The SPERP commenced in 2004, following assent of the Snowy Mountains Cloud Seeding Trial Act 2004 (NSW).

The first stage of the SPERP took place from 2004 to June 2009, targeting an area of 1000 km2.  Extensive lobbying by stakeholders following the 2006 drought resulted in amendments to the Act, expanding the area authorised for cloud seeding operation to 2150 km2. The duration of the trial was also extended to April 2015.

Operations over the expanded area first commenced in June 2009.

The Act prescribes a number of mandatory requirements. These include:

• Silver iodide must be used as the seeding agent;
• Operations may only be ground based (no aircraft may be used for seeding);
• Operations may only take place when precipitation is likely to fall as snow and not rain;
• Environmental effects must be monitored.

Silver iodide is used as the glaciogenic (ice nucleating) seeding material because it has physical properties very similar to natural ice crystals.  Indium (III) oxide is used as the inert tracer agent.  The tracer particles are similar in size to the seeder particles; however they have no ice nucleating properties.

The project uses ground based generators arranged along the western side of the mountain range to disperse very small quantities of the seeder and tracer agents into winter storm clouds suitable for seeding as they pass over the mountain range.  These particles are invisible to the human eye - so small that more than 300 million particles would fit on the head of a pin!

Throughout the winter season SPERP personnel continually monitor meteorological conditions and forecast for potential cloud seeding opportunities. Six hours prior to an expected event, atmospheric soundings commence using weather balloons, and data from instruments located in the target area are monitored. Data from all the critical instrument systems are transmitted to the Cloud Seeding Control Centre ("CSCC") in real time. Cloud seeding experiments begin once all of the stringent operating criteria are satisfied. These criteria include:

• Freezing Level must be 1600m ASL or lower;
• Cloud top temperature -7°C or colder
• Cloud depth greater than or equal to 400m above the -5°C level
• Excess SLW must be available
• Target model output indicates snow will fall in the target area
• At least 15 generators targeting and available for operation
• Precipitation in the target or control area in last 30 minutes
• The forecaster expects the event to last for at least 5 hours

SPERP infrastructure includes a radiosonde (weather balloon) launch site near Khancoban, two remote observing facilities, 23 ground generator sites along the western side of the mountains and over 60 surface meteorological stations.