Water quality rankings are provided for four parameters which were selected for their importance for ecosystem and human health (see table below):
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Total phosphorus
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Phytoplankton (chlorophyll-a)
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Escherichia coli
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Nitrate-nitrogen
Water quality was assessed in accordance with the guidelines provided by the National Policy Statement for Freshwater Management 2020 (NPS-FM), which ranks each parameter from A (good) to D or E (poor)11.
While the parameters are being measured in both lake and rivers, NPS-FM provides guidelines that allow us to obtain quality ratings for total phosphorus and chlorophyll-a for lakes only, not rivers; and rankings for nitrate can only be obtained for rivers not lakes.
Data Source
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Upper Clutha water quality measurement sites as available from the Otago Regional Council Environmental Data Portal website
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AQWebPortal
Data Source
| Description | ||
|---|---|---|
| Phytoplankton (chlorophyll-a) | Ecosystem health | Chlorophyll-a is the green pigment in plants and algae that is used for photosynthesis and is a good indicator of the total amount of algae in a lake. Elevated chlorophyll-a concentrations can indicate nutrient enrichment (eutrophication), leading to algal blooms that disrupt the balance of aquatic life. |
| Total phosphorus | High levels of total phosphorus in water can come from either wastewater or run-off from agricultural land. Too much phosphorus can encourage the growth of nuisance plants such as algal blooms. | |
| Nitrate-nitrogen | Nitrate-nitrogen is a very important plant nutrient but because it is highly water soluble, it leaches through soils and into groundwater very easily, particularly after heavy rainfall. | |
| Escherichia coli | Human contact | E.coli (Escherichia coli) is an indicator of the faecal contamination and the presence of disease-causing organisms. Common sources of E.coli bacteria are human wastewater discharges, animal waste, bird droppings and stormwater run-off. E.coli is harmful to human health in high concentrations. |
Data Source
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Data were obtained from the Otago Regional Council Environmental Data Portal website, and
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AQWebPortal
Monitoring water quality parameters provides a comprehensive understanding of the health of aquatic systems, their impact on human well-being, and the need for sustainable environmental management practices:
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Monitoring nitrate levels helps manage agricultural practices to minimise pollution and protect water resources.
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Monitoring E.coli ensures that water sources are safe for recreational activities, drinking, and agricultural use.
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Monitoring chlorophyll-a levels provides insight into the overall health of aquatic ecosystems.
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Monitoring total phosphorus allows for early detection of potential threats to native species and habitats and it helps to identify and manage nutrient pollution, preventing detrimental effects, such as an ecological imbalance characterised by harmful algal blooms and oxygen depletion.
ORC regularly monitors the water quality around Otago, which includes the Upper Clutha catchment. For the most recent measurements and evaluations of water quality, please visit the ORC Environmental Portal website.
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[11] Ministry for the Environment, National Policy Statement for Freshwater Management 2020, available online .
