11. Wellington (Including Wairarapa) Region
11.1 Catchment #22: Ruamahanga
This catchment has:
- an existing hydro-electric power station (e.g. Kourarau south-east of Masterton),
- no controlled lake storage.
Table 19: Hydropower Opportunities in the Ruamahanga Catchment with High to Medium Confidence of Proceeding in the Next 20 Years.| Name | MW | Average Energy Production (GWh p.a.) | Public Reference |
| Waiohine - Devils Creek | 6 | 26 | T&T 1981-1 |
| Waingawa - Kaituna | 7 | 30 | T&T 1981-1 |
11.1.1 Waiohine - Devils Creek (1A)
The Waiohine River exits the Tararua Ranges just north-east of Greytown. The concept of this scheme endeavours to combine the best features of a dam in a narrow gorge with a canal running along the highest terrace of the east bank of the Waiohine River.
There is a narrow constriction in the gorge which could be suitable for a concrete arch dam of height about 23m. The dam would form a relatively small reservoir contained almost exclusively within the river gorge.
A canal would run some 1900 metres, crossing Devils Creek on a culverted embankment, until constrained by the steep valley side and thence to a power station.
A catchment area of 173km2 gives a mean flow of 17.3m³/s and, with a nett head of 28.0m, and a 6MW plant would deliver approximately 26GWhp.a. (plant factor 50%).
11.1.2 Waingawa - Kaituna (4/2A & 4/2B)
The Kaituna area is just west of Masterton. In this area a short distance downstream of the confluence of the Atiwhakatu stream, the Waingawa River emerges from its gorge in the Tararua Ranges and flows in a wide alluvial flood plain. The two schemes envisage a shallow diversion weir diverting flows up to about 1½ times mean annual flow into an unlined canal running on the east bank of the river and climbing progressively up onto the terraces. At a point about 1.5km downstream of the intake, water could be returned to the river through a 3.3MW power station (Scheme 4/2B) or a diversion could be continued to the east, crossing the Plains road and feeding a storage head pond in a shallow eastern tributary valley. From this head pond would run a concrete pipeline and short steel penstock feeding a 7MW power station (Scheme 4/2A) from which water would return to the river by way of a tailrace channel, giving approximately 30GWh p.a. (50% plant factor).
Wairarapa Electricity carried out investigations and consultation for a scheme based on the use of this resource. The scheme was opposed by a group called "Wairarapa Electricity Shareholders and Consumers Association" (WESCA). The scheme was put aside by Wairarapa Electricity and WESCA was disbanded in 1997.
11.2 Other Opportunities in this Region
11.2.1 Prohibited
Water Conservation (Rangitikei River) Order 1993 may affect opportunities [MOC 1990].
11.2.2 Undefined
#22 - Ruamahanga River - Reef Hill / Stoney Flat - 10MW
#147 Hutt River - Pakuratahi / Kaitoke Saddle - 7MW
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