Methodology for mapping GDEs

Groundwater Dependent Ecosystems Atlas


The GDE Atlas was released in 2012, and was produced by conducting a national-scale assessment. This involved a nationally consistent methodology using remote sensing and GIS rules-based analysis, which mapped the potential for groundwater/ecosystem interaction. Since then, various States have conducted regional and State-wide studies, generating new GDE mapping. A range of approaches were used for these studies, including field work, remote sensing and application of rules/conceptual models. In 2016–2017 most of these regional datasets were added to the GDE Atlas.

As such, there are two broad methods of mapping used in the GDE Atlas, as outlined below.

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National Assessment

This methodology was applied separately to eight GIS analysis regions (called work packages). Each work package represented an area of broadly similar hydrogeological, ecological and climatic characteristics. It was assumed the interaction between groundwater and ecosystems was controlled by similar processes, and could be modelled by the same broad analysis rules within each work package.

A literature review enabled a conceptual understanding of the interaction between groundwater and ecosystems to be developed. From this, a set of rules describing the potential for groundwater/ecosystem interaction was developed for each work package.

GDE Methodology

In the data selection step, existing spatial datasets were compared against the rules to determine where analysis could be undertaken. The ability to implement the rules developed in the literature review was dependent on the availability of relevant spatial data.

Once the datasets were confirmed, GIS analysis combined the rules and data to provide an interim product that showed the outcomes of each rule for each ecosystem. The outcomes of each rule were then rated to indicate the potential for groundwater–ecosystem interaction to occur. The term 'GDE potential' has been used to indicate the potential for interaction between groundwater and ecosystems.

The original datasets from the national assessment are available by email request to groundwater@bom.gov.au

Download a copy of the national assessment methodology report or read the journal article.

Regional Studies

An update of the GDE Atlas was conducted during 2016–17, to account for progress in regional-scale GDE mapping which has occurred since the GDE Atlas was first developed. State and regional GDE datasets were collated from a number of agencies covering the three types of GDEs. Coverage was partial for most States, and datasets were created using a range of methods.

To convey information about differences in data source, the classification of GDEs was updated to clearly distinguish between existing data from the national assessment and new State datasets, while retaining information about the GDE potential. New consistent attributes were added to the data model to capture information about the data source.

Each dataset required a different approach for integration, and consultation with States/Territories helped in determining this process. The key steps for each State update were:

  1. Pre-processing of State datasets into new data model format
  2. Classification of known and potential GDEs according to new classification system
  3. Mapping of data, which involved replacing existing data or using precedence rules where overlap occurred
  4. Populating new data schema using State attributes
  5. Running script to populate national attributes

By integrating the new State data, retaining information about the data source and highlighting the difference in methodology from the existing national assessment, the quality and relevance of the GDE Atlas has been improved. Users of the GDE Atlas can access the most accurate and up-to-date information available for a wide range of uses, including natural resource management and environmental impact assessments.