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Hydro stations

Our hydro stations are located in some of the most scenic places in New Zealand, making them popular spots to visit. We own and operate six power stations in the Waitaki hydro scheme, as well as the country’s largest hydro station – Manapōuri.

Waitaki hydro scheme

The Waitaki hydro scheme is a series of interconnected lakes and canals used to generate electricity. It consists of eight power stations, and Meridian owns and operates six of these:

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    Ōhau A

    Ōhau A generates enough electricity each year for about 144,000 average New Zealand homes.

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    Ōhau B

    Ōhau B has four 55.5 megawatt generating units, and a generation output of up to 212 megawatts.

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    Ōhau C

    Ōhau C is a twin station with Ōhau B, and both hydro stations have the same generating capacity and use similar equipment.

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    Benmore is the country’s second largest hydro station after Manapōuri. It generates enough electricity each year for about 298,000 average New Zealand homes.

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    The Aviemore generators are the largest in New Zealand. The rotors are nearly 8 metres in diameter and weigh 210 tonnes.

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    Waitaki generates enough electricity each year for about 51,000 average New Zealand homes.

NZ’s largest hydro station

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    Manapōuri is the largest hydro power station in New Zealand, and is located on the edge of Lake Manapōuri’s West Arm in the Fiordland National Park, which has UNESCO World Heritage status as part of Te Wāhipounamu.

How hydroelectricity works

Typically, a dam stores water in a reservoir. Water released from the reservoir falls through a pipe called a penstock to a turbine. These turbines look like large wheels with wide spokes. The water hits the blades and pushes them to make the turbine spin. The turbine’s rotation drives a generator to produce electricity. In other words, this spinning ‘changes’ the force of falling water into electricity.

Most of Meridian's electricity is made from the energy of falling water. Our hydro stations generate enough electricity to power around 1.4 million homes each year.

It's not possible to store large amounts of electricity. But it is possible to store water in dams.

Keeping an eye on the water

We manage about 50% of New Zealand's total hydro storage. We collect information on lake levels, as well as the amount of water stored as snow, so we can estimate its impact on inflows.

Current lake levels    Current snow storage

Water stewardship

We work closely with iwi and a range of stakeholders to balance the different economic, social, cultural and environmental implications of water use in New Zealand.

Find out more

Dry river bed safety

Meridian's hydro stations are located in some of the most scenic places in New Zealand, making them popular spots to visit.

At times, we’ll release water from our stations. We’ll always update signage nearby to let you know when we’re going to do this. If you’re camping or fishing in a dry river bed, you must remain vigilant and follow all instructions. If you see water appear, the most important thing to do is get out of the water and stay out.

If you want more information on planned flow releases, head to: Ecan river flow data - website.

Waiai river

Habitat enhancement and restoration

We’re privileged as the kaitiaki of the local waters we use to generate electricity. It’s important to us that we take care of them, as well as the species that call them home. We're constantly monitoring the impact of our hydro stations and working with stakeholders on initiatives to lessen them. These mainly relate to effects on water-based species resulting from inundation, dry river beds or habitat loss.

  • Project River Recovery: We’re ongoing supporters of the Department of Conservation’s Project River Recovery, which preserves flora and fauna in the Upper Waitaki Basin’s braided river habitats. 

  • Waiau River Restoration: The Waiau River restoration work is a partnership between Meridian and the Waiau Fisheries and Wildlife Habitat Enhancement Trust (Waiau Trust). The Trust manages a number of habitat enhancement projects that improve the ecological health of the Waiau River.

  • Elver trap and transfer: The Waiau and Waitaki catchments are home to thousands of native eels. Building and operating dams in these areas has had impacts on their migratory habits. Check out what we’re doing to ensure the health of both the eels and their waters. 
People working on trap and transfer project

Hydro Asset Management Plan

From time to time we need to remove generation assets from service to enable their proper management, maintenance, and upgrade in accordance with prudent asset management practice.

In accordance with the Electricity Industry Participation Code 2010, we disclose all generation asset outages via the Planned Outage Co- Coordination Process (POCP) platform as soon as we have sufficient information about outages, their likely timing, and duration. There are also future works in Meridian’s Hydro Asset Management Plan with an outage impact which, as at the date of the table below, we do not yet have sufficient information to include in POCP. These outages are listed below.

Please note this list does not necessarily include all of Meridian’s regular maintenance outages. We will disclose them on POCP as the outages in the table become more definite, meaning after the date indicated on the table, the table may include outage information that is also listed on POCP. Please note, this is only a plan and is subject to change depending on a wide variety of circumstances. The table is correct as at the date indicated and we will aim to update it regularly.  

Meridian’s regular maintenance outages schedule 

As at 18 December 2023
FY2026 OHC 53 1 week 220 kV CT replacement
  AVI 55 10 weeks Headgate refurbishment
  OHA 66 30 weeks Unit refurbishment
  OHB 53 10 weeks Unit refurbishment
  OHC 53 10 weeks Unit refurbishment
FY2027 OHA 66 2 weeks 220 kV CB replacement
  BEN 90 6 weeks 220 kV CB replacement
  OHC 53 1 week 220 kV CT replacement
  AVI 55 10 weeks Headgate refurbishment
  OHA 66 30 weeks Unit refurbishment
  OHB 53 10 weeks Unit refurbishment
  OHC 53 10 weeks Unit refurbishment
FY2029 MAN 850 3 days Station outage