Canterbury Waterway Rehabilitation Experiment


The Canterbury Waterway Rehabilitation Experiment (CAREX) is a stakeholder-driven region-wide stream restoration experiment. We work with farmers, councils, iwi and the public to co-develop, co-design and trial solutions to rehabilitate freshwater ecosystem health. We focus on solutions that have the potential to scale and be applied across waterways in Canterbury, Aotearoa New Zealand and beyond.
CAREX is testing practical tools to address aquatic weed, sediment, and nutrient management issues in lowland Canterbury and to improve agricultural waterway health. We are also developing demonstration sites to showcase how our rehabilitation tools are working on local farms and best practice in riparian management.

The information provided on our website are based on preliminary findings and will be subject to revision and peer-review. We try to communicate our research findings and share our data in a timely manner to meet the need for best available science. Materials cannot be reproduced without our express permission.

Wetland Planting Day (13 October 2017)

Today we had fantastic weather for planting 400 native plants in the wetland at one of our CAREX sites! A big thank you to Fonterra Canterbury, Wai-Ora Landscapes, Department of Conservation, Environment Canterbury, Selwyn District Council, ESR, landowners and FERG members for helping plant the wetland that will be enjoyed by many generations to come. A great day in the sun!

Tamariki Day (5 October 2017)

We spent a fantastic day out with tamariki and whānau from Te Taumutu Rūnunga at our CAREX site, Silverstream. The tamariki explored the wetland and were freshwater scientists, as they learned how to sample water quality and identify stream bugs and fish. After fish and chips for kai, we did some harakeke/flax weaving – some of us trying for the first time and others practicing their skills.

UC Sustainability Award (26 September 2017)

The CAREX team received a UC Sustainability Community Gold Award for their work into achieving water quality and biodiversity improvements in Canterbury’s agricultural waterways. These annual awards celebrate all of the great work that has been undertaken at the University of Canterbury to make the world a better and more sustainable place.
Pictured: PVC-Science Wendy Lawson with Team CAREX members Jon Harding, Katie Collins, Kristy Hogsden & Angus McIntosh accepting the award

Sanford Science Fair (12 September 2017)

CAREX team members Angus and Katie were judges at this year's Sanford Science Fair in Timaru. Congratulations to Sam Fauthy, the winner of the 2017 CAREX Freshwater Scientist for a Day prize. Sam is in Year 7 at St Joseph's school in Timaru and his winning project tested the effects that different concentrations of fertiliser have on algae. The judges were also happy to see last year’s winner, Jessica Vogel, back with another great project. Jessica developed “WHET” kits for the Canterbury schools so that students can test the water quality of their own rivers. Well done!

Our research focuses on ways to rehabilitate waterway functions that support and sustain Canterbury livelihoods. We aim to:

  1. Reduce aquatic weed (macrophyte) cover to < 50% and reduce the need for cleaning of waterways;
  2. Reduce the amount of fine sediment cover to < 20% to improve ecosystem health;
  3. Reduce in-stream nutrients (nitrogen and phosphorus) levels by 10-30%; and
  4. Showcase successful riparian and in-stream management methods.

What are the best tools for improving the health of local waterways? We are developing a toolbox of different tools that can be used individually, or in combination, to address macrophyte, sediment, and nutrient management issues and testing their effectiveness in rehabilitation trials.

CAREX Toolbox

Several in-stream and laboratory trials are currently underway to evaluate rehabilitation tools designed to manage macrophytes, reduce and remove sediment inputs, reduce nutrient levels in waterways, and improve in-stream habitat and biodiversity in agricultural waterways.

Macrophytes – Macrophytes can fill waterways, raise water levels, and accumulate sediment. We are investigating practical alternative management tools that can be used to eradicate or control the growth and spread of macrophytes. We are also conducting trials to help us understand the importance of timing and placement of macrophyte control activities.

