Clutha Pumped Hydro

Project summary

The project is to construct and operate a large pumped hydro energy scheme at Lake Onslow in Central Otago. The enlarged Lake Onslow would store sufficient water to enable generation of up to 1,000 megawatts (MW) for approximately six months, producing around 4,000 gigawatt-hours (GWh) of electricity.

• Creating an upper reservoir by enlarging Lake Onslow to store water for energy generation when required, with a new minimum operating level of 730 metres above sea level and a maximum operating level of 769 metres (current lake level is approximately 684 metres).

• Inundating approximately 7,100 hectares of land.

• Constructing a new dam on the Te Awa Makarara / Teviot River to increase the size and storage capacity of Lake Onslow.

• Building structures to harvest water from the Mata-au / Clutha River and return water to the river.

• Constructing a buffer reservoir adjacent to the Mata-au / Clutha River to store water for pumping.

• Installing intake and outlet structures within Lake Onslow to transfer water between Lake Onslow and the buffer reservoir.

• Installing intake and outlet structures within the buffer reservoir to connect water between the buffer reservoir and the powerhouse.

• Constructing underground tunnels (waterways) to transfer water between the buffer reservoir and the powerhouse, and between the powerhouse and Lake Onslow.

• Constructing an underground powerhouse to connect the upper and lower water sources, generate electricity as water flows from Lake Onslow to the buffer reservoir and the Mata-au / Clutha River, and pump water back to Lake Onslow.

• Providing supporting infrastructure for construction and operation, including reading, concrete plant, construction equipment, accommodation, transmission lines (excluding grid connection, which will be addressed separately), relocation of existing infrastructure as required, and water supply systems.

Project location

The project area covers multiple sites covering an area of approximately 290km2 surrounding Lake Onslow in the Central Otago District of the Otago Region, including the Mata-au / Clutha River Valley, the Teviot Valley, and their associated river margins. A table of the titles relevant to the project area is included in Attachment 2 of the application.

Project referral

The Minister for Infrastructure referred the project to the Fast-track on 18 March 2026. The application was lodged on 12 November 2026.

Notice of decisions on application for referral of the Clutha Pumped Hydro project (PDF, 599 KB)