Co-designing solutions for a complex catchment network
The Ararira/LII River catchment is a significant spring-fed tributary of Te Waihora/Lake Ellesmere, New Zealand’s fifth largest lake and an important wetland ecosystem in lowland Canterbury. Te Waihora has special significance to Ngāi Tahu as a tribal taonga representing a major mahinga kai and source of mana.
Unique features of this 6,600 hectare catchment include headwater springs, an extensive network of drains/waterways, and two large wetland areas – Tārerekautuku/Yarrs Lagoon and Yarrs Flat. Despite significant modification, the catchment’s network of artificial waterways and remnant wetlands still provide some habitat for native fish, bird and plant species.
Prior to human arrival, much of the land in this area was swamp forest dominated by kahikatea and matai. Numerous waterways, arising as springs, followed irregular meandering courses through the swamp to Te Waihora. To enable European settlement in the mid 1800’s, drains were dug through the wetlands to lower the water level and create soils dry enough for farming. Although the swamp forest has long gone, the spring water, now channelled in artificial courses, still supports fish and invertebrates and its quality has a critical bearing on the health of the lake.
The waterways lack shade which allows aquatic weeds to flourish and choke the waterways and trap sediment. Water weeds and sediment are routinely removed using diggers. The mechanical clearance combined with sediment run-off from eroding banks, and nutrients and contaminants from farms and urban areas, have an adverse effect on freshwater quality. Sections of the waterway have clean gravels providing ideal habitat for native freshwater species such as tuna/eels, inanga/whitebait, koura/freshwater crayfish and some invertebrates. Brown trout also prefer the gravels for spawning.
While the water quality and habitat in the drains is poor, Sarah Yarrow, Living Water National Manager, says they provide the only habitat for aquatic invertebrates, plants and fish.
“That’s what motivated Living Water to select the Ararira catchment for its 10-year programme of trialling new tools, methods and approaches to enable farming, freshwater and healthy ecosystems to thrive side-by-side. Living Water’s key focus in the Ararira is transforming the drainage network into a healthy freshwater ecosystem in a productive agricultural landscape. From small scale trials conducted in this catchment, we now know that it’s possible to rehabilitate waterways with gently sloped and planted banks, pools and faster-flowing riffles without reducing the drainage capacity.”
Mending the mauri of Te Waihora/Lake Ellesmere
Living Water, a partnership between the Department of Conservation (DOC) and Fonterra, is a ten-year programme to find ways to improve freshwater ecosystem health while enabling farming to thrive. Five catchments, all with intensive dairying and challenging freshwater issues, were selected to trial a variety of tools and approaches.
The Ararira catchment was selected because although highly modified with waterways which are primarily managed for land drainage, it is a significant source of water for Te Waihora and contains remnant habitat for native fish, bird and plant species. Modification of the landscape in the catchment has impacted on cultural identity. That led to the decision to work with Te Taumutu Rūnanga to build capacity and capability for mana whenua to rejuvenate the mauri of Te Waihora.
Te Waihora and its contributing catchments have significance for Ngāi Tahu as a tribal taonga and mahinga kai. Te Taumutu Rūnanga is a key Papatipu Rūnanga with interests in Te Waihora, and in particular, the Ararira catchment. Living Water recognised that working in partnership with mana whenua was critical for freshwater aspirations to be realised.
“Our relationship with Te Taumutu Rūnanga was formalised in 2018 and an advisory group, Te Mana Ararira, established to provide structured engagement between the Rūnanga, Living Water and other groups and agencies who have an interest or are working in the Ararira catchment”, says Yarrow. “Building mutual respect and common understanding has included increasing capability and capacity for mana whenua to be involved in freshwater management. Through Te Mana Ararira we are working together to help realise the aspirations of mana whenua for the catchment – to rejuvenate the mauri and life supporting capacity of Te Waihora/ Lake Ellesmere”. Read about the Te Mana Ararira project.
Ararira Cultural Health Assessment
Addressing the sediment, smothering weeds and substandard habitat
Key issues to resolve in the Ararira are excessive fine sediment and aquatic weeds which lead to degraded habitat, poor water quality and a reduction in drainage capacity. These problems drive the annual mechanical clearance of weeds and sediment which, while maintaining drainage, causes habitat damage.
Living Water has trialled a variety of tools and approaches to manage waterways to provide effective drainage while minimising or eliminating mechanical clearing. Trial areas have been established along approximately 4 kilometres of drains/waterways. Steep banks have been re-shaped to reduce erosion, riparian planting has been added to provide shade to reduce aquatic weeds and increase habitat and large stones have been added to increase in-stream habitat variability.
“The Powell’s Road waterway enhancement project is a trial to evaluate and demonstrate new ways of sustainably managing a Selwyn District Council (SDC) ‘classified drain’ with the end goal of restoring habitat and water quality for freshwater biodiversity and mahinga kai while maintaining the waterway’s drainage function”, says Yarrow. “As a demonstration site it’s highly visible to surrounding landowners and the local community. Springston Primary School became involved in 2018 and their students learned about the waterway’s values and heard about waterway restoration from experts. They researched, designed and implemented a 50-metre section and shared their ideas with others. An excellent outcome.”
