Cloud seeding

Cloud seeding is the process of artificially generating rain by implanting clouds with particles such as silver iodide crystals. After extensive testing, the CSIRO has determined that cloud seeding is unlikely to be effective in much of Australia.

Cloud seeding is usually carried out by sprinkling particles from a plane. Using weather forecasting techniques, suitable clouds are identified based on the location of the target area and the prevailing winds. Given the appropriate conditions, cloud seeding can modify clouds and induce rain. This works in two ways: by producing rain when none would fall naturally; or by increasing the amount of rain that falls over a particular area.

Cloud seeding relies on a number of factors to be in place before it can be considered a cost-effective water supply solution:

• It is only effective in certain locations in a limited number of weather conditions. Also, cloud seeding requires existing clouds; it will not produce rain out of thin air.
• It works best in wet years where it can provide additional storage in dams.

Not all types of clouds are suitable for seeding. Clouds must be deep enough and of a suitable temperature (between -10 and -12 degrees Celsius) to be seeded effectively. The wind must also be below a certain speed. These conditions are most common in mountainous areas. This is a problem for much of the Australian mainland, including Perth, which is predominantly flat and therefore generally not conducive to cloud seeding.The most successful cloud seeding to date has been conducted in Tasmania, mainly in the mountainous west. Concerns have also been raised about the long term environmental effects of using silver iodide crystals.