Water quality monitoring in the Canning River. Photo by A. Gillies, DBCA
DBCA's Rivers and Estuaries Science Program has a key role in monitoring, evaluating and reporting on the environmental health of the Swan Canning Estuary and its catchment. Environmental monitoring is focused on water quality, biological indicators (fish communities and seagrass) and contaminants (including plastic).
Monitoring is important. It enables DBCA to:
- monitor the extent and severity of low oxygen and algal blooms
- identify changing conditions and inform the community if risks occur
- guide management decisions and incident response
- track trends, measure compliance and determine the effectiveness of estuary and catchment management measures
- inform and improve estuarine and catchment models
- Understand the condition of key assets.
Water quality monitoring
Water quality monitoring occurs on a weekly basis in the Swan Canning Estuary and fortnightly in its catchment. Parameters collected include salinity, temperature, dissolved oxygen, nutrients, and phytoplankton. The most recent reports are available below, with previous reports available from the DBCA Data Catalogue.
Latest water quality reports
Microalgae activity
The weekly Microalgae Activity Report (MAR) provides information on microalgae activity levels, the probability of discoloration and/or scum formation, and potential warnings. This is based on data collected at 20 routine monitoring sites throughout the Swan Canning river system. Concentrations of chlorophyll-a, a plant pigment, are used to estimate microalgal activity.
This week's Microalgae Activity Report
Week starting: Monday 23 March 2026 (next update scheduled for 3 April 2026)
- Microalgae activity was high from Rivervale to Middle Swan in the Swan Estuary and at Castledare on the Canning Estuary. Some orange discoloration and a fishy odour may be observed in the Swan Estuary upstream of Guildford in association with the high algal activity.
- As Cyclone Narelle crosses the coast it is anticipated that heavy rainfall will occur across the 126,000 sq km catchment of the Swan Canning Estuary
- Over the days to weeks following this rainfall, significant runoff is likely to occur, which is anticipated to disrupt algal activity. DBCA is monitoring the situation.
- Depending on the scale and timing of the runoff we may see environmental values impacted in the waterway.
- In addition, discoloration of the water and foaming may occur, along with increased likelihood of debris accumulation on shorelines.
- The community is reminded to avoid swimming in the waterway for at least 3 days of heavy rainfall Tips for healthy swimming. Longer periods may be necessary following significant flooding.
- The public should report any sightings of sluggish or dead fish to FishWatch on 1800 815 507.
- Stay safe when using the waterway by checking shark activity here to view latest sightings and tagged shark detections.
Key
| Low | Medium | High | Alert | |
|---|---|---|---|---|
| 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 |
