The Changing Face of Our Lakes: What You Need to Know

Wānaka, New Zealand – March 3, 2025 - Recent reports have raised concerns about declining

water quality in the Upper Clutha lakes - Lake Wānaka, Whakatipu and Hāwea. While these

lakes, on many measures, hold "good" to "excellent" ratings, there are subtle but significant

changes happening, indicating a need for greater community awareness and action.

What Is Changing?

The Otago Daily Times recently highlighted a decline in lake water quality ratings from

"excellent" to "good" in both Lake Wānaka and Whakatipu. This shift appears to align with

specific health and water quality measures, particularly those related to swimability - a key

indicator of water safety for recreational use.

Data from LAWA (Land, Air, Water Aotearoa) shows Roy's Bay in Lake Wānaka generally has a

“good” rating for swimability. However, this measure has only been monitored for the past five

years, meaning there is no long-term baseline for comparison. For Lake Whakatipu, the five-year

swimability trend remains “excellent”, but more recent short-term monitoring has reported

“good” ratings-suggesting localised degradation (or contamination) events. Swimability

measures are based on significant E coli contamination events – suggesting that Lakes Wānaka,

Hāwea and Whakatipu are receiving faecal matter probably from stormwater sources, prompting

intermittent caution and no-swimming warnings.

Ecological Health Under Scrutiny

Lake Submerged Plant Index (Lake SPI), another key indicator, reflects ecological health through

the presence of native and invasive submerged aquatic plants.

in Lake Wānaka, this rating has

shifted from “excellent” to “high”, a subtle but meaningful decline. Whilst there is no “good”

category for this measure (as reported by ODT), the change is significant in ecological terms. See

more on the LAWA ratings here.

The Role of Chlorophyll-a and Lake Snow

Chlorophyll-a, a measure of green plant pigment in the water, is also under review. Research

from Otago University and the Otago Regional Council (ORC) suggests that lake snow (Lindavia

intermedia) - a microscopic invasive drifting algae - may be influencing these water quality

changes. While lake snow does not pose a direct health risk, its presence can impact water clarity,

ecosystem balance, and recreational experiences.

What Can We (as a community) Do?

While these changes might seem minor now, they signal a shift in lake health that requires

proactive community engagement. Here’s how we (the local residents and Upper Clutha

communities) can help:

• Reduce overland flow contamination by planting riparian buffers and limiting chemical

fertilisers.

• Avoid sewage contamination of stormwater.
• Support water quality monitoring by staying informed and advocating for continued

research.

• Practice responsible recreation by ensuring boats, gear, and clothing are clean to prevent

the spread of invasive species. See more on Check, Clean, Dry.

Get Involved with WAI Wānaka

WAI Wānaka are committed to protecting these great lakes we’re so fortunate to have, but they

can’t do it alone. As a community, we all have a role to play in preserving freshwater ecosystems

and maintaining water quality.

We can support WAI’s work in several ways:

• Join community initiatives focused on lake health, restoration projects, and citizen

science programs.

• Volunteer your time to help with hands-on conservation efforts. See WAI’s calendar of

volunteer events.

• Donate to WAI Wānaka to support research, education, and action-oriented programs

that protect the health of local waterways.

• Every action counts. By working together, we can safeguard these precious alpine deep[1]water lakes for generations to come. Visit WAI Wānaka’s website to learn more and get

involved today.

About the author:

Ben Youngman is a transdisciplinary researcher, (Mphil- ecological economics, BA & Bsci, Bcom) and is the

Science and Research Lead at WAI Wānaka. With a background in freshwater ecology, his role includes

science communication, environmental/freshwater research projects and advocating for lakes monitoring.

Ben also represents WAI Wānaka on the Otago Regional Council Deep Water Lakes Technical Advisory

Group, convenes the Upper Clutha Fish Reference Group and is currently overseeing a research project

investigating the natural values of the Upper Clutha and the ecological economics associated with urban

catchment management and development.

WAI Wānaka Media Release March 2025 - More info