Whanganui Estuary

The Whanganui Estuary is a large, shallow, tidal river mouth located at the edge of Whanganui City. The shoreline is a patchwork of sandbanks, mudflats and a substantial coastal dune system that supports a range of native species. Defined river channels and flood protection works shape the elongated estuary.

Historical alterations have modified the surrounding land, and only 0.5ha of saltmarsh remains. Humans have cleared native forests from some parts of the catchment to create open pastures, cultivated lands and pine plantations. The river transports the sand, soil and silt particles that have washed into the river further upstream, down to the estuary.

The river mouth is strongly channelised and receives a large freshwater inflow from the Whanganui River. When the freshwater reaches the tidal currents of the Tasman Sea, most nutrients and fine sediments carried downriver pass directly through to the sea. This flushing helps keep the estuary in good health because it is less likely to experience an increase in nutrients (eutrophication) that can lead to the harmful overgrowth of aquatic plant life.

Estuary summary

What makes my estuary unique?

Explore the characteristics of this estuary

Overview

Estuary characteristics

Significant features
- The Whanganui Port is located along the banks of the estuary, transporting goods by sea and providing berthing facilities for coastal freight vessels and commercial boats.
- At least 25 wader and water birds have been recorded in the estuary and immediately surrounding lands

Total area
354 hectares

Total shoreline length
11 km

Tide
Spring (MHWS) 3.0 m, Neap (MHWN) 2.1 m

Key rivers
- Whanganui River

Highlighted reports

These links are from your regional councils and unitary authorities and provide additional information about this estuary

Fine Scale Intertidal Monitoring of Whanganui Estuary, April 2021 Whanganui Estuary, Broad Scale Habitat Monitoring, June 2017

Related factsheets

For more details on particular topics see these factsheets

Understanding estuaries Estuary types

Department of Conservation

Want to connect with restoration groups or explore your local estuary? You can find more information on the DOC’s interactive maps.

Restoring estuaries map Experiencing estuaries map

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.

Whanganui

20 sites

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.

Whanganui

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