15. Otago Region
15.1 Catchment #1: Clutha
This catchment has:
- the largest catchment area of New Zealand rivers.
- the highest mean flow
- existing hydro-electric power stations (e.g. Roxburgh, Clyde),
- controlled lake storage (Hawea)
Table 29: Hydropower Opportunities in the Clutha Catchment with High to Medium Confidence of Proceeding in the Next 20 Years.| Name | MW | Average Energy Production (GWh p.a.) | Public Reference |
| Manuherikia River | 7 | 23 | RSML 1982-1 |
| Luggate | 90 | 435 | MWD 1982-2 |
| Queensberry Hills | 180 | 860 | MWD 1982-2 |
| Hawea | 90 | 435 | SKM 2003 |
| Nevis | 45 | 197 | OCEPB 1984 |
15.1.1 Manuherikia River
The Manuherikia River has its source in the Hawkdun, Wether, Ewe and St. Bathans Ranges from where it flows south to the Falls Dam reservoir. From here the river flows south-west through Omakau to the Clutha at Alexandra.
The study area covers the section of the Manuherikia River above the Dunstan Creek confluence.
The Falls Dam was constructed to store some winter flows, for release in the summer for irrigation schemes downstream. However, the demand for irrigation water has increased and the present storage cannot cope with the demand. The Ministry of Works and Development had proposals to construct a new dam downstream of the existing dam. The proposed dam would be 25m higher than the existing dam with a storage capacity of 100 million cubic metres. The storage capacity would be ten times the existing scheme.
The proposed irrigation scheme would use an average of 60 million cubic metres of water out of storage each season from September to April. The additional 40 million cubic metres is reserve storage for consecutive dry winters.
The mean annual flow at the dam is 6.15m³/s.
The irrigation peak demand period is from December to February with an expected maximum irrigation flow of 8m³/s. A minimum residual flow of 1m³/s is expected to be required in the Manuherikia River downstream of the dam. Therefore, the maximum flow from the storage reservoir would be 9m³/s.
There is potential for a combined small hydro / irrigation development at this site although most of the generation would be outside the peak power demand period.
Mechanical plant for such a scheme may be expensive as the scheme would operate under variable head and flow.
Below the dam the river is confined to a narrow steep sided gorge for 3km. The proposed powerhouse would be constructed adjacent to the river near the 520m contour level. As the river is confined by 10m high rock walls the powerhouse site would have to be cut into rock. A single penstock would convey water from the dam to the powerhouse, a distance of 900m.
The outlet from the bottom of the dam would be a combined power and irrigation pipe conduit with a bypass at the powerhouse. The maximum head available would be approximately 90m and assuming a maximum flow of 9m³/s the installed capacity would be 7MW. The residual flow of 1m³/s in the winter months downstream of the powerhouse would have an output of 580kW from an average head of 70m.
The energy output from this scheme would be approximately 23GWh p.a. (50% load factor). This is based on a total average annual flow of 140 million cubic metres passing through the turbines at an average head of 70m.
In 2003 Pioneer Generation Ltd commissioned a 1.2MW power station at Falls Dam. As this uses a part of the available head it (adversely) alters the economics of this Manuherikia option.
15.1.2 Luggate and Queensberry
The upper Clutha has a mean flow of about 260m³/s, and a fall of about 83m from Lake Wanaka to the head of Lake Dunstan, which means that there is potentially a large hydro-electric resource available. The gorge within the river flats provides sites for dams which would retain water to levels which inundate only small areas of cultivated and farmed river flats.
The most appropriate combination of dams, diversion structures, spillways, powerhouses and canals relates closely to the topography. It has been found that an arrangement with one or two dams and one or two powerhouses is significantly more economical than one with three dams or powerhouses. The actual positioning of structures has required detailed study and is, in part, affected by the geology.
Luggate and Queensberry are two specific proposals for hydro development of the Clutha River upstream of Clyde Power Station / Lake Dunstan. It is preferable to consider them jointly, as they use the available head between the downstream limit of the Lake Wanaka Preservation Act (Clutha / Cardrona confluence) and Lake Dunstan.
It is possible that further investigation may result in other options with different capacities to utilise this available head and associated flows to best effect.
Possible Interest - Contact Energy (Owner of Clutha River based power stations etc, landowner in the Luggate, Queensberry area.)
15.1.3 Hawea
There are two schemes (30MW and 60MW) identified. The 30MW scheme at Hawea consists of replacing the existing works used to control the discharge from the lake with a 30MW hydropower scheme. The 60MW scheme diverts water downstream of the 30MW scheme and conveys it by canal across country where it would finally enter a 60MW power station on the Clutha River. Approximately 435GWh p.a. could be produced from these two stations (plant factor of 50%).
Possible Interest - Contact Energy (Owner of Clutha River based power station etc, landowner in the Luggate . Queensberry area.)
15.1.4 Nevis
The Nevis River rises in the Remarkables and the Hector Mountains to the west and in the Garvie Mountains to the east.
The Nevis River is a tributary of the Kawarau and their confluence is at the upstream end of the Kawarau Gorge, between Queenstown and Cromwell / Lake Dunstan. This scheme consists of two dams on the Nevis River storing and diverting water to a powerhouse further down the Nevis. The upper dam would be located at Nevis Crossing and would provide water storage for the scheme. The lower dam would be some 2km further downstream and would divert the water into a 6.5km tunnel.
