From our Chair: Tackling water quality issues in Christchurch streams

Jenny Hughey, Chair, Environment Canterbury

Jenny Hughey, Chair, Environment Canterbury

One of the privileges of being a regional Councillor is hearing directly from citizens about issues which concern them at our monthly council meetings.

At our most recent meeting, it was excellent to hear from the Cashmere Stream Care Group and the Ōpāwaho Heathcote River Network about the deterioration in water clarity of the stream from “very good” to “very poor” as it approaches the Opāwaho/Heathcote River.

The group’s representatives pointed out that ongoing erosion of the very fine clay-sized loess soil particles from the slopes of the Port Hills is also causing a gradual decline in water clarity in the stream as the months and years go by.

The working group’s worries are also ours at Environment Canterbury.

Working together to achieve compliance

In last week’s column, I talked about the crucial role the regional council plays in making sure our natural resources and advantages are not squandered and left depleted or despoiled for future generations, and our five-year compliance, monitoring and enforcement (CME) plan to strengthen our risk-based approach and ensure individuals or organisations who hold resource consents meet the conditions outlined on their consents.

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Our water management zones

Canterbury is divided into 10 water-management zones: KaikōuraHurunui-WaiauWaimakariri , Christchurch-West MeltonBanks PeninsulaSelwyn-WaihoraAshburtonOrari-Temuka-Opihi-PareoraLower WaitakiUpper Waitaki.

As part of the five-year CME plan, every six months we will focus on one of the zones and the CME work that has been carried out there.

First focus: Water clarity and quality of Cashmere Stream and the Ōpāwaho/Heathcote River

First under the microscope for 2020/21 is an appraisal of Christchurch and Banks Peninsula sediment erosion.

We want to take an integrated approach to improve the water clarity and quality of Cashmere Stream and the Ōpāwaho/Heathcote River by working closely with local rūnanga, communities and local councils, as well as by ensuring strict compliance with regional rules and consent conditions.

Geology, geography, and construction and development can conspire to increase erosion into our waterways.

In this case, the tiny, wind-blown loess particles of glacial origin can be especially problematic. Over thousands of years these sediments, which are particularly vulnerable to erosion, have accumulated on the Port Hills.

When this clay ends up moving downhill and clogging streams and rivers, it can damage ecosystems, impacting land or water quality, washing away scrub and trees, and killing fish, insects, birds and animals.

During last winter, Environment Canterbury staff scrutinised erosion and sediment control practices at building sites at Cashmere and across the Port Hills in the Christchurch West Melton zone. We visited several sites and found the majority were doing everything right. However, 11 notices of non-compliance were issued, meaning that the site had room for improvement.

Working group recommendations

At last month’s council meeting, the Cashmere Stream and Port Hills working group made several recommendations.

These included:

  • the fencing and native planting of the steepest and most erodible hill tributaries, transforming lower drainage areas into shallow,
  • wide wetlands to trap sediment before it enters Cashmere Stream,
  • reshaping some stream banks to allow floodwaters to spread out,
  • and improving habitats adjacent to the stream.

Many thanks to all the people who volunteer for water care groups across our City. Everyone needs to be aware of what they are doing on their properties as we all have a role to play in protecting our environment.

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