CAREX: a collaborative approach to waterway rehabilitation

What are the impacts of agriculture on water quality, and what could the solutions be? CAREX, a stakeholder-driven interdisciplinary stream restoration project, is an ongoing, collaborative approach towards finding some answers.

riparian planting
CAREX team members monitoring the progress that riparian planting is having on reducing weedy aquatic plants.

Currently, there is considerable interest around the impacts that agriculture is having on water quality. Nationwide the focus has been on highlighting the issues but little attention has been paid to what the solutions might be.

The Canterbury Waterway Rehabilitation Experiment (CAREX)* is a stream restoration project that has focused on finding solutions. CAREX has been running since 2013, designing and trialling solutions to rehabilitate freshwater ecosystem health. The project research has focused on testing practical tools to:

  • Reduce nuisance aquatic weeds (macrophytes),
  • Reduce the amount of fine sediment cover
  • Reduce in-stream nutrients (nitrogen and phosphorus)
  • Improve in-stream biodiversity and habitat

CAREX has attracted a multidisciplinary range of researchers from the core team of professors, post docs, students and technicians based here at the University of Canterbury, to the many research partners we have collaborated with. Some of these collaborations include Auckland University looking at greenhouse gases emissions, the Institute of Environmental Science and Research (ESR) looking at fecal bacteria and Living Water – a partnership between the Department of Conservation and Fonterra looking at solutions that will enable farming and freshwater to thrive together.

A collaborative approach

From the beginning of the project, we understood how important it was going to be to take a collaborative approach. We set about meeting landowners who were willing to be part of the project, by way of allowing research and trials to be conducted on their land and also helping co-design trials. Multi-generational knowledge of the surrounding environment from the landowners and their families, farm workers and friends has been invaluable for increasing our understanding of how different tools may function and their practicality. Working on farms from Rangiora to Hinds we have involved 23 landowners on a mix of dairy, sheep and beef and cropping properties. Having the support of the landowners from the beginning was crucial in allowing us to experiment on a much larger scale than we had done before, with each farm having at least one kilometre of waterway to work on.

Sharing our findings with local landowners at a CAREX Open Day.
Sharing our findings with local landowners at a CAREX Open Day.

The CAREX toolbox

Through the design, trial and development of solutions for freshwater waterway rehabilitation on these farms we came up with a CAREX rehabilitation “toolbox”. This toolbox has been designed to provide different tools and strategies for each of the four main issues we have focused on: macrophytes, sediment, nutrients and biodiversity.  The tools can be used individually or in combination to achieve optimal freshwater ecosystem health in each unique waterway. One example of a tool for reducing in-stream nutrient levels is a bioreactor. Bioreactors combine a low-oxygen condition with a carbon source (wood chips) which allows microbes to convert nitrate to nitrogen gas. This is termed denitrification. Nitrogen gas then enters the atmosphere and is harmless.

We have also developed a set of handouts which include steps and resources for landowners and stakeholders to apply the rehabilitation tools themselves.

CAREX rehabilitation toolbox
The CAREX rehabilitation toolbox showing tools for reducing weedy aquatic plants (macrophytes), sediment, nutrients and increasing biodiversity.
An edge-of-field bioreactor being installed at one of the CAREX sites. This type of bioreactor is designed to intercept a tile drain, reducing high nitrate levels that would otherwise flow into the main waterway.

Stakeholder involvement

CAREX is going beyond traditional methods for communicating scientific knowledge, which has made the project a success. We want to inform but also engage so that we can ultimately make a difference to waterway management practices. A key part of this has been to work in collaboration not only with landowners but with government agencies, the public, iwi and local communities.

Showing the public through one of our sites at a joint CAREX/Environment Canterbury Mahinga kai shed talk.
Showing the public through one of our sites at a joint CAREX/Environment Canterbury Mahinga kai shed talk.

CAREX has several demonstration sites functioning alongside working farms, each showcasing multiple rehabilitation tools working in combination in the waterway. These demonstration sites have been used as meeting points for discussions with council, drainage committees, local working parties and the general public. They have also been used as outdoor classrooms for students from primary to tertiary and as a way to involve local communities on the journey through riparian planting days.

Community riparian planting day at a CAREX site.
Community riparian planting day at a CAREX site.

Our hope is that there continues to be an ongoing collaborative approach between community, landowners, stakeholders and iwi long after the CAREX project finishes. Through inclusion and engagement, improvements to freshwater ecosystem health for agricultural waterways will be sustainable into the future.

For more information about CAREX see the following links:
Handouts, Resources, Newsletters:
Facebook: @UC.CAREX

Carex, puhio, nz native grass
* Incidentally Carex (also called pūhio) is also the scientific genus of an important plant used in riparian plantings throughout New Zealand waterways.

Hayley Devlin is a Research Technician at CAREX.