16. Southland Region
16.1 Catchment #4: Waiau
This catchment has:
- existing hydro-electric power stations (Manapouri and Monowai),
- controlled lake storage (Manapouri and Te Anau).
Table 31: Hydropower Opportunities in the Waiau (Southland) Catchment with High to Medium Confidence of Proceeding in the Next 20 Years.| Name | MW | Average Energy Production (GWh p.a.) | Public Reference |
| Te Anau Gates | 65 | 350 | SREA 2003 |
16.1.1 Te Anau Gates
The outflow for water from Lake Te Anau into Lake Manapouri is controlled by a gate structure at the entrance to the Upper Waiau River.
There is about 20m head difference between Lakes Te Anau and Manapouri. This head can be utilised for generation of electricity by either an in river low embankment/powerhouse scheme or by construction of a tunnel to a powerhouse on the shore of Lake Manapouri. Either of these schemes could have an installed capacity of around 65MW (350GWh). The area is on the edge of the National Park so care in design to protect the Park area would be necessary.
16.2 Other Opportunities in this Region
16.2.1 Prohibited
The Southland region has vast hydro potential but most of it is unavailable within the Fiordland National Park. There is also the Water Conservation (Mataura River) Order 1997.
#11 Mataura Catchment
Waikaia
The Waikaia river tributary of the Mataura offers potential for a 400m head scheme developing 19MW (80GWh) from a tunnel diversion. This is currently prohibited by the Water Conservation Order.
Mataura Canal Hydro
Although previous studies emphasised the potential of dams built in gorges it may be possible to develop an out of river canal type hydro generation scheme in parts of the Mataura catchment and so avoid impoundment. This would entail extraction of some flow from the main stream of the river and running this along canals to a power station where it would come back into the river. A canal project could be around 6MW and produce 30-35GWh.
#136 Lake Hauroko
While this project is within the National Park, the successful expansion of the Manapouri power station has shown that hydro projects can be constructed in National Parks without adversely affecting the environmental qualities. Lake Hauroko is approximately 125m head above Lake Poteriteri and by use of a tunnel and underground power station this head could be used to generate electricity. An alternative is a scheme that uses the head of about 160m between Lake Hauroko and Te Waewae Bay. In either case a residual flow regime for the Wairaurahiri River would need to be incorporated in any development.
16.2.2 Undefined
The area of the region outside the National Parks has only two significant catchments, the Waiau and the Mataura, and the smaller Oreti.
A comprehensive study of the hydro potential of the region was undertaken in 1983. However this was undertaken under a different era and the type of projects being investigated today are quite different in terms of concept and relationship with adjacent communities.
The possible Southland schemes range from run-of-river which produces base load electricity, to small niche schemes that are suitable for embedded generation similar to that of the existing 0.6MW Mataura hydro power station.
#4 Waiau Catchment
Lower Waiau Canal Hydro
The flow in the Waiau River is largely dependent on the generation requirements of the Manapouri power station although the Manapouri resource consent sets a minimum flow condition, which would have to be maintained with any generation development.
It may be possible to develop an out of river canal type hydro generation scheme in parts of the lower Waiau catchment. This would entail extraction of some flow from the main stream of the river and running this along canals to a power station where it would come back into the river. If a 12MW scheme were built it could produce around 55GWh. This has not been investigated but indications are that it may be possible.
Upgrade Monowai Power Station
The existing Monowai power station has a capacity of 6.3MW and produces 35-40GWh of electricity per annum. Resource consents have recently been obtained for continued operation of the station. Options for additional flow from the Borland River and additional generation using the existing flow have been identified but are not currently considered economic. There may also be environmental issues relating to the Borland option.
Lake Monowai storage could also be coupled with a nearby windfarm to firm the wind energy.
Upper Mararoa
Schemes have previously been considered on the upper Mararoa. Without site investigation it is unknown whether these are viable.
Mararoa Weir
The Mararoa Weir has a small head, which could be utilised for generation of electricity using the residual flow. Other than a penstock and generating equipment no structural work would be required as the weir already has the capacity to handle diversion floodwater.
#20 Oreti Canal Hydro
It may be possible to develop an out of river canal type hydro generation scheme in parts of the Oreti catchment. This would entail extraction of some flow from the main stream of the river and running this along canals to a power station where it would come back into the river. A canal project could be around 6MW and produce 30-35GWh.
Lake Wakatipu Flood Alleviation
The head difference between Lake Wakatipu and the Mataura River near Garston is about 5m. Investigations have been proposed to assess the viability of providing an alternative discharge from Lake Wakatipu via Garston and Athol possibly to the Upper Mataura or alternatively pumping water using windmills into the Upper Oreti catchment. This would provide opportunity for flow of water through a low head hydro generator, which could provide emergency discharge from Lake Wakatipu to eliminate potential flooding and/or supplement river flows during low flow events. Iwi support for such initiatives would be a fundamental requirement.
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