A stronger role for rainwater tanks


View story in H20 Thinking

Could it be that the growing number of home-owners who have installed rainwater tanks may be doing more good than they realise?

Rainwater tanks in urban backyards are sometimes dismissed as a waste of money, a largely feel-good, token effort by home-owners wanting some independence from local water supplies. However, a series of studies suggests they can be much more important than that.

Analysis and modelling by Dr Peter Coombes (of the University of Newcastle, Bonacci Water and the University of Melbourne) and Professor George Kuczera (of the University of Newcastle), both of whom are members of eWater CRC, has pointed out that rainwater tanks filled from roofs can potentially improve city water supplies and, at the same time, benefit the environment.

Roofs feeding rainwater tanks in urban areas appear to be actually more efficient than conventional water-supply catchments. A roof, being impervious, only experiences a small loss of water when rain first starts, and so it is able to harvest nearly all rainfall, up to the tank capacity,” says Coombes.

In a separate study of 12 areas of NSW in a range of climatic zones, Dr Coombes and his team analysed the impact of rainwater tanks on water security, replacement of water treatment and transfer infrastructure, pumping, water treatment and maintenance costs, and greenhouse gas emissions from the operation of each city’s water system. A single alternative scenario was investigated, involving installation of rainwater tanks to all new houses and to 2% of existing houses per year.

According to the analysis, widespread installation of rainwater tanks to supplement mains supplies can produce considerable reductions in operating costs and greenhouse gas emissions for regional water systems. The dollar savings ranged from $57 to $6,731 per rainwater tank, depending on NSW region.