Preston Donnybrook catchment
The Preston Donnybrook catchment is situated immediately upstream of the Donnybrook town site on the Darling Plateau. It receives inflow from the Upper Preston and Thomson Brook catchments.
Most of the cleared farm land is used for grazing, with the rest of the catchment forested by native vegetation or plantation timber. The nutrient loading in this catchment is sourced primarily from grazing cattle, however small pockets of horticulture can contribute a disproportionately large phosphorus load to the river relative to their area because of high fertilisation.