Science and monitoring

 

Scientific monitoring of water quality and biodiversity in the catchment’s waterways is an important part of the Toitū Te Hakapupu project. 

Monitoring at the beginning of the project was used to set a baseline. From here, comparisons can be drawn to understand how water quality changes over time. This work is ongoing and potential improvements of water quality won’t be visible via monitoring for a few years yet. The results gained from field measurements are also collected so that they can be compared to data gained from other waterways throughout the country. This enables us to see how Te Hakapupu / Pleasant River stacks up relative to elsewhere.

As the project progresses, more detailed monitoring will be used to target areas specific water quality issues are in the catchment to help guide action and solutions.

Then, once the project has finished, ongoing monitoring in the future can show that work done via the project has a lasting impact in the Te Hakapupu catchment. Future monitoring can highlight if work done via the project helped meeting the goals and values of mana whenua and the community.

 

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Water quality

 

Riverwatch Waka

In May 2023, Riverwatch ‘waka’ (floating water quality sensors) were trialled in the catchment’s three main tributaries, Te Hakapupu / Pleasant River, Watkins Creek, and Trotters Creek. These are little kiwi-made rafts with sensors for turbidity, temperature, oxygen levels, pH and conductivity. Each waka sends monitoring data to a website every 15 minutes.

Turbidity is a measure of water clarity and is related to the amount of sediment in the water. Sediment levels affect habitat quality for aquatic animals and plants. They can change noticeably in relation to river flow levels and rainfall. Wakas allow real-time monitoring of turbidity, giving insights to water quality changes during rain or storm events.

Dissolved oxygen is critical for aquatic organisms, such as fish and macro invertebrates. Like humans, they need oxygen to breath. Dissolved oxygen is the oxygen in water that is available to them. If a river has low and slow flows, air temperatures are high, or natural chemical and biological reactions occur in a stream, dissolved oxygen levels can decrease. Under extreme conditions, waterbodies can become anoxic (zero oxygen), making them unsuitable for organisms to live in.

Temperature is being measured because it affects the amount of dissolved oxygen and the speed of chemical reactions, both of which impact the survival rate of organisms.

Similarly, the acidity (pH) and conductivity (concentration of dissolved salts and minerals) of the water relate to the speed and nature of chemical and biological reactions — including metabolism — and these influence how habitable the test site is for aquatic animals and plants. Conductivity is also used to track saltwater intrusion and to see how far up a river tidal water is pushed during high tide.

A new model of these Riverwatch waka is currently being tested, and Te Hakapupu will be one of the first catchments to use these new waka.

 


A Riverwatch Waka in place on Te Hakapupu / Pleasant River.
Photo: Matt Dale, Waterscape Connections

 

Biodiversity

Life in Te Hakakpupu

Meet some of the fauna and flora living in the catchment below:

 

Poaka / pied stilt. Photo: JJ Harrison

Poaka / pied stilt. Photo: JJ Harrison

Poaka / pied stilt (himantopus leucocephalus), also known as the white-headed stilt, is a waterbird that feeds in shallow water, largely on aquatic insects and small molluscs. It can grow to just over 30 cm and emits a repeated yelping cry as it flies, swaying from side to side with its legs trailing. The poaka breeds in spring, choosing nesting sites of sand or shingle by an estuary or dried-up riverbed, usually on a flat bit of coast or in a grassy field near the sea.

Kawaupaka / little shag. Photo: JJ Harrison

Kawaupaka / little shag. Photo: JJ Harrison

Kawaupaka / little shag (microcarbo melanoleucos), known as the little pied cormorant in Australia, is a common Australasian waterbird found around coasts, islands, estuaries, and inland waters. It is a small, short-billed cormorant, usually black above and white below with a yellow bill and small crest and grows to nearly 60 cm. A mostly black, white-throated form is most prominent in New Zealand. There are also three subspecies.

