Monowai Station
Located near Fiordland National Park, the Monowai Scheme sits amongst native bush along the Waiau River. This historic power stations will turn 100 years old in 2025.
Commissioned: 1925
Operating Head: 48.2m
Annual Generation: 36 GWh
Monowai Power Station
Monowai hydro-electric power station lies on the banks of the Waiau River, approximately 50km from Tuatapere. The scheme was investigated as early as 1919, with major construction work starting in February 1922, by the Southland Electric Power Board. The project was completed by December 1924. The station was officially opened on 1 May 1925 with two machines; a third was commissioned in 1927. The Government bought the station from the Southland Electricity Supply in 1936. Before the Southland Network was linked to the national grid in 1939, the station was of major importance to the people of Southland. Pioneer Energy purchased the scheme in 2010.
This Scheme takes its water from Lake Monowai. The Monowai Dam is a low earth embankment built across the Monowai River, forming the 31sq. km Lake Monowai. At the river outlet, about 8.5km from the powerhouse, gates control the lake. Water flows down the Monowai River for some 6km to a small lake formed by a weir across the river. It is then diverted into a canal, 865m long, to a forebay, from there a 1036m, 2.6m diameter pipeline leads to the surge tank. Three penstocks (1.6m) take the water from the surge tank down to the turbines in the powerhouse. The water from the turbines is discharged into a tail water pond controlled by a weir. Water flows over the weir and into the Waiau River. The canal intake structure has a fish pass to the Lower Monowai River.
The Monowai Village Services Society has a pipeline, pump and some storage tanks located on Pioneer land to supply water, for domestic use, to the village. Pioneer owns the land for the dam, intake, pond, canal, pipeline, powerhouse, substation and access road to powerhouse.
The land for the dam is subject to a public easement for pedestrian right of way, and borders Fordland National Park. Extensive upgrades to the scheme have taken place with the most substantial upgrade between 2005 and 2008, when new turbines, generators and control systems were installed. The station is designed to run automatically in an unattended mode.
The Lake Monowai Head Gates