Perth
42.1 Evaporation from storages

Supporting Information

This line item refers to total evaporation from the surface water storages within the Perth region that supply water to the urban water system.

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

 

Total evaporation from each storage during the 2010–11 year

Storage

Evaporation (ML)

Canning

3,185

Churchman Brook

269

Mundaring

5,435

North Dandalup

2,993

Samson Brook

261

Serpentine

6,241

Serpentine Pipehead

889

South Dandalup

6,764

Stirling

3,548

Victoria

544

Wungong

3,954

Total

34,082

 

Quantification Approach

Data Source

Bureau of Meteorology, National Climate Centre: daily climate grids (rainfall, temperature and solar radiation), Bureau of Meteorology: Australian Hydrological Geospatial Fabric – waterbody feature class, Australian Water Resources Information System – water storages.

Provided by

Bureau of Meteorology.

Method

The Priestly and Taylor method to estimate potential evaporation (as calculated by the WaterDyn model) was used to estimate evaporation from the surface water store. Monthly, open water evaporation data produced by the Bureau were used based on daily gridded climate data that are available on a 0.05 degree (5 km) national grid.

As a potential evaporation dataset, it was an estimate of the evaporative demand of the environment. The daily gridded climate datasets are generated by the Bureau and include downward solar irradiance and maximum and minimum air temperature. The methods used to generate these gridded datasets are outlined in Jones et al. (2007).

The evaporation at each waterbody was estimated from the weighted 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 Perth region was calculated using this dynamic method.

Assumptions, Limitations, Caveats and Approximations

The Priestly and Taylor potential evaporation estimates are subject to approximations associated with interpolating the observation point data to a national grid detailed in Jones et al. (2007).

The dynamic storage surface areas calculated from the levels and storage rating 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.