11.1 Precipitation on urban water system

Supporting Information

Precipitation to urban water storages in the 2010–11 year was 2,052 ML. Precipitation, itemised by urban water storage, is provided in the following table.

Precipitation to urban water storages in the 2010–11 year
Urban water storages Volume (ML)
Barossa Reservoir 499
Happy Valley Reservoir 1,146
Hope Valley Reservoir 305
Onkaparinga Summit Reservoir 102
Total 2,052

Quantification Approach

Data Source

Bureau of Meteorology: Australian Water Availability Project (AWAP) monthly precipitation grids; Australian Hydrological Geospatial Fabric (AHGF) waterbody feature class; Australian Water Resources Information System (AWRIS) water storage.

Provided by

Bureau of Meteorology.


Monthly precipitation data were produced by the Bureau of Meteorology. This was 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)

Precipitation at each waterbody was estimated from the proportionally weighted average of grid-point cells that intersected each storage or weir (water feature). The precipitation volume was then estimated using the surface area of each waterbody. Surface area varied dynamically with changing storage level for storages, where the relationship between storage level and surface area have been derived.

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 dynamic storage surface areas calculated from the levels and capacity tables represent a monthly average and therefore will not capture changes that occur on a shorter temporal scale. 
  • Precipitation was only estimated for the urban water storages within the Adelaide region.

Uncertainty Information

The uncertainty estimate was not quantified.

Comparative year

This line item corresponds to part of line item 13.4 Precipitation on connected surface water reported in the 2010 Account. In the 2011 Account, the Bureau of Meteorology reclassified major storages located off-channel as part of line item 3.1 Urban water supply system to provide clearer information to users. The criteria for this reclassification required that storages were located offstream, harvested minimal runoff (due to a diversion channel around the perimeter of the storage) and were used only for urban water supply. Therefore precipitation to those storages reclassified as being part of the urban water system were reported at this line item.

This change and the respective volumes are detailed in the following table. The restated comparative year volume is 1,801 ML.

Restated comparative year information for line item 11.1 Precipitation on urban water system
2010 Account line item name Urban water storage Volume at 30 June 2010 reported in 2010 Account (ML)
Value difference to volume reported due to reclassification (ML) Volume at 30 June 2010 reported in 2011 Account (ML)
Not reported in 2010 Account
Barossa Reservoir   369 369
Happy Valley Reservoir   1,079 1,079
Hope Valley Reservoir   262 262
Onkaparinga Summit Reservoir   91 91
1,801 1,801