22 Dec 2023
Readiness, resilience and regulations: a spotlight on New Zealand’s dam infrastructure.
It’s likely that most Kiwis fail to appreciate Aotearoa’s reliance on dam infrastructure in our everyday lives. We can thank a dam engineer when we turn on a tap, switch on a light, or consume locally grown or processed food products.
Local government records suggest there are at least 3,200 dams of various sizes in New Zealand. The exact number is unknown due to regional variation in reporting requirements (with a focus on larger dams). Research suggests the number of dams of all sizes here could be up to 10,000. While this may seem like a large number, it’s important to note that dams range from very small farm dams, “dry” dams in parks and reserves that only hold water in storm events, through to large hydroelectric dams such as Benmore Dam, at 118m high.
Dams in Aotearoa typically serve one of four purposes: agriculture or horticulture; flood protection; water supply; and hydropower – powering us with up to 55 percent of the country’s electricity. They also provide reservoirs for firefighting, snowmaking, processing, waste management, water treatment and recreation.
Helping mitigate climate impacts
Climate projections from the National Institute of Water and Atmospheric Research (NIWA) suggest Aotearoa will experience both more extreme rainfall, and more dry days in the coming decades. Dams are one solution that – when appropriately scoped – can help communities mitigate climate impacts.
In recent years, we’ve seen well-publicised examples of dams serving our communities, in terms of both water security (protection from drought), and flood mitigation. In the 2000s and 2010s, off-stream water storage in Canterbury increased by millions of cubic metres per decade. Outside of Canterbury, we’ve seen the completion of significant dam infrastructure projects in 2023. This includes the Waimea Community Dam, a 53m-high dam capable of storing 13 million cubic metres of water and the largest dam built in New Zealand in more than 20 years. Other examples include the Matawii reservoir, providing 750,000m3 of water storage – the first of three planned reservoirs for the Te Tai Tokerau water storage project in Northland.
We’ve also witnessed the need for post-construction dam safety practices. Extreme rainfall events in the upper North Island have contributed to extreme loading on dams and ponds, contributing to several performance incidents and the failure of a stormwater dam in Glenview, Hamilton, in June.
Regulation an opportunity for advancement
In May 2024, the country’s first post-construction dam safety regulations will come into effect. Owned by the Ministry of Business, Innovation and Employment (MBIE) Building System Performance, the Building (Dam Safety) Regulations 2022 specify minimum dam safety requirements for classifiable dams. Classifiable dams are those meeting either of the following height and stored volume screening thresholds: 4m height and 20,000m3 stored volume, or 1m height and 40,000m3 stored volume. Dam owners, technical practitioners and regional authorities can learn more about the regulations and resources at building.govt.nz/managing-buildings/dam-safety
In preparation for the start of this regulation, many government, sector, consultant and owner groups have invested significant time preparing supporting resources, processes and communication. Throughout the country, we’re witnessing a step change in dam safety engagement within local government and the rural sector. While the new regulations provide an opportunity to reduce post-construction risks associated with unsafe dams, they also provide an opportunity to expand the dam safety community and to work together to understand and address needs in the broader dam sector.
A robust dam safety toolbox
Recent media attention has focused heavily on the new post-construction dam safety regulation. This new regulation brings us in line with most other Organisation for Economic Co-operation and Development member countries who have a consistent regulatory dam safety framework. However, we must remember that a post-construction dam safety regulation is just one of many tools owners and engineers use to ensure safe and appropriate dam operation.
Dam safety requirements and performance practices evolve over the lifecycle of a dam and involve a range of regulations, guidelines and recommendations, people and roles, often spanning generations. Design and construction requirements for large dams continue to be regulated under the Building Act (2004), including provisions for dangerous dams, and flood- and earthquake- prone dams. While MBIE is responsible for setting minimum regulatory requirements, the New Zealand Society on Large Dams (NZSOLD) continues to recommend the adoption of industry-recommended practice as outlined in the New Zealand Dam Safety Guidelines. Updates to NZSOLD’s New Zealand Dam Safety Guidelines are underway to encompass changes in recommended practice. While post-construction dam safety regulations may prove a useful entry point for some dam owners new to dam safety, NZSOLD continues to recommend the New Zealand Dam Safety Guidelines as the essential reference toolbox for any owner, operator or professional working with dams.
Dr Kaley Crawford-Flett is a Technical Project Manager, Honorary Academic at the University of Auckland, and Chair of NZSOLD.
This article was first published in the December 2023 issue of EG magazine.
