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Bang for buck in urban water security in Brisbane

Since the millennium drought in the mid 2000s, Brisbane has built new major infrastructure, including a water grid, desalination plant, and a now-decommissioned recycled water scheme. The city has also promoted widespread adoption of water-sensitive urban design (WSUD) measures including rainwater tanks, permeable pavements, and stormwater harvesting.

But value for money in urban water security requires more than just providing water supply to households and businesses at the lowest cost per megalitre—we need to consider the environmental impacts of water security measures as well.

NCEconomics resource and environmental economic practitioner Jim Binney says that when it comes to increasing water supply versus improving water use efficiency, there tends to be cycles. “A lot of analysis was done from 2007 to 2011. We found that when it comes to water savings or availability and their costs, you can’t just choose one option, you have to establish a portfolio of measures, which is why we ended up building a dam as well as desalination and promoting rainwater tanks and water use efficiency,” he says.

Binney notes that cyclical thinking can be a planning challenge. This often happens when once the large infrastructure is built, the issues falls onto the backburner. This can be detrimental to the consideration of smaller / incremental supply options such as stormwater harvesting. “Water supply planning and waterway management should be a continuous process, not just something that is front of mind during a drought”.

When it comes to determining the bang for your buck when it comes to different urban water security measures, Binney says that it is important to try and match growth in water demand with the best options to meet that demand. “This might mean choosing options with higher unit costs such as stormwater harvesting. These options can be cheaper in the long run as you don’t have significant excess capacity for decades, which often happens with large dam developments,” he says.

“One interesting thing that we’ve also found when considering alternative supply options is that with climate change, we’re observing that rainfall up the catchments is often declining but rainfall in coastal zones—where most people live—is often being affected to a lesser degree. This changes the relative efficiency (and costs) of options such as dams vs. smaller options in coastal zones. It will be fascinating to see how this plays out as the impacts of climate change become more pronounced.”

Binney believes that some options need to be taken into account more when it comes to effective water management planning. “Typically, we have measured costs in terms of lifecycle financial costs of delivering a particular volume of water. But that only works if only objective is only to supply water,” he says. “We know that initiatives such as harvesting stormwater and recycling have benefits beyond direct water supply such as reducing diffuse pollutant loads into waterways. We need to move from traditional dollars per kilolitre measures to inform investment decisions and move to a broader cost-benefit framework that considers all the benefits and costs of each option.”

There is a movement underway within the water management industry to consider cost-benefit analysis, which is already commonplace when looking at flood risk assessments and thresholds for pollutants in water.

For Binney, Brisbane is still not placing enough value on WSUD measures, which will prevent nutrients and sentiments flowing into creeks, rivers, and the ocean. “Often the building industry says the cost burden is too high,” he says. “We’re talking $2,800-$4,000 for WSUD per detached house. Putting WSUD into perspective of the total cost of building a new house, it is the equivalent cost of less than 3 m2 of the building footprint, or some fancy benchtops. Given the fact that new builds are now much larger, and for fewer residents on average, the tradeoff between a few square metres on a McMansion and sustainable water management is a trade off well worth making”.

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