Improving Downpipe and Gutter Configuration on a Residential Dwelling to Increase Rainwater Yield

The roof area connected to the rainwater tank is an important determinant for rainwater yield at the household scale. This study monitored the performance of a 'Rainwater Harvesting System' that supplies a rainwater tank using an innovative configuration of the downpipe and gutter system that maximises connected roof area. Roof runoff is redirected in the gutter system towards the rainwater tank by closing downpipes during rain events. Roof runoff from non-connected roof areas would otherwise be directed to street drainage. The system was installed on a residential dwelling in Brisbane (QLD, Australia) and the site was continuously monitored for rainfall, water demand and water levels in the rainwater tank (6-minute timesteps). Monitoring data was used to calibrate PURRS (Coombes, 2002) to determine the long term rainwater yield at the allotment scale based on an 83 year rainfall record (Brisbane). Rainwater yield increased from 72 kLyr (with 5 kL tank only) to 142 kL/yr after connected roof area was maximised using the Rainwater Harvesting System. Results also highlight household water demand and connected roof area is more important than the size of the rainwater tank for increasing rainwater yield at the household scale.