The Water Quality Report Card provides a snapshot of environmental water quality in Port Phillip Bay and waterways in its catchment. It provides an overall average of the water quality in the Bay after examining key indicators.

Key indicators of water quality are assessed against Victorian environmental quality objectives for relevant indicators in the Environment Reference Standard (2021). These are combined to calculate an overall Water Quality Index score (WQI), corresponding to a rating of Very Poor to Very Good. For the Water Quality Report Card, WQI scores dating back to 2000 have been updated to include the period from July 2021 to June 2022.

Key indicators gauge risks to aquatic ecosystems from key stressors, such as nutrient inputs, increased sediment, and algal blooms. The scores are summarised at the catchment and bay scale. The scores are calculated by considering the area of the sub catchments and marine zones that each site represents and calculating area-weighted average scores.

The water quality indicators used for catchment waterway sites are:

  • dissolved oxygen
  • metals
  • nutrients (total nitrogen and total phosphorous)
  • pH
  • salinity (not at estuarine sites)
  • water clarity.

Image of hand showing a container of water.

Photo Credit: Environment Protection Authority Victoria

The water quality indicators used for marine bays and lake sites are:

  • algae (chlorophyll-a)
  • dissolved oxygen
  • metals (where data is available)
  • nutrients (total nitrogen in the bays, total phosphorous in the Gippsland Lakes)
  • salinity (not at the estuarine Eastern Lakes)
  • water clarity.

Only sites that have a minimum of 6 samples that span the 12-month period are included so that the Water Quality Index (Report Card) more accurately reflects the conditions throughout the year.

The Port Phillip Bay Environmental Management Plan 2017-2027 (EMP) status categories are aligned with Environment Protection Authority Victoria (EPA) water quality reporting.

Very GoodHigh quality waterbodies generally not impacted by pollution.
GoodMeets Victorian water quality objectives.
FairSome evidence of stress.
PoorUnder considerable stress.
Very PoorUnder severe stress.

Page last updated: 17/04/24