South East Queensland
17.1 Evaporation from surface water

Supporting Information

The evaporation from each of the storages listed in line item 1.1 Storages can be seen in the following table.

Evaporation from storages within the South East Queensland region
Water resource plan (WRP) area Water supply scheme (WSS) Storage name Evaporation
(ML)
Gold Coast Nerang Advancetown Lake (Hinze Dam)1 12,412
Little Nerang Dam1 529
Total Gold Coast WRP area 12,941
Logan Basin Logan River Bromelton Off-Stream Storage3  
Cedar Grove Weir2 616
Lake Maroon1 4,166
None Tingalpa Reservoir (Leslie Harrison Dam)1 6,610
Wyaralong Dam3 0
Total Logan Basin WRP area 11,392
Moreton Central Brisbane River and Stanley River
Mount Crosby Weir2 727
Lake Wivenhoe1 142,341
Lake Somerset1 56,212
Central Lockyer Lake Clarendon1 3,328
Lake Dyer (Bill Gunn Dam)1 1,167
Cressbrook Creek Lake Cressbrook2 7,098
Lake Perseverance2 2,409
Lower Lockyer Lake Atkinson (Atkinson Dam)1 7,313
Pine Valleys Lake Samsonvale (North Pine Dam)1 27,871
Warrill Valley Lake Moogerah1 8,062
None Enoggera Reservoir1 729
Gold Creek Reservoir2 205
Lake Kurwongbah (Sideling Creek Dam)1 4,718
Lake Manchester (Cabbage Tree Creek Dam)1 3,269
Splityard Creek Dam2 1,538
Total Moreton WRP area 266,988
Total SEQ region 291,322

Notes:

  1. Evaporation calculated using variable surface area
  2. Evaporation calculated using static surface area
  3. Evaporation not calculated as surface area of the storage was not available.

Quantification Approach

Data Source

Bureau of Meteorology.

Provided by

Bureau of Meteorology.

Method

The Priestly and Taylor method to estimate potential evaporation (as calculated by the WaterDyn model [Raupach 2008]) was used to estimate evaporation from the surface water store. Monthly potential, open water evaporation data produced by the Bureau of Meteorology were used, based on daily gridded climate data that are 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 datasets used to produce this estimate are 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).

The evaporation at each waterbody was estimated from the proportionally weighted average of grid points 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 water storage level for water storages where the relationship between storage level and surface area had been derived.

Assumptions, Limitations, Caveats and Approximations

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.

Uncertainty Information

The uncertainty estimate was not quantified.

Comparative year

This line item corresponds to 14.1 Evaporation from connected surface waterreported in the 2010 Account. There was a change in the modelling methods for the 2011 Account.

It is recognised that the volume of evaporation estimated for the comparison year (307,166 ML) using the new modelling methods is less than the volume reported for the 2010 Account (370,192 ML). The difference between the prior estimate of evaporation and the estimate produced for the comparison year can be attributed to the choice of the Priestly and Taylor potential evaporation over the Penman open water evaporation.

The difference of 63,026 ML represents a change of approximately 17% of the originally published volume. The 2011 Account comparison year uses the volume of 370,192 ML reported in the 2010 Account as this change was not considered material.