Stormwater: Through the Lens of Urban Strategy and Community in Our Catchment
Written by Lottie Oatts & Jose Cranfield
Stormwater within WAI Wānaka’s Urban Strategy
It has been a particularly rainy summer here in the Upper Clutha, making it a good time to revisit what stormwater actually is – and why it matters.
Stormwater is rainwater that runs off roofs, roads, and other hard surfaces. As it flows, it picks up pollutants such as sediment, bacteria, heavy metals, and litter before entering drains and waterways. Known as stormwater runoff, this water is untreated and can significantly harm local ecosystems and water quality.
At WAI Wānaka, stormwater has been a focus of our mahi for several years. Initiatives such as Adopt a Drain launched in 2023, and the installation of LittaTraps, at four key locations in town, help prevent litter and debris from entering waterways. However, there are over 4300 storm drains across Wānaka, many of which lead directly into lakes, rivers, or urban streams.
With the significant growth in population, urban development, and the decline in water quality, stormwater has become a critical issue. That’s why WAI is shining a light on how stormwater is managed – and how we can all be part of the solution.
WAI Wānaka’s Urban Strategy: A Clear Direction
At the 2026 Wānaka A&P show, Prue Kane, WAI Wanaka’s Urban Lead, shared what the Urban Strategy will look like moving forward. The strategy sets a clear aspiration:
no polluted water entering our urban streams and lakes.
Over the next three years, the strategy focuses on turning knowledge into action. The last five years have shown a significant increase in community awareness of stormwater, and now WAI turns its attention to providing practical tools and guides for actions that reduce quantity and improve quality of the stormwater that reaches local freshwater.
This might be as simple as a guide for building a rain garden, or as complex as public private partnerships for infrastructure mitigations. The key to success of this work is WAI’s relationships with community, councils and experts. A great example of this is the Bremner Bay Catchment Group.
Over the next three years, the strategy focuses on:
- Building strong community and industry understanding of stormwater
- Embedding Water Sensitive Urban Design (WSUD) into local planning and development
- Strengthening collaboration between councils, industry, and communities
Three core projects will help deliver these goals:
Slowing the Flow
Empowering households and neighbourhoods to reduce, slow, and filter stormwater runoff.
Industry Best Practice
Working with the building and development sector to promote best practice and remove barriers to implementation.
Urban Catchment Plans
Using monitoring and community science to guide action at a catchment scale.
Together, these projects aim to create healthier, more resilient urban environments across the Upper Clutha. At the heart of this work, is a shift in thinking – seeing stormwater not just as a pollutant, but as a resource that can be managed better for people and nature. Also presenting at the A&P Show was Jose Cranfield, from the Bremner Bay Catchment Group, who shared how weekly E.coli testing is being used to highlight the concerns with human health and stormwater.
Community-Led Monitoring Highlights Stormwater Risks at Bremner Bay
The Bremner Bay Catchment Group is raising concerns about the volume of untreated stormwater entering Lake Wānaka, with new summer monitoring showing sharp spikes in E.coli bacteria levels after rainfall.
Much of the urban catchment surrounding Bremner Bay drains directly into the lake via a large 900 mm stormwater pipe – one of approximately 20 similar outlets discharging into Lake Wānaka from urban areas. Research completed by Victoria Grant (published in 2021) found that following rain events, these stormwater pipes can carry significant levels of contaminants, including E.coli, into the lake making the area temporarily unsuitable for swimming.
To better understand current conditions, the Bremner Bay Catchment Group launched a community monitoring project this summer, supported by Otago Catchment Community, Otago Regional Council, Queenstown Lakes District Council, and WAI Wānaka.
Weekly E.coli results and related swimming suitability were made publicly available via a QR code installed at Bremner Bay, which has been accessed 55 times over the season.
Elevated E.coli levels after rainfall
Under national LAWA guidelines, suitable swimming levels are defined as 0–260 MPN E.coli per 100 mL. For most of the summer, Bremner Bay has tested within this range.
However, after more than 10 mm of rain fell on 11 January, results changed dramatically:
- E. coli levels in mid Bremner Bay rose to five times the safe swimming threshold.
- At the stormwater outlet itself – where children often play in the temporary “stream” – levels reached ten times the suitable swimming limit.
Following this rain event, E.coli levels in the bay returned to safe levels after 24 hours. In contrast, levels at the stormwater outlet remained at an elevated health risk for 72 hours after rainfall had stopped.
Rain on 26 February showed similar E.coli results. Two other significant rain events later in January could not be measured due to courier and laboratory timetables over weekends.
“These results reinforce what many communities around the country are discovering,” said the Bremner Bay Catchment Group.
“Stormwater is not just rainwater. When it washes across roads, roofs, and urban surfaces, it can carry contaminants straight into the places where our families swim.”
Next Steps: Tracing Sources and Improving Safety
Building on this summer’s work, the group plans to undertake faecal source tracking and environmental DNA (eDNA) sampling to help pinpoint where E.coli may be originating. This information will support targeted education and behaviour‑change campaigns within the catchment.
The group is also exploring opportunities to investigate sediment quality within Bremner Bay, with a particular focus on the safety of children and other recreational users.
Longer-term, the aim is to combine this water quality data with rainfall and temperature information to help model and predict real‑time swimming suitability for the Bremner Bay community. Further monitoring and analysis will depend on securing funding.
Long-Term Vision: Slowing the Flow
Ultimately, the Bremner Bay Catchment Group hopes to work alongside council partners and the wider community to develop practical solutions that slow and treat stormwater before it reaches Lake Wānaka. Options could include retention areas, naturalised treatment systems, and wetland creation within the catchment.
“Our goal is simple: Bremner Bay will have safe, clean freshwater, improved biodiversity and great access for the community to use the bay to its fullest”, the group said.
“This summer’s monitoring shows that with the right information, we can make informed decisions and take meaningful action.”
Get Involved: Learn More at the Stormwater Showcase
Stormwater issues don’t start at the lake – they start in our neighbourhoods, driveways, roofs, and roads. Everyone in the catchment has a role to play in slowing the flow and protecting freshwater.
To help build understanding and action, WAI Wānaka is hosting a community Stormwater Showcase, designed for locals to learn about stormwater solutions from source to stream. You can:
- Learn how stormwater moves through our catchment
- Discover practical actions you can take at home
- See examples of nature‑based and community‑led solutions
- Connect with local groups working across the Upper Clutha
You’ll meet the WAI Adopt a Drain team, some awesome volunteers, the Bremner Bay Catchment Group, as well as representatives from Mitre 10, Queenstown Lakes District Council, and the Otago Regional Council.
Whether you’re curious, concerned, or already involved, this event is an opportunity to learn, share ideas, and be part of solutions that support healthy water for our whole community.
📍 Bremner Bay
📆 Tuesday 24 March
🕔 5pm-6pm
Find out more at: https://waiwanaka.nz/events/.
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