South East Queensland
17.1 Evaporation from surface water
The evaporation from each of the storages listed in line item 1.1 Storages can be seen in the following table.
|Water resource plan (WRP) area||Water supply scheme (WSS)||Storage name||Evaporation
|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|
|None||Tingalpa Reservoir (Leslie Harrison Dam)1||6,610|
|Total Logan Basin WRP area||11,392|
|Moreton||Central Brisbane River and Stanley River
||Mount Crosby Weir2||727|
|Central Lockyer||Lake Clarendon1||3,328|
|Lake Dyer (Bill Gunn Dam)1||1,167|
|Cressbrook Creek||Lake Cressbrook2||7,098|
|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|
|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|
- Evaporation calculated using variable surface area
- Evaporation calculated using static surface area
- Evaporation not calculated as surface area of the storage was not available.
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.
The uncertainty estimate was not quantified.
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.