Ōtūwharekai Ashburton Lakes

Lake Heron

Ōtūwharekai (Ashburton Lakes) is a significant and important part of our region, but threats to water quality mean we need to take action now. Sign up to the Ōtūwharekai Working Group mailing list to receive updates on this project

This webpage provides information and progress on the activities underway to address these concerns and is updated regularly.

Why are the lakes so special?

The Ōtūwharekai Lakes are one of the few remaining areas of native biodiversity in mid-Canterbury. The diverse range of wetland habitats mean this site is a nationally important and is home to more than 30 bird species, as well as many threatened plants and aquatic species.These include the wrybill and crested grebe birds, the upland long jaw galaxiids and tadpole shrimp, and plants like the endangered marsh arrowrush (Triglochin palustris) and pygmy forget-me-not (Myosotis pygmaea). The Department of Conservation has detailed information about Ōtūwharekai biodiversity, plants and animals.

The wider Ōtūwharekai area is of immense cultural significance to Ngāi Tahu Whānui – not only within their oral history but also being both an important seasonal mahinga kai area and a major travelling route between the settlements on the eastern coast of Te Waipounamu (the South Island) and those on Te Tai Poutini (the West Coast). Its restoration is of huge importance to rūnanga.

To the many people who visit the area and stay in campgrounds or baches around the lakes, they are a beautiful recreational site.

What is the problem?

In recent years, we've seen a decline in water quality in several of the lakes, with higher TLI (Trophic Level Index) levels putting some lakes in danger of "flipping" – that is, reaching a state of degradation from which it is very difficult to improve. 

Lake Clearwater in winter

Te Puna a Taka (Lake Clearwater)

Lake Camp

Ōtautari (Lake Camp)

Lake Emma

Kirihonuhonu (Lake Emma)

Why is lake water quality degrading?

There are a number of factors contributing to declining water quality in some of the Ōtūwharekai lakes. Each lake is unique and faces its own level or risk, with different factors contributing to water quality issues. 

The potential contributors to water quality decline include land use in the catchment (including fertiliser use and grazing); seepage from long drops and leaky wastewater tanks; pollution from recreational use; and warming associated with climate change.

A diverse group of interested parties is working to identify how we can better manage these factors to protect the Ōtūwharekai Lakes.

The Ōtūwharekai Working Group

The Ōtūwharekai Working Group was established in 2019 to instigate collaborative and urgent action to halt and reverse the degradation of Ōtūwharekai ecology and values.

The Group is made up of Papatipu Rūnanga with connection to the area – Te Rūnanga o Arowhenua, Te Ngāi Tūāhuriri Rūnanga and Te Taumutu Rūnanga – as well as Te Rūnanga o Ngai Tahu, Environment Canterbury, farmers in the area, Department of Conservation, Toitū Te Whenua LINZ, Ashburton District Council, Central South Island Fish & Game, the Ministry for the Environment and Ministry for Primary Industries.

A key concern for the group is the decline in water quality in several of the lakes, which has put some lakes in danger of "flipping" – reaching a state of degradation from which it is very difficult to improve. These changes are causing a loss of cultural values, including mahinga kai resource gathering, loss of healthy habitat for plants, birds and fish, and impacts on recreational and landscape values.

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Ashburton Water Zone Committee action plan

Ōtūwharekai (Ashburton Lakes) is a key focus for the zone committee's three-year action plan (July 2021–June 2024). It supports the recovery project by keeping abreast of the project implementation and assisting with recommendations where appropriate, which may include community engagement and education.

Work in progress

Ōtūwharekai Working Group members are progressing several programmes of work to address lake water quality under urgency. The next update will be presented to the Ashburton Water Zone Committee in November 2022.

Update 2 – Ashburton Water Zone Committee 23 August 2022 – Water Quality focus

Hundreds of water samples taken from the Ōtūwharekai Ashburton Lakes and streams over the past year confirm that water quality remains a concern and reinforce that ongoing action is required.

The water monitoring results were presented to the Ashburton Water Zone Committee by Environment Canterbury and the Department of Conservation (DOC), who are part of the Ōtūwharekai Working Group to restore lake health and cultural values.

