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.

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.

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

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).

Estuary survey

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

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.

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.

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).

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. 

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

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

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.

Below is a copy of the 10^th 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.