Talk of Melbourne needing a second desalination plant to meet future demand ignores a much more cost-effective solution – demand-side measures.
The value of demand-side efficiency can be demonstrated by comparing increases in Sydney Water customer bills with increases in Melbourne Water customer bills.
According to Michael Smit, technical and sustainability manager for Kingspan Environmental, the NSW Building Sustainability Index, BASIX has focused on promoting and supporting water efficiency through performance targets. By contrast, the Victorian six-star building control does not have minimum standards for water efficiency or a performance target.
“Sydney people save 90 billion litres each year through water efficiency and rainwater harvesting – more than half the Victorian desalination plant capacity,” Smit says.
And while Sydney water and sewage bills have risen by an average of $35 per household in 12 years, Melbourne households have seen an average hike of $150.
“Community-led water efficiency rescued Melbourne in the Millennium Drought but afterwards we have chosen to rely on big engineering projects like desalination plants and a water grid despite their record of high operating costs,” Smit explains.
In NSW, water efficiency and rainwater harvesting through the voluntary installation of rainwater storage are saving the state 90 billion litres of potable water annually – the same amount as the annual capacity of the Sydney desalination plant.
“Water efficiency is a proven, cost-effective solution. Water saving targets will produce a fair and equitable average of 50 per cent reduction in household water use across Greater Melbourne.”
Currently, Victoria has one desalination plant, which has a 150 billion litre capacity. Melbourne Water has recommended we use almost the whole capacity – 125 billion litres in 2020-21. This is likely to lead to a conversation about building a second desalination plant.
Smit says that if demand-side strategies are brought into play, it could not only negate the need for a second plant in the near future, it could result in overall savings to the Victorian public of around $1 billion by 2050.
The infrastructure to achieve these gains is not complex, or expensive, and it is already out there in the marketplace – the humble rainwater tank.
For around $3500 a household or business can install water efficient appliances and a rainwater tank to capture rainfall that would otherwise go to waste via the storm water system. A few pipes and connections installed by a plumber are all it takes to reticulate the water for toilet flushing, garden watering, laundry or other non-potable uses.
Often, the harvesting and use of rainwater has been termed “rainwater re-use”, but Smit says this is a misnomer.
“Rainwater use is not re-use,” he says. “Rainwater is coming straight from the sky – it is the most unused form of water there is!
“And because it falls on the roof of the building where it is used, it needs little transport or treatment.”
As well as saving on water bills through using less potable water research has shown a rainwater tank can deliver a capital value uplift of around $18,000 on a property.
Property buyers could have a perception that a rainwater tank indicates the owner has sustainable thinking, and that therefore the house will generally have been looked after well, Smit says.
“It might be value creation by association.”
Rainwater tanks also tend to be installed by keen gardeners – and a well-loved garden is another feature that adds capital value to a property.
Ultimately, water efficiency is not only about being green. It is clear from the costings available from water authorities that efficiency pays off, not just for the individual water user but for the whole community.
“One third of the [end] cost of water is energy – and that goes up to half when you look at desalination,” Smit points out.
“Household water bills should be no more than two per cent of available household income but relying entirely on desalination will see water bills exceed this figure in less than five years.”
More demand also means more costs across the whole system – the cost of energy to treat and reticulate it, the cost of treatment and disinfection, the cost of pipes, pumps and maintaining plants and reservoirs.
Melbourne currently has 10 major dams, a desalination plant, 64 reservoirs and 49 treatment plants. Yarra Valley Water is one of three water retailers and has over 18,000 km of pipes of its own.
“Water utilities provide high-quality reliable water, but it is expensive,” Smit says.
“We should use the rainwater first and utility water second. Doing so reduces the size of reservoirs and pipes and treatment plants across the whole system, reducing operating costs and infrastructure investment in the future.”
The environment is also a consideration, as it is what we depend on to live, Smit says.
“We need to use our water in ways that reduce human impact, and improve our waterways. Being water efficient will save 100 billion litres more than business as usual by 2050.”
Modelling has shown that greater uptake of rainwater harvesting in Melbourne could reduce stormwater by 17 per cent, flood risk by five per cent, nitrogen loads by 14 per cent, plus save over $1 billion in stormwater management costs.
“We need to use our resources smartly. Rainwater harvesting saves households, reduces stormwater and reduces water utility costs – that is a big return on one small water tank.”
Key research in this article is based on the work of Dr Peter Coombes of Urban Water Cycle Solutions and his report “Greater Melbourne Alternative Water Plan”, commissioned by Kingspan Environmental.