The old dam known as the lower dam including this spillway was constructed in the 1880s and was decommissioned in the 1950s. From the 1950s, Wellington’s water supply from Wainuiomata came from the Morton dam and the Orongorongo weirs. Around 1969-70, there was a reduction of approximately one meter in the spillways’ height to enhance safety measures, accompanied with opening of some sluices beneath the dam. Together, the sleuths below and spillway channel the river flow. Today, a natural wetlands area is located behind the old dam wall.
