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Delaware Inlet - Wakapuaka

Delaware Inlet - Wakapuaka is a 355 ha shallow, intertidally-dominated tidal lagoon estuary approximately 19 km northeast of Nelson City. The estuary is well-flushed with a single tidal opening east of Pepin Island, and extensive intertidal flats located to the west near Cable Bay and to the east near Delaware Bay. 

Although the estuary and its catchment have been subjected to a variety of human modifications during the past 160 years, these have not included industrial or municipal wastewater discharges or excessively high-nutrient catchment runoff. Thus the relatively natural functional qualities of the estuary are thought to have been largely preserved. The main pressure on the estuary has been identified as elevated muddiness from catchment runoff.


Ecologically, habitat diversity is high with a variety of substrate types e.g. cobble, gravel, oyster reef, shell, sand and mud, with intertidal salt marsh (8.7%) and seagrass (2.5%) important features. Sediments are dominated by sands, although 20% of the intertidal area, primarily near the Wakapuaka River delta, comprises mud-dominated sediment. Sediments have naturally elevated Ni and Cr concentrations due to geologically enriched rock types present in the catchment. 

Estuary summary

What makes my estuary unique?

Explore the characteristics of this estuary


Estuary characteristics

  • Significant features
    • 29.3 ha intertidal salt marsh
    • 8.9 ha intertidal seagrass 
    • 218.5 ha sand-dominated sediments
    • 67.9 ha mud-dominated sediments
  • Total area
    355 hectares
  • Flushing time
    <3 days

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.

Wakapuaka River

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
Monitored sites 4

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