The word ‚Wainui-o-mata‘ is a Māori name made up of the words Wai = water, Nui = big, O = of, and Mata – which could refer to a woman’s name. The origins of the word are disputed, but one commonly accepted translation refers to the women who came over the Wainuiomata Hill to evade marauding tribes from the north, and who sat wailing by the stream after the slaughter of their menfolk.
From this we have ‚faces streaming with water‘ or ‚tears‘ although it could equally refer to the large pools of water which lay over the swampy surface (face) of the northern end of the Valley, or the river itself which is known to flood the Wainui (Coast Road) valley.
Today it is commonly called the „Wainui River“ as the town of Wainuiomata is informally named „Wainui“.
The earliest settlements were based around the river where the timber mills supplied the Wellington region where the demand was great in the 1850s and 1860s. Today this area is known as „The Village“ or as „Homedale“.
In 1879 the Wellington ratepayers voted to extend their water supply, and by 1884 a dam was built in Sinclair Valley (Waterworks Valley) and a pipeline ran across the Wainuiomata Valley floor, through a tunnel under the hill, and on to Wellington. This dam was replaced in 1910 with the Morton Dam, since decommissioned, while the Orongorongo tunnel and pipelines were implemented by 1926. The establishment of the waterworks meant the coming of the telephone although, by 1921, there were still only two subscribers.
As of 2016 the Wainuiomata/Orongorongo Catchment Area is a restricted area as it supplies much of the Wellington region with water.