Caring for the River
More than 1.5 million people now live in the wider Swan-Canning catchment. The seemingly clear sparkling beauty of the Swan River masks a river under stress. This stress is a result of high concentrations of nutrients entering the river system from the large catchment. The two main nutrients are phosphorus and nitrogen and high levels have led to algal growth, low oxygen levels, fish deaths and general loss of biodiversity. Some algae are harmless, but some species are toxic to marine life or humans.
The main sources of these nutrients are fertilizers and animal wastes from rural and semi-rural land as well as urban gardens, unsewered areas, golf courses, light industrial areas and non point sources, far from the river itself. These nutrients flow into the river through drains, stormwater run off and groundwater and are also locked in the River sediments, to be released to fuel algal blooms in the right conditions.
The impact of nutrients is compounded by changes in estuarine hydrology from climate change, the diminished winter rainfall over recent years meaning less flushing of nutrients from the river to the sea. Increasingly saline conditions are occurring as marine water moves further up the river in autumn and summer.
Page last updated: Tuesday 23 November 2010 by Nick Cowie Asset ID 12448
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