Canberra

                                                                                                   

13.1 Precipitation on connected surface water

                             

Supporting information   


Storage

Volume (ML)

Reservoirs

Cotter Reservoir

271

Bendora Reservoir

641

Googong Reservoir

2,888

Corin Reservoir

1,710

Subtotal

5,510

Lakes and wetlands

Lake Burley Griffin

4,196

Lake Ginninderra

791

Lake Tuggeranong

538

Subtotal

5,525

Total

11,035

 

Quantification approach   


Data source

Raster spatial data; Australian Water Availability Project (AWAP) monthly precipitation grids, as produced from daily AWAP v3 grids as at 23 Aug 2010; geographical information system (GIS) layers; Australian Hydrological Geospatial Fabric (AHGF) waterbody feature class; Water Storage, Australian Water Resources Information System (AWRIS).

 

Data provider

Bureau of Meteorology (the Bureau).

 

Method

Monthly precipitation data was produced by the Bureau. It was based on daily data from approximately 6,500 rain gauge stations and interpolated to a 0.05 degree (5 km) national grid (Jones et al. 2007). The precipitation data were consistent with those used to calculate Line item 11.1 Precipitation on landscape to create the rural water balance.

The precipitation at each waterbody was estimated from the average of the grid-points within a 5 km radius of each water feature. The volume was then estimated using the surface area of each waterbody. The average monthly surface area of the major storages was calculated from daily storage levels and capacity tables.

The surface area of all of the storages in the Canberra region was calculated using this dynamic method. Storage rating table and regular level data were not available for the lakes in Canberra, so the default AHGF waterbody feature class was used to estimate a static surface area. In Canberra, the precipitation on the connected surface water store included storages and lakes.

 

Uncertainty

Ungraded.

 

Assumptions, approximations and caveats/limitations

  • The precipitation estimates were subject to approximations associated with interpolating the observation-point data to a national grid, as 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.
  • The use of the static default AHGF surface area is an approximation only. It represents the lakes at capacity and therefore likely results in an overestimation of precipitation on the lake.