Approaching water sensitive cities with adaptive rainwater diversion

Approaching water sensitive cities with adaptive rainwater diversion

Total water cycle management (TWCM) discussion mostly limits the role of residential rainwater harvesting to providing an alternate water supply to a fraction of fit-for-purpose end uses. However, with operational improvements, greater outcomes can be achieved. By increasing the portion of roof area connected and developing adaptive rainwater diversion (ARD), reliable stormwater management outcomes can also be achieved. ARD controls tank drawdown by adapting to changes in dwelling consumption and rainfall, thus allowing the available storage to mimic the pre-urbanised catchment storage recovery. The ARD approach has the basis that mains water savings can be achieved in two ways: 1) Rainwater supply - where the rainwater harvest is used directly to reduce
mains consumption of that dwelling; and 2) Rainwater diversion - where rainwater is diverted from the dwelling. This does not directly reduce mains consumption of the dwelling but produces a water resource that is used by others to reduce mains consumption. In this way, total rainwater yield and mains water savings is the sum of rainwater supply and diversion. This research investigates
rainwater supply, rainwater diversion, runoff volume and runoff flow frequency for South East Queensland. Results show, the average sized detached dwelling when fitted with a 5kL tank and ARD system is compliant with the mandated water saving targets and the Queensland Best Practices
Environmental Management Guidelines for stormwater flow frequency management. It is recommended that rainwater is diverted into the existing stormwater system where reuse
facilities exist. Otherwise, discharging into the sewer, has the potential to reduce sewer fouling and increase the substitution of mains supply with treated effluent. This improves sewerage reticulation by adding a secondary purpose and, by using existing infrastructure, removes many barriers for retrofitting TWCM and water sensitive urban design (WSUD). Also, as ARD brings adaptive and multifunctional infrastructure into our urban design, we begin to develop water sensitive cities. The outcomes of this research are most promising to established and future planned high density residential suburbia, where TWCM policy and WSUD is chiefly needed.

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