Action on the ground
The Selwyn Te Waihora catchment includes Te Waihora/Lake Ellesmere and the land that drains into it, bounded by the Waimakariri River to the north and the Rakaia River to the south. Read about what is being done to restore and rejuvenate the ecosystem health of Te Waihora and its catchment.
From the mountains to the sea, Selwyn’s water is an integrated, connected system with high interdependencies. Before we get to the nitty-gritty of the state of Selwyn’s water, we first need to understand where our water comes from and how it reaches us.
Rainfall, of course, is where all of our water originates, flowing across the plains and seeping into the gravels below. Some of the groundwater comes to the surface again lower down the plains as springs, and feeds the lowland streams that drain into the lake.
What is being done on the land that impacts the waterways across the Selwyn catchment
Land use consents for farming
Around 900 farmers now need a land use consent to farm, which includes a Farm Environment Plan, addressing mahinga kai values and further nitrogen reductions into the future.
Reduced nitrogen losses
On farms with nitrogen losses over 15kg per hectare per year, reductions of between 5% (horticulture) and 30% (dairy) are required from 2022.
Farming at Good Management Practice and better
After gaining a land use consent, the farm will be regularly independently audited to ensure good management practices are being followed, and nitrogen limits and reductions are being met.
Stock access rules are tighter in Selwyn than elsewhere, including drains as well as other waterways, wetlands and lakes. Within the cultural area, further restrictions apply for wetlands and beds of lakes, rivers and drains.
Cultural Landscape Values Management Area
This designation reflects the significance of mahinga kai, wāhi tapu and wāhi taonga (sacred or treasured) sites, and places additional requirements on farmers to address these values.
Rehabilitating Te Waihora/Lake Ellesmere will require actions in and around the lake as well as managing the nutrient loads from the catchment. (Note not all nitrogen losses from farming, community and industrial activities end up in the lake.)
Restoring the macrophyte beds in the lake and addressing the legacy phosphorus in the lake bed silts will be particularly challenging. The following are underway:
- Macrophyte (aquatic plant) trials behind artificial wave barriers
- A floating wetland trial
- Using a nutrient model to explore ways to address the lake’s phosphorus.
Hororata biodiversity corridor
More than a dozen areas of native vegetation including wetlands have been protected and restored in the Hororata catchment, creating biodiversity “stepping stones” from the top of the catchment.
Te Ara Kākāriki, with support from many other organisations, plants large areas in natives to establish a green network from the foothills across the Plains to Te Waihora/Lake Ellesmere.
Springheads and wetlands
Protection and rehabilitation of some wetlands and springheads is underway so nutrients can be removed, enhancing native vegetation and protecting special species like mudfish.
There are over 370 kilometres of drains in the catchment, which play an essential drainage role and provide habitat for fish, as well as being a valued resource for mahinga kai.
The CAREX project led by the University of Canterbury is looking at ways to manage drains that increase biodiversity, and reduce nutrients and nuisance aquatic plants while still fulfilling drainage function.
Silverstream joins the Selwyn River/ Waimakariri just above Coes Ford and is a major source of microbial contaminants at this swimming site. Environment Canterbury is working with landowners to identify and manage the streams and drains in the lower catchment, reducing run-off of sediment and microbial contaminants.
Water and Wildlife habitat Trust is leading the Snake Creek Restoration project to turn this 'drain' back into a living tributary that is once more an important trout spawning location.
This 10-year Fonterra and DOC partnership is trailing how sustainable dairy farming and healthy freshwater ecosystems can exist side by side. The Ararira/LII River catchment is one of the Living Water sites, focusing on improving drains in the area.
Catchment nitrogen load limits
The Selwyn Te Waihora Water Plan sets tough limits for nitrogen losses.
- From farming activities of 4,830 tonnes/year
- From community sewerage systems of 62 tonnes/year
From industrial or trade processes of 152 tonnes/year.
A large wetland is to be constructed in Ahuriri Lagoon near Te Waihora /Lake Ellesmere, to strip nutrients from some of the water flowing into the lake.
Central Plains Water
CPW will irrigate up to 60,000 hectares of the Plains using water from Lake Coleridge and the Rakaia and Waimakariri rivers. By replacing groundwater irrigation on half this land, it will leave more water in the groundwater “bathtub” and improve stream and river flows. In its first season, farmers who are now part of CPW Stage 1 reduced their groundwater takes by 75%.
CPW will result in more irrigated land use in the catchment, adding a small, temporary percentage increase to the nitrogen load. The Selwyn Te Waihora Water Plan addresses this by setting a load limit for CPW.
The main pipeline across the top of the Plains for the second stage of CPW will be built to allow water to be taken in a targeted way to supplement flows in the Selwyn River/ Waikirikiri. The water would be released into the gravels near the dry sections of the river and supplement flows at Coes Ford when the river is low.
New irrigation takes prohibited
The Selwyn Te Waihora Water Plan prohibits new irrigation takes.
Monitoring, compliance and enforcement
Environment Canterbury staff monitor over 1,400 consents each year, and more than 30 enforcement actions were taken in the first half of 2017.
Whakaora Te Waihora
Whakaora Te Waihora is an ecological and cultural restoration programme for Te Waihora/Lake Ellesmere — an internationally significant wetland and tribal taonga. It is governed by the Te Waihora Co-Governance Group, which includes Ngāi Tahu, Environment Canterbury, Selwyn District Council and Christchurch City Council. Read more about the restoration programme here.