More shopping trolleys have been pulled from Auckland's Puhinui Stream over the years than you'd find in a Countdown car park.

The 12km-long waterway snakes from Totara Park in Manurewa to the Manukau Harbour near Auckland Airport in Māngere.

Seven years ago it was considered the most polluted of the region's 31 monitored waterways.

And in 2010 hundreds of eels died after concrete was spilled into the stream, an incident described at the time as an "absolute disaster".

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A huge amount of work since then by various people, schools, businesses, organisations, and the Manurewa and Ōtara-Papatoetoe Local Boards saw it named New Zealand's most improved river at the 2016 NZ River Awards.

CHRIS HARROWELL Auckland Council biodiversity officer Leighton Simmons, left, and Manukau Beautification Charitable Trust community manager Barbara Carney encourage people to remove rubbish from and plant trees alongside the Puhinui Stream on September 19.

Almost 2000 volunteers removed more than six tonnes of rubbish, including about 200 supermarket shopping trolleys and 300 car tyres, from the stream and Ōtara Creek during a major clean-up the same year.

Tens of thousands of trees have been planted alongside the stream, including the 37,000 put in the ground at Totara Park in July as part of mayor Phil Goff's 'million trees' initiative.

The work being done to improve the waterway's health is far from over.

Supplied Some of the 200 supermarket shopping trolleys removed from the Puhinui Stream during a major clean-up in 2016.

On September 19 the Manukau Beautification Charitable Trust and Auckland Council staff are leading a community tree-planting at the stream as part of Conservation Week.

It's being staged with funding from the Manurewa Local Board.

Council biodiversity officer Leighton Simmons says the work is intended to restore the habitat of the stream's inanga whitebait population and other freshwater species.

"There are lots of other benefits for the stream [from tree-planting], such as stabilising the banks, filtering runoff, and providing more shade for the stream and habitat for birds.

"We'll be planting about the last 200 of 7000 plants and then moving onto pest control and that kind of work. Rats and mice are the pests we're targeting.

"They eat the eggs of the inanga while they're up on the banks."

NEIL DUDDY Jaden Smith, left, and Paul Woodard with some the hundreds of dead eels found in the Puhinui Steam in 2010. (file photo)

Trust community manager Barbara Carney says rubbish dumping in and near the stream and other local waterways is a "constant problem".

"We hope there will be changes to people's behaviour. Education is important.

"That's why we … work alongside communities. It's empowering communities to keep an area nice and clean."

CHRIS HARROWELL The 12-kilometre Puhinui Stream runs through Totara Park in Manurewa to the Manukau Harbour near Auckland International Airport.

Carney encourages people to turn out to Harbour Ridge Dr in Wiri from 10am-12pm on September 19 to lend a hand with the tree-planting.

"We're promoting it for people to come out and connect with the environment and nature, get involved, and learn about the inanga spawning as well as the importance of biodiversity.

"The trust provides all the equipment, but people need to bring their own gumboots and a raincoat."

CHRIS HARROWELL Leighton Simmons and Barbara Carney say much of the work being carried out at the stream will restore the habitat of its inanga whitebait fish and other freshwater species.

Phone 09 269 4080 or email paula@mbct.org.nz to RSVP.