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Motupipi Estuary

Motupipi Estuary is a moderate-sized (169 ha), shallow, well-flushed, seawater-dominated, tidal lagoon type estuary with one tidal opening and two main basins. The western arm, dominated by the Motupipi River, responds more like a tidal river system. The upper estuary experiences salinity stratification during stable baseflows (i.e. salt wedge effect). The resulting high salinity bottom layer is generally more stable (less well-flushed) and therefore experiences nuisance algae blooms when nutrient inputs are elevated. The eastern basin is seawater-dominated, elevated, which dries rapidly and remains exposed for much of the tidal cycle. Much of the immediate estuary margin is directly bordered by developed pasture/rural land, roads, and seawalls. Causeways separate small sections of saltmarsh from the main estuary.

Historically, the Takaka landfill was sited on the estuary margin, but heavy metals, used as an indicator of potential toxicants, were very low at sites around the estuarine perimeter of the landfill and at fine scale monitoring sites.

The catchment (41 km2) is dominated by high producing pasture (45%), native forest and scrub (37%) and exotic forestry (8%).

Ecologically, habitat diversity is moderate to high with much of the intertidal vegetation intact, extensive shellfish beds, large areas of saltmarsh (38% of estuary), and some seagrass (1.6% of estuary). However, the estuary is excessively muddy (36% soft and very soft mud in 2015), and much of the natural vegetated margin has been lost and developed for grazing. Since 1943 there has been a loss of 28ha of saltmarsh through drainage and reclamation, although significant saltmarsh modification is likely to have also occurred prior to this.

The major current estuary stressors are considered to be: excessive muddiness for ecological condition, disease risk for contact recreation and shellfish gathering, habitat loss and changes in biota as a result of climate change. Localised eutrophication is present in poorly flushed upper estuary arms at times.

Broad-scale mapping using the National Estuary Monitoring protocol was conducted in 2007 and 2015 and fine-scale surveys in 2008 and 2017-19.

Estuary summary

What makes my estuary unique?

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Overview

Estuary characteristics

  • Total area
    169 hectares

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.

Motupipi

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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