6. Bay of Plenty Region
Seven main river systems dominate the hydrology of the Bay of Plenty region. These main river systems are (from east to west) the Motu, the Waioeka, the Whakatane, the Rangitaiki, the Tarawera, the Kaituna, and the Wairoa. Along the coast between the Tarawera and Kaituna river mouths and again north of the Wairoa river mouth, there are a number of minor streams. These streams extend a short distance into the coastal foothills.
6.1 Catchment #116: Tarawera
The Tarawera River drains Lake Tarawera to the Bay of Plenty. The Tarawera has a catchment area of approximately 900km². The river falls approximately 300m in the 59km from Lake Tarawera to the sea.
Over its lower reaches, from Kawerau to the sea, the Tarawera River is generally of a flat gradient. However, in the upper regions there are a number of rapids and a waterfall.
This catchment has:
- no existing hydro-electric power stations,
- no controlled lake storage.
Table 6: Hydropower Opportunities in the Tarawera Catchment with High to Medium Confidence of Proceeding in the Next 20 Years.| Name | MW | Average Energy Production (GWh p.a.) | Public Reference |
| Tarawera - Fenton's Mill | 6 | 27 | MWD 1982-1 |
6.1.1 Tarawera - Fenton's Mill
This scheme proposes to take water from downstream of the Tarawera Falls by way of a diversion. The water would be channelled downstream approximately 4km by a concrete lined canal to a penstock on the right bank of the river. Approximately 55m of head could be developed by this scheme. This scheme, with a 6MW generator, would generate approximately 27GWh p.a. (50% plant factor).
6.2 Catchment #29: Rangitaiki
This catchment has:
- existing hydro-electric power stations (e.g. Matahina, Aniwhenua, Wheao)
- controlled lake storage (e.g. Matahina, Aniwhenua).
Table 7: Hydropower Opportunities in the Rangitaiki Catchment with High to Medium Confidence of Proceeding in the Next 20 Years.| Name | MW | Average Energy Production (GWh p.a.) | Public Reference |
| Kioreweku | 13 | 83 | MOC 1990, BOPE 1994 |
| Whirinaki (B3) | 25 | 110 | MWD 1982-1 |
6.2.1 Kioreweku
An option at Mangamako would develop the head which remains between the existing Matahina and Aniwhenua schemes. The form of the development is similar to that of the Aniwhenua scheme with a low dam and diversion, but in this case creating a new "waterfall" and "gorge" by means of river deepening downstream of the power station. This scheme would involve a dam with powerhouse below, and would be run-of-river with an installed capacity of some 13MW (giving approximately 83GWh p.a. at 50% plant factor).
This reach of the river was the focus of an unsuccessful application in 1994 by Bay of Plenty Electricity for resource consents for its proposed Kioreweku power station using a canal diversion scheme.
6.2.2 Whirinaki (B3)
A scheme involving a dam on the Whirinaki River was proposed in 1962. This envisaged an earth fill dam situated approximately 17km downstream of the Minginui confluence. From the dam a 4km long, 3m diameter tunnel would lead to a power station on the left bank of the Whirinaki River.
The dam would be approximately 70m in height and the total head of the scheme would be approximately 140m.
A mean annual flow rate of 13.0m³/s and a nett head of 140m would, with an installed capacity of 25MW produce approximately 110GWh p.a. (50% plant factor).
6.3 Catchment #48: Whakatane
This catchment has:
- no existing hydro-electric power stations,
- no controlled lake storage.
Table 8: Hydropower Opportunities in the Whakatane Catchment with High to Medium Confidence of Proceeding in the Next 20 Years.| Name | MW | Average Energy Production (GWh p.a.) | Public Reference |
| Waimana - Matahi | 9 | 39 | MWD 1982-1 |
6.3.1 Waimana - Matahi (A2C)
A scheme located near the settlement of Matahi envisages a diversion structure adjacent to Matahi, a 3.4km concrete lined canal along the right bank to the penstocks and a 9MW power station. The head would be 55m, and this would give approximately 39GWh p.a. (50% plant factor).
6.4 Catchment #339: Ruakokore
The Raukokore River with a catchment of 352km² rises at an elevation of over 1200m on the rugged north western slopes of the Raukumara Range near Mt. Honokawa.
This catchment has:
- no existing hydro-electric power stations,
- no controlled lake storage.
Table 9: Hydropower Opportunities in the Ruakokore Catchment with High to Medium Confidence of Proceeding in the Next 20 Years.| Name | MW | Average Energy Production (GWh p.a.) | Public Reference |
| Raukokore 12/2 | 14 | 61 | T&T 1978 |
| Raukokore 12/4 | 19 | 82 | T&T 1978 |
6.4.1 Raukorore 12/2
Some 8km from its mouth the Raukokore River follows around a sharp loop with localised steeply rising afforested banks at its downstream end. The mean annual flow rate of 21.1m³/s and nett head of 51m combined with a 14MW generator would give approximately 60GWh p.a. (50% plant factor).
6.4.2 Raukorore 12/4
Two km downstream of the Waikura River confluence the Raukokore River turns to flow north between locally steep banks which form a suitable dam site for a "conventional" hydro scheme. This scheme comprises a reservoir with an area of 7.4km² extending 13km upstream, with a power station at the front of the dam. The mean annual flow rate of 19.5m³/s, combined with nett head of 68m, with a 19MW generator would deliver approximately 82GWh p.a. (50% plant factor).
6.5 Other Opportunities in this Region
6.5.1 Prohibited
#243 Torere catchment
Torere - Takaputahi Diversion - 36MW (Diverts water from a part of a tributary affected by the National Water Conservation (Motu River) Order, 1984)
Torere - 7MW (Downstream of power station on Torere-Takaputahi Diversion. Relies on diverted water and not economic in its own right)
6.5.2 Undefined
#29 Rangitaiki - 8MW
#72 Kaituna at Mangorewa - 6MW
#112 Waioeka - 21MW
#116 Tarawera - Tarawera at Falls - 7MW (Mutually exclusive to Fenton's Mill (5.1.1) scheme, uses the head from the falls, would need compensating water over the falls [MOC 1990]
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