The Changing Face of Our Lakes: What You Need to Know
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.
So, 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
At WAI Wānaka, we are committed to protecting these great lakes we’re so fortunate to have, but we can’t do it alone. As a community, we all have a role to play in preserving freshwater ecosystems and maintaining water quality.
You can support our 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 our 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-water lakes for generations to come.
