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Adelaide

                                                                                                   

14.1 Evaporation from connected surface water

                             

Supporting information   


The value reported in the water accounting statement (27,692 ML) represents the total evaporation from SA water storages within the Adelaide region. The evaporation from each water storage is provided in the table below.

Storage

Volume (ML)

Barossa Reservoir

1,156

Barossa Weir

54

Clarendon Weir

137

Gorge Weir

14

Gumeracha Weir

37

Happy Valley Reservoir

2,909

Hope Valley Reservoir

917

Kangaroo Creek Reservoir

1,461

Little Para Reservoir

1,652

Millbrook Reservoir

3,136

Mount Bold Reservoir

4,396

Myponga Reservoir

3,442

Onkaparinga Summit Reservoir

194

South Para Reservoir

6,627

Warren Reservoir

1,559

Total

27,692

 

Quantification approach   


Data source

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

 

Data provider

Bureau of Meteorology.

 

Method

The Penman method was used to estimate evaporation from the connected surface water store. Monthly, open water evaporation data produced by the Bureau of Meteorology were used, based on daily gridded climate data that is available on a 0.05 degree (5 km) national grid. The Penman method estimates the evaporation that would occur from a small open waterbody and assumes the evaporation does not modify the meteorology through evaporative cooling. It assumes aerodynamic conductance of 0.01 m/s and saturation deficit is estimated as (saturation vapour pressure at Tmax) – (saturation vapour pressure at Tmin).

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

The evaporation at each waterbody was estimated from the average of the grid-points within 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 Adelaide region was calculated using this dynamic method.

 

Uncertainty

Ungraded.

 

Assumptions, approximations and caveats/limitations

  • The Penman 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 time-scale.
  • The total surface area of the surface water store within the Adelaide region included only the reservoirs (and not the river channels).