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South East Queensland

                                                                                                   

14.2 Surface water flow out of region

                             

Supporting information   


The end-of-system flow estimates have been modified to include discharges into the river systems that occur below the gauges. In the Gold Coast water resource plan (WRP) area, Elanora, Merrimac and Coombabah wastewater treatment plants (WWTPs) discharge into the river systems below the downstream-most gauge on the river. A combined discharge of 39,284 ML occurs from these WWTPs. This volume was added to the end-of-system flow estimates to provide the total outflow to the sea. Please refer to line item 20.4.1 Discharge of urban wastewater to connected surface water for individual quantification approaches.

The table below details the end-of-system flow estimates for the South East Queensland (SEQ) region.

End-of-system flow estimates for the South East Queensland region
Water Resource Plan (WRP) area River Volume (ML)
Gold Coast Coomera River 154,703
Currumbin River 26,110
Tallebudgera River 39,509
Nerang River 168,851
Discharge from WWTPs that discharge downstream of lowest gauge 39,284
Total Gold Coast WRP area 428,457
Logan Basin Logan River Basin 226,284
Total Logan Basin WRP area 226,284
Moreton Brisbane River 355,064
Caboolture River 199,640
Pine River 132,928
Pumicestone River 273,517
Total Moreton WRP area 961,149
Total SEQ region 1,615,890

 

Quantification approach   


Data source

Queensland Department of Environment and Resource Management (DERM), streamflow gauging station data and Seqwater.

 

Data provider

DERM.

 

Method

Regression relationships were developed between the historical recorded flow data at the most downstream gauging station and the modelled end-of-system flow for each river catchment. The modelled end-of-system flow was estimated using the DERM integrated quantity quality model for each catchment within the SEQ region.

The regression relationship was then applied to the 2009–10 recorded flow data at the most downstream gauging station to estimate the annual flow at the outlet.

For example, for Logan River, DERM used recorded flows at the Logan River at Yarrahappini gauge (145014A) and the Albert River at Bromfleet gauge (145102B) to estimate the end-of-system flows using regression analysis.

 

Uncertainty

Derived from modelled data. DERM reliability and accuracy rating is B3/B4 (see glossary).

 

Approximations, assumptions, caveats and limitations

In this analysis, it was assumed that the gauging station flow data are reliable and the regression relationships are valid. A comparison of alternative 'extrapolation' methods has not been undertaken.