The Regional Catchment Strategy for the Port Phillip & Western Port region
Pressures (Waterways and Wetlands)

This page describes pressures on waterways & wetlands across the whole region that were identified by Melbourne Water through the development of the Healthy Waterways Strategy.  They are barriers to achieving this strategy’s targets.  Planning and action will need to find ways to minimise their effects.

Some of the most significant threats to waterway values are:

Changes to natural water flows

Many fish rely on a particular level of flow at the right time of year to trigger breeding; modifications to the natural flow regime can have significant impacts.

Very low flows can lead to a reduction in habitat for values including platypus, frogs and fish, and very high flows can destroy important in-stream habitat and features such as pools and small rapids.

Poor water quality

Pollutants such as pesticides, pathogens, excess sediment and heavy metals threaten environmental values.  Litter and unsightly smells and odours detract from social values.

Vegetation clearing

Vegetation removal decreases bed and bank stability, reduces feeding and breeding habitat for environmental values, changes the temperature and light within streams, which affects aquatic habitats, and reduces the sense of naturalness that contributes to amenity.

Pest plants and animals

Pest animals threaten all environmental values.  Foxes, feral dogs and cats prey on birds, reptiles and mammals including platypus.  Grazing and browsing animals such as rabbits and deer reduce the cover of indigenous plants and prevent the establishment of new plants.  Pest plants displace indigenous vegetation.  Reductions in indigenous vegetation can have profound impact on the healthy functioning of waterways.


As vegetated surfaces are replaced with hard impervious surfaces (such as roofs, roads and paved areas) that drain directly into waterways via stormwater systems, there are increases in runoff (changed water flow rates) and reduced water quality.  Urbanisation also results in altered waterway structure, with rivers straightened, wetlands drained, estuaries artificially opened, vegetation cleared and predators such as dogs and cats introduced.

Climate change and sea level rise

Climate change is expected to expose waterways and wetlands to:

  • Increased long-term average temperatures
  • Increased hot-day temperatures
  • Lower and more erratic rainfall
  • Higher evaporation
  • Lower soil moisture
  • Increased fire-weather frequency and intensity
  • Declining and more erratic stream flows
  • Sea level rise and ocean acidification

For more information about potential climate change effects, go to the Downloads section of this website to consult:

  • PPWCMA summary of climate change predictions for the Port Phillip and Western Port region June 2016
  • Southern Slopes Cluster Report, Climate Change in Australia Projections for Australia’s NRM Regions.
  • The Victorian Government’s Climate-Ready Victoria brochure for the Greater Melbourne region.

Climate change effects on waterways and wetlands include:

  • Stream flows could be reduced by between 3% and 11% by 2020 and up to 35% by 2050
  • While stream flows decline, water supply demand may grow and larger parts of available stream flows could be diverted
  • More frequent bushfires will reduce water quality and catchment inflows
  • Increasing water temperatures and reduced flows will damage waterways and wetlands as natural environments
  • More intense rainfall and ‘flash’ floods will do economic, social and environmental damage to waterways.


The present condition of waterways and wetlands across the region has been assessed (Method Condition).  Lead organisations are committed to addressing the pressures to target attainment.  Arrangements are in place to monitor and report on progress.