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Mahurangi Harbour

The Mahurangi Harbour is a shallow, drowned valley estuary system in the north-east of the region. The harbour offers a diversity of habitats, with areas in the upper estuary containing mud and sand flats fringed by mangroves, while towards the mouth there are sandy beaches and rocky platforms. This physical variety provides a similarly varied community of plants and animals, including native and endemic wading birds, coastal vegetation, and benthic communities.   

Warkworth is the only major town in the estuary margins, with most of the catchment land use being rural. Mud content decreases and health improves as you move from the upper reaches to the estuary mouth.

Monitoring began in Mahurangi Harbour in 1994 as Auckland Council (then Auckland Regional Council) recognised the high potential for increasing pressure on land and water use, both in the estuary and its catchment.

The understanding that this might alter the environmental quality of the harbour lead to a major study where the plant and animal communities were documented, baseline data on the macrofaunal communities were collected, species likely to be sensitive to change were identified, and sites and methods for long-term monitoring of benthic communities were recommended. This formed the basis of the State of the Environment monitoring programme.

Estuary summary

What makes my estuary unique?

Explore the characteristics of this estuary

Overview

Estuary characteristics

  • Significant features
    • Within the Hauraki Gulf Marine Park
    • Significant areas of fringing pōhutukawa forest on Mahurangi East peninsula and Mahurangi Regional Park
    • Several Significant Ecological Areas identified within the estuary as defined in the Auckland Unitary Plan
  • Total area
    ~250 hectares
  • Total shoreline length
    ~95km
  • Key rivers
    • Mahurangi River
    • Te Kapa River

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. For example, the sandflats of estuaries surrounded by rural areas will typically contain contaminants related to rural activities (e.g., cadmium from crop fertilisers and copper from fungicides), whereas those surrounded by urban areas are more likely to contain contaminants associated with cities (e.g., zinc and lead from roads and building materials). 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.

Mahurangi River
Dyers Creek North

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

See this site

Monitored sites 6

Select a monitored site from the list below

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