Queensland

The evaporation observations used in this report are based on the amount of water that has evaporated from a Class A open evaporation pan.

Evaporation data, along with rainfall information, can be used to calculate water requirements for crops.

• High evaporation rates reduce soil moisture, impacting pasture growth and crop development.
• This can be critical in hot dry periods when water demand from plants is high, especially if there is already a reduced water supply (i.e. due to low rainfall).

Evaporation is dependent on many factors—air temperature, humidity, wind speed and cloud cover.

It is typically at its highest during hot, dry and windy conditions, and lowest in cold and wet conditions. Assessment of long-term pan evaporation trends is difficult due to high year-to-year variability, incomplete data sets, site changes and relatively short periods of record.

Average annual pan evaporation equals or exceeds 3,000mm in inland Queensland locations, such as Longreach and Mt Isa, where average annual rainfall is typically 500mm or less.

Average annual pan evaporation is less than 2,400mm in many coastal and sub-coastal areas.

• Townsville is the exception. It has a drier climate despite being on the coast, and an average annual pan evaporation of 2,588mm.