Wivenhoe Dam in flood

17 April 2012 – Direct potable use of rainwater could have saved Brisbane from the 2011 floods from Wivenhoe Dam, according to a University of NSW study.

Dr Stuart Khan, an environmental engineer at the UNSW Water research centre, says direct potable reuse of wastewater could free up billions of litres of water from reservoirs around Australia, giving cities a greater buffer to capture rain water and control major flooding events.

Current plans for water recycling in Australia generally involve Indirect potable reuse where reclaimed water is treated to a high standard and then returned to rivers, lakes and aquifers, where it mixes with environmental waters before being re-extracted for further treatment.

But a cheaper and less energy intensive idea is to bypass the dam altogether, Dr Khan says in a UNSW statement. With DPR, highly treated wastewater is introduced directly to drinking water treatment plants, without re-entering the natural environment along the way.

In Queensland alone, DPR would be the equivalent of immediately constructing a new 425-billion litre reservoir, without the cost of construction or having to relocate a single home or farm, he  said.

His research has showed that this  added “virtual” storage space represents a 30 per cent increase on the volume currently reserved for flood mitigation in this region.

“DPR probably would have saved Brisbane from the 2011 floods from Wivenhoe,” he said.  “The big inflow peak of around 1900 GL that occurred between 9 and 13 January could have been contained in the dam, rather than spilled.”

And DPR could have also mitigated recent floods in NSW. For example, it would have enabled Warragamba dam to have been managed with an available “flood control volume”, without compromising the security of future water supply.

“Other dams that have spilled recently should be closely investigated for opportunities to increase the flood control capacity in the future,” Dr Khan said.

This type of water recycling also has several environmental benefits compared to IPR: “DPR can mean a reduced need for pumping water, reduced operational costs, reduced energy consumption and a lower carbon footprint,” he said.

DPR would also provide an invaluable supply of emergency drinking water in the event that reservoir water quality is compromised, as sometimes happens after high rainfall events, algal blooms and bushfires.