The pipe that runs along the Exhibition Drive track may look like a historic relic but, despite being laid in 1912 and in poor condition, most of it is still in use taking all of the water from the Upper Nihotupu dam.
The pipe is actually the replacement of an earlier Emergency supply pipe known as the Auxiliary Supply which roughly followed the same route. In the late 1890s Auckland’s water supply was mostly from Western Springs. Quickly increasing usage (partly due to the introduction of flush toilets) meant water severe water shortages for several years. It got to the point where the water was being turned off at night.
The route of the pipe from the Upper Nihotupu dam (shown as the thin yellow line to the south of Scenic Drive). Some of the last section along Exhibition Drive has now been bypassed by feeding into the Huia Aqueduct.
There were already plans to build dams in the Waitakere and Nihotupu valleys, but it was decided that urgent action was required. A simple solution took water from wooden dams in Nihotupu Stream and Quinn’s Creek down a thin wrought-iron pipe into the city via Smyth’s saddle. The failed Titirangi Reservoir was part of this project. The track quickly cut to run the pipe was ‘tortuous’ and subject to continued damage due to slips. Incredibly part of this original pipe is still in use, now as a local supply pipe along Scenic Drive, supplying water to Titirangi Village.
The original pipe was too unreliable and was also too small for the planned Nihotupu dam so in 1912-13 it was replaced with a much heavier and lager cast iron pipe. They made the route shorter by digging tunnels through the spurs, which also made it more resistant to damage from landslides. As the pipe was so heavy a tramway was built to make construction simpler. Part of this was later used in the construction of the Nihotupu Dam and for maintenance of the pipe. The rainforest express tourist train ran along the tracks until the risk of landslides became too big.
The tracks originally went from Titirangi Village all the way up to the dam. Along the first section, the tracks were removed and the road widened to become the very popular tourist drive, Exhibition Drive. When the Nihotupu Water Treatment Plant was decommissioned, the last section of pipe was bypassed by a short pipe to feed into the Huia Aqueduct. This can be seen partly along the Exhibition Drive walk.
Along with most other pipes that form part of the Waitakere Scheme, the Nihotupu pipeline is due for replacement. Hopefully not too much of the forest of Waitakere Ranges Regional Park will need to be removed. Luckily tunneling technology has come along way since 1900 – even in 1946 when the Hunua scheme was started, a 5.6km tunnel was dug.