17.1 Evaporation from surface water

Supporting information

The volume reported (14,741 ML) represents the total evaporation from surface water storages and weirs in the Adelaide region during the 2012–13 year.

Evaporation, itemised by each surface water storage and weir, is provided in the following table.

Evaporation from surface water storages and weirs in the Adelaide region during the 2012–13 year

Surface water storage

Volume (ML)

Barossa Reservoir1


Barossa Weir2


Clarendon Weir3


Gorge Weir4


Gumeracha Weir5


Happy Valley Reservoir6


Hope Valley Reservoir7


Kangaroo Creek Reservoir8


Little Para Reservoir9


Millbrook Reservoir10


Mount Bold Reservoir11


Myponga Reservoir12


Onkaparinga Summit Reservoir13


South Para Reservoir14


Warren Reservoir15




6-12, 14-15
Evaporation calculation used dynamic surface area.

1-5, 13 Evaporation calculation used static surface area.

Quantification approach

Data source

National Climate Centre (NCC) daily climate grids (rainfall, temperature and solar radiation), Australian Hydrological Geospatial Fabric (AHGF) waterbody feature class, Australian Water Resources Information System (AWRIS)—Water storages.

Provided by

Bureau of Meteorology.


The potential evaporation estimate produced by the Australian Water Resources Assessment system landscape model (AWRA-L) version 3.0 (Van Dijk 2010) was used to calculate evaporation from the surface water store. The AWRA-L model uses a modified version of the Penman-Monteith method to produce the potential evaporation. Daily AWRA-L potential evaporation grids were produced based on daily gridded climate data that were available on a 0.050 (approximately 5 km) national grid.The daily gridded climate datasets used to produce this estimate were generated by the Bureau of Meteorology 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).

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 surface area of storages was either calculated dynamically or was a static value produced from the AHGF (refer to previous table). The surface area of all weirs was a static value produced from the AHGF.

Assumptions, limitations, caveats and approximations

  • The AWRA-L 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.
  • The use of the static default AHGF surface area is an approximation only. It represents the water features at capacity and therefore likely results in an overestimation of evaporation from the water features.
  • 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.

Uncertainty information

The uncertainty estimate was not quantified.

Comparative year

The comparative year volume for line item '17.1 Evaporation from surface water' was restated in the water accounting statements from the 2012 Account due to an error identified in the method used to calculate this volume. Please refer to Restatement of comparative year information in the 'Water accounting policies' for more information.