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Manukau Harbour

The Manukau Harbour is a large, shallow, drowned valley estuary system on the west coast. The shoreline is complex, comprising numerous sheltered creeks and inlets, rocky outcrops, coastal lava flows and boulder and sand beaches.

Humans have affected the health of the harbour through an extensive history of direct pollution of urban and industrial contaminants, as well as excess nutrients from sewage treatment. Despite some recent improvements to these practices, human activities continue to impact the ecological health of the harbour’s low energy tidal creeks. By contrast, the large tidal movements in the main body of the harbour help to dilute and disperse contaminants as they enter, meaning health is good on the open sandflats.

Approximately half of the water drains out of the narrow harbour entrance at each low tide. This exposes extensive sand and mudflats that support diverse communities of macrofauna and are designated as Significant Ecological Areas. Thousands of endemic and migratory shorebirds roost and feed on these exposed flats.

Estuary summary

What makes my estuary unique?

Explore the characteristics of this estuary


Estuary characteristics

  • Significant features
    • Second largest estuary in the country
    • ~60% of estuary is intertidal
    • Monitored since 1987
    • Identified as an 'Important Bird Area' with up to 30,000 shorebirds using the sandflats daily to feed 
    • Within the West coast North Island marine mammal sanctuary
  • Total area
    36,500 hectares
  • Total shoreline length
    450 km
  • Key rivers
    • Puhinui Stream
    • Whangamaire Stream
    • Ngakoroa Stream
    • Papakura Stream
    • + many more!

What's happening upstream?

See results from monitored river quality sites influencing this estuary

River quality

What's happening upstream?

The physical characteristics and health of estuaries are influenced by the rivers and streams flowing into them. For instance, when it rains the mud and contaminants generated on land can be washed into rivers and eventually flow into the estuary. The health of our rivers and streams can therefore be very important for Estuary Health, and understanding the upstream pressures can help with interpreting estuary monitoring data.

Monitoring is undertaken for a range of river health indicators (e.g., water quality and ecology) in many catchments across the region. Where there are monitored river catchments that influence this estuary, these are shown below. You can click through to view monitoring results from these River Quality sites to see current state and how health has changed over time.

What surrounds my estuary?

See land cover information from monitored catchments that surround this estuary

Land cover

What surrounds my estuary?

The physical characteristics and health of estuaries are influenced by local geography and the way we use our land. This is because estuaries are the receiving environments for many of our land use activities. Land cover information can be used as an indicator of land use, therefore knowing the surrounding land cover can help us understand which pressures might be affecting Estuary Health.

Where there is land cover information available for nearby catchments, these are listed below. These figures show the types of vegetation and built or natural features that surround the estuary margins and the rivers that flow into this estuary. You can click through to the Land Cover topic to see these land cover classes broken down into further detail, and view changes over time.

Puhinui Stream
Whangamaire Stream
Waitangi Stream
Ngakoroa Stream
Papakura Stream

What do the Broad Land Cover Classes mean?

Land cover information on LAWA is grouped into land cover classes at two levels of detail – broad and medium. For this overview we are showing the six broad-level classes for the catchment.

  • Forest

    Inclusive of; indigenous and exotic forest.

  • Scrub / shrubland

    Inclusive of; indigenous and exotic scrub / shrubland.

  • Grassland / other herbaceous vegetation

    Inclusive of; tussock and exotic grassland and other herbaceous vegetation.

  • Cropland

    Inclusive of; cropping / horticulture.

  • Urban / bare / lightly-vegetated surfaces

    Inclusive of; natural bare/lightly-vegetated and artificial bare surfaces, and urban area

  • Water bodies

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Monitored sites 33

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