Summary and conclusions

The change in surface hydrology predicted due to the additional coal resource development in absolute terms is predicted to have a median decrease of less than 0.01 GL/y, which corresponds to a change of about 0.01%. These changes are several orders of magnitude smaller than the observed mean streamflow (Table 26, Section of companion product 2.1-2.2 for the Clarence‑Moreton bioregion (Raiber et al., 2016)). Their effect on mean and high-flow hydrological response variables will therefore be minimal. Even the effect on low-flow hydrological response variables will be very small, especially in the perennial streams.

In addition to this, such low changes in flow are extremely hard to observe as the largest uncertainties in the rating curves used to transfer measured stage heights to flows are associated with low-flow measurements (Tomkins, 2014).

For some model nodes, notably CLM_003 and CLM_008, the 95th prediction interval of change in surface watergroundwater flux is of the same order of magnitude as the 1st percentile of historical observed or simulated flow.

The simulated increases in low-flow metrics are considered to be an erroneous overestimate due to artefacts in the simulation of low flow and the definition of the hydrological response variables. Accurately measuring and simulating low-flow conditions is very challenging and requires further efforts.

Last updated:
18 October 2018
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