When TasWater was formed five years ago by combining all the water authorities throughout Tasmania, they also inherited more than 300 dams.

The dams vary in size from the size of a swimming pool to 15,000 megalitres, which is pretty big. As a reference that is more than 5,700 Olympic sized swimming pools of water. 

All of the dams owned by TasWater are either for supplying water to their customers or are for wastewater as part of their sewage treatment processes. 

In an effort to understand and assess works that need to be carried out to the dams, TasWater is currently undertaking a five-year plan.

“It is a pretty busy dance card; we have a number of larger sized dams in our portfolio which need to comply with modern engineering standards,” manager of dam safety, Fraser White said. 

“Currently we are working on nine dams, and over the next few years, all of the dams will be brought up to those modern standards.

“Some of the work will involve decommissioning dams; if they are no longer required, we will see if we can find a potential new owner for the dam otherwise we go through with the decommissioning process.” 

When it comes to decommissioning a dam, TasWater will investigate if it is need for core activities, discuss the plans with stakeholders and determine if a new owner can be found and if decomissioning is then required they will remediate the dam site and return it to its natural state. 

TasWater will be investing $40 million over the next few years to bring them up to standards set out by the Australian National Committee On Large Dams (ANCOLD). 

ANCOLD, is a not for profit organisation who drive best practice for dams across Australia. They prepare a set of guidelines which represent best engineering practice covering such matters as design, construction and through to decommissioning.

One of TasWater’s priorities is to ensure best practice when it comes to dam safety. 

“There can be risks involved with large weather events, we have a small team of dam safety engineers who will decide our best course of action, depending on how severe the weather is going to be,” Fraser said. 

“In some instances we would lower the water level if we thought we would get a large amount of water entering that particular storage dam.”

While there is plenty of maintenance and upgrading to the current 300 TasWater Dams, Fraser said there were no plans for any new dams. 

Managing TasWater’s portfolio of more than 300 dams is a challenging job, especially during periods of extreme rainfall.

Ensuring the safety of each dam requires a system that can process real time and forecast data, keep pace with ever changing storm conditions and produce information efficiently and accurately.  

​“To forecast rainfall events and resultant runoff we need to be innovative, have a system that is simple to use, visually easy to understand and capable of handling extensive real-time information from sources like weather stations and forecast data from the Bureau of Meteorology,”  senior dam safety engineer, David Krusjka said. 

Working closely with technical consultants TasWater developed a process which matches up rainfall data with specialist hydrology and hydraulics predictions to provide an assessment of what is likely to happen.

“Our system is recognised as world best practice and is only possible by drawing on the skills and support of our own TasWater specialists,” said David. 

TasWater’s forecasting system proved its worth during last month’s extreme rainfall event in Hobart.