Harrison Grierson was commissioned by Greater Wellington
Regional Council (Greater Wellington) to develop a model of
rainwater tanks in the urban environment for the cities in the
Wellington region; Lower Hutt, Upper Hutt, Porirua and
Wellington.

This report presents the findings for Wellington City and
discusses the costs of installing rainwater tanks. The model is
set up to calculate the volume of water in the tank each day
using the rainfall over the roof area as the flow into the tank
and the household demand as the flow out of the tank. The
tank was assumed to supply only outdoor usage and toilet
flushing.