Hydro Tasmania is aware of the devastating impact of the recent floods and extends
its sympathies to all who have been affected. Hydro Tasmania’s operational focus at this time is on the safety of our people, the public and our assets.
Hydro Tasmania understands community concern about its cloud seeding program. Due to the unprecedented dry conditions since September 2015, Hydro Tasmania began its cloud seeding season in April, one month earlier than has been the practice in recent years, to help rebuild storages affected by record low rainfall during Spring 2015 – Autumn 2016.
As part of that program a cloud seeding flight was undertaken on Sunday morning, 5 June. It was targeting the Upper Derwent catchment, specifically Lake Echo, one of the storages that remained below its desired level.
There were no flood warnings in effect for the Upper Derwent at the time of the flight. This area received a substantial, but not excessive, amount of rain after Sunday morning’s flight.
Water in the Ouse River came from the overtopping of Lake Augusta due to the flood event. Lake Augusta is not in the catchment targeted by Sunday’s cloud seeding flight.
Hydro Tasmania’s cloud seeding program is currently on hold. We believe that operation of our dams and waterways did not contribute to the flood flow. We had been operating storages to reduce levels following the significant inflows in May.
Many small and medium storages have been spilling, which is not unusual during times of high inflows. These storages have been spilling on and off since strong rainfall started in early May. When they are approaching full or on spill, we generate as strongly as possible to avoid or minimise spilling.
Our dams are not designed for flood mitigation. When they reach full supply level what flows in, flows out. During extreme flood events, spill is inevitable.
Inspections to date have found minor damage to non-critical elements of some dams. This minor damage will be repaired over coming weeks, and poses no issue for power generation or dam safety.
Floodwaters have also caused damage to some of Hydro Tasmania’s secondary assets, mainly landslips and road damage, damage to some canals, as well as failure of some river flow monitoring sites. We continue to assess the extent of that damage.