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Lake Waahi

Located west of Huntly in a predominantly pastoral catchment, Lake Waahi is the third largest lake in the lower Waikato. It receives water from a range of sources and discharges to the Waikato River via the Waahi Stream.

Lake Waahi has been considerably affected by nutrients and sediment, ongoing issues related to its modification, riparian management, and exotic and invasive fish and plant species. Its level has been substantially reduced, and many of the surrounding wetlands converted to pasture for farming.

The lake has played a significant role in commercial coal mining operations since 1876, both as a water source, and a receiving environment for discharges. Coal mining has contributed large quantities of sediment to the lake, altering the lake’s colour, clarity and chemistry. Coal mining was reportedly responsible for up to 90 per cent of the sediment entering the lake at times.

Waikato Regional Council has monitored the water quality of Lake Waahi since 1995, and installed a monitoring buoy in 2014 to collect real-time information. Recent monitoring results indicate the lake has low water clarity, high nutrient levels, and high phytoplankton density. Blue-green algae have been abundant in recent years.

Lake Waahi is identified as a priority 1 waterbody for stock exclusion in the Waikato Regional Plan. Planting and fencing have been undertaken as part of a collaborative project between Solid Energy, Waikato Regional Council, and private landowners. Lake Waahi has been partillay fenced and in 2011, a holistic restoration programme was established, including riparian management, wetland enhancement, establishment of a community nursery, and control and management of koi carp, in a collboartive effeort involving Waikato-Tainui, Waahi Whaanui Trust, Waikato Regional Council and Genesis Energy.

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 and unitary authorities for two lake water quality and ecological condition measurements. LakeSPI (Lake Submerged Plant Indicators) and TLI (Trophic Level Index).  Select an indicator to see the historical monitoring data.

  • 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

    TLI history for Lake Waahi

    What do the icons mean?

    Very good water quality. Trophic Level Index of 0-2. 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.
    TLI history for Lake Waahi data table
    Year TLI Score
    Year TLI Score
  • 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
    LakeSPI history for Lake Waahi

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

Monitored sites on Lake Waahi

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