The new economy of rainwater harvesting, stormwater management vs traditional water management

two storey house with rainwater tanks

Urban tanks, courtesy PJ Coombes


Water Sensitive SA and the Rainwater Harvesting Association of Australia held a thought-provoking seminar in the Adelaide Town hall on 15 December with a keynote address by Professor PJ Coombes. The discussion brought together the elements of economics, rainwater harvesting and stormwater management and potentially leading edge Australian integrated water policy.

Professor PJ Coombes presented startling nation-wide evidence that building scale water appliances and behaviours and rainwater harvesting already make a very significant contribution to water efficiency and stormwater management in our cities, and economic viability of households, water authorities and state governments. Evidence was presented at a metadata level from the National Performance Reports by the Bureau of Meteorology showing a rapidly increasing impact on household welfare from rising household water bills supplied by the traditional water approaches. Data on the value of water savings delivered by water efficient appliances and rainwater harvesting to households was presented for all capital cities in groundbreaking research. Peter also outlined the water security, stormwater management and nutrient levels outcomes. To support the high-level findings the presentation included three case studies of sustainable homes demonstrating the scale and accessibility of savings that can be achieved. Consistent savings of 70% of normal household energy use, water use and stormwater reduction were regularly achieved in the case studies. The presentation concluded that a sustainable approach to building policy has multiple benefits including integrated water management and is an underutilised policy response.

Peter calibrated systems capital cities graph

Rainwater harvesting and water efficient appliances – calibrated systems analysis (ABS & BOM data) Prof PJ Coombes, 2016

Michael Smit presented on behalf of the Rainwater Harvesting Association of Australia and Urban Water Cycle Solutions on two topics. The first topic was an overview of common misconceptions about rainwater harvesting systems as discussed in Rainwater Harvesting Myths. One myth is that rainwater is not a significant source of water in Australia, however, rainwater represents 15% of household water use in South Australia with a household saving of $88 million.

Mains Switching System

Mains Switching System

The second topic was a presentation on the key concepts and content of a joint project to develop a new rainwater harvesting design specification to assist householders and industry realise maximum benefits and water quality from their rainwater harvesting systems. This document has been identified as critical to the rainwater harvesting industry because good initial design provides significantly larger yields, good water quality and minimal maintenance.

Mellissa Bradley from Water Sensitive SA discussed their important work to enable stormwater to support a Living Adelaide the 30 Year Plan for greater Adelaide review. Mellissa showcased a practical tool currently being developed to support industry to maximise the benefits of stormwater harvesting at the allotment scale. Of particular interest were the policy context for WSUD in Adelaide, including a commitment to 20% more tree canopy cover by 2020 and that 85% of all new housing be infill housing. The SA WSUD objectives include 80% reductions in suspended solids and no increase in the 5 year ARI peak flows. The Water Sensitive SA online stormwater assessment tool will place a greater emphasis on opportunities for stormwater runoff volume management by providing a mechanism for development applicants to consider retention and re-use solutions as part of the design mix. Applying this policy to all development including small scale development such as renovations through to commercial buildings, is a very important policy position for the future of all Australian cities. Rainwater Harvesting and retention is seen as a critical tool in achieving these policy goals.

Christie Walk, photo courtesy Baden Myers

Christie Walk, photo courtesy Baden Myers

Christie Walk is an Adelaide example of a community-based housing development incorporating

  • onsite detention
  • onsite retention and reuse of rainwater and stormwater on site
  • rainwater tanks
  • rain gardens
  • vegetated swales and buffer strips
  • direction of flow from impervious ground surfaces to landscaped areas.
  • reduced impervious areas
  • site coverage (up versus out)
  • permeable paving
  • green roofs


Copies of the all the presentations are available on the Water Sensitive SA website

This event was free for Rainwater Harvesting Association members and other participating Associations and $30 for others.