9.1 Precipitation on surface water
The volume reported (10,974 ML) represents the total precipitation falling onto surface water storages and weirs within the Adelaide region during the 2010–11 year. Precipitation to each surface water storage and weir during the 2010–11 year is provided in the table below.
|Surface water storage/weir||Volume (ML)
|Kangaroo Creek Reservoir||667|
|Little Para Reservoir||592|
|Mount Bold Reservoir||2,177|
|South Para Reservoir||3,170|
Monthly precipitation data were produced by the Bureau of Meteorology. These 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)
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 has 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 surface water storages and weirs (for which data were available) within the Adelaide region and did not include river channels.
The uncertainty estimate was not quantified.
This line item corresponds to line item 13.4 Precipitation on connected surface water as reported in the 2010 Account. In the 2011 Account, major storages located off-channel were reclassified 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 off-stream, 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 was not reported at this line item.
This change and the respective volumes are detailed in the following table. The restated comparative year volume is 8,785 ML.
|2010 Account line item name||Source||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)|
|13.1 Precipitation on connected surface water||Barossa Reservoir||369||(369)|
|Happy Valley Reservoir||1,079||(1,079)|
|Hope Valley Reservoir||262||(262)|
|Kangaroo Creek Reservoir||566||566|
|Little Para Reservoir||579||579|
|Mount Bold Reservoir||1,926||1,926|
|Onkaparinga Summit Reservoir||91||(91)|
|South Para Reservoir||2,196||2,196|