Reduced water usage doesn't mean cheaper bills

Posted August 15, 2013 19:33:38

West Australians have reduced their water consumption by more than 30 per cent over the past decade, so you would think it would correspond to a decrease in water bills.

But that isn't the case.

With climate change leaving our dams with just a fraction of the water they held 50 years ago, the Water Corporation has had to come up with alternative methods to ensure the state's water supply.

And unfortunately, those methods do not come cheap.

"Up until the mid 1950s dams were the full story," the Water Corporation's Water Efficiency manager Ben Jarvis said.

"Perth uses about 300 billion litres of water per year and we used to average about 380 billion litres a year of inflow.

"So if we were still getting the same sort of rainfall and inflow you know we would have enough water to meet Perth's needs now, just with dams alone.

"Unfortunately that didn't continue and we've seen that steady reduction in inflow into our dams so by the early 1990s we were looking at dams for about two-thirds of the story with ground water making up one-third of the story."

Dam inflows continued to decrease and in 2010 there was only 30-billion litres of inflow across the Corporation's 15 dams for the entire year, less than a tenth of the volume of just 50 years previous.

"So far this year we've had between 10 and 15 billion litres so not a very successful start," Mr Jarvis said.

As a result, this year, half of the state's water supply will come from desalination plants with the majority of the rest coming from groundwater and then dams providing the smallest proportion.

And while people are using less water, they are not necessarily paying less.

Mr Jarvis says that's because the cost of producing potable water has gone up significantly.

Expensive water

"The cheaper sources are dams and traditional ground water sources," he said.

"And things like desalination and ground water replenishment are a lot more expensive sources.

"Ideally, we've already got the dams and the bores and we'd prefer to get more water from them but if it's not available, we have to source them through the other mechanisms."

Groundwater replenishment is the latest technique the Corporation will use to bolster Perth's water supplies.

Treated wastewater is further treated to drinking water standards and recharged into groundwater supplies.

But as the Water Minister Terry Redman points out, all these new technologies cost money.

"In the metropolitan area, prices are nearing cost reflective levels, but most country regions are subsidised by the State Government, so customers pay the same for the first 300 kilolitres of water used across the State," he said.

"Cost reflective prices are important as they ensure those who use the water are responsible for paying it, contributing to the funding of new sources and providing genuine price signals to water users.

"Water charges pay for the cost of building, operating and maintaining the infrastructure for collecting and treating water and delivering it to customers."

Behaviour change

Ben Jarvis has applauded the people of Perth for the changes they have made to help the state conserve water.

"People really understand where things are at [in terms of] the importance of saving water, so it's a real credit to the people of Perth for the savings that we've actually seen."

"Over the last 10 years or so, Perth's per capita consumption has reduced from 191 kilolitres to now 132 kilolitres per person, per year," he said.

In fact people have been so good saving water, the Corporation will soon revise its savings target.

"The target, which was set back in 2008/2009, was 125 kilolitres by 2030 and the way we've gone over the last few years we look like we'll make that very comfortably so we're looking at options to see what another more demanding target might be for the future."

He says despite the challenges thrown up by climate change and general cyclical variations, it is the Corporation's job to ensure supply is be constant.

"It's our job to hope for the best, but plan for the worst," he said.

"I guess that's why our focus has been on those climate independent sources such as desalination and groundwater replenishment.

"And as I was saying before, those water savings we've made; that reduction from 191 kilolitres to 132 kilolitres per person per annum is the equivalent of just over 100 billion litres per year.

"So that's 100 billion litres per year that we didn't have to source, we don't have to treat, we don't have to pump, we don't have to take back again from households once it's been contaminated and then pump and treat and reuse of or dispose of again."

Reason indeed to be water wise.

Topics: water-supply, perth-6000