One of the gaps in the surface water modelling relates to the creation of model nodes in the link-node network where there are no observations of streamflow or river geometry. The approach used to derive cross-sections and the estimates of streamflow from AWRA-L should not significantly affect predictions of the differences in hydrological response variables due to the additional coal resource development (ACRD), because they are represented the same way in both baseline and the coal resource development pathway (CRDP).

The data obtained from the NSW Environment Protection Authority in relation to discharges under the Hunter River Salinity Trading Scheme (HRSTS) covered the period from 2006 to 2012 (the HRSTS was established in 1995). Given the short duration of record, the set of rules implemented in the model to simulate discharge may not adequately represent the real pattern of discharges. Mine discharge management is complex – for example, participants can come up with alternative ways of using or disposing of water produced as a result of their operations; salinity credits can be traded between scheme participants – and the rules developed from the six years of data can only be a simplistic representation of what really happens. The implementation of HRSTS discharges is not expected to impact on predictions of the differences in hydrological response variables due to the ACRD because the salinity credits are set within the scheme, the same rule set is applied to baseline and CRDP, and high rainfall and dam releases, and not mining operations, are the key determinants of discharge windows.

The mapping of links to nodes for interpolation and extrapolation of model results to other parts of the river network shows that there are reaches in the stream network where interpolating results from model nodes is not recommended. The incorporation of additional, strategically placed model nodes within the link-node network would largely address this for non-headwater reaches, but the simulations would need to be re-done to generate outputs at these nodes. The distance upstream to where results can be extrapolated to is limited. Thus streamflow changes beyond the link-node extent are a knowledge gap. Not all streams in the stream network were included in the link-node network.

More information on data gaps will be provided in Section and Section of companion product 2.6.1 for the Hunter subregion (Zhang et al., 2018), because the modelling and analysis contributes to identifying main gaps. Likewise, recommendations for monitoring will be reported in later products.

Last updated:
18 January 2019
Thumbnail of the Hunter subregion

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