Snowy Mountains Cloud Seeding Act 2004
The Snowy Mountains Cloud Seeding Act 2004 enables Snowy Hydro Limited to conduct permanent cloud seeding operations within the Snowy Mountains in accordance with an Environmental Management Plan (EMP) approved by relevant Ministers.
Under the Snowy Mountains Cloud Seeding Act 2004 (the Act), Snowy Hydro Limited (Snowy Hydro) carries out cloud seeding operations in the Snowy Mountains to enhance snowfall. Snowy Hydro commenced cloud seeding via a trial in the NSW Snowy Mountains area in 2004 to investigate the potential for enhancing precipitation over defined water catchments within the Snowy Mountains. Following a comprehensive evaluation of the trial by the NSW Natural Resources Commission, the NSW Government amended the Act on 31 May 2013 to enable Snowy Hydro to conduct permanent cloud seeding operations within an expanded area of the Snowy Mountains.
Cloud seeding operations are permitted in accordance with an Environmental Management Plan approved by the Minister administering the Environmental Planning and Assessment Act 1979 and the Minister administering Part 4 of the National Parks and Wildlife Act 1974 (the relevant Ministers).
The Environmental Management Plan specifies requirements that must be met during operations, including the seeding agent that can be used, the location and type of discharge of the permitted seeding agent, and environmental monitoring requirements that includes the evaluation of monitoring results to assist in identifying any emerging environmental issues.
In accordance with the Act, the Environmental Management Plan must be reviewed at least once every 5 years. The EPA coordinated the 5-yearly review in 2023 in consultation with relevant stakeholders. The revised Environmental Management Plan was approved by the relevant ministers in July 2023.
The Act also authorises aerial application of existing and alternative cloud seeding chemicals and prescribed a review and oversight role for the NSW Environment Protection Authority (EPA).
Snowy Hydro Limited is required to provide a report to the EPA detailing its compliance with the Environmental Management Plan and the results of any research and monitoring into the impact of cloud seeding operations on the environment by 31 March each year. The EPA is required to review this report and convey its findings, along with any recommendations, to the Board of the Environment Protection Authority and the relevant Ministers.
Cloud seeding is a process used to improve the capacity of orographic clouds (clouds formed as moist air rises over mountains) to yield precipitation as snow. To achieve this, chemical particles are introduced, or seeded, into these clouds. Snowy Hydro Limited (SHL) uses silver iodide as the seeding particle in the Snowy Mountains. Silver iodide has physical properties very similar to natural ice crystals. In addition, silver iodide is practically insoluble in water, tends not to dissociate to its component ions of silver and iodine, and does not become biologically available in the environment. Instead, it remains as a solid in soils and sediments.
During cloud seeding operations, the seeded silver iodide particles combine with naturally occurring supercooled water droplets in the clouds to form ice crystals. These crystals then grow until they become too heavy to stay within the cloud and fall as snow.
To seed the clouds, ground based generators are arranged along the western side of the Snowy Mountain range. The generators are able to disperse minute quantities of the seeding agent into winter storm clouds as they pass across the range. Cloud seeding operations only target cloud systems travelling from west to east and when temperatures guarantee that precipitation will fall as snow above 1400 metres.
Snowy Hydro Limited has been conducting a winter cloud seeding trial in the NSW Snowy Mountains since 2004. Independent evaluation of the trial indicates that snowfall can be increased by an annual average of 14% through cloud seeding. Environmental monitoring has to date not detected any significant adverse environmental impacts. The 2023 cloud seeding operations comprised 36 hours and 16 minutes of cloud seeding between 25 June 2023 and 9 September 2023. Approximately 13.8 kilograms of silver iodide were dispersed during these operations, covering a target area about 2110 square kilometres.
Under the Snowy Mountains Cloud Seeding Act 2004 (the Act), cloud seeding operations may only occur in accordance with an Environmental Management Plan that has been jointly approved by the relevant Ministers. The current Environmental Management Plan was approved by the relevant Ministers in July 2023 following the five yearly review as required under the Act.
The Act requires that Snowy Hydro Limited provide an annual report to the NSW Environment Protection Authority (EPA) and the relevant Ministers by 31 March, detailing its compliance with the Environmental Management Plan and the results of any research and monitoring into the impact of cloud seeding operations on the environment. The EPA is required to review this report and convey its findings, along with any recommendations, to the Board of the EPA and the relevant Ministers.