28.1 Precipitation on landscape
This line item represents the precipitation on the landscape across the whole of the Canberra region. For the 2011 Account the volume reported was 4,732,674 ML.
Monthly precipitation data were produced by the Bureau of Meteorology. They were based on daily data from approximately 6,500 rain gauge stations and interpolated to a 0.05 degree (approximately 5 km) national grid (Jones et al. 2007).
The average precipitation depth across the Canberra landscape was determined as the weighted mean of precipitation occurring onto the relevant grid points within the region boundary. Points were weighted upon the area they represented within the Canberra landscape to remove edge effects (where the area represented is not wholly within the reporting region) and the effect of changing area represented with changing latitude. The depth of precipitation was converted to a volumetric estimate by multiplying by the total area of the Canberra landscape.
Only precipitation falling onto the landscape is considered here. Precipitation falling onto surface water and off–channel storages (farm dams) is not included.
Assumptions, Limitations, Caveats and Approximations
The precipitation estimates were subject to approximations associated with interpolating observation point data to a national grid detailed in Jones et al. (2007).
The uncertainty estimate was not quantified.