Temporal scope, hydrological response variables and receptor impact variables

The temporal scope for the floodplain ecosystem is the same as that described for the other landscape classes of the Galilee subregion. For groundwater variables the reference assessment interval is defined as the 30 years preceding 2012 (i.e. 1983 to 2012). For groundwater, maximum drawdown (metres) and time to maximum drawdown are considered across the full 90-year assessment period (i.e. 2013 to 2102). At the time of the workshop, it was uncertain whether the time of maximum drawdown would vary in that 90-year window. The elicitation was thus conditioned on that variable as well.

For the floodplain ecosystem, the qualitative modelling workshop identified two variables –groundwater and surface water – as the key hydrological elements.

The hydrological variables were interpreted as a set of hydrological response variables that can be modelled (Table 25), and the receptor impact variable was formally defined during the receptor impact modelling workshop. As a result, the relationships identified in the qualitative modelling workshop were formalised into a receptor impact model. The model related the response of annual mean percent foliage cover in a 0.01 km2 (1 ha) plot to changes in dmaxRef (maximum drawdown) and EventsR2.0 (overbank flood events).

Table 25 Summary of hydrological response variables used in receptor impact models for the ‘Floodplain, terrestrial GDE’ landscape group, and the corresponding variables for the signed directed graphs

Hydrological response variable

Definition of hydrological response variable

Notation used for corresponding signed digraph variable


Maximum difference in drawdown under the baseline future or under the coal resource development pathway future relative to the reference period (1983 to 2012)



The year that the maximum difference in drawdown relative to the reference period (1983 to 2012) occurs



The mean annual number of events with a peak daily flow exceeding the threshold (the peak daily flow in flood events with a return period of 2.0 years as defined from modelled baseline flow in the reference period (1983 to 2012)). This metric is designed to be approximately representative of the number of overbank flow events in future 30-year periods. This is typically reported as the maximum change due to additional coal resource development.


GDE = groundwater-dependent ecosystem

Last updated:
6 December 2018
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