Cloud seeding not to blame for June floods

Hydro Tasmania’s cloud-seeding program remains on hold, but the state-owned electricity generator said analysis shows a cloud-seeding flight did not have a measurable ­impact on last month’s floods.

Hydro Tasmania handed its final report on the cloud seeding over the upper Derwent catchment on June 5 — the day before devastating floods hit the region — to the State Government. Post-flight analysis showed the clouds seeded on that day had high levels of ice content, which made seeding ­ineffective.

Cloud seeding works by using silver iodide to introduce ice nuclei to clouds with high levels of super-cooled liquid water and low or no ice content. The process aims to convert the super-cooled liquid water droplets to ice, which will then fall as precipitation – rainfall or ice crystals.

If a cloud has high levels of ice content and is already readily precipitating, introducing further ice nuclei will not enhance this process.

Hydro Tasmania CEO Steve Davy said he appreciated the high level of community concern, and the company’s cloud seeding program will not resume until a full internal review of the program has been completed.

“We will now review the cloud seeding program to make improvements in our processes, including in relation to seeding when there is a risk of floods, so that future decisions about cloud seeding are more in line with community expectations,” he said.

Cloud seeding will not likely be undertaken again this season.

“Given the unfortunate loss of life during the floods, we anticipate that there may be formal inquiries in the future in relation to the floods, including the cloud seeding flight, and we look forward to co-operating with any such processes and explaining our conclusions further at that point,” Mr Davy said.

Hydro Tasmania started cloud seeding earlier than usual this year to try to fill rapidly diminishing storages.