The Swan and Canning estuaries cover an area of approximately 40 km2 and extend approximately 60 km upstream from Fremantle to the confluence of Ellen Brook with the Swan River, and 11 km upstream from the Canning Highway Bridge to the Kent Street Weir on the Canning River.
The health of the rivers and estuaries is in decline: over the few past decades they have been displaying increasing signs of eutrophication including fish kills, cyanobacterial blooms, red tides and accumulation of organic matter in the bottom sediments. Algal blooms, which generally occur in the upper reaches of the Swan and Canning estuaries, are driven by the nutrients in catchment inflows, or nutrients that have built up in the sediments and remobilised under anoxic conditions.
