This section presents the predictive posterior distribution for each hydrological response variable. To guide the interpretation of the results, Table 7 summarises the location and catchment area of each model node.
As described in the uncertainty analysis (refer to Section 220.127.116.11), the maximum raw change (amax), maximum percent change (pmax) and year of maximum change (tmax) reported here are for the hydrological response variables for streamflow: annual flow (AF), interquartile range (IQR), daily streamflow at the 99th percentile (P99), number of flood (high-flow) days (FD), number of low-flow days (LFD), number of low-flow spells (LFS), longest low-flow spell (LLFS) and zero-flow days (ZFD).
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 18.104.22.168 of companion product 2.1-2.2 for the Clarence-Moreton bioregion ). Their effect on mean and high-streamflow hydrological response variables will therefore be minimal. Even the effect on low-streamflow hydrological response variables will be very small, especially in the perennial streams.
The maximum change in surface water – groundwater flux simulated by the groundwater model is several orders of magnitude less than the observed or simulated historical streamflow. 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.
This section presents the predictive posterior distribution for each . To guide the interpretation of the results, Table 7 summarises the location and catchment area of each , which are also shown in Figure 5 in Section 22.214.171.124.1 . In Table 7 and the figures in this section, the model nodes are grouped per catchment and ordered from upstream to downstream.
Table 7 Summary of model nodes with their upstream contribution area
The streamflow in the prediction catchments is only likely to change due to coal resource development in this bioregion via a change in the – flux. As described in the section (refer to Section 126.96.36.199), the maximum raw change (amax), maximum percent change (pmax) and year of maximum change (tmax) reported here are for hydrological response variables for streamflow: annual flow (AF), interquartile range (IQR), daily streamflow at the 99th percentile (P99), daily streamflow at the 1st percentile (P01), number of flood (high-flow) days (FD), number of low-flow days (LFD), number of low-flow spells (LFS), the longest low-flow spell (LLFS) and number of zero-flow days (ZFD). Zero streamflow is identified using the minimum detectable flow. For ease of applicability, a threshold of 0.01 ML/day is set for determining the number of ZFD for all surface water nodes (see companion submethodology M06 for surface water modelling ).
It is important to reiterate that both the calibration and uncertainty analysis indicate that the Australian Water Resources Assessment landscape model (AWRA-L) predictive capability is adequate for high-flow aspects of the hydrograph, while the predictive capability is not as good for low-flow metrics in the . 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 .
Product Finalisation date
- 188.8.131.52 Methods
- 184.108.40.206 Review of existing models
- 220.127.116.11 Model development
- 18.104.22.168 Calibration
- 22.214.171.124 Uncertainty
- 126.96.36.199 Prediction
- 188.8.131.52.1 Annual flow (AF)
- 184.108.40.206.2 Interquartile range (IQR)
- 220.127.116.11.3 Daily streamflow at the 99th percentile (P99)
- 18.104.22.168.4 Flood (high-flow) days (FD)
- 22.214.171.124.5 Daily streamflow at the 1st percentile (P01)
- 126.96.36.199.6 Low-flow days (LFD)
- 188.8.131.52.7 Low-flow spells (LFS)
- 184.108.40.206.8 Longest low-flow spell (LLFS)
- 220.127.116.11.9 Zero-flow days (ZFD)
- 18.104.22.168.10 Summary and conclusions
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