Cloud-seeding trials
The search for new water supplies is taking to the air. As the drought continues and traditional sources dry out, the Queensland Government's four-year cloud-seeding project is getting under way. Subject to conditions, from November onwards, to coincide with South East Queensland's wetter spring and summer seasons, aircraft will be doing initial cloud seeding and investigating local weather systems and cloud microphysics. A CP2 Doppler radar recently installed by the Bureau of Meteorology at Redbank Plains will provide valuable data for this research. Information is available on the research and seeding aircraft page.
The aim of the project is to find out if cloud seeding is a viable way of enhancing the rainfall over South East Queensland's dam catchments, including those of Somerset and Wivenhoe. However, it's important to realise that cloud seeding will not break the drought. The results will be used to decide if it's worthwhile investing in cloud seeding in the long term to increase water storage, and there is great interest in the project at the national level. Queensland Water Commission has information on the status of water storages.
Can we make it rain?
Cloud seeding as a way of generating increased rainfall is not new—it has been experimented with in various parts of Australia and overseas since the 1940s, and is currently used in southern parts of the country to improve water supplies for hydroelectric power generation. Very specific conditions are required for cloud seeding to be effective, and the purpose of the research project is to establish if these circumstances exist in South East Queensland.
The project, which is scientifically rigorous, has two components. The first is to study the inner workings of clouds—their shape and size and how they react with the environment and seeding treatment—and the second is to carry out cloud-seeding trials under local conditions.
Read a summary of the project.
How it works
Clouds form when water vapour present in the air condenses into minute water droplets, but these don't fall as rain until enough of them coalesce to form drops heavy enough to fall to the ground. This process is initiated by the presence of particles—dust, salt, sand, smoke or other atmospheric pollutants—which are the nuclei around which the water vapour condenses. In the cold conditions in clouds, the water freezes and forms ice crystals. Snowflakes then form and these melt to form raindrops.
One technique the project will consider is this glaciogenic cloud seeding—adding particles such as silver iodide crystals to the supercooled water already present in clouds to promote the onset of ice crystals. Another is hygroscopic seeding of 'warm' clouds using salt flares, which produce tiny particles of sodium, magnesium and calcium chlorides after burning to enhance the growth of cloud droplets by coalescence.
More information can be found in the commonly asked questions and answers section.
Supporting the project
The Queensland Government is fully sponsoring the project, which is being managed by the Queensland Climate Change Centre of Excellence (QCCCE).
Part of the project was to establish the Scientific Advisory Group, which is chaired by Professor Roger Stone (Director of the Australian Centre for Sustainable Catchments (ACSC) at the University of South Queensland), and includes experts on cloud seeding from the Australian Bureau of Meteorology, the Bureau of Meteorology Research Centre, CSIRO, and Monash University.
Last updated 08 November 2007.
