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Lake Okaro

Okaro is a small lake with very high productivity and is classed as super-trophic. It is subject to frequent and severe blooms of cyanobacteria (blue-green algae) during summer. It has been the focus of an extensive water quality management programme, including land-based interventions such as agricultural detention bunds, wetlands and in-lake remediation (flocculation and sediment capping).

Lake Okaro is surrounded by pasture and is fed by several small streams. It has an outlet stream (Haumi Stream) to the east, which drains to Lake Rotomāhana. The lake’s average depth is 12m and sampling occurs at the maximum depth of 18m. Poor water clarity in Lake Okaro restricts aquatic plant growth. While the lake contains few invasive weed species, the native condition index is the lowest of the 12 lakes and subsequently the LakeSPI (submerged plant indicators) score is one of the lowest recorded. Restoration initiatives for Lake Okaro have focused on reducing the external and internal nutrient loads. A 2.3ha wetland was completed in 2007 to intercept dissolved nutrients through incorporation into organic matter within the wetland, and through denitrification of nitrate to nitrogen gas. A detainment bund upstream of the wetland was completed in 2014 to balance peak flows and settle out particulate matter. Other key actions that are being or will be implemented include full riparian protection, allophane treatment of the main inflow to remove phosphorus, storm water detention on farmland and ongoing monitoring.

Lake Summary
  • Lake size
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  • Maximum depth
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  • Catchment size
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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):

  • Water Quality

    Trophic Level Index (TLI)

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    This measure is the Trophic Level Index (TLI). The TLI indicates the lifesupporting 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 Okaro
    Year
    TLI history for Lake Okaro data table
    Year TLI Score
    Year TLI Score

    What do the icons mean?

    VERY GOOD
    Very good water quality. Trophic Level Index of less than 2. Microtrophic lake conditions.
    GOOD
    Good water quality. Trophic Level Index of 2-3. Oligotrophic lake conditions.
    AVERAGE
    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.grades[0].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.grades[0].NativeIndex}}%
    Invasive Impact N/A
    Invasive Impact {{spiData.grades[0].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 Okaro
    Year
    LakeSPI history for Lake Okaro 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.

Download Data

.ZIP file of lake data.
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Disclaimer

 LAWA Partners shall not be liable, whether in contract, tort, equity or otherwise, for any loss or damage of any type (including consequential losses) arising directly or indirectly from the inadequacy, inaccuracy or any other deficiency in information supplied irrespective of the cause.  Use of information supplied is entirely at the risk of the recipient and shall be deemed to be acceptance of this liability exclusion.

Sites

Monitored sites on Lake Okaro

...retrieving sites.

No sites found.

Live Data

A monitoring buoy on Lake Okaro measures water temperature, chlorophyll and pH continuously. Lake level is measured periodically only and so is not available here. 

Disclaimer

The Environmental Data produced by 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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