31.3 Off–channel water abstraction
This line item refers to the water used from off–channel water storages. The volume reported for 2012 was 4,715 ML.
The Bureau of Meteorology (The Bureau), National Climate Centre daily climate grids (rainfall, temperature and solar radiation); Geoscience Australia, mapping of human-made waterbodies spatial dataset, built up areas spatial dataset and 9 arc-second digital elevation model (DEM).
A water balance based FORTRAN code tool was used to determine the volume of water abstracted from the private water store. The model was provided inputs in the form of climate from gridded climate datasets, runoff from the AWRA-L v2.0.0 (Van Dijk 2010) model and dam details derived from spatial data.
The Canberra region was divided up into five subregions for the purpose of estimating the water balance of the private store. Four of the subregions were the catchments of the major storages and the fifth was the remaining land.
The private store consisted of off–channel storages filled primarily by rainfall-runoff. These were determined from waterbody mapping provided by Geoscience Australia and were waterbodies that were greater than 50 m from built-up areas in the Canberra region.
The water balance based FORTRAN code tool determines the water stored in each private reservoir at each time point and determines the volume required for use from the reservoir. FORTRAN code tool assumes that water will be abstracted from the reservoir at the rate required unless reservoir empties, at which time, abstraction will cease.
Assumptions, limitations, caveats and approximations
- The gridded climate input data are subject to approximations associated with interpolating observation point data to a national grid detailed in Jones et al. (2007).
- The estimated volume available in storage for evaporation is subject to the assumptions associated with the water balance based FORTRAN code tool and the parameters used.
- The spatial extent of waterbodies subject to the assumptions and methods associated with the data provided by the Geoscience Australia.
The uncertainty estimate was not quantified.
This line item corresponds to line item 31.3 'Water use' reported in the 2011 Account.