Adopt a Drain – Winter 2025

Welcome to our ‘Adopt a Drain’ Winter newsletter

Winter changes the way water behaves. When snow and ice build up, stormwater drainage systems can become blocked, frozen, or overwhelmed. This winter, we are focusing on sediment. Sediment might sound harmless, but in winter it’s a big deal for our stormwater system.  

• Cold temperatures slow sediment settling, making it more likely to stay suspended and clog up drains. 
• NIWA research shows sediment flocs (clusters) behave differently in cold water – they settle slower and clog easier. 
• More winter runoff = more suspended solids in our stormwater. If drains are blocked by leaves, soil, or rubbish, sediment backs up into our streams and Lake Wānaka and Hāwea.

Urban Streams feel the impact – Sediment in stormwater does more than make the water murky and is one of the top stormwater contaminants in urban areas. 

• It smothers streambeds, harming fish and insect life. 
• It carries other pollutants like phosphorus, heavy metals, and hydrocarbons. 
• It clogs pipes and culverts, causing flooding and maintenance costs. 
• Sediment + stormwater = a bigger load on Lake Wānaka and Hāwea’s water quality. 

Auckland Council have put together this awesome diagram on how the differences between a well managed and badly managed Urban Streams, with regards to soil erosion:

WINTER PLEDGE

Say ‘No’ to sediment!

You can do this by:  

• Clean your car on a permeable surface like your lawn so that it captures sediment. Or head to a commercial car wash as this also gets captured!  
• For the Skiers and Snowboarders amongst us: how about catching the bus from Pines to Cardrona this year? They have paved the road up to Pines, which means both Treble Cone and Cardrona have mountain road shuttles, where you don’t have to drive on dirt road at all! See here for the Cardrona & TC bus timetable. 

Less sediment on your car + less sediment in your stormwater = a win for your drain  

I pledge to clean my car in a sediment capture spot!

We’d love to see a before and after photo and any details regarding the debris you’ve found. Click here to add your photos and any comments.

We’ve been seeing sediment around town, as shown in the photos below. This sediment can stick to your car, wash onto the road, and eventually flow into stormwater drains.

SPOTLIGHT

On Swales 

Swales are shallow, vegetated channels that help soak up stormwater and trap sediment before it enters drains. 

• They can remove 70–90% of coarse to medium sediment. 
• BUT: In winter, resuspension happens more easily — so maintenance matters! 

Want to learn more? Check out NUWAO’s Swale Guide. 

WATER HEALTH IN THE UPPER CLUTHA

What you need to know

Climate projections suggest more frequent heavy rainfall and snowmelt events in the Southern Lakes. The Clutha District is predicted to experience an overall increase in mean annual precipitation, with increases felt especially during the spring and winter months. Currently, annual precipitation for the Clutha District ranges from between 600 and 1500 mm. By 2040, most of the district can expect a 0 to 5% increase in annual precipitation.  

(Griffin, C.E. & Goldsmith, M.J., 2020. The impacts and implications of climate change for the Clutha District, GHC Consulting Report 2020/03, April 2020.) 

That means:  

More runoff + more erosion = more sediment.  

Our current stormwater systems may not be built for this.  

We need people power (like yours!) to help keep it under control.  

Explore NIWA’s climate change + stormwater summary 

New Zealand is losing 192 million tonnes of soil each year due to erosion, the equivalent of more than 7 million dump-truck loads. Read more here.  

GAINING MOMENTUM

One neighbourhood at a time

Do you know a business or household in Wānaka, Hāwea or Luggate that might be interested in Adopt a Drain?

Share this webpage and help us to grow this initiative. We encourage anyone interested to fill out our Adopt a Drain sign-up form.

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