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Estuary water quality

Through its Rivers and Estuaries Science program, the Department of Biodiversity, Conservation and Attractions (DBCA) conducts weekly water quality monitoring at 40 sites throughout the Swan Canning Estuary. Data from this monitoring program is reported in a number of formats including weekly water quality profile reports, microalgae activity reports and annual estuarine data reports.

Hydrodynamic conditions

Extensive water quality sampling is conducted in the Swan River from Fremantle to West Swan, and in the Canning River from Mount Pleasant to Langford. Parameters measured include salinity, oxygen content and water temperature.

Water quality profile reports are prepared weekly to convey information on the prevailing conditions within the river system. These reports are available for the Swan River and the Canning River. Reports published after October 2019 are published on the Department of Biodiversity, Conservation and Attractions website. Earlier reports are available on this website for the Swan River and the Canning River.

The data used in these plots is available to the general public through the Water Information Reporting Portal or by emailing This email address is being protected from spambots. You need JavaScript enabled to view it..

Microalgae Activity Report

DBCA officers monitor microalgae on the Swan Canning river system on Mondays and Tuesdays at 20 routine monitoring sites. Samples are processed and reported within 48 hours for preparation of the weekly Microalgae Activity Report (MAR). The report  informs the public on microalgae levels, the probability of discolouration and/or scum formation and potential warnings for sites throughout the Swan Canning Estuary.

The MAR is updated on the website on Friday and in the weather report in 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.

The Microalgae Activity Report is published on the Department of Biodiversity, Conservation and Attractions website.

Annual estuary water quality reports

Data collected from 20 estuarine sites as part of the Swan Canning Water Quality Monitoring project is summarised into an annual report on the water quality for six ecological management zones (see map below). Within each report, data is presented in graphical and tabular form for 13 key water quality and biological parameters. The most recent and historic water quality reports can be downloaded below.

Reporting against estuary targets

The Swan Canning Water Quality Monitoring project supports reporting against measures of Riverpark health. Targets have been set for estuarine and catchment water quality, conditions in the oxygenation zone, and fish communities. Progress against these targets are reported every two years through the River Protection Strategy Biennial Report. This is available on the Department of Biodiversity and Conservation website

DBCA's key performance indicators of water quality for the Swan Canning Estuary and its catchment, reported in the biennial report, are:

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

Targets for ecological management zones

The surface waters of the estuary are divided into four ecological management zones – Upper Swan Estuary, Middle Swan Estuary, Canning Estuary and Lower Swan Canning Estuary – and annual targets have been developed for each. These are based on Australian and New Zealand Environment and Conservation Council (2000) trigger values and statistical principles, to detect the smallest change in water quality. The targets for the zones 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

19.98

81.2

Middle Swan

8.75

75.1

Canning

11.67

49.1

Lower Swan Canning

3.55

82.1