Thursday, April 18, 2024

New test sites improve understanding of Christchurch waterways

Eleven new water quality monitoring sites are giving Christchurch City Council a better understanding of the state of the district’s rivers and streams.

The Christchurch Surface Water Quality Report 2021 and summary brochure have just been published. The report is an analysis of monthly data collected at 51 sites across the city and Banks Peninsula during 2020.

The new monitoring sites are Ōpāwaho-Heathcote River at Warren Crescent, Steamwharf Stream (Ōpāwaho-Heathcote River catchment), Huritini-Halswell River at Wroots Road, Aylmers and Balguerie Streams in Akaroa, Stream Reserve Drain and Zephyr Stream in Governors Bay, Ihutai-Avon-Heathcote Estuary, Cass Bay, Akaroa Harbour, and Lyttelton Harbour.

Results for most monitoring sites have remained steady since 2007, with some sites improving and some worsening, says the Council’s Waterways Ecologist, Dr Belinda Margetts, who leads this research. 

The site recording the best water quality was the Ōtūkaikino River at the Groynes. The next best sites (jointly) were Smacks Creek at Gardiners Road (Pūharakekenui-Styx River catchment), Waimairi Stream (Ōtākaro-Avon River catchment), Ōtākaro-Avon River at Carlton Mill, Wilsons Stream (Ōtūkaikino River catchment), followed by Pūharakekenui-Styx River at Gardiner’s Road.

The worst sites were Curletts Road Stream at Motorway (Ōpāwaho-Heathcote River catchment), Nottingham Stream at Candys Road (Huritini-Halswell River catchment), Haytons Stream (Ōpāwaho-Heathcote River catchment), and Addington Brook (Ōtākaro-Avon River catchment).

“The Huritini-Halswell River catchment did not meet many of the water quality standards and recorded the poorest water quality,” Dr Margetts says.

“One of our new monitoring sites, Nottingham Stream, has highlighted that this waterway has poor water quality. This wasn’t on our radar before and its poor water quality will be due to contaminants entering the waterway from both urban and rural land use.”

The Council uses this water quality information, along with sediment quality and aquatic insect data to create waterway report cards for each of the city’s five main river catchments. The catchments are then given a score from ‘A’ (very good health) to ‘E’ (very poor health).

As in the past three years, no waterway scored an A and no waterway scored an E. The Ōtūkaikino River catchment again recorded the highest score (B), Pūharakekenui-Styx River catchment scored a C and Ōtākaro-Avon RiverHuritini-Halswell River and Ōpāwaho-Heathcote River catchments all scored a D.

Dr Margetts says that like most cities, Christchurch waterways suffer from a condition known as ‘urban stream syndrome’.

“Our waterways are contaminated with runoff from hard surfaces such as roofs, driveways and roads, and with faecal contaminants from waterfowl and dog droppings,” she says.

“The Council, other organisations and landowners are working hard to improve the health of our waterways, especially through improving the quality of the water and carrying out restoration projects, but it may take many years to see this work flow through to a big improvement in water quality.”

The 2021 surface water quality report recommends that the Council:

  • Prioritises Curletts Road Stream, Nottingham Stream and Addington Brook for contaminant source control and stormwater treatment
  • Prioritises sediment control, particularly in the Ōpāwaho-Heathcote River and Cashmere Stream
  • Cements a whole-of-community approach to addressing stormwater contaminants through the Community Waterway Partnership
  • Investigates faecal contamination, particularly from waterfowl, to identify how best to reduce levels
  • Develops an action plan for achieving the Healthy Water Bodies Community Outcome

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