Water management

Water is vital to our business as it is essential to our 100% renewable generation sources – hydro and geothermal.  

We have a long heritage with the Waikato River dating back nearly a century as it is home to our eight hydro dams which make up the Waikato hydro system. This drives our strong commitment to the environmental health and well-being of the river for all.

Mercury's Commitment


Our hydro plants produce about 10% of New Zealand’s electricity.  We aim to achieve maximum efficiency and optimal output from the hydro system in line with resource consents. The water we use for hydro generation is not consumed by our activities and remains available for other users.


Our central North Island geothermal power plants produce around 40% of our generation. Across our geothermal sites, all geothermal fluids used through our stations are injected back into the reservoir to maintain the sustainability of those resources.

We are strongly committed to understanding, managing and minimising any impacts as a result of our operations. We work closely with iwi, the community and local government to ensure we understand the effects of our operations. Some of the activities we carry out to meet compliance include hydrological analysis, geomorphological studies and ecological monitoring. We have demonstrated a strong and consistent compliance record, and in 2015 we achieved full compliance with the Waikato Regional Council for hydro operations for the second year running.

In December 2014 we entered into a long-term agreement with Tuwharetoa Maori Trust Board in respect to the storage of water in Lake Taupo. Lake Taupo is the primary source of Mercury’s Waikato hydro storage, and through the agreement we have committed to working with the Trust Board into the future.


Mercury has a deep respect for the close links that iwi have with water, including the tupuna awa relationship held by many Waikato River iwi. We acknowledge and respect Te Ture Whaimana o Te Awa o Waikato (the vision and strategy for the Waikato River).
We work closely with iwi, hapu and marae identifying how we can best manage freshwater.
In the spirit of partnership, we look for mutual mana-enhancing opportunities with the people and organisations that make up the river iwi. Mercury supports a range of programmes, including social enterprises, educational initiatives, environmental and ecological restoration projects along with a number of Māori cultural initiatives.

Waikato Catchment Ecological
Enhancement Trust:

Through our long-standing partnership with the Waikato Catchment Ecological Enhancement Trust (WCEET), we’re helping to protect and enhance the ecology and biodiversity of Lake Taupo and the Waikato River.
Over the past 13 years, WCEET in partnership with Mercury, has worked on hundreds of projects to the value of $5.5m. Learn more about the WCEET




Lindavia Intermedia

Government scientists have identified the algae Lindavia intermedia in a number of North Island lakes including Lake Taupo. It was identified in South Island lakes in 2004 and there has led to a sticky bloom known as lake snow, that can look like slime on fishing gear and boat hulls and cling to swimmers. There is no evidence of it affecting the health of the waterways, but it’s important to prevent its spread. We’re asking everyone who enjoys the rivers and lakes of the central North Island to follow the Ministry for Primary Industry’s guidelines when moving between waterways.
Learn more

Water Policy and Reform

At Mercury we make sure we’re part of the conversation.
We actively contribute to water policy and reform at both a regional and national level, and regularly participate in discussions with Government and local authorities on freshwater management.This includes:

// The National Land and Water Forum
// Ministry for the Environment’s consultations on national water policy reform (including the National Policy Statement Freshwater Management and the Resource Management Act)
// Waikato Regional Council’s Healthy Rivers / Wai Ora: Plan Change
// Waikato Regional Council’s “Let’s Talk Water”/Water Strategy
// Waikato River Authority’s Waikato River Restoration Strategy
// Restoration and rehabilitation projects in partnership with the Waikato River Authority