Lower Preston catchment
The Lower Preston catchment lies on both the Darling Plateau and the Swan Coastal Plain, and consists of land draining to the Preston River and Crooked Brook. The lower reaches of the Preston River are tidally influenced from the Leschenault Estuary and experience some mixing with estuary water.
Around two thirds of the catchment is cleared, with most of this area covered with soils that have a low capacity to retain nutrients. The catchment contains multiple sources of nutrient pollution including urban areas, beef and dairy grazing, rural and horse keeping lots, several abattoirs, Dardanup waste water treatment plant, and septic tanks. Because of the poor quality soils all of these sources can easily leach nutrients to the river through groundwater and the agricultural drainage network.