Deep within Nelson Lakes National Park on New Zealand’s South Island lies a lake of extraordinary clarity and cultural significance. Tucked among steep alpine forests and fed by the pristine waters of Lake Constance, this small but remarkable body of water has captivated visitors for generations.
Known as Rotomairewhenua, meaning “the lake of peaceful lands,” this serene spot has been sacred to the Ngāti Apa iwi for centuries. Traditionally, it served as a resting place for the remains of the deceased, ensuring their spirits a smooth passage to their ancestral homeland. Today, while the rituals have ceased, the lake remains deeply intertwined with the iwi’s cultural heritage.
The World’s Clearest Freshwater
Scientists studying the lake have confirmed what many hikers and travelers have long suspected—Rotomairewhenua holds the title for the clearest freshwater ever recorded. Its visibility, ranging from 70 to 80 meters, rivals that of distilled water. This incredible transparency, combined with the lake’s deep blue and violet hues, creates an almost surreal landscape that has drawn increasing numbers of visitors, particularly during New Zealand’s summer months from December to March.
However, this growing popularity has sparked concerns among conservationists and the Ngāti Apa iwi. The main threat comes from lindavia, a microscopic alga known as “lake snow” or “lake snot” due to the slimy strands it produces. This invasive species, believed to have arrived from North America, has spread across New Zealand’s lakes, often hitching a ride on hikers’ boots or in water bottles. Already present in nearby lakes, lindavia poses a serious risk to Rotomairewhenua’s pristine waters.
The Fight to Preserve Purity
Efforts to protect the lake have intensified. Conservation experts warn that even the tiniest particle of lindavia could permanently alter the lake’s ecosystem. Though not harmful to humans, the alga produces mucilage that could cloud the lake’s remarkable clarity.
To combat this, the Department of Conservation (DOC), Ngāti Apa ki te Rā Tō Trust, and Te Araroa Trust have introduced biosecurity measures along the hiking trails leading to the lake. Cleaning stations have been installed near affected lakes, where visitors are urged to scrub their gear before proceeding. Educational signage and messages on the Te Araroa trail app emphasize the importance of keeping the lake untouched—not just for environmental reasons but also out of respect for its sacred status.
Respecting the Sacred Waters
Visitors are strongly discouraged from swimming, touching the water, or even dipping towels and cameras into the lake. During peak hiking season, wardens—often representatives from the DOC or Ngāti Apa—are stationed at the lake to educate visitors about its significance and the importance of minimizing human impact.
While many travelers respect these guidelines, some still overlook the cleaning stations, assuming the problem lies with others rather than themselves. Conservationists stress that safeguarding Rotomairewhenua requires collective responsibility.
Balancing Access and Preservation
As part of a national park, restricting access to the lake is not a preferred solution. Instead, the focus remains on education and responsible tourism. While increased visitation brings challenges—such as higher maintenance costs and environmental strain—it also presents an opportunity for people to experience and appreciate this unique natural wonder.
Ultimately, the goal is to strike a balance between allowing people to enjoy the lake and ensuring its protection for generations to come. By following conservation guidelines, visitors can help preserve Rotomairewhenua’s stunning clarity and deep cultural significance, ensuring it remains a place of peaceful beauty for years to come.
