Proposed dam across the lake, across the ditch

Following geotechnical investigations, the New Zealand Government will decide in December whether it will move forward with a detailed business case for a concrete dam on Lake Onslow in Central Otago on the South Island.

The country’s Energy and Resources Minister, Megan Woods, suggested the best option would be a roller compacted concrete dam to seal the natural rock basin of the lake east of Roxburgh. The suggestion comes from a recently released Cabinet paper about the proposed dam on the artificial lake which sits at an altitude of 700 metres in the southern end of the South Island.

Ms Woods told the NZ Cabinet that Lake Onslow could be used as a ‘battery’ when hydro generation lakes are low and that the scheme is technically feasible.

In the meantime, however, geotechnical investigations are underway in the Teviot Valley, to be completed over the coming months. The results will be used to analyse potential construction, costs, engineering, consent, timing, and the integration necessary with the electricity system.

More work needs to be done though to look at environmental, cultural and social findings with a view to potential design options. Early analysis has shown that using the lake could reduce the ‘dry year’ issue and support a path to 100% renewable electricity for Australia’s nearest neighbour, across the ditch, moving it away from reliance on coal and gas.

Image: Onslow dam which creates the present Onslow Reservoir, showing water release to the Teviot River. Source: Mohammed Majeed via The University of Waikato.

About the author

Desi Corbett

Desi is the Editor of Concrete in Australia and at the helm of our magazine for 8 years. She was behind the Institute's weekly news bulletins from 2016-2021 and is now writing our focused news items. Desi has been an engineering news and features journalist/editor across all disciplines since 2013 - part of a 30-year career writing for a wide range of industries.