Upper Nihotupu Reservoir, reservoir in New Zealand

Upper Nihotupu Reservoir is a water storage lake in the Waitākere Ranges of the Auckland Region, held back by a concrete gravity dam completed in 1923. The dam wall rises at the end of a walking track from Piha Road, where steep steps climb its face. Watercare Services manages the reservoir and dam as part of Auckland's water supply.

The dam was constructed in the early 1920s and completed in 1923 to supply water to the growing city of Auckland. The project faced challenges due to World War I limiting labor and materials availability.

The Nihotupu Falls and the Nihotupu area drew tourists in the late 19th century, before the dam existed. The tramline built for construction later carried passengers on Watercare's Rainforest Express until it was permanently closed in November 2014 after a geological report identified 20 at-risk sites along the tramline paths.

Visitors can reach the reservoir via walking trails from Piha Road, with steep steps leading up the dam face to provide views of the water below. The area has minimal facilities, so bring your own water, snacks, and sturdy footwear.

The tramline built for the dam's construction later carried the Watercare-run Rainforest Express tourist train. In November 2014 Watercare closed both the Nihotupu and Waitakere tramlines permanently after a geological report identified 20 at-risk sites along the paths.