Emulating pre-urban initial rainfall losses and restoring baseflow with rainwater harvesting

The ability of rainwater systems to emulate pre-urban initial rainfall losses and restorecatchment baseflow is investigated in Brisbane, Canberra and Melbourne, using low, medium and high rainwater demand scenarios, and adopting three 5 kL rainwater system configurations of: 1) Conventional; 2) Leaking - a fixed 1.25 kL leaking compartment; and 3) Adaptive rainwater diversion (ARD) - a variable leaking compartment responding to change in rainfall and rainwater demand. Baseflow is restored by leaking rainwater at the rate of 240 L/day. Storm initial loss is the sum of rainfall from the start of an event until the tank overflows. Results show the ARD system provides superior initial loss emulation, reduced mean annual overflow and increased baseflow, under the low demand scenario. Leaking and ARD systems provide similar results under the high demand scenario. However, the ARDsystem is recommended as rainwater demand can change with occupant water use habits. These stormwater management outcomes can potentially create an avenue for retrofitting WSUD in urban catchments and improving urban stream health, without duplicating or redesigning municipal services, and while maintaining an alternate water supply.