Coombes and Barry unlock the System

A contest of ideas is playing out at the Engineers Australia Water Sensitive Urban Design 2018 and Hydropolis 2018 conferences in Perth. At stake is how Australians, and the world, understands water management in our cities.

Engineering Australia recognized the paper on Big Data and Systems Analysis by Peter Coombes and Michael Barry as one of the top five papers of 2015. Coombes was invited to present his work at the London Imperial College and to key UK agencies in December 2017. This year the pair are challenging the basic paradigms of water management.

The battle lines are drawn around something called a systems approach. Systems thinking is complex, it is not intuitive and it challenges the status quo which is 100 years of highly respected water management.

Conventional thinking is that large cities are too complex to analyse at the level of individual buildings, we have to make top-down assumptions about average household water use and average growth rates and a hundred other aspects to simplify the model so we can get sensible answers.

Coombes and Barry have shown the way cities use water is a ‘bottoms up’ process, each individual house or building behaves in different ways based on factors including their garden, their appliances and the weather. The sum of this behaviour becomes hourly and annual water flows in the city that have to be managed and can be predicted. Coombes and Barry use high end computing to account for billions of behaviours and build a highly accurate model which changes the way we understand water management in our cities. For example, the systems approach uses rainfall data for individual postcodes recorded every 6 minutes over 100 years.

The Barry and Coombes paper at the Hydropolis conference uses systems thinking to show that the conventional averages approach provides unreliable water security estimates, underestimates the benefit of water sensitive urban design and overestimates peak flows and infrastructure requirements. It should be a great discussion.