CAREX - Freshwater Ecology Research Group - Biological Sciences - University of Canterbury - New Zealand

Freshwater Ecology Research Group

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CAREX Newsletters
News Archive
Project Overview
Research Objectives
The CAREX Toolbox
Rehabilitation Trials
Publications, theses, posters & handouts
Current Research Team

CAREX Newsletters


Crazy and Ambitious 2017 (14 June 2017)

Watch team member 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”.

CAREX article in the Ashburton Courier (1 February 2017)

In the news this week - PhD student Brandon Goeller features in both the Ashburton Courier and Central Rural Life. Read about his wood chip addition and how they can benefit waterways by lowering nitrate and creating habitat for fish and stream invertebrates.

Re-building Healthy Resilience - RadioNZ (26 January 2017)

CAREX team member Dr. Catherine Febria spoke with Kathryn Ryan on Radio NZ's Nine to Noon this morning on rebuilding healthy resilience in streams and rivers. In case you missed it, listen here: "Rebuilding healthy rivers".

CAREX article in Central Rural Life (21 December 2016)

CAREX member, Kristy Hogsden, outlined some of our research findings to Central Rural Life this week. Read about how dealing with oversteepened and slumping banks can make a big difference to the health of a waterway and see the difference that the combination of fencing, planting and bank re-shaping can make.

  • 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 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).
  • 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).

Project Overview

We have called this phase of the project CAREX, which is an acronym for the Canterbury Waterway Rehabilitation Experiment. Carex (also called pūhio) is also the scientific genus of an important plant used in riparian plantings throughout New Zealand waterways. 

Fencing and planting of riparian margins are widely promoted and undertaken to improve water quality throughout Canterbury and New Zealand. Although this is a very important first step, frequently riparian management alone often results in limited improvement in either water quality or waterway health. Our aim is to overcome this problem.

Our research from Phase 1 indicates that several factors influence the effectiveness of fencing and planting on waterway health. In many cases, the riparian management is not in the right place, or “hotspots” of sediment and nutrient inputs into the waterway remain. Moreover, controlling the source of impacts does not solve the legacy of long-term contaminants which have accumulated in a waterway over decades, nor does it restore key species that have been lost.

Our aim is to trial management tools and strategies that are practical and sustainable using existing resources that are widely available. We have ten waterways across Canterbury (from Rangiora, and Te Waihora/Lake Ellesmere to Hinds) typical of those in need of rehabilitation. The waterways represent gradients of agricultural intensity, extent and/or age of riparian management activities and in-stream water quality and biodiversity.

From left: sediment 'hotspot'; excessive macrophyte growth; young riparian plantings.

Research Objectives

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.

Rehabilitation Trials

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.


nutrientsNutrients – 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.


  • CAREX: Improving restoration tools for small lowland agricultural streams (PDF 1.05MB)
  • CAREX: Trialling sediment traps and the sand wand to remove excessive fine sediment in agricultural waterways (PDF 8.52MB)


Current Research Team

Professor Angus R. McIntosh 
Mackenzie Foundation Chair in Freshwater Ecology
School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch
Phone: +64 3 369 5186 extn 95186



Professor Jon S. Harding
School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch
Phone: +64 3 369 5135 extn 95135
Cellphone: +64 3 21 704 797


Dr Catherine Febria (Postdoctoral Research Fellow)
School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch
Phone: +64 3 369 5148 extn 95148



Dr Kristy Hogsden (Research Associate & Community Liaison)
School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch
Phone: +64 3 369 5179 extn 95179




helenDr Helen Warburton (Research Fellow)
School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch
Phone: +64 3 369 5212 extn 95212

Hayley Devlin (Research Technician)
School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch
Phone: +64 3 369 5144 extn 95144



Katie Collins (PhD Student)
School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch


Brandon Goeller (PhD Student)
School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch


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