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Michael Smit and Professor PJ Coombes: An important debate in this country is about the health of people using rainwater, however much of the commentary is research funded by water utilities which has a centralised water distribution perspective quite different to how rainwater harvesting works. One of the recent rebuttal papers by PJ Coombes has just been published and we thought we should discuss some of the issues and assumptions, as much to demonstrate there is a difference of opinion. A presentation at the RHAA seminar in Sydney about widespread use of rainwater and the absence of health epidemics is compelling. Australia has a substantial real world case study with over 2.3 million Australians relying on rainwater for drinking water and more than 6.3 million people using rainwater for some household use. In spite of claims of widespread health concerns, there are no health epidemics or widespread notifications of lead contamination by chief medical officers.

Prof. PJ Coombes and Michael Smit. Manage Water and Energy in your House using systems theory and real data. We were having a bit of a grizzle recently, trying to work out when opinions became more important than facts in this country, and of all things we started to talk about water pumps for rainwater tanks. One quite obvious point that most people grasp is that when you use a pump for rainwater the energy use in the house increases. Obviously if you did not have a pump, and then you get one, and you run the pump, you will use more energy right? This logic is completely sound until you measure it. We measured energy consumed at one of our houses with a rainwater pump and found a 12% decrease in energy consumption from 15 kWh/day to 13 kWh/day. Then we fixed leaking appliances and energy use reduced to 10 kWh/day.

Prof. PJ Coombes and Michael Smit. “Water bills to rise as desal plant gets the go-ahead to start making water for the first time”. This heading caught our eye from our respective desks, so we called up and had a yarn, and some questions came up for us. We make a living from these kinds of questions but some of the answers were a little startling. Desalination is one of the many tools for provision of water security in Australia. However the important question is whether or not it is the best solution. NSW has 10 years of data showing that something is very different in that State compared to the rest of Australia and Melbourne, and one consistent feature affecting water management across the whole state is the BASIX program. Australia is considering a second round of desalination plants. We may be able to provide water security without another 93% increase in household water expenditure by combining different types of technology. Centralised infrastructure solutions could be combined with supplementary decentralised solutions like water efficient appliances and rainwater harvesting in the BASIX program. These combined approaches may mitigate growth in household expenditure and water utility operating costs.

Systems Framework for analysis of policy and strategy by Peter J Coombes and Michael E Barry. Acknowledged by Engineers Australia as one of the best scientific contributions to hydrology and water resources during 2014/15. The Systems Framework is discussed in many publications focused on describing projects or policies. This presentation provides an overview of the Systems Framework methodologies for analysis of policy, strategy and design developed over the last decade. The framework integrates water cycle, environmental and economic processes from the “bottom up” using all available data and integrating spatial and temporal scales of behaviour. Advances in computing power allowed this quantum process to be underpinned by continuous simulation of local behaviours and Monte Carlo methods. This expansionist approach to analysis reveals hidden challenges and opportunities for urban areas. The Systems Framework can be reliably and robustly applied to detailed and targeted ‘what if’ analyses, including assessments of future water security and economics under a range of climatic and population growth scenarios, and future alternative strategies or policies.