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MPhil in Engineering for Sustainable Development

global challenges, engineering solutions

Studying at Cambridge

Raymond Siems


Water and energy supply systems are being placed under increasing pressure due to the consequences and mitigation of climate change, as well as continued population growth and urbanisation. Creating synergies and minimising trade-offs in the water-energy nexus is thus crucial for the sustainable management of these highly interdependent resources. However applications of this remain underexplored in the literature and in practice at the city scale. This research explores this challenge via a case study of Sydney, Australia which investigates how the city’s water and energy infrastructure can be better managed to improve outcomes with respect to flood risk mitigation, water security, environmental flows and renewable energy generation. A quantitative system dynamics model was built to allow different management scenarios to be compared and contrasted over a 25 year planning horizon. The model simulates the operation of key aspects of Sydney's water and water-energy supply system. It includes a sub-model which simulates buying and selling electricity on the national spot-market, in order to estimate the revenue of existing potential future hydropower infrastructure at Warragamba dam. It was found that actively managing the reservoir level through increased hydroelectric generation can provide a similar level of flood risk mitigation as a proposed development which will raise the height of the dam wall by 14m; thereby saving $A690 million in construction costs and preventing 3,500 hectares of UNESCO World Heritage area from being flooded. Further, the increased utilisation of the hydropower facility could generate up to $A20 million per year in high inflow years. This demonstrates that integrating the operation of currently independent water and energy infrastructure can deliver improved outcomes across multiple and even conflicting objectives. This application of a systems approach has potential to realise a paradigm shift, with traditionally single-function infrastructure becoming multi-functional. System dynamics modelling is shown to be a valuable tool allowing water resource planners to evaluate alternative policies for managing complex systems amidst changing expectations and uncertainty.