What can be done to rescue the Avon?
The enduring sickness of the Avon river is one of the city's most puzzling challenges.
The river enjoys the prestige of an icon, but is frequently derided as one of the city's most critical failures.
In news reports dating to the 19th century, it has been described as a "germ nursery," a "dirty ditch," and a "cesspool".
The striking contradiction of the Avon river, which is picturesque on the surface but poisonous below, is a century old problem with no clear solution.
The symbol for the city's life has become a receptacle for its waste — according to just-released research from the Canterbury District Health Board, it is contaminated with duck, dog and human faeces, and with e.coli spiking to unsafe levels after rainfall.
Data showed at the Antigua Boatsheds, near the hospital, the water had "similar quality to that seen during active sewage discharge." At popular rowing spot Kerrs Reach, human fecal waste was detected during normal weather conditions.
Canterbury medical officer of health Dr Alistair Humphrey declared the Avon's water "always unsafe" after rainfall, and not much better at other times. He says no-one should swim in or consume food from the river.
As pressure builds to recover the river, so too does the tireless optimism of those charged with saving it.
Bryan Jenkins, professor of strategic water management at the University of Canterbury, said the Avon problem could be put down to the city's old age.
Its Victorian-era sewerage system was the product of archaic design, which actively intended to use it to dump waste.
"When they designed the system 100 years ago, they were very keen to get surface water out of the urban areas and into the river, because the thought then was that ponded water was a public health risk. It's actually designed to carry as much water as possible into the river system.
"The new designs, they're much more geared to the retention of water on site, of settling out sediments, allowing for bacterial die-off before it gets to the river system. We need to be retro-fitting those requirements to the older parts of the city."
In a post-disaster city infatuated with the idea of renewal, there was potential to finally resolve the Avon problem, he said.
"We've got a unique opportunity now, especially in the lower reaches of the Avon, with the large land areas that could potentially become available from the residential red-zone.
"We can address this with stormwater retention ponds and wastewater storage facilities that could be put in place along the margins of the river."
In the eastern part of the city, the river meanders alongside shattered homes and wilderness, before trickling out into a muddy estuary and dissolving out to sea.
It's a jarring dissonance from the river's beginnings, where it meets the cherry blossoms of Mona Vale and carves through the city, where it will take centre stage as part of the Avon River Precinct.
A key element of bringing back the Avon was addressing that dissonance, said Avon-Otakaro Network co-chair Evan Smith.
"The longer it remains in the state it is now, hope dissipates, particularly in the east. It's hard to maintain that hope when you don't see any improvement anywhere."
The red-zone had become home to invasive weeds and species including Canada Geese, which had dirtied the river with their faeces. Getting rid of them would be a start.
"Driving away the pest species, I think, can be done with a combination of a concerted effort and investment in professional expertise. It's not something you can get a school group down to do.
"There's also need for quite a lot of work just generally around containing rubbish flowing down the stream. The rubbish tends to accumulate, which means the far eastern suburbs end up receiving the rubbish from further west.
"In the short term, that's what would solve the immediate problem, and give us some time to work out what's happening long-term and give us a breather."
Long-term action was a trickier prospect, he said. Community cleanup efforts were helpful, but a "drop in the ocean" against the broader pressures weighing on the river.
Ultimately, what was needed was co-operation and investment.
"It needs a long term commitment — a partnership, really — between the community and authorities that have the budget and expertise.
"As long as we act now, and as long as the community is involved in decision-making, then I'm optimistic. We can't afford not to be, otherwise we lose all hope."
There is hope on the horizon, according to the Christchurch City Council.
Water manager Tim Joyce said work rebuilding the wastewater and stormwater network would finish next year, which would reduce contamination of the river.
"[I]n some areas of our city, it's likely that stormwater is being contaminated after coming into contact with the wastewater system after rainfall, contributing to the contamination of our waterways," he said.
"The council has allocated $75 million to improve the wastewater system so it performs better after rainfall."
It was currently looking at the best way to spend that money, to reduce the amount of the city's waste that goes into one of its last remaining icons.