Sediments – Excessive fine sediment can clog stream beds, reduce habitat for aquatic biota, and enable macrophytes to grow more easily. We are trialling ways to reduce “hot spots” where sediments may enter waterways and remove sediment legacies that have accumulated over decades.

Nutrients – Establishing riparian buffers and adopting nutrient limits are commonly used tools to reduce nitrate levels in agricultural waterways. We are developing denitrifying bioreactors to remove nitrates from tile drain outflows, which can be highly-localised point sources of nitrates, in our experimental waterways. We will also be trialling in-stream organic matter additions to help stimulate nitrogen removal.

Biodiversity – Most agricultural waterways lack important habitat for freshwater biota. We have added in-stream habitat, including boulders or wood, to one of our waterways to demonstrate the value of habitat for fish and invertebrates. We are monitoring the effectiveness of native riparian plants for providing shade and improved habitat.

  • Goeller, B.C., Febria, C.M., Harding, J.S. and McIntosh, A.R. (2016). Thinking beyond the bioreactor box: Incorporating stream ecology into edge-of-field nitrate management. Journal of Environmental Quality 45(3): 866-872. doi.10.2134/jeq2015.06.0325.
  • WATCH: Katie Collins' talk from Crazy and Ambitious 2017. This was the first national meeting of the New Zealand’s Biological Heritage Ngā Koiora Tuku Iho National Science Challenge. The talk is titled “Moving beyond riparian fencing: partnering ecosystem scaling, services and society to achieve stream restoration” (14 June 2017).
  • WATCH: Professor Angus McIntosh's talk on the problems facing Canterbury's fresh waterways and some of the CAREX findings so far. This talk was part of the UC Connect public lecture series (5 July 2016).
  • RadioNZ Interview: "Rebuilding healthy rivers" - Dr. Catherine Febria spoke with Kathryn Ryan on Radio NZ's Nine to Noon on rebuilding healthy resilience in streams and rivers. (26 January 2017).
  • WATCH: MPI's "Growing our future" interview - We chatted with Ministry for Primary Industries (MPI) about the work CAREX is doing on a Canterbury arable farm as part of Katie Collins PhD research. The interview is part of MPI's "Growing our future" initiative showcasing local champions in the primary industry (9 September 2016).
  • NZ Farmer Article - read about the transformation of a boggy piece of land into a thirving wetland and how CAREX is involved along with DOC and Fonterra as part of the Living Water partnership (24 June 2016).
  • Country Life on RadioNZ - listen and read about the collaboration of CAREX with the DOC-Fonterra Living Water project and ESR at one of our sites near Lincoln (20 May 2016).
  • WtW Article "starting at the top" - Recently Whakaora te Waihora (WtW) spoke to Professor Jon Harding about the work that the CAREX team are doing. Two of the ten research sites from this project are in the Te Waihora/Lake Ellesmere catchment. Read what Professor Harding says about how "starting at the top" is critical for restoration of the lake (18 November 2014).

Current Research Team

  • Professor Angus R. McIntosh
  • Professor Jon S. Harding
  • Dr Catherine Febria (Postdoctoral Research Fellow)
  • Dr Kristy Hogsden (Research Associate & Community Liaison)
  • Dr Helen Warburton (Research Fellow)
  • Hayley Devlin (Research Technician)
  • Katie Collins (PhD Student)
  • Brandon Goeller (PhD Student)
Mackenzie Charitable Foundation logo

Mackenzie Charitable Foundation

The Ashburton-based Mackenzie Charitable Foundation was formed in 1976 by brothers Alan and Don Mackenzie, who were both successful farmers in mid-Canterbury. A key purpose of the foundation is to focus on development of the science and practice of agriculture. The Mackenzie Charitable Foundation has funded the Freshwater Ecology Research Group for 10 years to research the effectiveness of riparian management (2008 – 2013) and to trial management tools and strategies to improve ecosystem health in agricultural waterways (2013 – 2018).