Facing ongoing influences such as climate change, dam owners are under increasing pressure to ensure the safety of their assets. The consequences of failure are becoming more significant too, in light of factors like downstream urbanisation. With asset owners integrating new solutions to help them rise to the challenge, Hunter Water has turned its eyes skyward in a bid to advance its asset monitoring performance to the next level.
As dam assets age, accurate monitoring becomes increasingly important to ensure safety. With the impact of broad trends such as increasing urbanisation and global warming, the challenges facing dam owners and the potential consequences of failure are mounting.
Urbanisation, for example, is seeing more people living downstream of a dam than ever before. This represents a significant increase in the consequences of failure and associated catastrophic risk.
Meanwhile, global warming is introducing far more volatility to weather events, making them much harder to predict and manage.
“The biggest problem with climate change, particularly with dams, is the unpredictability of precipitation causing too much or too little water,” Mark Maslin, Professor of Earth System Science at University College London, said.
“Climate change is already causing more intense rainfall bursts, which are shorter and more unpredictable and are a major worry for dam owners.”
Under the influence of climate change, Australia’s already highly variable rainfall is likely to become far less predictable with one in 20-year maximum rainfall events predicted to become one in 15 or even five-year events by the end of the century.
At the same time, while dams are extremely long-lived, many are already decades old. Nonetheless, even dams which have been constructed relatively recently can present problems.
The spillway at Paradise Dam near Bundaberg, QLD, was damaged during 2013. This dam was only built in 2005.
Ensuring dam safety
For dam safety engineers the growing consequences and changing risks have prompted a reappraisal. However, the need for comprehensive monitoring presents a number of challenges.
“Dams are very large assets, and very high or extreme consequences result if they are to fail,” Daniel Turnbull, Dam Safety Engineer at Hunter Water, explained.
Among other assets, Mr Turnbull is responsible for the Grahamstown Dam in NSW. Constructed between 1955 and 1965, Grahamstown holds a reservoir of some 182,305 million litres behind a 5km-long embankment.
“You’re doing your best to monitor all the key points, but it is very hard to have absolute coverage of a dam,” Mr Turnbull said.
“It’s not physically practical to monitor every aspect of the dam, especially with a dam like Grahamstown where we’ve got over 5km of the embankment.
That’s one of the big challenges we face, making sure that our monitoring is targeted and effective.”
Faced with these challenges to effective monitoring and keen to ensure its assets are safe, Hunter Water began exploring alternative approaches to the traditional measurement survey and visual inspection.
“We were looking at other options that we could implement where we would actually get some measurements and start plotting trends,” Mr Turnbull said.
In September 2020, Hunter Water signed a three-year contract with UK-based Rezatec to provide satellite-based data and geospatial analytics to monitor structural and environmental changes at Grahamstown.
A three-year retrospective data analysis establishes a baseline of normal behaviour for the dam and therefore allows anomalies, where observations are outside the threshold of acceptable, to be identified.
Data from Hunter Water, such as water level information affecting movement, is overlaid to help pinpoint exactly where issues are down to a few millimetres of displacement.
In addition to precise movement, satellite data can also pick up other indicators of problems with dam infrastructure, such as vegetation. Vegetation is a good indicator of seepage, for example.
Switching to satellite but keeping people
Adopting high-tech observations from space enables resources to be more efficiently focused on potential problems before they become significant issues.
The Hunter Water team still carries out routine daily inspections, with team members visually noting any changes. “We wanted something to compliment that,” Mr Turnbull added.
“Now, if visual monitoring picks up that there’s a potential issue, we’re able to refer to satellite monitoring and reveal if there is something measurable to support that theory.”
Consistency and safety
The use of frequent millimetric surveys allows asset owners to go beyond regulatory requirements to establish a key measure to assess asset risk.
“Regulations for an extreme consequence category dam require a movement survey once a year, for a high consequence category dam, then it’s every two years. We wanted to have a bit more scrutiny than the bare minimum that we’re required to,” Mr Turnbull said.
Satellite observations also address the challenge to increase frequency of monitoring remote dam assets.
“In Australia, we’ve got some dams in rural areas which take several hours’ drive or flights to get there. In terms of being able to monitor those sites without having to send a team of surveyors out there to do it is very attractive,” Mr Turnbull said.
More importantly, though, satellite observations are repeatable, testable and achievable at a much higher frequency and more accurately than physically sending a survey team out to a site.
These key abilities are becoming far more significant considering climate change and other megatrends like urbanisation.
“With carefully thought-through monitoring, you should be able to understand exactly how your dam or dams are performing, so you know what is normal and, more importantly, what is not,” Ian Garside, Director at ProjectMax, one of the project partners, said.
“Robust monitoring can go further and allow you to manage the risks across your reservoir portfolio, helping to drive your business and regulation in a targeted way.
Possibly most importantly though, good monitoring takes you from managing your dams reactively to proactively with all the benefits that will bring.”