In New South Wales (NSW) the Department of Primary Industries (DPI) sets onerous regulatory requirements on waterway extraction projects and directs designs towards having no impact on waterway base flows and no online storage or works within the waterway channels.
By designing event-based stormwater harvesting systems, the frequency and flow rate of downstream runoff can be reduced without removing waterway base flows and meeting NSW regulatory requirements. Stream bank diversions and offline storage can be used to capture storm events without impacting existing waterway channels. Detailed hydraulic modelling of an example project at the Blacktown Sports Park in NSW shows that waterway conditions downstream of an event based stormwater harvesting system to be more closely aligned with that of a rural stream than that of an urban stream. With a reduction in the frequency of high velocity runoff events improvements to downstream waterways are expected.