One of Living Water’s partnerships in the Ararira was with the University of Canterbury CAREX (Canterbury Waterway Rehabilitation Experiment) team. From 2017 CAREX worked with dairy farmers to identify the major sources of contaminants (nitrogen, phosphorus, bacteria and sediment) entering waterways in the catchment and trialling 'edge of field' tools to treat and prevent contaminants from entering waterways. Yarrow says through the CAREX catchment-wide tool-scoping and monitoring work, priority actions were identified and implemented in the right place and monitored. Sediment traps, an on-farm two-stage channel and a wood-chip bioreactor to reduce in-stream nitrate were designed and built and their performance was monitored.
“Baseline monitoring of the catchment started in 2018, and enabled us to assess priority actions for 2019 and beyond”, says Yarrow. “By involving landowners, they learnt what tools are available and how they work. Pleasingly 8 out of 9 Fonterra farms in the catchment have completed Farm Environment Plans, and prioritised actions for reducing nutrient and sediment loads to improve freshwater ecosystems. On-farm trials used by farmers include sediment traps, bank re-battering and planting, nutrient filters and fencing of springs. We know the future of farming will be different and these trials are charting a path to a future for freshwater and farming thriving together.”
One of the most significant remaining biodiversity hotspots on the Canterbury Plains is Tārerekautuku/Yarrs Lagoon, a 77-hectare reserve in the heart of the Ararira catchment. The lagoon is a wetland remnant and a key biodiversity site. It provides habitat for many species of once common wetland plants as well as tuna/eels, bullies, inanga and introduced brown trout. Living Water has supported SDC, who own and manage the lagoon, to build capacity within the Council, control willow and other weeds at priority sites, support the development of a plan for the Lagoon and the sourcing of funding for wetland rehabilitation.
A Memorandum of Understanding was signed with SDC, and funding provided by Living Water from 2016 to 2018 to co-fund a Biodiversity Coordinator role. SDC confirmed the Biodiversity Coordinator role as a full-time, permanent position from 2018. The Biodiversity Coordinator is working alongside the Living Water Ararira Site Lead to progress waterway restoration initiatives across the catchment. Yarrows says progress has been swift.
“Since we began work with willow control at key sites in the lagoon in 2016 we haven’t looked back”, says Yarrow. “Baseline environmental assessment work was completed to support SDC’s development of a Tārerekautuku/Yarrs Lagoon Management Plan. A landowner wetland care group has been established to continue the ongoing management and restoration of Tārerekautuku /Yarrs Lagoon with the aim that it becomes a wetland reserve valued by the community”.
Living Water is supporting DOC to manage and enhance Yarrs Flat Wildlife Reserve, a significant lake edge reserve, downstream from Tārerekautuku /Yarrs Lagoon. Initiatives have included developing a restoration plan, annual restoration plantings with volunteers, ongoing willow control since 2013 and ongoing predator control. The restoration plan led to additional funding and planting of 40,000 native plants through the One Billion Trees programme.
Living Water – Ararira-LII, Canterbury catchment project
Co-designing a new catchment network
Based upon the success of the trials to transform the drains in the catchment, Living Water approached the SDC and Te Taumutu Rūnanga with a proposed Memorandum of Understanding (MoU) to work together on re-designing the entire Ararira Drainage District. The goal is to combine small-scale trials with other mitigations, such as strategic land use change, surface water treatment wetlands, large scale sediment traps, and other ideas from around the world to create a plan that supports ecological, cultural and drainage values across the whole catchment.
The MoU was signed in October 2020, and officials from DOC, Fonterra, Taumutu, SDC, Environment Canterbury (Regional Council) and the LII Drainage Committee began work in January 2021 to develop a shared vision for the Ararira catchment and support the development of an integrated catchment plan. Advice will be sought from local stakeholders and consultants have been engaged to support the preparation of a plan and implementation guide.
The ideal outcome will be SDC working with community input to implement an integrated catchment plan in the Ararira and other similar catchments under their management. Yarrow says if successful, other councils could use a similar approach in catchments across New Zealand.
“We’re creating partnerships like this because no single organisation or sector has all the skills, knowledge and influence to improve freshwater health and we know it requires more than just on-farm action’, says Yarrow. “By partnering we are making it easier for farmers, iwi and communities to improve freshwater which is a goal we all share.”
In the Ararira catchment this new approach will continue to provide landowners with drainage enabling productive land use to continue and will also allow iwi and the wider community to reconnect with a healthy freshwater environment that supports native biodiversity. Yarrow says it’s not a choice of farming or the environment when both can and must co-exist.
“Farming needs uncontaminated freshwater as much as native biodiversity”, says Yarrow. “From what we’ve learnt from the trials in the Ararira, we know that with careful planning and rehabilitation, waterways that support native plants, fish and birds can also effectively provide land drainage. Imagine the difference it will make to the Ararira catchment and waterways across New Zealand as we restore our drains to the life-giving places they once were and can be again.”
We’re creating partnerships like this because no single organisation or sector has all the skills, knowledge and influence to improve freshwater health and we know it requires more than just on-farm action’, says Yarrow. “By partnering we are making it easier for farmers, iwi and communities to improve freshwater which is a goal we all share