the habitat of the species rather than the species per se. However, it is necessary to present species-based information to best reflect available data. The water dependency of the species habitat was ranked as ‘likely’, ‘possible’, ‘unlikely’ or ‘unsure’ based on profile descriptions contained within the Species Profile and Threats Database (SPRAT; Bioregional Assessment Programme, Dataset 9). Assets listed as ‘likely’ are those with a clear and demonstrated link to aquatic ecosystems (e.g. aquatic species). Assets listed as ‘possible’ may have some overlap with habitat that may be water dependent (e.g. species that may visit riparian areas). Assets listed as ‘unlikely’ show no evidence of surface water or groundwater dependence in habitat requirements. Where assets were recorded as ‘unsure’, the precautionary principle was applied and the asset retained for inclusion in the water-dependent asset register.

For ecological and sociocultural assets such as historic buildings, nature reserves, national parks, important bird areas etc., a spatial analysis using multiple data sources was used to assess the preliminary water dependency of the assets. Water-dependent assets were those that met at least one of the following criteria:

  • intersected with existing mapping of the flood inundation 1-in-100 year extent for the Murray-Darling Basin (CSIRO, Dataset 23)
  • occurred over shallow groundwater, where shallow groundwater is defined as regions where depth to groundwater is less than 10 m (Geoscience Australia, Dataset 24)
  • occurred in regions where depth to groundwater ranged between 10 to 20 m. This criterion considered those assets that may access groundwater intermittently (Geoscience Australia, Dataset 24)
  • intersected with existing wetland mapping or riparian networks (Department of Sustainability, Environment, Water, Population and Communities, Dataset 25).

In all cases, assets attributed as ‘likely’ or ‘possible’ were flagged as ‘on’ with respect to M2 and included in the asset register. Assets attributed as ‘unlikely’ were flagged as ‘off’ in the asset database and are not included in the preliminary water-dependent asset register.

Last updated:
6 October 2016