South East Queensland
17.2 River outflow from the region
Supporting information
The volumetric value for the line item at the end of the 2012–13 year was 7,154,690 ML.
This line item consists of the end-of-system flow from rivers into estuaries, inlets and the sea. The following table details the end-of-system flow estimates for the South East Queensland (SEQ) region.
| Water resource plan (WRP) area | River |
Volume |
(ML) |
||
| Gold Coast | Coomera River | 309,764 |
| Currumbin Creek | 66,002 |
|
| Tallebudgera Creek | 116,284 |
|
| Nerang River | 300,713 |
|
| Total Gold Coast WRP area | 792,763 |
|
| Logan Basin | Logan River Basin | 1,258,736 |
| Total Logan Basin WRP area | 1,258,736 |
|
| Moreton | Brisbane River | 3,788,756 |
| Caboolture River | 231,198 |
|
| Pine River | 636,951 |
|
| Pumicestone River | 446,286 |
|
| Total Moreton WRP area | 5,103,191 |
|
| Total SEQ region | 7,154,690 |
|
Table Note:
1. – = data not available
Quantification approach
Data source
Queensland Department of Natural Resources and Mines (DNRM): stream flow gauging station data; Bureau of Meteorology (the Bureau): National Climate Centre (NCC) daily climate grids (rainfall, temperature and solar radiation), Australian Hydrological Geospatial Fabric (AHGF) waterbody feature class, Australian Water Resources Information System (AWRIS) water storage.
Provided by
DNRM; the Bureau.
Method
The runoff at the most downstream gauges of the major rivers within the South East Queensland (SEQ) region were received from DNRM. The runoff downstream of these gauges was calculated using Australian Water Resources Assessment Landscape (AWRA-L) model version 3.0 (Van Dijk 2010) outputs. The gauging stations considered in this calculation covered 65% of the total area of SEQ catchments and relevant flow data were received from DNRM. The rest 35% of the total area was ungauged and it had to be modelled to estimate the flow volumes.
Daily AWRA-L runoff were produced based on daily gridded climate data that were available on a 0.050 (approximately 5 km) national grid. The catchments of the downstream river sections were defined using the Australian Hydrological Geospatial Fabric (AHGF) stream network. The average runoff depth from the landscape into the surface water was determined as the weighted mean of the relevant grid points within the catchment boundary. Points were weighted based upon the area they represented within the catchment boundary. Mean runoff depth was converted to a runoff volume by multiplying runoff depth by the catchment area of the relevant end point of the river (excluding reservoirs).
To estimate outflow to the sea, the water balance equation was applied on the measured surface water volume at the upstream gauging station and estimated surface water volume at the near-sea outlet for the listed rivers, water diversion for the water treatment plant, wastewater disposal to the surface water within the catchment from the wastewater treatment plant, change in storages, rainfall volume directly on to the storages and evaporation from the storages.
Assumptions, limitations, caveats and approximations
- It was assumed that the gauging station flow data are reliable and the water balance equations are valid. A comparison of alternative 'extrapolation' methods has not been undertaken.
- The runoff estimates were subject to the assumptions of the AWRA-L model detailed in Van Dijk (2010).
Uncertainty information
The uncertainty estimate was not quantified.