Between 2004 to 2023, cloud seeding was used to enhance snowfall over the Snowy Mountains during the cold months
2025 CLOUD SEEDING UPDATE: Following a comprehensive review, Snowy Hydro is permanently ceasing its cloud seeding program. This decision follows a review that determined the escalating costs of the program outweighed its benefits.
Snowy Hydro is working with stakeholders to decommission cloud seeding related equipment. For more information, see here.
In 2004, Snowy Hydro began a cloud seeding program to enhance snowfall over the Snowy Mountains during suitable conditions in the cold months. The cloud seeding program was backed by extensive scientific research, independent review and stringent environmental regulation.
While there are a number of different cloud seeding techniques in operation worldwide, Snowy Hydro’s cloud seeding program used ground-based generators to introduce a seeding agent into suitable existing clouds in a process called ‘glaciogenic cloud seeding’ that encourages the formation and growth of ice crystals. This process can enhance the amount of snow falling from the cloud.Snowy Hydro’s cloud seeding program began as a scientific trial in 2004, enabled by NSW legislation, the Snowy Mountains Cloud Seeding Trial Act 2004 (NSW). An independent scientific evaluation of the trial found that under suitable conditions, cloud seeding increased precipitation by an average of 14 percent and that there were no adverse environmental impacts on rainfall downwind of the target area. The evaluation was supported by scientific peer-reviewed publications. The NSW Natural Resources Commission conducted an independent review of the trial, evaluation and the environmental monitoring program. It was found cloud seeding increased snowfall in the target area and there was no evidence of adverse environmental impacts.
In 2013, Snowy Hydro began an operational cloud seeding program under the amended Snowy Mountains Cloud Seeding Act 2004 (SMCS Act).
Key aspects of Snowy Hydro’s operational cloud seeding program (that ceased after 2023) can be found below:
- Cloud seeding operations were carried out in accordance with an approved Environmental Management Plan (EMP).
- The NSW Environment Protection Authority (EPA) reviewed compliance of cloud seeding operations with the SMCS Act and the EMP. Snowy Hydro reported annually on its cloud seeding operations to the NSW Government and EPA.
- The area targeted for cloud seeding was approximately 2,110 km2 within the Snowy water catchment in the Snowy Mountains region.
- Silver iodide was the approved seeding agent. Silver is already present in the atmosphere, soil and sediments of the Snowy Mountains from natural and distant industrial sources, unrelated to cloud seeding. Silver iodide is commonly used for cloud seeding because it has similar physical properties to an ice crystal. It is also insoluble in water and does not readily become biologically available in the environment.
- The use of a ‘tracing agent’ during cloud seeding operations ceased following the 2011 season.
- Land-based aerosol generators were used to dispense the seeding material. Snowy Hydro’s cloud seeding program did not involve the use of aircraft.
- Operations were only carried out when precipitation was likely to fall as snow to at least 1,400 metres, as stipulated by the SMCS Act. Cloud seeding operations only took place during suitable atmospheric conditions in the cool-season, between May and October each year until 2023.
- Snowy Scheme storage levels were assessed before each cloud seeding event to ensure additional snowmelt from cloud seeding would not contribute to flooding downstream.
- On average 90 hours of cloud seeding were carried out each year, however, this depended on the frequency of suitable weather systems for cloud seeding, which varied year to year.
- Environmental management was always a critical component of Snowy Hydro’s cloud seeding program. Silver concentrations were monitored in a range of environmental matrices and potential accumulation zones within and around the target area. Over 10,000 environmental samples were collected through the course of the cloud seeding program. Samples underwent chemical analysis at an independent laboratory and the results were subject to independent statistical analysis and a verification audit.
- There is no evidence of any significant adverse environmental impacts associated with Snowy Hydro’s cloud seeding activities.
- There is no evidence of any effect from cloud seeding on precipitation outside of the target area.
- Independent evaluation has shown that under suitable conditions, cloud seeding increased precipitation by 14%. When the snow melted the additional water was valuable for renewable hydroelectricity, the environment and other downstream water uses.
Click here to access the annual cloud seeding operations reports.