WATER SERIES: According to water expert Professor Stuart Khan, droughts – and the rate at which we can run out of water as a consequence – are speeding up. Around the country coastal cities now rely on desalination plants as a matter of course to provide water security. There’s a “purification” or recycling plant ready and waiting to supply Brisbane should the dams fall below 40 per cent, and a small demonstration plant in Sydney that’s just been completed to start educating the people around what many other global cities have been doing for decades. Dams are not an option, he says, because so we’ve already tapped out the most efficient locations.
Professor Stuart Khan, one of Australia’s pre-eminent experts on water supply, says all the forecasts suggest Australia is heading into a drier period, with each drought more severe than the last. Not necessarily in terms of duration, he says, but in terms of intensity and how quickly, we can start to run short of water.
“In the drought of 2017 to 2020 Sydney, we’ve never seen Sydney’s water supplies be depleted as quickly as they were during that three years – much faster, [nearly] twice the rate really – as they depleted for the Millennium drought.”
The Millennium drought duration was longer, he says, but the most recent drought was a wake up call on how quickly things can happen.
Khan, who recently moved from the University of New South Wales to take up the role of Head of School Civil Engineering at the University of Sydney says water efficiency is definitely a good opportunity. It’s often the cheapest but in relation to the amount of water places such as Sydney are going to need over the next 20 years – it’s a drop in the proverbial bucket.
“We’re talking about hundreds of gigalitres of additional water supply. You’re not going to get hundreds of gigalitres from improved water efficiency.”
Part of the reason for that is that after the Millennium drought a lot of efficiency measures were put in place. Some were behavioural, but the biggest contribution came from infrastructure measures, such as the BASIX sustainability rating system for residential property in New South Wales. “BASIX is an infrastructure measure. It requires people putting in rainwater tanks, it requires people putting in water efficient devices, low flow showerheads, dual flush toilets. We now have efficiency ratings and standards on white goods, refrigerators, dishwashers, cones, washers, etcetera that we didn’t have before,” Khan says.
All measures that have been strongly taken up in the past 20 years since the Millennium drought. The results have been lower amounts of water used per person.
Severe water restrictions at the time helped but then, when the dams started to fill again, something strange happened.
“Everybody expected that there’d be a big rebound in the per capita use. But it actually never came.
“If you look at how much water we were using a year or two after the Millennium drought, it flatlined. And it’s only recently, in the last five years or so with population growth that we’ve started to use more than we were using in the early 2000s.”
There was some behavioral change, Khan says but most of the savings came through infrastructure. People didn’t rip out the water savings measures in their taps and toilets for instance when the drought ended.
In Sydney the biggest impact was in newer houses that triggered the BASIX building clauses, rather than older houses.
So that’s good, right? Yes and no, Khan says.
“We’re now per person much more water efficient than we used to be 20 years ago. But it also means that that low hanging fruit has been picked to a degree. You can’t go and put another water tank in, once it’s in.”
What about behaviour change?
Infrastructure was the most significant component of that reduction, Khan says. “And some of the behavior change and infrastructure are kind of interrelated. I mean, very few people now have a hose without a nozzle without a trigger on it.” And there’s a swathe of new water efficiency appliances that have been brought to the market bearing the water efficiency labelling system created by the federal government, WELS.
The problem is that as we’re more water efficient now it’s going to be a lot harder to find significant savings when the need comes.
Khan says we currently use about 550 gigalitres per year and ideally that should be about 10 per cent less.
But how do we get greater efficiencies? Stopping water leaks is one, and this is a significant big problem. Sydney, for instance, loses quite a lot of water through leakage, broken pipes and so on but 70 per cent of usage is in residential.
“So the big gains have to come through residential properties. Which again, I think is challenging in new areas developed under BASIX but potentially in some of the older areas, there might be more opportunities.”
Around the country though, most jurisdictions outside of NSW don’t have the baked in efficiency that BASIX demands through mandatory building codes.
They rely on behaviour changes and water restrictions at a time of need.
In Queensland, he says, there’s reliance on communications to encourage water savings, particularly in South East Queensland, where authorities try to get people “to understand the importance of conserving water and buildings; social support for the idea that conserving water is the right thing to do.”
Big infrastructure investments are inevitable
“They’re quite active in doing that. But like everywhere else, South East Queensland and Sydney are also looking at what are the next big infrastructure investments to meet the demand beyond what can be clawed back through water efficiency.”
