Department for Environment and Water - Alternative water: Cloud…

Cloud seeding involves the artificial generation of rain in targeted locations by introducing very fine, chemically inert ‘seeds’ or crystals into the atmosphere or directly into clouds. The seeds are usually dispersed by plane or ground-based emitters and encourage the formation of ice crystals, which can increase the chance of rain or snowfall.

Silver iodide is commonly used as the seeding material, however clouds may also be seeded with dry ice pellets or flares that generate smoke full of salt.

Cloud seeding experiments and programs have been undertaken in many countries. In Australia, the CSIRO’s research and experimental trials into cloud seeding commenced in the 1940s and continued until the late 1980s (Table 1). Active cloud seeding programs have been undertaken in Australia’s principal cold-weather mountainous areas by Hydro Tasmania until 2016 and in New South Wales by Snowy Hydro until 2023^{^[1]}.

High-level mountainous regions are required for successful cloud seeding operations. In Australia experimental trials in lower lying areas have failed to validate the value of cloud seeding as a rain enhancement technique (Table 1).

Cloud seeding does not generate rain in times of drought due to the absence of rain-bearing clouds.

Table 1 Timeline of key historical cloud seeding trials in Australia

Period	Cloud seeding activities
Late 1940s-early 1950s	CSIRO scientists used aircraft to drop dry ice into the tops of cumulus clouds.
Mid 1950s	The CSIRO carried out experimental trials including in South Australia, Queensland and elsewhere using both ground-based and airborne silver iodide generators.
Late 1955- 1963	The CSIRO carried out four intensive experiments over Yorke Peninsula in South Australia, the Snowy Mountains, the Warragamba Dam catchment area west of Sydney and the New England region of NSW. Of the trials, only the Snowy Mountains results were seen as having some prospect of having produced higher levels of rainfall.
Late 1960s to 1971	CSIRO’s experiments in this period in Tasmania were also successful and a subsequent cloud seeding program operated in Tasmania for a number of decades until June 2016.
1970s	The CSIRO conducted cloud seeding experiments in Emerald, Queensland and in Western Victoria, but did not demonstrate a statistically significant increase in rainfall
Early 1980s	The Government of Western Australia ran a cloud seeding study in the early 1980s in the northern wheat belt, but failed to demonstrate it would provide an economical, reliable way of increasing rainfall.
Late 1980s	The CSIRO acted as scientific advisors to Melbourne Water in a cloud seeding assessment conducted over the Baw Baw plateau, a major water catchment area east of Melbourne. This work failed to conclusively show any enhancement of rainfall.
Early 2000s	The South Australian Government considered cloud seeding as a prospective rainfall augmentation option during the early 2000s. That work suggested further extensive trials over a long period would be needed to determine whether or not cloud seeding would provide any benefit.

Is cloud seeding a viable option for increasing rainfall in Adelaide and other regions of South Australia?

Based on our current understanding, cloud seeding and other approaches for artificially inducing rainfall are not seen as a reliable or cost effective means for South Australia to increase water supplies because:

Previous cloud seeding experiments in South Australia have not demonstrated an increase above natural rainfall.
Those areas where cloud seeding has been considered successful, have common features that are absent in South Australia, including the presence of rising terrain greater than 1000 metres above and upwind of the adjacent plains.
Cloud seeding is not an effective strategy during drought conditions when there is an absence of rain and cloud.
South Australia is likely to become even warmer and drier in the future.

Cloud seeding is also controversial, with concerns raised that cloud seeding might:

Increase asthma risk or impact soil and livestock;
Increase the severity of floods; or,
Rob downstream areas of rain that they would otherwise have received.

Cloud brightening

Southern Cross University is leading field trials of an innovative new technique that aims to prevent coral bleaching by spraying microscopic seawater particles into the air. Made possible with the support of the partnership between the Australian Government’s Reef Trust and the Great Barrier Reef Foundation, the technique known as marine cloud brightening enhances the clouds by helping them to reflect solar energy away from the reef; in turn helping protect coral from bleaching.