Recent heavy rainfall means there is a lot of water flowing through Hydro Tasmania’s network and members of the public should exercise caution around lakes and dams. 

When there is a lot of rain, Hydro Tasmania’s dams go ‘on spill’ – that’s a normal part of how a hydropower scheme operates. 

‘Spill’ is the excess water that leaves a dam when a lake is full. It exits via the dam’s spillway, which is a common feature of hydroelectric dams.  

Hydro Tasmania’s Head of Generation Operations Jack Penny advised the public to avoid the lakes, waterways and dams during the wild weather. 

“Safety is always our number one operational priority. During extreme weather events, water conditions are likely to change very quickly and can create hazardous conditions. We ask the public to exercise caution and avoid our lakes and dams.” 

After two of the driest years on record, the recent rain has boosted the Hydro Tasmania's multi-season storages and put around half of its dams on spill. 

“We’ve gone from not much rain at all to having lots of water in the system. This variability is part of operating a hydropower system and we are well equipped to manage it,” said Mr Penny. 

“The rain has topped up our larger storages, and many of our smaller hydropower lakes are full and spilling. It’s a normal part of how our dams operate and it’s what they are designed to do.” 

While Hydro Tasmania has a few large multi-season storages like Lake Gordon, Lake Pedder and yingina/Great Lake, most of the business’s 52 lakes are part of ‘run of the river’ hydropower schemes.  

These schemes harness the natural flow of the river and generate electricity through a series of power stations as the water flows downstream and eventually out to sea. 

“This means we can generate electricity using the same water as it travels through each power station, one after the other,” said Mr Penny. 

Run of the river storages do not increase or decrease the risk of flooding downstream. 

Mr Penny said Hydro Tasmania adjusts its operations during heavy rains to manage the water in the system. 

“The incoming water either goes through the machine or over the spillway, so the amount of water downstream remains the same,” Mr Penny said. 

In some run of the river schemes, some water is diverted between storages via tunnels or penstocks, like in the Mersey-Forth Scheme in Tasmania's North-West, but these are still considered to be run of the river systems. 

Ends.