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
• 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.

Evaporation is typically:

• highest during hot, dry and windy conditions
• 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 record periods.

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

Average annual pan evaporation is less than 2,400mm in many coastal and sub-coastal areas. Townsville is the exception, as it has a drier climate despite being on the coast. Townsville’s average annual pan evaporation is about 2,500mm.

Manual observations of annual pan evaporation are not readily available for recent years.  However, estimates for most of the Queensland pan evaporation locations in this report suggest that annual pan evaporation tended to be near or above average (based on 1970 to 2016) in 2019 to 2020 and below average from 2021 to 2023.

For each location, annual pan evaporation totals are plotted for the extent of the high-quality dataset records. Rolling ten-year averages are plotted if there are ten consecutive years of annual data.

High-quality evaporation data beyond 2016 was not available at the time of publication.