Access

From SH1 north of Mangaweka, turn into Ruahine Road and after 1.6 km turn left into Kawhatau Valley Road. The track begins from a parking bay on the left after 300 metres.

Track

Across the road to the right is the track to the dam. This is narrow and slippery in places with a few thistles to contend with. The convoluted holes and patterns sculpted into the papa rock by the Mangawharariki River are down to your left.

A staircase and tunnel remain with the intact structure of the dam, which froths up the waters of the river.

European History

Mangaweka was one of the first towns on the Main Trunk Line to receive its own power. The hydro dam was constructed across the Mangawharariki River in 1910 under the supervision of Mr W Walters, the main contractor. It measures 32 feet across and was capable of holding 4.5 million gallons of water, which was released through a 52 foot spillway.

Provision was made in the design for the high flood range of the Rangitikei River, which was prone to high fluctuations because of the rapid response time generated by the friable papa geology. In an 1897 flood, a 29 foot rise in river level was recorded, so the floor level of the power house was set at 6 inches above this record flood level.

In times of flood, two underground sluice gates could be opened to release pent up water. During a flood in 1913, these became blocked with large tree trunks. The Town Board Chairman, Mr J Georgette, repeatedly dived down to try and put chains around the offending logs blocking the structure, an act of civic heroism. The town was in darkness for a few weeks until the logs were eventually removed and 100 foot of flume repaired.

The power house measured 25 foot by 17.5 foot and the water was conveyed down a 36 inch diameter pipe to a Boving Vertical Turbine with a 45 brake horse power output, revolving at 675 revolutions per minute.

The turbine exhibited a vertical shaft connected to a horizontal shaft by a beautifully cut double helical bevel gear, revolving at 1000 revolutions per minute. This was coupled to a 25 kW 3 phase alternator supplying 2.4 kV. Power was transmitted via aluminium wires suspended on totara or Australian hardwood poles.

The plant automatically shut down at midnight.