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Lake Rototoa

Lake Rototoa is a large, deep lake located behind a series of dunes in the South Kaipara Heads area. It has the best water quality of the lakes monitored by the Auckland Council and remains as one of Auckland’s gems. The catchment has relatively steep slopes at the lakeshore, and this effectively prevents stock from entering the area around the lake. The lake catchment has farmland on the eastern side and exotic pine forest on the western side with a crown reserve on the western shores.

Lake Rototoa is one of the largest and deepest lakes monitored by the Auckland Council. There is a permanent stream and several intermittent streams that drain into the lake. This deep lake regularly stratifies causing anoxic bottom waters; however, the lake is in a mesotrophic state with high ecological condition. Lake Rototoa is the lake with the best water quality in the Auckland region.

However, previous monitoring data suggests the water quality is declining due to increasing nutrient and sediment concentrations and a reduced water clarity.

The lake boasts a diverse native plant community and is dominated by rotifers indicative of a low trophic state. Recent in-lake impacts like deteriorating water quality and the collapse of kākahi populations have been in part attributed to pest fish (perch and rudd) and macrophytes (hornwort).

Auckland Council is currently controlling hornwort in the lake and is investigating innovative methods for perch control including; hydro acoustic fish tracking, identifying spawning triggers and testing artificial spawning substrates.

Lake Rototoa was part of the Lakes380 project and information can be found here. A more in-depth interactive journey into the ecological history of Lake Rototoa can be found here.

Lake Summary
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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 Rototoa
    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 Rototoa 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 Rototoa
    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 Rototoa 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 Rototoa

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No sites found.

 Live Data

Disclaimer

The Environmental Data displayed on this page should be used as a guide only. LAWA takes no responsibility for the accuracy of information presented, and accepts no liability for actions taken of others based on this information.
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