Streams landscape groups

The total length of stream landscape classes within the zone of potential hydrological change is 6285 km. Of this length, 45% are ‘Streams, GDE’, which are considered to be groundwater dependent. All four of the landscape classes within this group occur in the zone. The remaining 55% are ‘Steams, non-GDE’. The latter category is considered to be predominantly rainfall dependent. Four of the six landscape classes within this group occur in the zone. The exceptions are the two estuarine stream classes ‘Near-permanent, estuarine stream’ and ‘Temporary, estuarine stream’ which only occur outside of the zone of potential hydrological change and thus are very unlikely to be impacted by coal resource development.

For the purposes of qualitative and quantitative modelling, these two landscape groups were merged to produce a single composite landscape group category – Streams. Initially, during the qualitative modelling workshop a separate modelling effort was conducted for both temporary and permanent stream systems; however, after completion of a model for temporary streams in a flowing state the various external experts concluded that the essential dynamics of both systems could be adequately addressed by the same model.

Two qualitative mathematical models were developed that describe the general dynamics of the aquatic community associated with the streams landscape groups. The two models differ in the relationship between surface water and near-surface (shallow) groundwater. Specifically, an uncertain link in the modelling process was the degree to which stores of near-surface groundwater could contribute to surface water that enters the stream channel. This uncertainty led to the development of two alternative models, one with and one without a link from near-surface groundwater to surface water.

Two receptor impact models were developed based on expert elicitation during the quantitative modelling workshops. The first model examined the response of woody riparian vegetation to changes in flow regime and groundwater. Therefore, the model is applicable to streams where both surface water and groundwater are key hydrological components. The model is therefore relevant to the ‘Streams, GDE’ landscape group. This model used annual mean percent foliage cover of the woody riparian vegetation as the receptor impact variable.

The second model examined the response of high-flow macroinvertebrates to changes in flow regime. High-flow macroinvertebrates were represented by a mayfly species in the genus Offadens, for which data were available for streams outside the zone of potential hydrological change but within the broader Burdekin river basin. These data informed the expert elicitation process. This model is applicable to streams where surface water is the key hydrological component (i.e. it is relevant to the ‘Streams, non-GDE’ landscape group). The receptor impact variable was the annual mean density of the mayfly species, three months after the end of the wet season.

Last updated:
6 December 2018
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