A large volume storage lake would be obtained in the lower valley by an arch dam constructed just downstream of the Nevis bridge. An intake dam also of concrete arch construction would be erected at the mouth of the gorge about 2km downstream and would include the additional flow of the Nevis Burn stream. The average flow here is 10.5m³/s and the area drained is 510km2. At this point a concrete lined tunnel would be driven 8km parallel to the river to a point above the power station and a steel penstock installed to carry the water to it. The head developed would be 300m and with 45MW, would give approximately 197GWh p.a. (50% plant factor). The elevation of the power station is 300m.
Possible Interest - Pioneer Generation (publicity about investigations).
15.2 Catchment #9: Taieri
This catchment has:
- existing hydro-electric power stations (e.g. Waipori, Paerau),
- associated controlled lake storage (Mahinerangi)
Table 30: Hydropower Opportunities in the Taieri Catchment with High to Medium Confidence of Proceeding in the Next 20 Years.| Name | MW | Average Energy Production (GWh p.a.) | Public Reference |
| Taieri Falls | 8 | 35 | RSML 1982-1 |
| Lower Taieri | 18 | 79 | RSML 1982-1 |
| Taieri - Deep Stream | 7 | 30 | RSML 1982-1 |
| Taieri - Lee Stream | 7 | 31 | RSML 1982-1 |
15.2.1 Taieri Falls
In 1977 a scheme to use the head from the Taieri Falls to Canadian Flat was investigated by the Otago Electric Power Board's Consulting Engineers.
The proposed Taieri Falls scheme would require a 40m high earth / rockfill dam above Taieri Falls. The original proposal was for a 2.25m diameter 900m long tunnel, to divert water from the dam to emerge on the hillside above Canadian Flat at a surge chamber. From the surge chamber penstocks would carry the water to a powerhouse on Canadian Flat.
However, subsequent high tunnelling costs in a nearby scheme indicate that a pipe conduit benched into the side of the hill may be more economic. The other scheme details would remain the same.
With an installed flow of 4.8m³/s giving a 50% plant factor and with a head of 201m, the installed capacity would be 8MW, giving approximately 35GWh p.a. (50% plant factor).
15.2.2 Lower Taieri
The second possible site for a dam storage scheme on the Taieri is just upstream of Hindon, where the river loops around through 180º. The river is confined in rock for a considerable distance upstream and downstream of the proposed site and therefore the storage would be limited to the river channel.
A 45m high earth or rockfill dam could be constructed at this site with the storage lake extending some 5km upstream.
The gauged mean annual flow at Hindon is 34.5m³/s and an installed flow of 55m³/s giving a 50% plant factor, seems reasonable. At this installed flow and with a head of 40m, the installed capacity would be 18MW, giving approximately 79GWh p.a.
15.2.3 Taieri - Deep Stream
Deep Stream drops quite rapidly over its final 5km, but a scheme on this section of the river would have to abstract water at the 300 m contour level to achieve a practical race alignment. This requires an intake 90m higher and a further 13km upstream to where the 300m contour crosses the river. This intake would be approximately 26km downstream of the diversion into Lake Mahinerangi. Part of the headworks system would be in pipe conduit but the majority would be in open race with a total length of 23km. The proposed penstock route and powerhouse site is in Deep Stream near its confluence with the Taieri River. Some storage may be available along the race alignment.
The mean annual flow available is 3.9m³/s after subtracting present and future water commitments (1982). With an installed flow of 4.2m³/s giving a 50% plant factor, the installed capacity would be 7MW from the 194m head, giving approximately 30GWh p.a.
15.2.4 Taieri - Lee Stream
Lee Stream rises in the hill country to the north of Lake Mahinerangi and to the south-east of the Lammermoor Range from where it flows generally south-eastwards to join the Taieri River about 5km upstream of Outram. The river drops rapidly over its last 4km and it is this section of river that affords potential for small hydro development.
A tunnel diversion scheme was proposed for Lee Stream at the beginning of the 1900's. The proposed tunnel had a 2.13m diameter and was some 2150m in length. The construction of the tunnel was started from both ends and some 610m of tunnel had been excavated before the contractor went bankrupt, and the project was abandoned around 1903.
The Dunedin City Electricity Department had extensively investigated scheme options, using the 1903 part tunnel but they have all been uneconomic.
An alternative to the above scheme would be to sidle around the hillside with a conduit following the contours using the same head as the 1900 tunnel proposal.
The estimated mean flow is 2.9m³/s from the 284km². With an installed flow of 4.2m³/s giving a 50% plant factor and a head of 200m, the installed capacity would be 7MW, giving approximately 31GWh p.a.
15.3 Other Opportunities in this Region
While there are a number of power stations on the two main river systems (Clutha and Taieri, including its main tributary, the Waipori) as well as specific opportunities (e.g. Luggate, Queensberry) being identified, these rivers also contain almost all of the other opportunities in the region. In large part the continuing interest in the Clutha especially is a result of it having the largest flow of all New Zealand rivers, some suitable locations to use the available head and a predominately lake-fed system.
15.3.1 Prohibited
Relevant Restrictions in this region include:
Water Conservation (Kawarau River) Order 1997
Pomahaka River - ex Local Conservation Notice
#1 Pomahaka River - 6MW
15.3.2 Undefined
#1 Clutha catchment
Lower Clutha - 350MW
Dumbarton Rock - 110MW
Manuherikia River Irrigational Hydro Dunstan Creek - 7MW
Upper Fraser River - 7MW (h-bend)
Teviot River "C" - 6MW
Staircase Creek - 5MW
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