 

Ōtūwharekai/Ashburton Lakes results summary

Here’s a summary of the results for the lakes in the area:

  • Te-Puna-a-Taka, Lake Clearwater: Slightly better than last year’s results and less algal biomass.
  • Lake Ōtautari/Camp: Increase in algal biomass since 2012. This year’s results are slightly worse than last year.
  • Lake Denny: Improvement in water quality from highly nutrient-enriched state 10 years ago.
  • Lake Emily: Relatively steady water quality since 2008, with the exception of high algal biomass in 2018-2020.
  • Lake Kirihonuhonu/Emma: Water quality this year slightly better than last, despite high turbidity due to floods. Degrading trends in water quality since 2012.
  • Ōtūwharekai Māori Front Lake: Large fluctuations in water quality. Reduction in phosphorus since 2012.
  • Ōtūwharekai Māori Back Lake: Degrading water quality since 2012.
  • Ōtūroto/Lake Heron: Steady and large increase in algal biomass since 2018. This year was worse than last year, with continued increase in algal biomass.
2018-22 Ōtūwharekai Trophic Lake Index (TLI) scores
  2018 2019 2020 2021 2022 TLI Limit
Lake Emily 3.95 4.83 4.96 4.07 4.01 3
Ōtūwharekai/Māori Front Lake 4.13 4.7 3.99 3.8 3.63 3
Ōtūwharekai/Māori Back Lake 3.94 3.77 4.65 4.77 4.51 3
Lake Denny 6.22 3.88 5.19 4.54 3.98 3
Ōtūroto/Lake Heron 3.45 3.54 3.67 3.97 4.48 3
Kirihonuhonu/Lake Emma 4.28 5.12 4.35 5.25 4.72 3
Ōtautari/Lake Camp 3.19 3.22 3.55 3.64 3.84 3
Te-Puna-a-Taka/Lake Clearwater 3.62 3.85 4.54 5.35 4.54 3

Description of trophic states and Trophic Level Index (TLI) scores:

TLI Tropic state General description
<1 Ultra-microtrophic Practically pure, very clean, often have glacial sources
1-2 Microtrophic Very clean, often have glacial sources, very low nutrient concentrations
2-3 Oligotrophic Clear and blue, with low levels of nutrients and algae
3-4 Mesotrophic Moderate levels of nutrients and algae
4-5 Eutrophic Green and murky, with higher amounts of nutrients and algae
5-6 Supertrophic Very high nutrient enrichment and high algae growth
Additional science investigations
In addition to the long-term lake and stream monitoring, other science investigations have also been taking place since 2019. These include continuous in-lake monitoring stations to better understand lake dynamics, continuous nitrate monitoring in Gentleman Smith Stream, and a groundwater study using piezometers in the Lake Camp/Clearwater settlement area.

DOC commissioned NIWA to assess the state of kākahi (freshwater mussels) populations in eight of the Ōtuwharekai lakes in summer 2021 (you can read the full report). Kākahi were found in all eight lakes, with their populations remaining similar for most lakes compared with the last survey (in 2012). However, there was a concerning decrease in the number of kākahi found in Lake Emily and Māori Lake West. Also, the shells of kākahi from Te-Puna-a-Taka/Lake Clearwater were in poor condition. Like the 2012 survey, there was a concerning absence of smaller kākahi in the lakes, which likely indicates that recruitment has been impacted for many years.

DOC also commissioned NIWA to undertake stream health surveys (focused on aquatic invertebrate and habitat) on multiple streams throughout the basin this past summer.

The fieldwork is complete, and the data is currently being written up with DOC hoping the surveys will help determine the current state of stream health across the basin, and also see if any changes have occurred since the previous surveys from 2008 to 2012.

A mātauranga Māori cultural health assessment, led by rūnanga, was also carried out over late summer and the results are being reviewed. This mahi enables the gathering of information from iwi, including cultural heritage and mahinga kai resource gathering, to report on the health and mauri of the freshwater environment and identify areas of focus.

All the information collected will be used to increase knowledge and understanding of the lakes, streams and wider catchment, to better inform ongoing actions to reduce nutrients.
Action already underway
The Ōtūwharekai Working Group provided an update on work to the Ashburton Zone Committee in July and Environment Canterbury’s Council received this update on the collective actions and workstreams to improve outcomes for the lakes, including the voluntary nutrient reductions already made by landowners (see Update 1 below).

