Water from rivers in Wainuiomata are directed into a water treatment plant, then distributed through a pipeline network through the valley and into Wellington.
The Wainuiomata pipeline system is part of the Wainuiomata/Orongorongo Water Collection system. On the Orongorongo side, weirs in the Orongorongo River, Big Huia, and Little Huia Streams are piped to the Wainuiomata treatment plant via a 5.6km pipeline and tunnel, with pressure release valves installed upstream of the plant intake. Next to the valves, the water passes through turbine generators housed in a small brick building before the water reaches the plant. In tandem, weirs along the Wainuiomata River are piped to the same treatment plant.
From the plant, water is directed to various locations such as Wainuiomata, the Wellington City Business District, and the southern and eastern suburbs of Wellington City. This is achieved through a combination of gravity and pumping stations. The water supply for Wellington originates from two primary bulk water systems, which are interconnected at Nguaranga. This connection between the Kaitoke to Karori and Wainuiomata to Wellington pipelines ensures water security by enabling the transfer of water between them, thus allowing for multiple water sources.
