Sydney
42.1 Evaporation from storages

This line item refers to total evaporation from the surface water storages within the Sydney region that supply water to the urban water system.Total evaporation recorded from storages was 101,062 ML.

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

Evaporation from storages managed by the Sydney Catchment Authority

Storage	Evaporation (ML) – Sydney Catchment Authority
Cataract	6,274
Cordeaux	4,598
Avon	7,087
Nepean	5,340
Woronora	1,496
Lake Burragorang (Warragamba Dam)	46,196
Prospect	5,340
Wingecarribee	5,759
Fitzroy Falls	5,492
Lake Yarrunga (Tallowa Dam)	8,050
Blue Mountains*	279
Total	95,911

 * Blue Mountains storage reservoirs include Medlow Reservoir, Greaves Creek Reservoir, Upper Cascade Reservoir, Middle Cascade Reservoir and Lower Cascade Reservoir.
 

Evaporation from storages not managed by the Sydney Catchment Authority

Storage	Evaporation (ML) – Bureau of Meteorology
Bamarang	765
Danjera	938
Flat Rock Creek	259
Pejar	1,768
Sooley	1,344
Farmers Creek No. 2	77
Total	5,151

Bureau of Meteorology.

Bureau of Meteorology (the Bureau).

The Priestly and Taylor method to estimate potential evaporation (as calculated by the WaterDyn model, Raupach et al. 2008) was used to estimate evaporation from the connected surface water store. Monthly, potential water evaporation data produced by the Bureau were used, based on daily gridded climate data that is available on a 0.05 degree (5 km) national grid.

Potential evaporation is an estimate of the evaporative demand of the environment. The daily gridded climate data sets used to produce this estimate 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 proportionally weighted average of grid-pixels that intersected each water feature. The volume was then estimated using the monthly average surface area of each waterbody. The surface area varied dynamically with changing reservoir storage level for storages 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.
• The total surface area of the surface water store within the Adelaide region included only the storages, urban storages and weirs listed in the supporting information.

The uncertainty estimate was not quantified.

Daily Return System (DRS) database.

Evaporation from following storage reservoirs is managed by SCA: Cataract Reservoir; Cordeaux Reservoir; Avon Reservoir; Nepean Reservoir; Woronora Reservoir; Lake Burragorang (Warragamba Dam); Prospect Reservoir; Wingecarribee Reservoir; Fitzroy Falls Reservoir; Lake Yarrunga (Tallowa Dam); Blue Mountains reservoirs (Medlow Reservoir; Greaves Creek Reservoir; Upper Cascade Reservoir Middle Cascade Reservoir; Lower Cascade Reservoir).

Measured pan evaporations were adjusted by a pan factor.

Nil.

The evaporation volume is based on measured data. Estimated uncertainty based on measurement accuracy, professional judgment on the calculation method and organisational practice is +/– 10%.