Hydro power provided 72.9% of electrical energy in 1990, but by 2007 this had dropped to 54.9%. The electricity generated by gas and coal increased substantially over this period, with a resulting increase in carbon dioxide emissions. However hydro provided 82.5% of electricity generated from renewable sources.
Public attitudes and the consent process
In the early 2000s further development of hydroelectricity was hindered by concern about negative environmental and social impacts. The effects of a large dam and new lake on the environment are often considerable, and affect local landowners and communities.
Since the debate over raising the level of Lake Manapōuri in the 1960s and early 1970s, hydro development has been politically contested. Public attitudes hardened further in the wake of the impact of the controversial Clyde dam in Central Otago.
Engineering and environmental investigations are complex, lengthy and expensive, with uncertain outcomes. Consents need to be obtained under the Resource Management Act 1991.
Potential hydroelectric development, 2004
In 2004 a government-funded study identified a total of 2,460 megawatts (MW) of hydroelectric capacity that could potentially be developed. Potential schemes ranged from large – Waitaki (590 MW), Clutha (410 MW), Grey (350 MW), Waiau (235 MW) and Ngaruroro (135 MW) – to a number of much smaller schemes of less than 100 MW.
The schemes would add to the 5,366 MW of existing hydro capacity, and extend New Zealand’s renewable energy sources. But it remained questionable whether the schemes would be developed.
The study suggested that rather than persisting with the traditional large dam- and storage-based schemes, realistic future hydro development was likely to be smaller, using canals which diverted river water. They would be determined by the level of extraction permitted by residual river flows, sharing water for irrigation or other supply purposes, and would be integrated with the demands of other water users.
Lower Waitaki River
In 2003 power company Meridian Energy applied for resource consents for Project Aqua: six stations and 60 kilometres of canal on the lower Waitaki River, with a capacity of 540 MW. The project was shelved as a result of public opposition, and difficulties getting it through the consents process.
Power for the future
Meridian’s Project Aqua provoked strenuous opposition. It would have required the diversion of more than 70% of the river’s water, destroying wildlife habitat and 1,000 hectares of farmland, and preventing recreational and tourist use. People opposing the project included local farming families, canoeists, recreational fishers, tourists, local businesses and conservationists. Project Aqua’s cancellation highlighted the issue of how New Zealand might resolve its energy supply issues.
Meridian then promoted a smaller scheme, with less environmental impact, involving one station generating 200 to 285 MW, with a 34-kilometre tunnel on the north bank of the Waitaki River. In 2008 it was granted water-related consents, as a first stage of the project.
In 2007 the company also applied for resource consents for a dam and lake in the Mōkihinui gorge, on the West Coast, with a capacity of 65 to 85 MW.
Rival company Contact Energy announced in 2008 that it was reviewing potential large-scale hydro developments on the Clutha River.
Hydroelectricity in the future
In the 20th century New Zealand’s extensive water resources were harnessed for cheap and reliable electricity generation. Governments decided that water rights should be regulated in the interests of the country as a whole. The interaction of politics and local and environmental concerns may once again lead to further hydro developments, as the country’s energy needs continue to grow.
It is generally thought that New Zealand’s easily exploited large-scale hydro resources have largely been exhausted. Concern over the global impact of climate change may lead to a revision of this view. The environmental benefits of renewable hydroelectricity may come to the forefront.