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Waituna Lagoon

The Waituna Lagoon is one of the best remaining examples of a natural coastal lagoon in New Zealand and is unique in Southland and New Zealand.

Waituna Lagoon is classed as a Intermittently Closed and Open Lake and/or Lagoon (ICOLL). From time to time, the lagoon has been mechanically opened to the sea initially for fish passage and more recently to help manage drainage for surrounding farms.

More information on Waituna Lagoon, including current and forecast levels and salinity dynamics can be found at


It is a highly valued, large, brackish coastal lagoon that is fed by three creeks, and drains to the sea through a managed opening. Historically the lagoon was surrounded by peat bog wetland, the drainage from which gave the lagoon its characteristic clear brown stain, low nutrient status, and low pH. It had high ecological habitat diversity, a unique macrophyte community (Ruppia dominated), internationally important birdlife, and large areas of relatively unmodified wetland and terrestrial vegetation. In addition, it is highly valued for its aesthetic appeal, its rich biodiversity, duck shooting, fishing (for brown trout primarily), boating, walking, and scientific appeal. The Waituna Lagoon is part of the internationally recognised 20,000ha Awarua Wetlands. The lagoon and immediately surrounding wetland (an area of 3,500ha) known as the Waituna Wetland Scientific Reserve, was designated a Ramsar Wetland of International Importance in 1976, with the wider wetland complex being included in 2008. The cultural significance to the local Ngai Tahu people was recognised under a Statutory Acknowledgement with the Ngai Tahu claims Settlement Act 1998. From time to time, the Lagoon is opened mechanically to the sea. When this is the case, the Lagoon acts more like an estuary rather than a lake. Because of many years of land development in the catchment, including drainage of wetland areas and clearance of indigenous vegetation, the lagoon is now experiencing a number of problems. In an agricultural catchment like Waituna, the primary concerns are excessive nutrients and sediment leading to eutrophication.

Lake Summary
  • Lake size
  • Maximum depth
  • Catchment size
  • Mixing pattern
  • Geomorphic type
Scientific data for this lake

This dashboard shows information on the data collected by the regional councils and unitary authorities for two lake water quality and ecological condition measurements. LakeSPI (Lake Submerged Plant Indicators) and TLI (Trophic Level Index).  Select an indicator to see the historical monitoring data.

  • Water Quality

    Trophic Level Index (TLI)

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    This measure is the Trophic Level Index (TLI). The TLI indicates the life supporting capacity of a lake and is based on four water quality indicators.

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    Trophic Level Index (TLI) history for this lake

    Trophic Level Indicator (TLI) which measures four parameters: water clarity, chlorophyll content, total phosphorus and total nitrogen. From these parameters a TLI value is calculated. In cases where water clarity data is missing a three parameter TLI is calculated. The higher the value, the greater the nutrients and fertility of the water which encourages growth, including algal blooms. As a rule, higher TLI scores mean poorer water quality. View a factsheet on TLI

    TLI history for Waituna Lagoon

    What do the icons mean?

    Very good water quality. Trophic Level Index of 0-2. Microtrophic lake conditions.
    Good water quality. Trophic Level Index of 2-3. Oligotrophic lake conditions.
    Average water quality. Trophic Level Index of 3-4. Mesotrophic lake conditions.
    Poor water quality. Trophic Level Index of 4-5. Eutrophic lake conditions.
    Very poor water quality. Trophic Level Index of greater than 5. Supertrophic lake conditions.
    No data available.
    TLI history for Waituna Lagoon data table
    Year TLI Score
    Year TLI Score
  • Ecological Conditions

    Lake Submerged Plant Indicators (LakeSPI)

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    The LakeSPI status describes the ecological condition of the lake and is based on plants present.

    LakeSPI data provided by NIWA

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    LakeSPI history for this lake

    LakeSPI (Lake Submerged Plant Indicators) is a method of characterising the ecological condition of lakes based on the composition of native and invasive plants growing in them. A higher LakeSPI percentage result is associated with better ecological health:

    LakeSPI N/A
    LakeSPI {{spiData.details.Value}}%

    The overall LakeSPI score is calculated using a Native Condition Index ('good' plants) and an Invasive Impact Index (introduced, non-native plants):

    Native Condition N/A
    Native Condition {{spiData.details.NativeIndex}}%
    Invasive Impact N/A
    Invasive Impact {{spiData.details.InvasiveIndex}}% NA

    A higher Native Condition value indicates better ecological condition, but a higher Invasive Impact value indicates invasive plants are negatively impacting native plant communities.
    View a factsheet on LakeSPI for more information on these indicators.

    • LakeSPI
    • Native Condition
    • Invasive Impact
    LakeSPI history for Waituna Lagoon

    What is this graph showing me?

    This graph is displaying the overall LakeSPI score over time. The results denote the ecological condition of the lake.

    Excellent ecological health. A LakeSPI score of 75-100%.
    High ecological health. A LakeSPI score of 50-75%.
    Moderate ecological health. A LakeSPI score of 20-50%.
    Poor ecological health. A LakeSPI score of 0-20%.
    Non-vegetated. A LakeSPI score of 0% (there are no plants present).
    No data available.
    LakeSPI history for Waituna Lagoon data table
    Sample Date LakeSPI Status LakeSPI % Native Condition Index % Invasive Impact Index %
    LakeSPI information has been provided by NIWA.

Monitored sites on Waituna Lagoon

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No sites found.