Karapiro Power Station
| Karapiro Power Station | |
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Part of the Karapiro Dam.
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 Location of Karapiro Power Station in New Zealand
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| Country | New Zealand |
| Location | near Cambridge, Waikato |
| Coordinates | 37°55′26″S 175°32′21″E / 37.92389°S 175.53917°ECoordinates: 37°55′26″S 175°32′21″E / 37.92389°S 175.53917°E |
| Status | Operational |
| Construction began | 1940 |
| Opening date | May 1948 |
| Owner(s) | Mercury Energy |
| Dam and spillways | |
| Type of dam | Arch dam |
| Impounds | Waikato River |
| Height | 52.4 m (172 ft) |
| Length | 335 m (1,099 ft) |
| Width (crest) | 2.4 m (7 ft 10 in) |
| Width (base) | 15.2 m (50 ft) |
| Spillways | Four |
| Reservoir | |
| Creates | Lake Karapiro |
| Surface area | 7.7 km2 (3.0 sq mi) |
| Maximum water depth | 30.5 m (100 ft) |
| Power station | |
| Type | Conventional |
| Hydraulic head | 30 m (98 ft) |
| Turbines | 3 × Kaplan |
| Installed capacity | 90 MW |
| Annual generation | 525 GWh |
The Karapiro Power Station is a hydroelectric power station on Waikato River, in the North Island of New Zealand. The power station lies on Lake Karapiro, a major rowing regatta venue. Karapiro is 30 kilometres (19 mi) upstream from the city of Hamilton and is the last of the eight hydroelectric power stations on the Waikato River.
Karapiro is a baseload power station, as it is required to maintain water flow in the lower Waikato River even during low inflows to the catchment and during low electricity demand. Only two turbines are required to keep the river flow at a reasonable level, with the third turbine being available for peak generation and maintenance on one of the other turbines.
Like all of the hydroelectric power stations on the Waikato River, Karapiro is operated by electricity generator Mercury Energy.
Karapiro was the second power station built in the Waikato hydro scheme. Construction of the dam and power station began in 1940, but a materials and labour shortage due to World War II meant progress was slow. The station was completed in 1947, four years behind schedule.
The creation of Lake Karapiro behind the dam flooded the Horahora Power Station, the first power station built on the Waikato River.
The bridge over the spillway is the only road access to the turbine hall. The first bridge had a supporting column in the center of the bridge. The bridge was destroyed by the water running through the spillway in a significant flood event (Source: Mighty River Photo archives). The replacement bridge is as you see today with no supporting column.
To the left of the four spillway gates are three siphon tubes. These were designed for the management of the lake level under normal river flow and the spillway gates were to be used in only extreme conditions. The design of the siphon tubes was faulty: The flow of water was supposed to be stopped by a blast of air, but this never worked properly - resulting in the spillway gates to be used for lake level control.
Karapiro's powerhouse is located on the northern bank of the river, with a diversion tunnel and spillway also on the northern bank. The river is dammed by a concrete arch dam south of the powerhouse, with the electricity substation on the southern bank of the river.
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Wikipedia