Where we used to swim: The turning point for Canterbury's Selwyn River

Tuesday, 24 December 2019

Where we used to swim: At Chamberlains Ford, the river is fine to swim in. A few kilometres downstream, warning signs are up, Michael Hayward reports. 

For Canterbury's Selwyn River, whether or not it is safe to swim depends on how far upstream you are – with those living near the lower reaches saying it has been 'Chernobylised'. 

At Chamberlains Ford, the river is OK for a dip most of the time. But a few kilometres down at popular campsite Coes Ford, people are advised to stay out of the water.

Land Air Water Aotearoa (LAWA), which provides advice on where it's safe to swim, said Coes Ford has 'a history of poor or highly variable water quality'.

The degradation at Coes Ford mostly comes from Silverstream creek, used as a drain outlet by many of the dairy farms in the area – though farmers are working hard to clean it up. 

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The main issue is bacteria, from animal faeces flushed off paddocks and into waterways during heavy rain.

However, toxic slime becomes an issue during the dry summer months. The Canterbury District Health Board issued a warning after the algae was found in the river at the end of December.

The Selwyn later flows through the Selwyn Huts settlement, a cluster of about 90 dwellings set-up to take advantage of the world-class trout fishing the river once boasted. 

Though heron wade its banks and shag dive into the pools next to the settlement, there are no people swimming in the green waters.

Graeme Young, a resident of 15 years, said the river has been 'Chernobylised'.

It was a different place when he first moved there: he remembers children swimming and an annual gala with several events on the water. But now there is a cloud over the river, and the settlement's focus has shifted away from it. 

'It used to mean everything to the huts … the river was the life of the huts.

'It's gut-wrenching really, to be in a place that potentially is just a fantastic place for Kiwis to bring their kids and splash around in the water, and now they can't do that.'

Environment Canterbury (ECan) science analyst Emily Gray regularly tests the water quality at several sites on the Selwyn.

Standing in the water in waders, she takes samples using a sterilised jar on a pole that is dipped into the water upstream. That goes in a chilly bin kept at 4 degrees Celsius to be tested for E coli, a sign of faecal contamination. Results are processed in 24 hours. 

Gray also looks for Phormidium, a type of toxic cyanobacteria or slime. It grows in a thick black mat in fast moving water and has a distinct smell that attracts dogs, who can die if they eat it. The Selwyn and Ashley rivers are particularly bad for it over summer. 

​ECan Chief scientist Tim Davie said E coli was used as an indicator of faeces as it was easy to test for, but the more serious risks to people were other bacteria from faeces such as campylobacter.

He said people should not swim in any river within 48 hours of heavy local rainfall, or if it was brown and murky, as there would have been run-off washed into it. 

Davie said farmers were working to put in good riparian buffers – plantings on stream or drain banks, often natives or long grass, that filter out faeces from the run off. It worked reasonably well but relied on there being a decent sized buffer. 

He wanted more wetlands put in, so the water was slowed down and natural processes that kill the bacteria could happen. 

Davie said a complicating factor was that E coli guidelines were introduced only in 2003, and ECan records from the late 90s showed these sites had sometimes tested poorly back then – but there had been farming intensification in the area since. 

The fact people used to swim at a site did not mean there were not problems with it back then, he said.

National standards consider a site unswimmable if there is a 5 per cent chance someone would become infected, Davie said. Of those infected, about half would get ill.

He said the standard were 'quite strict'. 

Federated Farmers North Canterbury president Cam Henderson said farmers were minimising the effect of run-off in three key ways: meeting new regulations, working collectively within the catchment area, and on-farm mitigation efforts such as fencing to keep stock away from waterways and planting along banks to trap runoff.

New regulations meant farmers had to have environment plans that were signed off by ECan as part of their consent.

A local water zone committee has a particular focus on getting Coes Ford swimmable again, going over and above what regulations require. It has created a plan for fencing, plantings, and contaminant reduction. 

'Many farmers are quite proud of their efforts to go beyond what is required of them, by broadening their judgement of what constitutes a good farmer to encompass environmental impact,' Henderson said. 

Farmers would like to be viewed as partners for improving water quality, he said.

'Farmers are now in that space where they are owning the issues, and for those farmers who are leading the charge, constantly being thumped in the public arena when they should be positively recognised both undermines their own efforts and doesn't incentivise others.'