The Goyder Institute's Managed Aquifer Recharge and Stormwater Use Options (MARSUO) project has been the first to lay down a serious and rigorous body of evidence in support of harvesting stormwater to augment urban water supplies. It has transparently examined the social, technical, economic and environmental facets.
In Adelaide there is strong public support for stormwater for drinking and non-potable supplies and it has been in use by innovative local councils for 20 years, for public open space irrigation. Stormwater presents opportunities for securing city water supplies at much lower unit costs than desalination; indeed, had this project been completed siz years ealier, several states might have significantly reduced major capital outlays.
Owing to the mainly impervious nature of urban catchments, stormwater yields are more reliable and less drought-prone than rural runoff. The challenge of storage can be met by using surface reservoirs or aquifers, sometimes in combination. Urban stormwater quality is similar to that from open catchments that source drinking water for a number of Australian cities. The treatment and distribution technologies required are little different than those for conventional sources.
Despite the intuitive appeal of stormwater harvesting, the science and technology are not trivial, especially when aquifers are involved. This effectively places lower limits on project size to achieve economic sustainability. As is the case with any field of endeavour, a body of empirical practice rules has to be generated to ensure practical success. This project has made a good start in that direction.
The political realities of creating innovative systems have to be addressed too, as agencies and water businesses weigh up the threats and opportunities which are opened up, and the different relationships that have to be managed. Regulators need to create an environment which encourages innovation and fosters a market driven climate for all the players.
For many potential stormwater/MAR projects around Australia, there is insufficient value ascribed to environmental benefits, so more attention is needed in that respect.
Although the evidence from this project suggests that stormwater harvesting can be competitive in overall cost terms, every project is unique and a rational evaluation of costs and benefits is needed.