Jamie Morton is the NZ Herald's science reporter.

River clean-up battle hailed with top award

Wai Care volunteer John Smith looks over the waters of the Puhinui Stream in the green belt off Alicante Road, Hillpark, near the Manukau Botanic gardens where the stream starts. Photo: File
Wai Care volunteer John Smith looks over the waters of the Puhinui Stream in the green belt off Alicante Road, Hillpark, near the Manukau Botanic gardens where the stream starts. Photo: File

A grassroots community effort to clean up a South Auckland waterway has been hailed with a national award naming the Puhinui Stream the country's "most improved river".

The years of work that has gone into the Manurewa stream was acknowledged tonight with a top prize at the River Awards, run by the NZ Rivers Trust and the Morgan Foundation to recognise long-term improvement in waterways around the country.

The stream, which flows through Totara Park, the Auckland Botanic Gardens and industrial Manukau before emptying into the harbour not far from Auckland Airport, rates poorly on most water quality indicators.

It rates in the bottom quarter of rivers for E.coli, ammoniacal nitrogen and total phosphorus, and the former Auckland Regional Council not long ago ranked it the dirtiest of all 31 streams it monitored.

Over recent times, however, it's been the centre of a community project, with schools and local groups mucking in to grow plants along its banks and remove pollutants from the water.

Auckland Botanic Gardens has introduced a sustainable water trail - using swales and rain gardens to take sediment and heavy metals out of the water and reduce nitrates and phosphorus - to explain to visitors how to improve water quality.

Last April, the Manukau Beautification Trust led a huge clean-up, involving 1900 volunteers and fishing out 13 tonnes of rubbish, including 200 trolleys and 300 tyres.

A clean-up last April fished 13 tonnes of rubbish out of the Puhinui Stream in Auckland. Photo / Supplied
A clean-up last April fished 13 tonnes of rubbish out of the Puhinui Stream in Auckland. Photo / Supplied

Auckland Council has meanwhile retired more than 20ha of land from grazing on its banks, while Wai Care has worked with children from eight local schools to raise and help plant more than 25,000 native plants in the middle of its catchment.

Local residents have helped improve the water quality of Puhinui Stream in South Auckland through planting and clean-up efforts. Photo: Supplied
Local residents have helped improve the water quality of Puhinui Stream in South Auckland through planting and clean-up efforts. Photo: Supplied

Local resident and retired engineer John Smith has also spent 16 years battling to rehabilitate the bottom few kilometres of the stream, and was pleased to now see pukeko, swans and herons wading in its waters.

Pupils at The Gardens School in South Auckland have joined planting days to help the Puhinui Stream. Photo / Supplied
Pupils at The Gardens School in South Auckland have joined planting days to help the Puhinui Stream. Photo / Supplied

Despite the efforts, the stream still had a poor score in the macroinvertebrate community index (MCI) - a biotic index drawing on habitat preferences of different types of macroinvertebrates, often used to measure pollution level and picked as the benchmark indicator of this year's awards.

The Puhinui Stream flows through Totara Park, the Auckland Botanic Gardens and industrial Manukau before emptying into the harbour not far from Auckland Airport. Photo: File
The Puhinui Stream flows through Totara Park, the Auckland Botanic Gardens and industrial Manukau before emptying into the harbour not far from Auckland Airport. Photo: File

"It may seem odd that a less than perfect stream has won, but the point is that it's consistently getting better, and that is what matters here," awards manager Andrew Gawith said.

The stream showed a trend improvement in MCI over 12 years of 5.604 per cent per annum, making it the country's most improved river nationally.

"This result shows that, with enough goodwill and hard work, people can restore even degraded rivers."

The second most improved river nationally was the Maitai River, which flows through Nelson City, and the third placed was the Maketawa Stream in Taranaki.

National picture remains bleak for NZ rivers

Gawith said the awards - judged by Dr Roger Young of the Cawthron Institute, Dr Clive Howard-Williams of Niwa and Dr Mike Scarsbrook of Dairy NZ - accentuate the positive by recognising the most improved rivers in each region.

"Nationally, though, there are few rivers showing a significant and meaningful improvement in water quality as measured by the MCI."

The judges had MCI data from 820 freshwater monitoring sites around the country and of these, just 62 demonstrated a significant trend improvement in MCI - a rate of about 7 per cent.

Most of the others showed no trend.

But Gawith said it was encouraging that more councils, communities and individuals now recognise that the cumulative impact of many actions could help improve river health.

Fixing leaking waste water pipes, clearing rubbish from streams, narrowing the river bed to speed up the flow, riparian fencing and planting, soil conservation planting and careful forest harvesting all helped.

"There's a steady change in attitude, particularly among farmers, that they have a responsibility to protect their local waterways by changing their management practices," he said.

"A combination of encouragement, publicity and coercion will keep pushing this transformation."

- NZ Herald

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