Raupo / bulrush. Photo: André Richard Chalmers

Raupo / bulrush. Photo: André Richard Chalmers

Raupo / bulrush (typha orientalis) is a wetland plant that grows on the edges of ponds, lakes, salt marshes, and slow flowing rivers and streams.

The plant was quite useful to Kāi Tahu and considered taoka (treasured). The rhizomes (underground stems) were cooked and eaten, while the pollen was baked into cakes. The leaves were prized for making mōkihi - small, temporary river craft - as well as used to make roofs, walls and occasionally for canoe sails, as well as a material for making kites.

Oioi / jointed wire rush. Photo: Arnim Littek

Oioi / jointed wire rush. Photo: Arnim Littek

Oioi / jointed wire rush (apodasmia similis) is a plant that is endemic to New Zealand. It is a coastal plant but is also found around peat bogs and hot springs.

In an attempt to reintroduce these colourful, native wetland rushes to the area, and to learn the best ways to re-establish the plant around the estuary, more than 1600 oioi were planted around the south arm of Te Hakapupu estuary in December 2022. This was thanks to the hard work and collaborative efforts of the Kāti Huirapa Rūnaka ki Puketeraki marae nursery and Tūmai Beach Restoration Trust.

 

Below are reports prepared by the Tūmai Beach Community relating to the oioi trial: 

 

 

 

eDNA analysis

eDNA stands for environmental DNA, which is all DNA found in an environment. eDNA testing can pick up traces of genetic material from all sorts of organisms, including fish, plants, bacteria and mammals that live in or nearby a waterway. Samples of water can be analysed in very fine detail to identify exactly what species are present at the testing site and further upstream. 

eDNA sampling helps to inform on the presence and absence of species.  Some of those species identified might be very rare or are potential indicators of good water quality. Therefore, knowing what is present tells us a lot about the health of the river. 

In December 2022, eDNA analysis was performed at six sites by ORC, assisted by East Otago Catchment Group. 

The findings have been summarised in the tables below as: 

  • Ten species of freshwater fish and seven estuarine/marine species were detected in the catchment. 
  • Three of the freshwater types are considered threatened.  
  • Four are considered mahika kai species. 
  • There is no evidence yet of the non-migratory types of galaxiids, which are becoming very rare throughout the country. If they do appear in future rounds of monitoring, options for their protection will be considered, as trout will eat them and compete with them for habitat. 

Freshwater survey

Ten species of fish were detected at the five freshwater sites. Of these, the banded kokopu and both long and short fin eels are considered threated (at risk-declining).

SPECIES STATUS

 Banded kokopu

 Threatened / mahika kai

 Bluegill bully

 Not threatened

 Common bully

 Not threatened

 Redbin bully

 Not threatened

 Īnaka – migratory galaxiids

 Not threatened / mahika kai

 Tuna – NZ longfin eel

 Threatened / mahika kai

 Tuna – shortfin eel

 Threatened / mahika kai

 Brown trout

 Introduced

 European perch

 Introduced

Estuary survey

At the sixth site, the estuary at the mouth of Te Hakapupu, seven species of marine fish were identified.

SPECIES STATUS

 Kahawai

 Mahika kai

 Patiki (Sand flounder)

 Mahika kai

 New Zealand smooth skate

 Mahika kai

 Yelloweye mullet

 Mahika kai

 Clingfish

 Not threatened

 Spotty

 Not threatened

 Thornfish

 Not threatened

Fish passage assessment

Project partner, Kāti Huirapa Rūnaka ki Puketeraki, completed an assessment of potential fish passage barriers in the Hakapupu catchment and made recommendations on actions to be taken where barriers have been identified.

 

 

Inaka spawning report

Rosemary Clucas from the Department of Conservation (DOC) investigated and reported on inaka spawning in Coastal Otago. Her report is linked below and is aimed at:

  • Providing a current inventory of eastern coastal Otago inaka spawning sites.
  • Prioritising the sites where significant inaka populations exist and the spawning sites which require securing and protecting.
  • Providing information to landowners as to the biodiversity value of their streams and likely threats.
  • Identifying the range of threats to spawning sites and suggest remediation.

