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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.

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New Toolbox Handouts! (6 September 2018)

We have four new CAREX Toolbox Handouts available! The step by step guides in these handouts can be applied by farmers and stakeholders to help along the journey of rehabilitation for agricultural waterway health. There are four handouts in the series so far; CAREX keys steps, aquatic weeds, sediments and nutrients. You can download them from our figshare page or on our website below.

Latitudes Magazine Article (15 August 2018)

Latitudes magazine recently did a piece on CAREX titled ‌"Clean Up Our Waterways". Read about how bioreactors and riparian planting are effective tools at reducing nitrates in a waterway on a mid-Canterbury farm. Full article by Joanne Taylor - Latitudes Article (PDF 461KB).

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.

  • Collins, K.E., Febria, C.M., Warburton, H.J., Devlin, H.S., Hogsden, K.L., Goeller, B.C., McIntosh, A.M. and Harding, J.S. (2018). Evaluating practical macrophyte control tools on small agricultural waterways in Canterbury, New Zealand. New Zealand Journal of Marine and Freshwater Research
  • O'Brien, J.M., Warburton, H.J., Graham, E.S., Franklin, H.M., Febria, C.M., Hogsden, K.L., Harding, J.S. and McIntosh, A.M. (2017). Leaf litter additions enhance stream metabolism, denitrification and restoration prospects for agricultural catchments. Ecosphere  8(11). doi.e02018. 10.1002/ecs2.2018.
  • 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: Part One and Part Two of Catherine Febria's talk from the AGRI Innovation Mid Canterbury Seminar 2018. The seminar was about sharing knowledge and advancements with science and technology in agri-innovation. Catherine gave a talk about bioreactors and the CAREX project (2 may 2018).
  • 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).
  • Latitudes Article (PDF 461KB) "Clean Up Our Waterways" - Latitudes magazine recently did a piece on CAREX. Read about how bioreactors and riparian planting are effective tools at reducing nitrates in a waterway on a lowland, mid-Canterbury farm (15 August 2018).
  • UC Chronicle (PDF 1.0MB) - The CAREX team won the 2017 Canterbury Aoraki Conservation Board award for improving freshwater biodiversity and ecosystem health (18 July 2018).
  • NZ Farmer Article "Scientists work on simple ways to clean streams" - Read about how sediment traps are a simple method for reducing fine sediment load in waterways (23 April 2018).
  • Fonterra Article "Stirling Silverstream Effort" -  The journey of a wetland at one of our CAREX sites (27 October 2017).
  • WATCH: Fish&GameNZ "Snake Creek Restoration Baseline Sampling" - Catherine and Hayley helped set up a sampling regime for the data collection of the three year project to restore Snake Creek, a tributary of the Selwyn River (16 October 2017).
  • 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).
  • Ashburton Courier Article (PDF 303 KB) "Into the trenches with pine chips" - Read about what Brandon Goeller is doing with untreated pine woodchips as part of his PhD research (26 January 2017).
  • Central Rural Life Article (PDF 377KB) "Restored drains better every way" - Dr. Kristy Hogsden talks about the importance of rebattering before riparian planting to reduce slumping and sediment erosion (21 December 2016).
  • UC Chronicle (PDF 919KB) "Can we rehabilitate our problem waterways?" - Professor Angus McIntosh talks about the CAREX research objectives (20 September 2016). 
  • 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 thriving wetland and how CAREX is involved along with DOC and Fonterra as part of the Living Water partnership (24 June 2016).
  • Central Rural Life Article (PDF 682KB) "Boots on for planting" - Read about the community planting day CAREX held down in Hinds (25 May 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).
  • Ashburton Guardian Article (PDF 513KB) - Professor Jon Harding meets with the Hinds Drains Working Party to discuss weed management (14 April 2016).
  • WtW Article "starting at the top" - 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).