Perth
41.1 Precipitation on storages

Supporting Information

This line item refers to total precipitation on the major surface water storages used for urban water supply within the Perth region.

Total volume of rainfall on each storage during the 2010–11 year within the Perth region is provided in the following table.

 

Total precipitation on each storage during the 2010–11 year. Data collected by Water Corporation are also shown.

Storage

Rainfall (ML) - Bureau

Rainfall (ML) – Water Corporation

Canning

1,190

1,061

Churchman Brook

101

98

Mundaring

1,777

1,653

North Dandalup

1,295

1,349

Samson Brook

106

103

Serpentine

2,424

2,721

Serpentine Pipehead

375

356

South Dandalup

2,492

2,752

Stirling

1,447

1,576

Victoria

229

203

Wungong

1,467

1,474

Total

12,903

13,345

 

The table shows that rainfall estimated by the Bureau of Meteorology is similar to that measured by the Water Corporation. To calculate the volume of runoff into storages (line item 41.3), rainfall data estimated by the Bureau were used.

Quantification Approach

Data Source

Bureau of Meteorology: monthly precipitation grids, Australian Hydrological Geospatial Fabric waterbody feature class and water storages.

Provided by

Bureau of Meteorology.

Method

Monthly precipitation data were produced by the Bureau. Precipitation 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 on 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 the storages in the Perth region was calculated using this dynamic method.

Assumptions, Limitations, Caveats and Approximations

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 total surface area of the surface water store within the Perth region included only the storages (and not the rivers).

Uncertainty Information

The uncertainty estimate was not quantified.