The Leschenault catchment is located 160 km south of Perth, Western Australia, and drains an area of almost 2000 km² to the Leschenault Estuary. The catchment includes several river systems – the Preston, Ferguson, Brunswick and Wellesley rivers, and the Collie River below Wellington Dam.
Artificial drains have been introduced in the flat Swan Coastal Plain areas to enable agricultural and urban land uses. The catchment contains the irrigation districts of Collie and part of the Harvey. Harvey Water supplies summer irrigation through an open channel and pipeline network. This has led to a complex hydrological network of drains and natural rivers. Dams located on the Collie, Brunswick and Preston rivers have also modified natural flows in the Leschenault catchment.
Areas of the catchment located on the Darling Scarp and Plateau have large areas of uncleared native forest and woodland. The river valleys of the Preston and Ferguson, and the Swan Coastal Plain have been subject to significant clearing, and are currently used predominantly for beef and dairy cattle grazing. Coastal areas of the catchment have been developed for urban land use, and include Bunbury and Australind. There are isolated areas of viticulture scattered along the Preston and Ferguson valleys, and horticulture on the Swan Coastal Plain.
Nutrient intensive land uses in the catchment have resulted in poor water quality in the lower reaches of the major rivers, which presents an ongoing risk to the health of the Leschenault Estuary.