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Freshwater in Hawke's Bay

Hawke’s Bay Regional Council monitors over 70 rivers sites and 5 lakes in Hawke’s Bay for ecosystem health. During summer we also monitor popular swimming sites so you know they are good to go.

Freshwater in Hawke's Bay 

All regional councils in New Zealand are required to report on freshwater for the ‘State of the Environment’ (SOE) as specified in Section 35(2A) of the Resource Management Act (RMA). 

Mai i te kāhui maunga ki tangaroa - From the mountains to the sea

Why we monitor freshwater

Hawke’s Bay Regional Council’s environmental science team gathers information so we can understand changes in the health of the freshwater ecosystems and identify the main threats to humans, animals or life in the water.

When we identify a threat, we come up with a strategy to tackle it, often working with the community to help solve issues.  It can take a long time to get stream, wetland, rivers and lakes healthy again, so some solutions are inter-generational.

The Regional Council monitors freshwater in Hawke’s Bay for two different purposes:

LAWA is a national site for sharing water quality data. 

What we monitor for human health

Regional Council staff monitor over 30 popular swimming sites during summer 1 November – 31 March so you can know where it’s good for swimming and other water recreation – and that it's safe for your dogs.

We monitor for:

  • Bacteria and viruses -  the Regional Council monitors E. coli concentrations in fresh water and enterococci in salt water to assess the likelihood of health threatening viral or bacterial contamination from cattle, human, bird, and sheep faeces (poo).  We take water samples which are processed in a laboratory.  
  • Toxins released by certain types of algae - these can potentially cause health problems for humans and animals.  These can particularly be a risk for dogs which can be attracted by the smell. We make visual inspections for algal blooms at high risk sites, and rely on the public to tell us of other locations.
  • The black mat algae (Phormidium) - in rivers this algae like bacteria forms mats that can release toxins into the water or be eaten by dogs.  Dogs are also attracted to the drying mats of algae on river banks. 
  • The blue-green or green coloured algal blooms or cyanobacteria in lakes - these blooms can make the water can look like green spilled paint or petrol.  A red coloured bloom which can appear in lakes is a non-toxic algae called Ceratium.

You can learn to identify algae here

People swimming in the shallows of lakes can also be affected by “duck itch” or “swimmers itch”, a minor skin irritation. This is not related to water quality issues.  See your pharmacy or doctor for treatment.

What we monitor for ecosystem health

Our network of over 70 routine water quality sites on Hawke’s Bay rivers and streams provides us with a picture of habitat and water quality. We use this data for State of the Environment reporting as the life within a waterway reflects the wider area - upstream and downstream - and tells us about conditions over previous months (e.g. flood or drought). 

We report on the life supporting capacity of our rivers and lakes each year - see our report cards - and work with our community on solutions to any problems we find. 

Our Regional Council staff check for:

  • Macroinvertebrates (koura, mayflies, snails, mussels, and worms) – these tiny animals are in all types of freshwater, so are used all over the world to describe river health (although not so much for lakes where phytoplankton is monitored). A river contains many different species that tell us different things about conditions; for example, some macroinvertebrates are more sensitive to certain types of pollution or habitat degradation than others.
  • Plants and algae - these provide habitat for fish and macroinvertebrates. These help healthy rivers and lakes by binding soft sediments and locking up nutrients, but can reduce water quality if they become overgrown because of too many nutrients or higher water temperatures. Excessive growths of ‘black mat bacteria’ (Phormidium) is a particular problem (especially on the Tukituki river), as it has the potential to cause harm to humans and dogs, so we check known problem sites weekly during summer.
  • Habitat features such as the riparian zone (interface between land and water), shading, physical habitat, and shape of river channel are recorded for each of State of the Environment monitoring sites.
  • Fish are only monitored for special investigations, such as understanding the impact of potential fish barriers  However other monitoring work (e.g. macroinvertebrates) provides an indication of the likelihood of a healthy fish community at monitoring sites and beyond.

How do we measure water quality?

freshwater of Andy HicksWe can measure water quality on site using handheld probes and other basic equipment, although some important indicators need to be measured in a specialist laboratory.

What we measure live:

  • Water Temperature – temperature has direct  influences upon aquatic life and has a strong influence on oxygen levels and the solubility of potential pollutants.
  • pH – aquatic life (especially fish) cannot survive if pH is too high or low (alkaline or acidic), and any change in pH can stress animals and plants sufficiently to put their lives at risk. Also, how well various chemicals including plant nutrients and other potential pollutants dissolve in water (solubility) depends on pH.
  • Dissolved oxygen – oxygen enters the water from the atmosphere, and from aquatic plants. Under certain conditions dissolved oxygen can become sufficiently low to cause stress leading to death for fish and macroinvertebrates. Risk factors for low oxygen include: high temperatures, low river flows, excessive plant growth, and organic pollution.
  • Conductivity - these measurements are related to salinity (saltiness) and dissolved solids. Changes in conductivity provide an early warning of changes caused by drought, flooding, and/or pollution.
  • Water clarity – is measured by using black disk equipment under the water; the clarity is determined by the horizontal distance that the black disk can be seen.

What do we use laboratory tests for?

  • Nitrogen and Phosphorous – in rivers we monitor Dissolved Inorganic Nitrogen (DIN), and Dissolved Reactive Phosphorous (DRP) which are the forms which can result in nuisance levels of aquatic plant growth. 
  • Nitrate and Ammonia toxicity - Nitrate and Ammonia are natural components of freshwater. However, various human activities (farming, wastewater) can result in high levels which are toxic to aquatic life, especially fish.
  • Suspended solids - in rivers these can cause problems when they reduce water clarity, and settle out and smother riverbeds. They can also can carry a variety of potential pollutants.

We also use laboratory tests for Biochemical Oxygen Demand (BOD) which is usually monitored for compliance with resource consents, rather than the state of the environment. This measures the impact of organic material (e.g. slurry, silage, sewage, milk, etc) on macroinvertebrates and fish. In polluted conditions, bacterial populations can grow so large that oxygen is removed from the water.

Algae in Rivers and Lakes

Most algae in rivers and lakes is harmless – it might be messy and slimy and sometimes smelly when water levels drop, but will not cause you health problems. 

However there are algae-like bacteria that can cause health problems.

Phormidium – black mats in river

What does it look and smell like?  Soft black mats that form on rocks in parts of stony rivers.  These can lift off and when they dries on a river bank and look pale, like dried leaves or a cow pat.  The mats have a musty smell.

What’s the problem?  The mats can turn toxic and scientists don’t know when or why.  So treat these always as toxic.  These can affect human health with skin irritations and breathing problems. Algal mats have been linked to dog deaths although this is inconclusive as the symptoms have been similar to heat exhaustion (out on the hot, river gravel) or poisoning (pest control in river areas can leave carcasses around).  Dogs are attracted to the strong musty smell of these mats. 

What to do? Do not touch the mats and keep dogs under control in river areas.  Alert Hawke’s Bay Regional Council on 0800 108 838 or


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