Members of the group are now working on the next steps needed to significantly reduce nutrient loads, including developing a lake-by-lake land use risk analysis, which will include the required nutrient reductions to improve lake water quality. The outcome will be an agreed set of mitigation actions for farms and lakes, which will build on voluntary actions taken to date to accelerate positive environmental change in this catchment. In addition, rūnanga partners are leading work to understand the changing environment through a mātauranga lens.
Update 1 – Ashburton Water Zone Committee 26 July 2022
Lake Monitoring

Lead: Environment Canterbury

This programme includes Environment Canterbury’s long-term monitoring programmes, as well as new site-specific monitoring.

  • Detailed water quality information is being collated and analysed by the science team to give a better understanding of each lake’s unique ecology and how nutrients, algae, and oxygen are interacting with each other.
  • Helicopter sampling to test water quality at the Ōtūwharekai Lakes occurs between December and April each year. Monitoring takes place monthly at Lake Heron / Ō tū Roto, Lake Denny, Lake Emily, Lake Emma / Kirihonuhonu, Lake Camp / Ōtautari, Lake Clearwater / Te Puna a Taka and the Māori lakes, for nitrogen, phosphorous, algal biomass and turbidity.
  • We take monthly mid-lake water quality samples at Lake Heron / Ō tū Roto (since October 2020), Lake Emma / Kirihonuhonu (October 2020–September 2021) and Lake Clearwater / Te Puna a Taka (since September 2021).
  • We test the main swimming sites at lakes Lake Camp / Ōtautari and Clearwater / Te Puna a Taka for bacterial contamination weekly over the summer months. This programme is now complete for this season and data is being analysed.
  • Lake Heron / Ō tū Roto and Lake Clearwater / Te Puna a Taka have continuous monitoring equipment installed, which measures dissolved oxygen and temperature, plus turbidity, and chlorophyll a at Lake Clearwater / Te Puna a Taka.
Stream Monitoring

Lead: Department of Conservation and Environment Canterbury

The Department of Conservation’s stream water quality monitoring sites are illustrated in Appendix 1 (PDF file, 1.81MB). The lake catchment boundaries are delineated in blue and are associated with Lake Heron, Māori Lakes, and Lake Clearwater. Sites shown as red points have been sampled since 2012, while sites in green have been sampled since December 2019. In addition,

  • DOC has commissioned NIWA to undertake stream health sampling (aquatic invertebrates) of streams in Ōtūwharekai. This work is ongoing and is due for completion by the end of 2022.
  • report on Kākahi (freshwater mussel) populations is publicly available on the DOC website and it provides a commentary of the lake surveys that have been undertaken.

Environment Canterbury added a new continuous nitrate logger was installed at Gentleman Smith Stream in October 2021.

Groundwater Monitoring

Lead: Environment Canterbury with Ashburton District Council

In late February, a series of shallow monitoring bores were installed between Lake Camp/Ōtautari and Lake Clearwater/Te Puna-a-Taka to monitor ground water levels and determine rates of water movement between these water bodies. In addition, monthly water quality sampling is being undertaken of the groundwater.

This monitoring will inform understanding of the effects of the settlement on groundwater quality being received into Lake Clearwater / Te Puna a Taka and the effectiveness of ADC’s programme to decommission long drop toilets.

Farm Nutrient Risk Assessments

Lead: Environment Canterbury

Environment Canterbury and landholders are working together to identify high nutrient loss areas and the mitigation options to reduce nutrient loss.

All four farms are working together on a holistic approach for the whole catchment.

Mātauranga Māori and Cultural Health Assessment

Lead: Aoraki Environmental Consultancy and mana whenua

Arowhenua rūnanga have been leading the work on the cultural health monitoring in the catchment.

Arowhenua have applied to Ministry for the Environment for funding to support ongoing Mātauranga Māori monitoring in the catchment.

Oversight of LINZ-leased land

Lead: Toitū te Whenua (LINZ)

The Crown Pastoral Land Reform Bill has now been passed and has received royal ascent. LINZ is currently working through the implementation of the Bill and what this will look like in terms of LINZ administration. Tenure review has formally ended for all those without a substantive proposal put to them.

  • LINZ has begun consultation on proposed regulations and standards to support the implementation of the Crown Pastoral Land Reform (CPLR) Act which will come into effect on 17 November 2022
  • LINZ has worked closely with our Treaty partners, High Country Accord, High Country Advisory Group, and the Department of Conservation to develop the proposed regulations and standards.
  • LINZ is seeking feedback to ensure the regulations and standards are robust and workable while supporting the outcomes of the CPLR Act.
  • Consultation on the proposed regulations and standards closes Friday 19 August 2022.

