Lower Nihotupu Reservoir, lake in New Zealand

Lower Nihotupu Reservoir is a 52.9-hectare reservoir in the Waitākere Ranges that holds 4.6 million cubic metres of water for Auckland, managed by Watercare Services. Its earth dam was built between 1945 and 1948 at Paruroa, near the site of the Te Taoū base of Ngāti Whātua.

The dam was built between 1945 and 1948 and was one of the first projects in New Zealand to apply soil mechanics in construction. This pioneering work transformed how engineers understood building stable dams on different ground conditions.

Pipeline Road runs north of the reservoir and has several lookout points over the water. The dam lies at Paruroa, with the final battle site of Te-Rangi-hinganga-tahi around the reservoir and Parau to the south. The reservoir is managed by Watercare Services.

The construction project pioneered soil mechanics in New Zealand, directly leading to the establishment of engineering geology as a new field of study. Lessons learned from building this dam continue to be applied in construction and safety planning today.