Aquatic Biodiversity

The South West NRM region of Western Australia has an incredible diversity of rivers, wetlands, estuaries and bays, many of which have high conservation values.

Waterways are the natural drainage system for our catchments. They are complex, interconnected systems that provide habitat for our unique flora and fauna. They also provide social, economic, cultural and aesthetic values for the community. It’s no wonder that people love to visit and live around our iconic rivers, estuaries, wetlands and bays.

Many wetlands and waterways have been modified due to urban development, drainage, and agricultural activities. Some have become degraded as a result, impacting on the ecological, economic, social and aesthetic values they provide. The changing climate will exacerbate these issues, as reduced rainfall reduces the amount of water reaching our waterways and recharging our groundwater aquifers.

“Waterways are complex ecosystems with intricate relationships between the flora, fauna and non-living components such as water quality, flow regime and habitat. The balance between these living and non-living components can be changed by human activities in waterways and their catchments, and can lead to the deterioration of waterway health (DWER, 2015).This has consequences for the economic, social and environmental values of our waterways. (DWER, 2015).

Key threats to our aquatic biodiversity include pollution, salinisation, acidification, eutrophication, land clearing, introduction of pest species, fishing, land use practices, sedimentation and loss of connectivity as well as competition for water with industry, water supply and agriculture.

Banner photo: Scott River. Photo: Tim Swallow

Threats and Risks

In Western Australia the threats and risks to the health of our waterways include:

  • Poor water sediment quality including eutrophication (nutrient enrichment), non-nutrient contaminants, salinisation and low dissolved oxygen.
  • Altered flow including through climate change
  • Barriers to connectivity
  • Clearing of vegetation in the catchment and riparian zone
  • Erosion and sedimentation
  • Livestock access to waterways which increases nutrients and erosion
  • Algal blooms and fish kill events
  • Introduced animal and plant species” (DWER, 2015).

Nutrients and other pollutants from urban and agricultural areas can have a significant impact on our waterways. The majority of nutrients entering waterways in urban areas come from fertiliser:

  • Fertilisers contain nutrients and trace elements that plants need to grow. If used inappropriately, excess nutrients from fertiliser can run off into stormwater drains or leach into groundwater systems, eventually ending up in our waterways. Once there, they help the tiniest of plants, algae, grow in plague proportions.
  • Excessive application of fertilisers can lead to the eutrophication (nutrient enrichment) of waterways.

Call for Action

  • Hold off on the fertiliser till spring this winter
  • Fertilising at the right time of year will keep your lawns and gardens looking green. Nutrients are absorbed more easily in spring and this is when many plants start their new growth cycles. Most lawns are warm season grasses and actually stall their growth in winter. Winter rains simply wash fertiliser into our waterways and create problems for iconic species like the Blue Swimmer Crab. For more information visit homeriverocean
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Carter’s Freshwater Mussel

Freshwater Mussel

Carter’s Freshwater Mussel, Westralunio carteri is unique in being the only species of freshwater mussel found in south-western Australia and the only member of the genus Westralunio in Australia. Until recently, however, almost nothing was known about the biology or conservation status of this species. The range of W. carteri has contracted by 49% in less than 50 years, principally as a result of secondary salinisation and reduced water flow from a drying climate (Klunzinger et al. 2015). The species is now confined to non-salinised rivers and streams mostly in forested catchments along the west and south coasts. The species is classified as Vulnerable under the Wildlife Conservation Act the EPBC Act and the IUCN Red List of threatened species

Carter’s freshwater mussel, Westralunio carteri.  Photo: Steven Beatty

Case Studies


DWER. 2015. Threats to Waterways. [Link]. [Accessed 13 Apr. 2018].