Adelaide
42.1 Evaporation from storages

The volume reported (14,924 ML) represents evaporation from surface water storages within the Adelaide region during the 2010–11 year. Evaporation, itemised by surface water storage, is provided in the following table.

Potential evaporation is an estimate of the evaporative demand of the environment. The Priestly and Taylor method was used to estimate potential evaporation – as calculated by the WaterDyn model (Raupach et al. 2008) – from surface water storages and weirs.

This method used monthly, open water evaporation data produced by the Bureau of Meteorology. These data are based on daily gridded climate data that are available on a 0.05 degree (5 km) national grid and included downward solar irradiance, and maximum and minimum air temperature. The methods used to generate these gridded datasets are outlined in Jones et al. (2007).

Evaporation at each waterbody was estimated from the proportionally weighted average of grid-points that intersected each storage or weir (water feature). The volume was then estimated using the monthly average surface area of each waterbody. The surface area varied dynamically with changing storage level where the relationship between storage level and surface area had been derived.

• The Priestly and Taylor potential evaporation estimates are subject to approximations associated with interpolating the observation point input data to a national grid as described 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 timescale.
  
• Evaporation 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.