 

 

State of the Environment (SOE) monitoring reports

Salt Ecology is a consulting and research service that specialises in the ecological assessment and monitoring of freshwater, estuary, lake and marine habitats. They have prepared these reports below for the Pleasant River (Te Hakapupu).

 

 

Sediment

The goal of the Toitū Te Hakapupu is to improve water quality of the estuary through a reduction in sediment (e.g., mud and silt) and nutrients entering waterways in the upstream catchment. These actions are expected to reduce the risk of algal bloom formation and enhance dissolved oxygen conditions in the estuary, avoiding the development of oxygen depleted zones.

To understand the sources of sediments found in the estuary, the National Institute of Water and Atmospheric Research (NIWA) has undertaken sediment tracing using isotopic signatures. Think of these signatures like fingerprints; molecules released to the soil by plant roots.

Each plant community in a land use type, such as forestry or agriculture, has a specific fingerprint. By analysing the mixture of fingerprints observed in sediment particles in the estuary, information on the most common contributor of sediment to the estuary can be identified.

The report provides a greater understanding of how different land uses contribute to sedimentation within Te Hakapupu | Pleasant River catchment river and estuary system. It also highlights the different contributions of sediment from each river and how some rivers such as Trotters Creek have contributed 70% of suspended sediment from Te Hakapupu.

The report highlights how complex the receiving environments are, with both marine and land sediment sources causing deposition and how the estuary’s capacity to absorb sediment has been reduced due to legacy sedimentation. Streambank and subsoil erosion are highlighted as the primary sources of sediment depositing in the river system at most sampling sites.

The project has determined how certain land use activities can impact estuary and riverine deposits and it has shown how some land uses have a greater impact on sediment deposition relative to the footprint of their activity. The findings of this study contribute to understanding what the key sources of sediment might be and where in the catchment the sediment comes from to help guide interventions on land implemented by the project, and beyond.

You can read a shortened summary report of sediment in the catchment: "Tracing the sediment in the Pleasant River Te Hakakpupu Catchment 2023" and the full technical report: "Sources of sediment depositing in the Pleasant River (Te Hakapupu) Catchment and Estuary 2023". 

 

Following the results from the isotopic fingerprinting of sources of sediments, geotechnical consultants GeoSolve were asked to map erosion within the catchment to help the project develop targeted actions to improve these sedimentation ‘hotspots’.

This analysis included the use of aerial imagery, Lidar (maps of the ground surface created via pulsed laser), geological mapping and previously published information. Areas where erosion was identified were classed by their certainty of erosion being present (definite to possible), the severity of erosion (high to low), the connectivity to waterways (high to low) and the potential to remedy these conditions (high to low).

 

Following the report by GeoSolve, specialists from the ORC science teams have undertaken a fly-over across the catchment to validate the mapping and get a snapshot of active erosion to better target sediment mitigation efforts.   

 


The view from the air; active erosion seen during the recent fly-over in the Pleasant River catchment

 

 

Historic sediment and erosion reports

 

 

Environmental Data Portal

ORC's Environmental Data Portal (EDP) gives you the latest environmental data, such as water levels, rainfall, flow, temperature and much more. More quality data means you will be able to make better decisions. With this portal you are able to:

  • Explore more than 350 monitored sites
  • Easily find, view and interact with maps and tables
  • See all available historical data
  • Download data so you can view it offline anytime, anywhere

There’s a monitoring site in Pleasant River at the Patterson Road Ford.

You can find the latest readings on water flow, water temperature, pH and nitrate levels and more.

 

Info Sheets

Ahīka Consulting have prepared this set of four information sheets detailing, and in some cases, summarising some of the efforts made in the monitoring of water, stream habitat health, fish and sediment.

 

 

 

Other reports

Below is a copy of the 10th iteration of the New Zealand Enviromental Perceptions Survey (EPS) conducted in 2022. It shows findings and key trends since 2010 and details around a disconnect between perceptions and the actual state of the environment.

 

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