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Lake Orakai

Lake Orakai is a 4 ha lake, described as being one of the most eutrophic lakes in New Zealand by the Minister of Agriculture and Fisheries in 1986. It is a sister to Lakes Tūtira and Waikōpiro, although it is on the southern side of the landslip which formed the two lakes, and drains south directly to the Waikoau River, rather than outflowing north like Tūtira. It is shallow, with a maximum depth of about 5m.

The catchment of Lake Orakai is 13.91 ha of rolling to steep hill country, which was predominately pasture during the 1980s but vegetation cover has increased in conjunction with the Guthrie Smith Arboretum, which owns the bulk of the lake’s catchment. Vegetation includes pine forest, Californian redwoods, kanuka, and a variety of other natives and exotic specimen trees. The lake supported small populations of black teal, dabchick, pukeko, black swan, mallard, grey duck and paradise duck. Shortfin eels and common bullies have been recorded in the lake. The lake bottom is covered with black organic sludge with minimal submerged aquatic vegetation, but there is emergent vegetation around the lake margins.

Lake Summary
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  • Mixing pattern
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Scientific data for this lake

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

  • Water Quality

    Trophic Level Index (TLI)

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    The TLI score is an indicator of lake health and is determined from a suite of water quality measurements.

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    Trophic Level Index (TLI) history for this lake

    The TLI score for a lake is calculated from four water quality measurements – chlorophyll a, total nitrogen, total phosphorus and water clarity. If water clarity is unavailable, TLI is calculated using the other three water quality measurements. A higher score indicates poorer water quality.

    View a factsheet on TLI

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    TLI history for Lake Orakai
    Year

    What do the icons mean?

    VERY GOOD
    Very good water quality. Trophic Level Index of 0-2. Microtrophic lake conditions.
    GOOD
    Good water quality. Trophic Level Index of 2-3. Oligotrophic lake conditions.
    FAIR
    Average water quality. Trophic Level Index of 3-4. Mesotrophic lake conditions.
    POOR
    Poor water quality. Trophic Level Index of 4-5. Eutrophic lake conditions.
    VERY POOR
    Very poor water quality. Trophic Level Index of greater than 5. Supertrophic lake conditions.
    NO DATA
    No data available.
    TLI history for Lake Orakai data table
    Year TLI Score
    Year TLI Score
     Download data
  • 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
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    LakeSPI history for Lake Orakai
    Year

    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
    Excellent ecological health. A LakeSPI score of 75-100%.
    HIGH
    High ecological health. A LakeSPI score of 50-75%.
    MODERATE
    Moderate ecological health. A LakeSPI score of 20-50%.
    POOR
    Poor ecological health. A LakeSPI score of 0-20%.
    NON-VEG
    Non-vegetated. A LakeSPI score of 0% (there are no plants present).
    NO DATA
    No data available.
    LakeSPI history for Lake Orakai data table
    Sample Date LakeSPI Status LakeSPI % Native Condition Index % Invasive Impact Index %
    LakeSPI information has been provided by NIWA.
Sites

Monitored sites on Lake Orakai

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