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16-year clean-up of Christchurch river wins award – and furthers a father’s work.

A slice of father-son history has played its part in an environmental success story taking place along a Christchurch river.

Arthur Adcock, a Christchurch City Council parks ranger, has been one of the key figures in a long-running project to clean up the Otukaikino River – this month named as the most improved river at the 2018 New Zealand River Awards.

Adcock is following in the footsteps of his father – and namesake – in his work for the environment. Adcock Snr, for years a parks manager in Christchurch and a councillor on the former Waimairi District Council, was at the forefront of many conservation issues of the day.

"The environment, that was his strength," says Adcock. "He managed Spencer Park and had a big involvement in a lot of issues. That's where I got it from."


Although he has since passed away, Adcock Snr's work was of such significance that a city reserve, the Arthur Adcock Memorial Reserve, has been named in his honour.

Now it seems Adcock Jnr is leaving a similar mark on the city in the work he does. A parks ranger for 48 years, he has been heavily involved in coordinating the restoration work along the Otukaikino River for the last 16 years.

Located in semi-rural land near the suburb of Belfast on the city outskirts, the river took out the Supreme Award at the awards ceremony in Wellington last week.

Phosphorus levels in the river have decreased by 17.5 per cent per annum over the past 10 years, a key factor in the improvement in its water quality. Phosphorus is a nutrient which, if present in streams and rivers in excessive amounts, can cause water quality issues by promoting bthe growth of aquatic plants and algae that smother the habitat of freshwater organisms and lead to the growth of unsightly slime on riverbeds.

Phosphorus contamination can occur as a result of wastewater treatment plant and farm-shed effluent discharge, accelerated erosion of phosphorus-rich spoils and run-off of fertiliser used on land.

The river runs through a 13 hectare reserve, a surviving area of former wetland that once dominated the city's landscape.

Most of the original native vegetation around the river disappeared as it came under pressure from agriculture and encroaching urban sprawl – which in turn impacted on the environmental health of the river and its water quality.

Long earmarked as a key restoration project, work began after talks 16 years ago between the Christchurch City Council and local landowners.


Dr Morgan Williams, chair of Cawthron Foundation (a charitable trust which runs the river awards) and the NZ Rivers Trust, says the talks led to farmers fencing off land to prevent stock entering the waterway, creating a buffer zone of up to 100 metres wide.

"This made way for an extensive planting zone, which has been a key factor in reducing phosphorus," he says. "Today nearly the entire length of the river is fenced - estimated to be around 10km - meaning stock can't cross."

Otukaikino track. Photo / Cawthron Foundation.
Otukaikino track. Photo / Cawthron Foundation.

In that time Williams says an estimated 195,000 native and locally-sourced plants have been planted.

He says the river has very good water quality with its phosphorus levels decreasing by 17.5 per cent per annum over the past 10 years. Levels of ammoniacal nitrogen, total nitrogen and total oxidised nitrogen also decreased.

Williams says although the Canterbury Regional Council (also known as Environment Canterbury or ECAN) has been involved for much of the project, the wider community has been the real champions.

As well as ECAN and the city council, other groups which have helped with funding, providing plants or taken part in planting and weeding days include the Christchurch West Melton Zone Committee, DOC, QEII Trust, Trees for Canterbury, Z Energy, Fish & Game New Zealand, local schools, scout groups and private landowners like Isaac Conservation Trust and Clearwater.

Adcock says although more work is needed at the river, increasing numbers of native birds have returned to the wetland and stream since the project began while fish monitoring has shown similar results.

"The native planting along the stream's edge provides insects for birds and the plants also provide protection for fish spawning before they return to the Waimakariri River," he says.

"There are lots of places where we've lost clean water," he says. "Our vision is to restore the Otukaikino back to what it once was. What I'm most proud of is the fact that a lot of people in the community have been involved in this. I'm just the coordinator, it's really been a big team effort."

Second place in the awards went to the Oroua River at Fielding (a 13.3 per cent reduction in phosphorus per year) while third place was awarded to the Ruamahanga River at Gladstone Bridge near Wellington which has recorded a 13 per cent reduction per annum.

Regional winners were: Rangitopuni River at Walkers (Auckland); Tarawera River at Awakaponga (Bay of Plenty); Mangaehu River at Ruapuha Rd Bridge (Taranaki) and Waituna Creek at Marshall Rd (Southland).