Canberra

This line item refers to the volume of water that was received by the connected surface water store via runoff based on modelling provided by the Bureau of Meteorology.

280,116 ML of runoff to connected surface water.

Data source

Bureau of Meteorology: National Climate Centre (NCC) daily climate grids (rainfall, temperature and solar radiation); Australian Hydrological Geospatial Fabric (AHGF) waterbody feature class.

Commonwealth Scientific and Industrial Research Organisation (CSIRO): WaterDyn and AWRA-L model parameters; CSIRO monthly climatological average radiation grids data.

Geoscience Australia: Murray–Darling Basin human-made waterbody feature class and built-up area feature class.

Bureau of Meteorology and reporting partners: agreed list of storages considered to be water assets for the purpose of the Canberra subaccount.

Data provider

Bureau of Meteorology.

Method

Rainfall-derived runoff into the connected surface water store was estimated based on the average of modelled discharge from the CSIRO WaterDyn model and modelled streamflow from the CSIRO AWRA-L model.

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

Runoff from the landscape is divided into two components: (i) runoff into the connected surface water store (major reservoirs, rivers and drains); and (ii) runoff into local catchment reservoirs. Only runoff into the connected surface water store is considered here.

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

Uncertainty

Ungraded.

Assumptions, approximations and caveats/limitations

• The estimated runoff 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 runoff 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 runoff corresponds to the runoff expected from an unimpaired catchment. The impairment on runoff from local catchment reservoirs is estimated using a local catchment reservoir water balance model (STEDI). Where this is applied, the runoff estimates inherit the approximations, assumptions and caveats of STEDI and the parameters used.
• Landscape runoff 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 fully included in runoff calculations for the catchment. This had a limited influence because the average of runoff from all grid-cells was multiplied by the area determined by the catchment boundary, not the total grid-cell area.