Cashmere Stream needs help, locals say

The water quality and clarity of Cashmere Stream became an important subject at a recent Christchurch West Melton Zone Committee workshop.

The workshop, held at Te Hapua/Halswell Library saw a joint presentation from Cashmere Stream Care Group chair Ken Rouse and WSP Opus representative Dave Hewson.

Mr Rouse and Mr Hewson spoke on the 2017 Port Hills fire and the effects it had on the Cashmere Stream - including the worsening of suspended sediment present in the waterway.

Water tends to run clear through the majority of the waterway, but close to the Hoon Hay Stream end, and the Princess Margaret Hospital end, the water becomes a shade of brown.

The reasons for that, Mr Rouse suggested, included the introduction of sediment from the Hoon Hay Stream; the construction of eight new subdivisions in the area; and ongoing issues arising from the Port Hills fires.

What are the problems Cashmere Stream faces?

"Not only has the stream's water clarity been degraded in the past two years, but the amount of sediment (due to fine 'loess' soils entering the stream after heavy rainfall) suspended in the water has increased," Mr Rouse told the workshop.

"The Cashmere Stream is dying from a thousand cuts. Challenges include new subdivisions, the adventure park not meeting its environmental obligations, forest harvesting, and ongoing issues from the fires.

"Clarity data we've collected year by year shows a four per cent decline. We’ve had a severe decline in such a short time and it requires urgent action.

"Eighty-five per cent of hill tributaries have a very poor quality reading. The needs of the Cashmere Stream cannot be met by community groups alone," he said.

Mr Hewson echoed Mr Rouse's sentiment, saying preventative action can be taken to ensure sediment discharge into the stream is minimised.

"Identifying and prioritising sediment sources by venturing out to look at waterways during heavy rainfall (extended periods or days of rain) – the sources of sediment will present themselves and it becomes clear where the priority areas lie."

Get involved with the zone committee

The Christchurch West Melton Water Zone Committee will next meet on 28 November at Te Hapua: Halswell Centre - Piharau Room. 

Find out more about what's been done in the Christchurch West Melton Zone and the zone committee.