In 2015, New Zealand and other UN Member States adopted the 2030 Agenda for Sustainable Development and the Paris Agreement. Central to the 2030 Agenda are the 17 Sustainable Development Goals (SDGs), whereby SDG7 ‘ensure access to affordable, reliable, sustainable and modern energy for all’ plays a significant role in achieving other SDGs and the Paris Agreement on climate change. Hydropower has been one of the popular renewable energy options pursued by many nations to achieve such goals. With more than 80% of its electricity supply already renewable, New Zealand seeks to fulfil its climate commitment by achieving a 100% renewable electricity system.

The aims of this study were to examine the sustainability impact of the proposed Lake Onslow pumped hydropower project using the Hydropower Sustainability Assessment Protocol (HSAP) framework; to assess the applicability of the framework to this case; and to recommend how the framework might be improved to make it more suitable for assessing sustainability impacts of infrastructure projects in local contexts. Through a triangulated approach of data collection, drawing on: semi-structured interviews with local stakeholders and rūnanga, expert interviews, and analysis of published case studies of international hydropower projects, I examined a range of perspectives on the proposed project as a case study.

The HSAP – Early Stage Assessment framework is helpful when assessing potential sustainability impacts of the Lake Onslow project, despite a need for further refinement. The study found that the Lake Onslow project, if carefully planned, could be a solution to addressing the ‘dry year’ energy security problem in New Zealand. However, several factors would need to be thoroughly investigated before a final decision could be made on whether to proceed with the Lake Onslow scheme. The natural environment, endemic species, trout fisheries, and downstream impacts need comprehensive investigation to understand how lake level variations will impact on these ecosystems. Social and cultural impacts, and indigenous values also need careful consideration. A strategic plan should be devised to manage disruption, safeguard ecological sites, and address compensation issues. Notably, ensuring benefits are equitably distributed across the community will be crucial.

Ultimately, the sustainability impact of a project significantly depends on public acceptance and participation. New Zealand could benefit from the proposed Lake Onslow project to address the energy security challenge, while reducing carbon emissions if local perspectives and international lessons from past failures of hydropower projects are seriously considered.