Energy and economic impacts of rainwater tanks on the operation of regional water systems

Abstract

This study has analysed the reductions in operational costs (pumping, water treatment and maintenance) and greenhouse gas emissions from regional water supplies that include installation of rainwater tanks used to supply domestic laundry, toilet and outdoor water uses across New South Wales. The household cost of rainwater supply ranged from $7.95/kL at Broken Hill to $0.88/kL in the Central Coast region. However, installation of rainwater tanks produced considerable reductions in operating costs of a city’s water system ranging from $57 to $6371 per household installing a rainwater tank. Significant reductions in greenhouse gas emissions of up to 75% from including rainwater tanks in regional water systems were also observed. In addition, significant improvement in the security of regional water supplies with subsequent deferral of the requirement for augmentation of supply (new dams or desalination plants) was observed for coastal cities. These benefits were seen to be dependent on the average annual rainfall depth, distance from the coast, and availability of reliable operational and augmentation data of a regional water system. This study reveals the importance of including rainwater tanks or, indeed, any other decentralised water management option in analysis of the operation of regional water systems to provide a realistic understanding of combinations of centralised and decentralised water management strategies.

Keywords:

• Rainwater tanks
• regional water security
• operational costs
• greenhouse gas emissions

Additional information

Notes on contributors

P J Coombes

Dr Peter Coombes is a conjoint Associate Professor of Integrated Water Cycle Management at the University of Newcastle and a director of the consulting company Urban Water Cycle Solutions. He is also a founding director of Bonacci Water, a research project leader in the eWater CRC, and an Honorary Research Fellow in Engineering and Molecular science at the University of Melbourne. Peter has recently served as a member of the Prime Minister’s Science, Engineering and Innovation Council working group on Water for Cities, and as a member of the urban advisory panel to the National Water Commission. His research interests include integrated water cycle management, water sensitive urban design, hydrology, analysis of complex systems and molecular sciences, including water quality.