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

This dashboard shows information on the data collected by the regional councils for two lake water quality and ecological condition measurements. Lake SPI (Lake Submerged Plant Indicators) and TLI (Trophic Level Index):

  • 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

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    TLI history for Lake Orakai
    Year
    TLI history for Lake Orakai data table
    Year TLI Score
    Year TLI Score

    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.
  • Ecological Conditions

    Submerged Plant Indicators (SPI)

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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}}%

    A higher Native Condition percentage is also good, but a higher Invasive Impact percentage is bad. View a factsheet on SPI

    • SPI %
    • Native Condition %
    • Invasive Impact %
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    LakeSPI history for Lake Orakai
    Year
    LakeSPI history for Lake Orakai data table
    Sample Date Status LakeSPI % Native Condition Index % Invasive Impact Index %
    LakeSPI information has been provided by NIWA.

    What do the icons mean?

    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.
Sites

Monitored sites on Lake Orakai

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