What are the Nitrogen (N) and Phosphorus (P) sources and contributions?
Nitrogen and phosphorus are nutrients that can reach the Swan and Canning rivers from anywhere in the catchment and fuel algal blooms. Nutrients are transported to the rivers by streams, stormwater drains and groundwater flow. Sediments, especially in the upper Swan River, are a major source of nutrients particularly in the low flow summer period. The Swan Canning Catchment is more than 2,000 square kilometres. It also receives inflow from the Avon River. The catchment includes rural areas along tributaries such as the Ellen Brook and Helena River as well as many urban tributaries such as the Bayswater Main Drain. All drains and streams flowing into the Swan River (particularly upstream of the bloom), groundwater seeping into the river and nutrients already stored in the sediments contribute to blooms. Nutrients come from a range of sources. In rural areas, some of the main sources are inappropriate fertiliser use, leaching of animal wastes and erosion of nutrient rich soils. In urban
