The potential for cloud seeding in the Snowy Mountains was recognised more than fifty years ago, with a study undertaken by the CSIRO and the Snowy Mountains Hydro-electric Authority between 1955 and 1959.

This early research reported a 19% increase in precipitation for those storms that were seeded.  The outcomes were challenged however because of issues relating to trial design, and the evaluation and interpretation of the results.

Cloud Seeding Trial, Stage I (2004 – 2008)

An extended period of drought during the second half of the 1990s prompted Snowy Hydro to further investigate and confirm the effectiveness of cloud seeding for enhancing snowfall. During 2003, Snowy Hydro gave evidence to the House of Representatives Standing Committee on Agriculture, Fisheries and Forestry Inquiry into “Future water supplies for Australia’s rural industries and communities”, outlining a proposed cloud seeding research trial. The Committee subsequently found that cloud seeding should be considered as potential generator of additional water.

In 2003, an independent Expert Panel was commissioned to investigate any environmental issues associated with cloud seeding. The Panel reported to the NSW government that cloud seeding would be unlikely to have a significant adverse impact on the environment.

On 25 February 2004 the NSW Minister for Agriculture and Fisheries announced that after careful consideration of the Expert Panel Report, the NSW Government would make the necessary legislative arrangements for a six year cloud seeding trial to be undertaken. The Snowy Mountains Cloud Seeding Trial Act 2004 (NSW) (SMCST Act) was subsequently proclaimed on 7 April 2004.

This legislation authorised a target area of approximately 1000 km2, with a trial duration of six years. The SMCST Act established the role of the NSW Natural Resources Commission (NRC) to supervise authorised cloud seeding operations and report back on any environmental impacts of cloud seeding.

The trial commenced in the winter of 2004, with all suitable storms seeded during this start-up year. All of the necessary infrastructure, instrumentation, experimental and operational procedures were developed, installed and tested during the winter of 2004. The Cloud Seeding trial was fully funded by Snowy Hydro.  Cloud seeding experiments commenced during the winter of 2005.

Commonwealth Grant

In late 2006, the outstanding scientific merit and national benefit potential of the trial was recognised by the Commonwealth government, and Snowy Hydro was awarded a grant of $4.02 million under the Renewable Energy Development Initiative to support the research.

Cloud Seeding Trial, Stage II (2009 – 2012)

With protracted drought conditions persisting in south eastern Australia, and early promising results, by late 2006 stakeholders commenced vigorous lobbying of the NSW government to increase the size of the cloud seeding target area, and to extend the duration of the trial to maximise effectiveness and benefits. Interim results from the trial were found to be very promising, and comprehensive environmental monitoring undertaken since the commencement of the trial had shown no evidence of any adverse environmental impacts.  On this basis the NSW government passed amending legislation in May 2008, increasing the size of the target area to around 2000 square kilometres, and extending the duration of the trial until 2014.

By the early winter of 2009, sufficient cloud seeding experiments had been completed to allow for a robust independent scientific evaluation of the trial to be undertaken. That evaluation found cloud seeding increased precipitation by an average of 14%, and that there were no adverse impacts on rainfall downwind of the target area. Two separate, independent scientific peer reviews supported this result, with the research subsequently published in the peer-reviewed Journal of Applied Meteorology. It is interesting to note that the results are similar to those reported by the CSIRO study undertaken during the 1950s.

Independent Review

The NRC also conducted its own independent peer review, consulting extensively with stakeholders and engaging further independent experts to assess both the outcomes of the experiment and environmental monitoring.  The key findings were:

“Overall, the NRC confirms that the trial is being conducted in compliance with the Act, is of a high scientific standard and the evaluation plan is statistically sound.

There is no evidence that cloud seeding operations have had adverse environmental impacts over the first phase of the trial (SPERP 1), based on Snowy Hydro’s environmental monitoring results. There is no evidence that the chemicals used as the seeding agent … have accumulated in sampled soils, sediments, water or moss in the areas being tested.

The monitoring results have detected no adverse impacts on rainfall in downwind areas during the first phase of the trial.

Snowy Hydro’s 2009 SPERP report provides evidence that cloud seeding has increased snowfall in the target area under defined weather and operating conditions. Its primary statistical analysis of the trial data yielded a positive but inconclusive result. However, Snowy Hydro also analysed physical evidence and carried out a number of secondary statistical analyses of the trial data. Together, these indicate that cloud seeding has had a positive effect in increasing snowfall in the overall target area.”

The final review by the NRC was in 2012. In a letter to the Ministers the NRC reported:

“The trial… continues to comply with the Act and to be of a high scientific standard. There is no evidence of adverse environmental impacts, or of adverse impacts of rainfall in down-wind areas.”

Operational Program

Snowy Hydro continued cloud seeding experiments, pending a decision by the NSW government on the future of cloud seeding in NSW, before the legislative cut-off date of 2014.

In October 2012, the exceptional scientific merit of the Cloud Seeding Program and absence of adverse environmental impacts were sufficiently compelling for the government to pass the necessary legislation for an ongoing, operational program, to commence from the winter of 2013.

The Environment Protection Authority is appointed to review compliance of cloud seeding operations with the governing legislation under the operational Program.