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Lake Kuwakatai

Lake Kuwakatai lies a short distance due south of Lake Ototoa and, although the catchment size and type are essentially the same, the lake has very poor water quality and is ranked as second worst after Lake Spectacle. The lake is highly turbid and nutrient enriched. It is surrounded by pasture and exotic forestry. This lake has fallen into disrepute due to the infestation of invasive fish and aquatic macrophytes as well as a swimming restriction being implemented.

Lake Kuwakatai is a moderately deep monomictic dune lake with about 85% of the catchment in pastoral land use. It is classified as super-eutrophic (supertrophic) with low water clarity, high nutrient concentrations and frequent algal blooms. The lake regularly stratifies during summer, resulting in anoxic bottom waters and the release of ammonia and dissolved reactive phosphorus (DRP). The poor water quality of Kuwakatai is partially due it being shallow enough for wind induced mixing to re-suspend bottom sediments and partly because of inputs from the associated farming practices within the catchment. Even though Lake Kuwakatai lies a short distance due south of Lake Ototoa and both of them fall within the same catchment the water quality in Kuwakatai is significantly worse. The major differences between Lake Kuwakatai and Lake Ototoa are a shallower water depth, axial orientation of the long narrow lake to the prevailing westerly wind, land management practices and the presence of invasive organisms in the lake. The catchment also supports 3 dairy farms. Stock access to the lake and invasive fish both contribute to the destabilisation of sediments near the shore, and hence the turbidity. Lake Kuwakatai also exceeds the proposed chlorophyll a bottom-line according to the National Policy Statement for freshwater (NPS-FW). The exotic macrophyte hornwort has almost completely covered the lake bed between 5 to 7.5m deep, with only a few native macrophytes remaining. Hornwort invaded the lake between 1988 and 1999 and has increased in range since then. The presence of coarse fish and Koi carp are also attributed to the deteriorating water quality. Large blooms of cyanobacteria that have the potential to produce toxins that are harmful to humans have been noticed in sufficient enough frequencies to implement a swimming restriction. In recent years the surface waters of Lake Kuwakatai showed a decline in total phosphorus, pH, nitrate, total ammonia and DRP. The bottom waters exhibited a decline in nitrate, pH and dissolved oxygen and an increase in DRP, TP and total ammonia. Although Lake Kuwakatai has shown an improvement in its trophic level index over the long term, there are still signs of deterioration..

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 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

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

    What do the icons mean?

    Very good water quality. Trophic Level Index of less than 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.
  • 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 %
    LakeSPI history for Lake Kuwakatai
    LakeSPI history for Lake Kuwakatai 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 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.

Monitored sites on Lake Kuwakatai

...retrieving sites.

No sites found.

Live Data


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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