More information, including how to make a submission, is available on the LINZ website.

The proposed regulations include prescribing the information required for consent applications, matters the Commissioner of Crown Lands (Commissioner) must consider in deciding the level of adverse effects of a pastoral activity on inherent values, and infringements.

Two new standards have also been proposed:

  • A standard set by the Commissioner for accessing applications for easements, transfers, and subleases of Crown land pastoral land.
  • A LINZ Chief Executive Standard providing a framework for the Commissioner to follow when considering applications for discretionary pastoral activities, commercial recreation permits and stock exemptions.

LINZ is holding a series of sessions over the coming weeks for leaseholders and the public to attend to ask any questions they may have. This will be promoted shortly and details will be available on the LINZ website.

Future of Clearwater Settlement Area Consultation

Lead: Ashburton District Council

This public consultation was undertaken earlier this year to inform the creation of a future strategy for the hut settlement and recreation around Lake Clearwater and Lake Camp. Feedback from more than 150 people who shared their views on the future of the area was received.

The draft plan was subsequently shared with the Ōtūwharekai Working Group agencies for feedback in June recognising that the discussion through Ōtūwharekai Working Group meetings also informed aspects of the plan content.

The plan will go to the Ashburton District Council meeting on 27 July 2022 and the working group members will be involved in implementation as appropriate going forward.

Game Bird Survey

Lead: Central South Island Fish and Game

Central South Island (CSI) Fish & Game currently undertake an annual survey in late January/early February of paradise shelduck and black swan within the Ōtūwharekai area. 

More detail around this programme of work is provided in Appendix 2 (PDF file, 1.81MB).

Geese Population Management

Lead: Department of Conservation and Toitū te Whenua (LINZ)

Canada geese were monitored by CSI Fish & Game annually in June/July between 1986 and 2010. Counts were undertaken using the same method as for paradise shelduck and black swan.

In 2011 Canada geese were removed from the schedule 3 (game) and placed on schedule 5 (unprotected wildlife) and as a result annual surveys for the species ceased.

Earlier this year LINZ, DOC and landholders co-ordinated efforts on controlling geese populations in Ōtūwharekai

Collective approach to managing inappropriate 4WD use in area

Lead: Multiple agencies

ADC, ECan and DOC are all agencies that all have some regulatory role on the impact and effects of the inappropriate use of Four-Wheel Drive vehicles (4WD), either in the environment or on their respective land.

Inappropriate 4WD use also impacts farmers in the area and it clashes with the values that other groups or individuals have in utilising this environment.

We recognise that this issue is not unique to Ōtūwharekai and that there are some very real challenges to implementing compliance actions. We will continue to work together and communicate non-acceptance of inappropriate use of these vehicles.

Pest Plant control on DOC land

Lead: Department of Conservation

The Department of Conservations has an ongoing programme of work relating to the control and plant pest species on its land. This also includes the control of willow species.

Clearwater Settlement long drop decommissioning

Lead: Ashburton District Council

In 2021 ADC began a programme of work to decommission all long drops in the Clearwater settlement area. This has now been completed.

Joint Agency Communications Group

Lead: Multiple agencies

Communications staff from across the crown agencies and Ngāi Tahu meet online monthly. A key focus has been creating website information and updating each other on the progress of the work taking place to share with stakeholders.

More information

Information on water quality and nutrients

A report on Canterbury's high-country lakes published in late 2020 (PDF File, 10.32MB) found high concentrations of nitrogen and algae in many of the lakes. Between 2015 and 2019, all but one failed to reach the TLI objectives set in the Canterbury Land and Water Regional Plan (LWRP).

A 2021 report by the Cawthron Institute (PDF File, 2.27MB) estimated the nitrogen and phosphorous load reductions the lakes would need in order to meet LWRP nutrient limits.

Information for hut holders

  • There has been recent degradation of water quality in Lake Clearwater and the lake needs urgent action to improve water quality and prevent the loss of the aquatic plants (macrophytes).
  • Ashburton District Council is your key contact in terms of managing your wastewater and toilet upgrades.
  • A Master's thesis looking at nitrogen and water balances of Lake Clearwater found that nitrogen and water inputs to the lake were much lower than nitrogen and water exported from the lake, suggesting an additional source of both nitrogen and water other than the surface inflows. This was confirmed in the CLUES catchment modelling. A potential pathway is groundwater moving under the hut settlement, a theory which is now being investigated. 

Information for recreational lake users