South East Queensland

Data source

• Bureau of Meteorology, daily climate grids (rainfall, temperature and solar radiation)
• Commonwealth Scientific and Industrial Research Organisation (CSIRO), WaterDyn and AWRA-L model parameters
• CSIRO, monthly climatological average radiation grid data
• Bureau of Meteorology, waterbody feature class
• Agreed list of storages considered assets for the purpose of the South East Queensland (SEQ) region

Data provider

Bureau of Meteorology.

Method

Rainfall-derived run-off into connected surface water was estimated using the average of outputs from two CSIRO water balance models known as WaterDyn and AWRA-L.

Using climate grid data for the SEQ region (including precipitation, temperature and solar radiation data), WaterDyn and AWRA-L were used to estimate the run-off depth at each grid-point within the region. Only run-off from the landscape is considered; therefore, the surface areas of the major reservoirs and the local catchment reservoirs were excluded from the analysis.

Run-off from the landscape is divided into two components:

• run-off into the connected surface water store (major reservoirs, rivers and drains)
• run-off into local catchment reservoirs.

Only run-off into the connected surface water store is considered here.

The average run-off depth from the landscape into the connected surface water store was determined as the unweighted arithmetic mean of modelled run-off data from grid-points within the region boundary. Mean run-off depth was converted to a run-off volume by multiplying run-off depth by the total area of the region (excluding reservoirs).

Uncertainty

Ungraded.

Approximations, assumptions, caveats and limitations

• The estimated run-off into rivers was not verified by real-time analysis of streamflow records. The reported value was an estimate of water that was likely to have entered the connected water store from the landscape.
• The run-off estimates were subject to the assumptions of the WaterDyn model (detailed in Raupach et al. 2008) and the AWRA-L model (detailed in van Dijk 2010).
• The estimated run-off corresponds to the run-off expected from an unimpaired catchment. The impairment on run-off from local catchment reservoirs is estimated using a local catchment reservoir water balance model (STEDI). Where this is applied, the run-off estimates inherit the approximations, assumptions and caveats of the water balance model (STEDI) and parameters used.
• Landscape run-off attributed to grid-cells (5 km x 5 km) that intersected the catchment boundary (i.e. that had some part of the grid-cell falling outside the catchment boundary) was included fully in run-off calculations for the catchment. This had a limited influence because average run-off was multiplied by the area determined by the catchment boundary, not the total grid-cell area.