Australian water

Climate change: 'water supply at risk from back-to-back extreme events'

Increased incidence of extreme weather poses greatest danger to drinking water supply, say University of NSW experts

the Guardian,

22 January, 2014

More needs to be done to protect Australia’s drinking water supplies from extreme weather events driven by climate change, a new report has warned.

Analysis of 41 water utilities in Australia and the US found water quality was put at most risk by a combination of extreme weather events, such as bushfires and then a flood, rather than a single event.

Bushfires can cause ash and phosphorus to enter waterways which feed drinking water catchments, while extreme hot weather accelerates the growth of bacteria that can prove harmful to people.

Bushfires and cyclones can also introduce turbidity to the water that can be difficult to treat and lead to the growth of algae and bacteria, which can cause the taste and odour of water to change.

The severity of extreme weather events is expected to increase due to climate change, with the number of people affected by climate-related disasters expected to grow to 375m a year by 2015.

Dr Stuart Khan from the UNSW school of civil and environmental engineering, who led the study of water utilities, told Guardian Australia resilience needs to be built into system to ensure future water supplies.

“We have always had extreme weather events, that’s nothing new, but we are already seeing the impact of them and it’s broadly accepted these instances will increase,” he said. “The water supply isn’t secure or cordoned off – we draw water from the environment and that water is subject to a number of different things,” he said.

“The ultimate failure is if the water companies have to ask people to boil water before they drink it. We saw case studies where that has happened after all sorts of events, such as cyclones, big rainfall and snowstorms.

“You’d expect around 10 boil-water events around the country a year, not all down to extreme weather, but you’d expect that number to rise unless there’s action to mitigate it.”

Khan said that while Australia is fairly well prepared for threats to its water supply, more needed to be done to diversify supply and establish overarching principles to ensure its safety.

One way of diversifying water supply is through seawater desalination. This has proved expensive and, in some cases, environmentally controversial, such as in the case of Melbourne’s $5.7bn desal plant. But Khan said it will have to be an option for water utilities.

“Last year Brisbane nearly ran out of water because it couldn’t treat high turbidity of water in time to meet demand,” he said. “They had to use the Gold Cast desal plant to deliver water to Brisbane.

“There needs to flexibility, and that doesn’t just mean desalination, it can be recycled water and groundwater. Adelaide draws upon numerous sources, such as the Murray river, desal and groundwater.

“We need to engineer flexibility to move water around the grid rather than have rigid protocols on where our water comes from. That will help preparedness for extreme weather.”