A stream which once flowed through Ilam gardens is now a long, muddy pit.











Why are Christchurch's city streams drying up? Charlie Mitchell reports residents want to know what is happening to their waterways.

CHARLIE MITCHELL/FAIRFAX NZ A Halswell stream which once fed a lake in the Canterbury Agriculture Park. It is still identified as a stream on maps.

For 44 years Val Saxton has lived, almost stubbornly so, at her home in Ilam, which backs onto the Waimairi Stream.

"There wasn't anywhere that could tempt us away. It was just peaceful, tranquil, lovely," she says.

She would drop her sons at Burnside Park, arming them with two shillings for an emergency phone call before they snaked their way home along the stream, which at times flooded so generously they could launch their surf-skis from the back deck.

CHARLIE MITCHELL/FAIRFAX NZ The Waimairi Stream in Fendalton.

Now, the stream is completely dry. Saxton describes its disappearance earlier this year as "like a tap being turned off."

She recently stepped into the dry stream-bed to look at what she thought was a dirty stick. It was actually a rotting, fly-blown eel.

"There's a vague sense of responsibility when you've been around so long, because you know what is normal," she says.

SUPPLIED Sam Saxton using a surf-ski on the Waimairi Stream after a flood in 1990. The stream is now empty.

"It's not like someone who has just bought-in a couple of years ago and thinks that maybe this has happened before.

"During our time here, we've experienced all sorts of highs and lows [with the stream] but it never, ever, even looked vaguely like running out of water."

Saxton's experience is mirrored in other parts of the city.

CHARLIE MITCHELL/FAIRFAX NZ When water does fill the vanished streams, it is stormwater loaded with contaminants.

Christchurch streams have withered and died in the past year, which has some wondering if they will ever return.

Disappearing waterways have been reported in Fendalton, Ilam, Halswell, Wigram and Shirley.

Streams including the Waimairi, which once flowed mightily, are now bone-dry and littered with rubbish, interrupted by small, toxic puddles near dead eels swarmed with blow-flies.

Former streams are now only identifiable by lonely bridges crossing long tracts of mud and grass, and signs illustrated with cartoon fish pointing to something no longer there.

Though explanations range from low-rainfall to over-eager irrigators, locals who have lived with their streams for decades say whatever is happening is unprecedented.

Several of these streams are tributaries of the Avon River, which raises a question: how will the already ailing river fare, if water from its tributaries stops flowing?

Fendalton resident Richard Simpson says the once lovely stream near his home has become a receptacle for stormwater.

"We have had dead eels, dogs running up and attacking ducks, mosquitoes and an unpleasant smell. It seems to us the stream is now only a storm water drain. It fills up when pouring with rain and within a few days, it has disappeared again."

In Wigram, near the Canterbury Agriculture Park, some waterways have gone entirely as new subdivisions get built.

"It was so beautiful and peaceful to sit there with nothing but the sound of the water flowing over the rocks," says one resident, who bought her home largely for the brook that ran through the front yard.

"Now it is just a muddy, weed ridden mess that attracts mozzies. In the last substantial rainfall we had, the creek appeared again but with a green scum all over the top."

The cause

While explanations for the dying streams vary from low rainfall to over-eager irrigators, the true cause is complex.

Professor Bryan Jenkins, water resource management expert at the University of Canterbury, says there is an interplay of factors causing the streams to dry up.

While some blamed irrigation on the Canterbury plains, the true cause was closer to home, he says.

"The amount of water we're taking out for Christchurch's water supply is one of the more significant components, rather than necessarily irrigation by private interests.

"The current levels in groundwater monitoring bores in the unconfined aquifer west of Christchurch are the lowest on record."

The Christchurch City Council has a bore at Burnside Park, where Saxton used to drop her kids, which takes groundwater from the aquifer that supplies the streams.

Combined with the long-term trend of urbanisation - surfaces such as roads and roofs increase stormwater flows, and decrease the amount of rainwater going into groundwater - the result is a lack of groundwater to flow through the streams.

One of the long-term victims will be the Avon and Heathcote rivers, Jenkins says.

Instead of groundwater flushing through the tributaries and into the rivers, it will be stormwater, with all of its contaminants.

"What we are getting is more stormwater peaks, so it's a change in the hydrology - it goes from being a groundwater fed river system as it was in the past, to much lower base flow with much higher peaks as you get stormwater events.

"We've got some very polluted components of the Avon and the Heathcote already from stormwater run-of - it's the predominant cause of water quality impairment in the Christchurch river system."

The council says it is unlikely that its water abstraction is responsible for low groundwater levels.

"The earthquakes and the dry weather have a lot to do with the changes in ground and surface water," says head of Three Waters and Waste John Mackie.

"Abstraction for water supplies are unlikely to be the cause, as they are from deep, mostly confined bores not directly connected to surface water, for obvious reasons of the potential for cross contamination."

He says all bores are flow monitored and operate within their resource consents.

Because it is a natural phenomenon, there are no plans to artificially return water to dried up streams.

"However, this would not prevent a particular community group from proposing their own initiative to restore aesthetic flows in dried up channels," the council says.