Average annual, monthly and seasonal evaporation

At a glance

These evaporation maps show the amount of water which evaporates from an open pan, distributed across Australia.

What do the maps show?

These maps show the average amount of water which evaporates from an open pan each month, season and annually. Evaporation is measured by the use of a "class A evaporation pan".

Average annual evaporation is calculated by adding evaporation totals over a specified period (1975 to 2005) and dividing by the number of years in that period (29 years in this case). Similarly, average monthly and seasonal evaporation are calculated by adding monthly or seasonal evaporation totals and dividing by the number of years in the specified period. The rate of evaporation depends on factors such as cloudiness, air temperature and wind speed. Measurements are made by the addition or subtraction of a known amount of water, which then tells us how much water has evaporated from the pan.

These maps are indicative of the amount of water evaporating from bare ground or open water, evaporation from land surfaces covered by vegetation is better estimated by evapotranspiration.

Areas in central Australia are very dry, and therefore have a high rate of evaporation. In contrast, coastal areas tend to have a lower evaporation rate as a result of their proximity to a large water source. Compare these maps to the maps showing average rainfall and humidity. Areas with low rainfall and low humidity tend to have a high evaporation rate, whilst areas with high rainfall and high humidity tend to have a low evaporation rate.

Further information

• About the maps - metadata and related information.
• Find out how climate statistics are calculated.
• Information about the range of gridded climate data we can provide.
• Information about additional climate products and other data available from the Bureau of Meteorology.
• Learn about the influences on the Australian climate.
• Explore other topics relating to climate education.