Collie Lower 1 catchment
The Collie River within this catchment is tidally influenced and is located almost entirely on the Swan Coastal Plain. It receives relatively clean water from upstream reaches on the Collie, and poor quality water from the Brunswick and Wellesley catchments, before eventually discharging to the estuary at the Collie River delta.
There are multiple sources of nutrients in this catchment, exacerbated by poor quality soils, extensive drainage and substantial volumes of irrigation water. In rural parts of the catchment dairy grazing and sheds, and beef cattle grazing contributes nutrients to the river through animal waste and fertiliser surplus. Urban areas around Australind and Bunbury are also nutrient sources as a result of increased runoff and fertilisation. Septic tanks are another nutrient source in the catchment, but the Water Corporation is addressing this source through infill sewerage.