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Lake Wairarapa

Lake Wairarapa is part of the largest lake/wetland complex in the southern North Island, and is situated just a few kilometres south of Featherston on the Eastern side of the Wellington Region.

The lake is considered to be of both national and international importance due to its significant cultural, ecological, recreational and natural character values. A National Water Conservation Order was placed on Lake Wairarapa in 1989 recognising the high ecological values of the area.

Water quality in the lake hasn’t changed much since monitoring began in 1994.

Lake Wairarapa is the largest lake in the Wellington Region, with an area of 7,850 hectares. It is very shallow – only around 2.5 metres at its deepest point – and is considered to be isothermal, which means that it remains at a constant temperature throughout its depth. Pastoral land cover makes up just over 50% of the lake’s existing catchment area and is generally located to the north and east of the lake. Indigenous forest and scrub makes up the remainder of the catchment and is largely associated with the Rimutaka Range to the west of the lake.

Historically, Lake Wairarapa and the surrounding wetlands were an important source of mahinga kai and even in present times the area still has significant traditional and spiritual values and is considered a taonga. The lake also provides habitat for a wide variety of plant, fish and bird species, including rare and threatened species. The high ecological values associated with Lake Wairarapa are recognised in the Proposed Natural Resources Plan for the Wellington Region, with the lake listed in Schedule A2 as being a lake with outstanding indigenous ecosystem values.

The lake has been significantly modified through flood protection and drainage activities carried out under the Lower Wairarapa Valley Development Scheme (LWVDS). The most significant changes took place in the 1960s and 1970s and included the diversion of the Ruamāhanga River from the lake and drainage of vast areas of wetlands. Barrage gates were also installed at the outlet of the lake to regulate water levels. The LWVDS is considered to have had major socio-economic benefits in terms of flood protection and development of land for agricultural use. However, it is also considered to have had significant negative impacts on the lake ecosystem and surrounding wetlands.

Lake Wairarapa is the only lake in the Wellington Region that is routinely monitored by the Greater Wellington Regional Council. Assessments for water quality commenced in 1994 and are attempted on a quarterly basis at three sites in the lake. However, due to strong winds safe access to the sites is not always possible.

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 Wairarapa

    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 Wairarapa 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 Wairarapa

    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 Wairarapa data table
    Sample Date LakeSPI Status LakeSPI % Native Condition Index % Invasive Impact Index %
    LakeSPI information has been provided by NIWA.

Monitored sites on Lake Wairarapa

...retrieving sites.

No sites found.

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