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Estuary water quality

The Parks and Wildlife Service, in collaboration with the Department of Water and Environmental Regulation, conducts weekly water quality monitoring at 40 sites throughout the Swan Canning estuary. Data from these monitoring programs is reported in a number formats including water quality data plots for the Swan and Canning rivers, microalgae activity reports and quarterly estuarine data reports.

Weekly water quality plots

Each week the Parks and Wildlife Service and Department of Water and Environmental Regulation (DWER) conduct extensive water quality sampling, from Bicton to West Swan in the Swan River and Mount Pleasant to Langford in the Canning River.

This information is presented in weekly water quality plots featuring key parameters - salinity, oxygen content (mg/L and percentage saturation) and water temperature.

This data used in these plots is available to the general public from the DWER website or by emailing This email address is being protected from spambots. You need JavaScript enabled to view it..

Microalgae Activity Report

The Microalgae Activity Report (MAR) is a weekly report which informs the public on microalgae levels and the probability of discolouration and/or scum formation at sites throughout the Swan Canning estuary. The MAR is updated on the website on Friday and in the weather page of The West Australian newspaper the following Monday.

Officers from Parks and Wildlife Service and DWER monitor the Swan and Canning rivers on Monday and Tuesday at 20 routine monitoring sites, unless delayed by a public holiday. Samples for microalgae analysis are collected, with processing and reporting taking up to 48 hours.

Concentrations of chlorophyll-a, a plant pigment, are used to estimate microalgal activity. This is presented by the use of low, medium and high activity categories. An alert category may also be used and is based on the types of algal species present and their cell concentrations rather than chlorophyll-a. The alert may be used where an algal species occurs at concentrations that may be harmful to aquatic life or human health and requires public advice.

  Low levels of microalgae with no likely visible impact Possibility of discolouration and/or scum formation High probability of discolouration and/or scum formation Presence of species potentially harmful to aquatic life, OR human health requiring public advice
Chlorophyll-a (µg/L)
< 4 4 - 10 > 10 N/A

This week's Microalgae Activity Report

Week starting: Monday 14 October 2019

  • Microalgae activity was high from East Perth to Maylands in the middle Swan, at Shelley in the lower Canning and from Wilson to Cannington in the upper Canning.
  • Looking after the catchment looks after the rivers. Plant a native tree this weekend.
  • Never allow oil, paint or chemicals to enter a stormwater drain.
Use the map below to view this week's microalgae levels. Select the map icons for more information.
Note: Levels are published each friday. Trouble viewing the map below? view in a new window..

Map legend - Microalgae Activity Report

 Quarterly estuary water quality reports

Data collected weekly as part of the estuary water quality monitoring program is summarised each quarter in a report produced by the Department of Water. and Environmental Regulation This quarterly data report presents background and current data collected from 20 sites in the Swan and Canning rivers (see map below), representing six ecological management zones:

  • Lower Swan Estuary: BLA, HEA, ARM and NAR
  • Middle Swan Estuary: NIL, STJ, MAY and RON
  • Upper Swan Estuary: KIN, SUC, WMP and MSB
  • Swan River: JBC and POL
  • Canning Estuary: SCB, SAL, RIV and CASMID
  • Lower Canning River: KEN, BAC, NIC and ELL

Within each report, data is presented in graphical and tabular form for 13 key water quality parameters:

  • Total nitrogen
  • Ammonium nitrogen
  • Total oxidised nitrogen
  • Dissolved organic nitrogen
  • Total phosphorus
  • Soluble reactive phosphorus
  • Silica
  • Dissolved organic carbon
  • Total suspended solids
  • Alkalinity
  • Chlorophyll-a
  • Secchi depth
  • Phytoplankton

Annual reporting against estuary targets

The Parks and Wildlife Service's key performance indicators of water quality for the estuary and its catchment, reported in the annual report each year, are:

  • total nitrogen and total phosphorus concentrations in 15 priority sub-catchments
  • chlorophyll-a concentration and dissolved oxygen saturation in surface waters of the estuary

Targets for estuary basins

The surface waters of the estuary are divided into four estuary basins – upper Swan, middle Swan, Canning and lower Swan Canning – and annual targets have been developed for each. These are based on ANZECC 2000 trigger values and statistical principles, to detect the smallest change in water quality.  The targets for the estuary basins relate to chlorophyll-a concentration (a measure of algal biomass) and dissolved oxygen saturation in surface waters.

Estuary Basin

Chlorophyll-a (µgL-1) target

DO Saturation (%) target

Upper Swan



Middle Swan






Lower Swan Canning