Tongariro Power Scheme facts for kids
The Tongariro Power Scheme is a huge system in the central North Island of New Zealand that makes electricity using water. It's a hydroelectricity scheme, which means it uses the power of flowing water to create energy. This system can make up to 360 megawatts (MW) of electricity! It's currently run by a company called Genesis Energy.
This amazing system collects water from many rivers and streams around Ruapehu, Ngauruhoe, Tongariro, and the Kaimanawa Ranges. This area covers about 2,600 square kilometers. The water then travels through a big network of canals and tunnels to three power stations: Rangipo (120 MW), Tokaanu (240 MW), and Mangaio (2 MW). After the water has helped make electricity, it flows into Lake Taupo. Here, it's stored to be used again by other power stations along the Waikato River.
The Tongariro Power Scheme creates about 1,350 gigawatt-hours (GWh) of electricity every year. This is about 4 percent of all the electricity New Zealand uses!
How the Tongariro Power Scheme Works
The Tongariro Power Scheme is like a giant plumbing system designed to move water from high up in the mountains to power stations. It has different parts, called "diversions," that collect water from various places and bring it together.
Eastern Diversion: From Whangaehu River to Rangipo Dam
The Eastern Diversion starts at a stream called Waiharakeke, which flows into the Whangaehu River. Water from this stream and 22 other streams, like Waihianoa and Makahikatoa, goes into a long underground tunnel called the Wahianoa Aqueduct. This tunnel is 8.4 kilometers long! It even goes under the Whangaehu River itself. However, it doesn't take water from the main Whangaehu River because that water comes from Mount Ruapehu's crater lake and is too acidic.
At the end of the aqueduct, near State Highway 1, the water goes through the 1.4-kilometer Mangaio Tunnel. From there, it either goes to the Mangaio Power Station or flows into Lake Moawhango through the Mangaio Stream.
Lake Moawhango is a lake made by people. It was created by building dams on the Moawhango River and Mangaio Stream. Water from Lake Moawhango then travels through the 19.2-kilometer Moawhango Tunnel to the Rangipo Dam.
The Rangipo Dam is built on the Tongariro River. Water from the eastern side of Ruapehu and the western side of the Kaimanawa Ranges also joins the scheme here. Water from the Waihohonu Stream is also collected and sent through the 960-meter Waihohonu Tunnel to the Rangipo Dam.
Tongariro Diversion: From Rangipo Dam to Lake Rotoaira
The lake behind the Rangipo Dam acts like a storage pond for the Rangipo Power Station. Water from this lake goes into the 8-kilometer Rangipo Headrace Tunnel. This tunnel takes the water 63 meters below ground to the Rangipo Power Station. After the water has passed through the power station, it flows through the 3-kilometer Rangipo Tailrace Tunnel to the Poutu Dam on the Tongariro River.
More water from the Tongariro River (which now includes water from the eastern sides of Ngauruhoe and Tongariro) joins the system here. The water then flows through the Poutu Canal, going under State Highway 1 and State Highway 46. It then joins the Poutu Stream and enters Lake Rotoaira. Here, it mixes with water from the Western Diversion.
Western Diversion: From Whakapapa River to Lake Rotoaira
The Western Diversion starts at the Whakapapa River. Water from this river goes into a 16.5-kilometer tunnel that leads to Lake Te Whaiau. Along the way, it picks up water from other streams like Okupata, Taurewa, Tawhitikuri, and Mangatepopo.
Water from the Whanganui River is also sent through a short tunnel into the Te Whaiau Stream, where it joins the water from the Whakapapa and other streams. Water from Lake Te Whaiau then flows into the Otamangakau Canal, which leads to Lake Otamangakau. Here, it's joined by water from the Otamangakau Stream.
From Lake Otamangakau, water from the Western Diversion goes into the Wairehu Canal. It travels under State Highway 47 and finally reaches Lake Rotoaira, where it meets the water from the Eastern Diversion.
Rotoaira Diversion: From Lake Rotoaira to Lake Taupo
Lake Rotoaira is a very important lake in the scheme. It stores water from both the Eastern and Western Diversions. It also collects water flowing off Mount Pihanga and Mount Tihia. This lake also acts as the main storage for the Tokaanu Power Station.
Water is taken from the northern end of Lake Rotoaira into the 6.1-kilometer Tokaanu Tunnel. This tunnel carries the water under State Highway 47 and through Mount Tihia to the Tokaanu Power Station. After the water has passed through the station, it flows into the 3.8-kilometer Tokaanu Tailrace Canal.
The canal goes under a special bridge called the Tokaanu Tailrace Bridge. This bridge is unique because it's both a road bridge for State Highway 41 and an aqueduct (a water channel). The Tokaanu Stream, which is important for trout to lay their eggs, flows under the road surface. Finally, the canal drains into Lake Taupo at Waihi Bay.
Power Stations of the Scheme
Quick facts for kids Tongariro Hydro Scheme(Tokaanu, Rangipo) |
|
|---|---|
| Location | Central North Island |
| Commission date | 1973 (Tokaanu) 1983 (Rangipo) 2008 (Mangaio) |
| Owner(s) | Genesis Energy |
There are three power stations in the Tongariro Power Scheme: Rangipo, Tokaanu, and Mangaio. All of them are controlled from a special room at the Tokaanu station.
Rangipo Power Station
Rangipo Power Station is part of the Eastern Diversion. It's built 63 meters underground so that it doesn't spoil the look of the landscape. It was only the second hydro power station in New Zealand to be built underground! This station has two big machines called turbines. Each turbine can make 60 MW of electricity, so the whole station can make 120 MW. It started working in 1983.
Tokaanu Power Station
Tokaanu Power Station is on the Rotoaira Diversion. It has four turbines, and each one can make 60 MW of electricity. This means the Tokaanu station can make a total of 240 MW, making it the biggest power station in the scheme. It started making electricity in 1973. The control room for the entire Tongariro Power Scheme is located here.
Mangaio Power Station
The Mangaio Power Station is the smallest of the three. It can make 2 MW of electricity.
