The Murrumbidgee to Googong pipeline is meant to pump up to 100 million litres of water a day from the Murrumbidgee River to Googong Dam in drought conditions to ease the likelihood or length of water restrictions in Canberra.

The pipeline has never been used for its intended purpose since it was completed in 2012. It was turned on for a month last year to maintain pumps and had been used previously to only maintain the pipes.

As Canberra's combined dam levels last week fell below 50 per cent for the first time in 17 years and residents faced the looming prospect of water restrictions, Icon Water is now in the invidious position of still not being able to use the emergency pipeline because there is not enough water in the Murrumbidgee River.

The pipeline is meant to be triggered when Canberra's total water supply falls below 62 per cent.

On Friday it was just under 50 per cent full but there was no prospect of the pipeline being used. Googong Dam is one of four dams that supply Canberra's water supply.

Icon Water says it remains confident the pipeline can be used in dry conditions and modelling had shown it could have been used in the Millennium Drought of the mid-2000s.

However, Icon Water says this year has simply been exceptionally dry and there is just not enough flow in the Murrumbidgee to use the pump station. Also, Icon Water's "environmental obligations prevent us from pumping in the driest 20 per cent of conditions".

"There are normally significant periods when we can use the M2G [pipeline], even during dry overall conditions," a spokesperson said.

"Unfortunately, the last three years have had the lowest dam inflows ever recorded in Canberra and it has not been possible to pump large quantities of water through the pipeline.

"However, the pipeline could still be very useful in reducing the impacts of the drought and helping us to recover."

Icon Water senior engineer Tim Purves said that after the pipeline had been completed in 2012, Canberra's dams were plentiful and the pipeline had not been needed to be activated.

But retired NSW bureaucrat and Burra resident Peter Duffy said even "Blind Freddy" could have seen the pipeline would never work in a drought and it was "most definitely a white elephant".

"It was always extremely unlikely at a time when we really needed the water it wasn't going to be in the Murrumbidgee, unless it was released from Tantangara Dam," he said.

Mr Duffy rejected Icon Water's claim that this year needed to be treated as one out of the box.

"I don't think it's that exceptional. Droughts come and droughts go," he said.

Icon Water has had a financial arrangement with NSW to release water from the Tantangara Dam in the Snowy Mountains into the Murrumbidgee River.

Mr Duffy maintains the only way the pipeline would work in a drought was a release from Tantangara.

Icon's Tim Purves said that deal had ended some time ago and there were no plans to try to seek any future releases from Tantangara Dam.

"It's definitely not being considered at the moment. It's not economically viable," he said.

An Icon Water spokesperson said the Tantangarra transfer "was considered to provide marginal benefit to the community on review".

"We have provided notice of our intention to terminate this agreement but still have a trailing option to exercise it over the next 18 months," they said. "So, Icon Water still has the option to utilise the Tantangara transfer option for up to three years following cessation of the contract through to June 2021, if required."

It's not certain there would even be excess water from the dam available for purchase

Tantangara Dam was 45 per cent this time last year. It was now just over 10 per cent full.

The Murrumbidgee to Googong pipeline was completed and commissioned in August, 2012 as part of a suite of water security projects initiated during the Millennium Drought.

Water is extracted from the Murrumbidgee River, at Angle Crossing, and transferred via a 12km pipeline prior to it being released into Burra Creek, which then flows into Googong Dam. Three kilometres of the pipeline is in the ACT and nine kilometres in NSW.

Burra resident Chris Devitt agreed the pipeline had been a waste of money while also causing stress to landholders as they fought for appropriate compensation to have the infrastructure cross their properties.

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Mr Duffy said the huge outlet infrastructure at Burra Creek was also, aesthetically, a disaster.

"The issue for Canberra residents is the cost of the pipeline and the fact it's a white elephant," he said.

"The issue for Burra residents is that they've built a bloody great trench in this valley with a huge World War Two bunker right at Burra Creek. It's an environmental insult as well as anything else."

Icon Water maintained the pipeline was an important asset for the ACT's long-term water security and when asked if it represented value for money replied:

"Source water infrastructure is designed to withstand droughts, and is not necessarily used during normal conditions.

"It is too soon to evaluate the benefits of the infrastructure in the current drought, but modelling for the business case to build the pipeline identified that it can significantly improve Canberra's water storage during drought conditions.

"This reduces the likelihood of Canberra experiencing water restrictions and can also reduce the length and severity of water restrictions if they are required."

The Bureau of Meteorology's forecast for summer predicts no major rainfall for the region until at least February, and a drier than usual season.