And the big answer they have alighted on is seawater desalination plants and – at last and tentatively – purified recycled water.
In Melbourne, he says, the concern is more around long term water supply capability.
“They’re in a bit more of comfortable position than Sydney, in that the seawater desalination plant they have in Melbourne is actually huge – so, you can supply, I think, 400 megalitres per day; in Sydney is 250 megalitres.”
Different stories apply.
Sydney’s desalination plant wasn’t operational for nearly 10 years until the last drought and most people assumed that the plant would be turned off after the drought broke. But water then was very poor quality, which is difficult to treat, Khan says. Next came floods and a build up of mud and sediment. Which made it even harder to treat.
So the desal plant was kept operating.
Khan says this piece of infrastructure can supply 50 per cent of Sydney’s drinking water and it’s been running ever since.
The reason for that is simple. “You actually get a lot more benefit from the seawater desalination plant, if it’s running right from the start of the drought. And you never know where you’re at the start of the drought. So, you have to keep it running all the time. And that is that’s the new operational policy for Sydney.”
Which implies big electricity bills.
“It is our most expensive supply. Yeah, it does have an impact on customer bills. But the argument has been made and accepted by the pricing regulator, that that additional cost is a valid cost for the extra water security that you get by keeping it running.”
Does Khan agree with that?
“Yes, because it really is a problem. If you if you don’t have that desal plant operating upfront, then the dams are going to be dropping, dropping, dropping before you get it brought online, you’ll find yourself in a much more perilous situation.”
Currently wind farms supplement the plant and the planning approval from the NSW government in around 2006-07 was that all of the energy it would need would come from energy credits from a wind farm at Bungendore near Canberra.
In Melbourne the desal plant runs differently. Each financial year, the state government puts in an order for how much water it needs. And this year the order was zero because the dams are full, so it is shut down.
But how quickly can that surplus disappear? Do we need more dams?
In 2017 to 2020, Khan says, NSW went from 80 per cent full to 40 per cent in two years.
So, what is the answer for our water security? Are dams still the way to go?
Khan says we’re not building more dams. For our big cities at least.
“And that’s because most of the best opportunities for taking water from the environment are already tapped into.”
When our cities evolved, planners took the easiest options first – where to capture the most water for the least cost.
“If you’re going to dam another river, you’re going to be going further away. So you’re going to have a the cost benefit ratio of any subsequent dams are going to get lower and lower because you start off with the best. So big cities like Sydney, Brisbane, and Melbourne have built all of the really optimum dams.
“If Sydney was going to be building another dam, we’re talking about building further upstream on the Shoalhaven River and pumping it 200 kilometers to Sydney.”
With that scenario desalination becomes the cheapest, less energy intensive option.
Most major coastal cities are doing the same, Khan says.
Inland is another story.
A lot of regional areas have looked at purified recycled water – taking water from wastewater treatment plants and purifying it so that it can be used in a way that can get back into the drinking water supply.
There are no inland examples at the moment but Perth has a purified recycled water scheme, Brisbane has one that it’s not using yet and “Sydney is just starting to talk about it.”
But inland environments are going to be a much greater challenge.
With projections for rainfall shortages even in places such as Tasmania, what’s Khan say about the mid to longer term prospects for water security in Australia?
Part of the problem is the uncertainty. “We’re sort of modeling what’s going to happen with rainfall. We think we know, but there’s a lot of uncertainty. Things could be much worse than we realised, or in some cases, maybe not quite as bad as we’re forecasting.”
Khan says the most interesting development is a rapidly growing interest in purified recycled water as an alternative supply.
One development that hasn’t gotten much publicity yet is Sydney Water’s demonstration plant at Quakers Hill, required by Greater Sydney water strategy.
It’s using advanced technology to take water from the sewage treatment plant and purify it. The plan is to use it for educational purposes. There is still not approval from NSW to use it for drinking.
It’s a technology that is used around the world but in Australia a plan to use such a technology in Toowoomba in 2006 was knocked back.
South East Queensland has a big water recycling scheme that can provide water for Brisbane, which is part of the water supply strategy, and which can be triggered to supply the city if the dams fall to 40 per cent.
At present it is used only for industrial purposes, and some power plants, Khan says.
But even further north where areas rely on seasonal downpours there are changes in weather patterns.
Monsoons have failed in India for instance and resulted in large cities such as Chennai coming very close to running out of water as a result.
Perth is another area in Australia that’s already relying on engineered supplies, Khan says. Without them the city would have already run out of water.