Two weirs were installed to replace Morton Dam on the Wainuiomata River, complementing the existing weirs in the Orongorongo Valley.
Prior to the establishment of the present weirs in the Wainuiomata Catchment, the lower dam stopped supplying water in the 1950s. This transitioned the Morton Dam and the Orongorongo weirs into the primary water sources for the Wellington region. Subsequently, in the 1980s, Morton Dam underwent decommissioning, which involved dismantling a section of the dam near the spillway, to drain the lake bed and facilitate the flow of the Wainuiomata River.
The existing system, along with the new replacement system, comprises two strategically located weirs within the Wainuiomata Catchment: one on the Wainuiomata River and the other on George Creek. Water from these weirs is directed towards a treatment facility. This revamped infrastructure boasts a capacity to generate up to 60 million litres per day. This amounts to 15 percent of the water supply for the Wellington region today. The supply matches that of Morton Dam when it was operational.
Complementing this upgrade, the three weirs already operational in the Orongorongo Valley provide an additional 5% of the water supply for the Wellington region, boosting the total supply to 20%. They are located in the Orongorongo River, Big Huia Creek and Little Huia Creek.
