Reusing stormwater runoff can improve water security by reducing demand for ground water and potable water supplies. Whilst the number of stormwater harvesting schemes in Australia is increasing, the full potential of stormwater as an alternate water source is yet to be realised. Understanding the range of chemicals and microorganisms likely to be present in untreated stormwater will assist stormwater managers to maximise the potential of this water resource in a manner that is protective of human and environmental health.

Samples of untreated urban stormwater runoff (n=94) were collected during rainfall events at 10 diverse urban catchments across Australia, and analysed to identify chemical and microbial hazards to human health.  The microbial quality of stormwater was observed to vary both between site-specific events, as well as between sites, with few determinable patterns. The data collected in this national investigation into the microbial quality of stormwater demonstrates that treatment is required to manage the health risks associated with stormwater harvesting schemes.