The Vasse Wonnerup and Geographe Bay catchment occupies the majority (approx 2000 km2) of the Busselton Coast drainage basin, comprising the area that drains north into Geographe Bay (the Margaret River system in the south and west of the basin is outside the catchment).
The Lower Vasse, Sabina, Abba and Ludlow Rivers drain into the Vasse Wonnerup wetlands and the main sub-catchments draining directly into Geographe Bay include Capel, Carbanup and Buayanyup Rivers, Gynudup and Annie Brooks and the Vasse Diversion Drain.
Busselton is the largest urban area and is centrally located on Geographe Bay adjacent to the Vasse Wonnerup Wetlands. Also on the coast, Dunsborough is inside the north-western catchment boundary while Dalyellup and the City of Bunbury lie just beyond the boundary to the north-east. Inland, Kirup is located inside the south-eastern boundary and Cowaramup is just outside the south-western boundary with the Whicher Range forming much of the boundary in between the two towns.
Values to be protected
- The Vasse Wonnerup and Geographe Bay system has a high abundance and richness of waterbirds, including Blackwinged Stilt, Red necked Avocet, Australian Shelduck and Australasian Shoveler, and the largest known breeding colony of Black Swan in Western Australia (50–150 pairs).
- more than one per cent of Ramsar populations of Blackwinged Stilt, Red necked Avocet, Australian Shelduck and Australasian Shoveler.
- Largest known breeding colony of Black Swan in Western Australia (50–150 pairs)
The wetland also includes cultural and heritage values and parts of the wetland are used for summer grazing by cattle.
Geographe Bay values include significant recreational activities (contact, active), and fishing. Ecological values include highly diverse sponge, coral and invertebrate communities. Geographe Bay is soon to become a marine park.
Water quality issues
Excessive algal blooms caused by high nutrients loads in the lower estuary channels have frequently resulted in sudden, mass fish deaths, mostly during the summer period. The principal cause of the deaths is thought to be temporary declines in dissolved oxygen concentrations due to night-time respiration of algal blooms. Blooms of macroalgae and phytoplankton also regularly occur.
The bulk of the land area in the catchment is utilised by nutrient-intensive agricultural industries, with dairy and beef grazing dominant and intensifying. The Vasse Wonnerup Wetlands and Geographe Bay also receive flow from nutrient-rich groundwater sources.
Population growth in the catchment is among the highest in the country. This growth is fuelling rapid urban expansion of the Busselton, Dunsborough and Capel town sites into surrounding agricultural areas. Recent surveys of urban nutrient use have demonstrated that nutrient loads from urban areas can be much greater than from agricultural grazing land due to the large quantities of fertilisers added to home gardens by urban householders.
Key water quality improvement projects
- Vasse Wonnerup Wetlands and Geographe Bay Water Quality Improvement Plan - March 2010
- Achieving better urban water management in Western Australia
- Water Quality Monitoring Programme for Vasse Georgraphe Catchment
- Nutrient Modelling in the Vasse Georgraphe Catchment
- Landuse Nutrient Model Framework Development Report
- BMP scenarios fro the Vasse Geographe Catchment
- Ecological Character Description of the Vasse Wonnerup System Ramsar wetland (Draft)
Key stakeholders / agencies
- Department of Water WA
- Department of Agriculture and Food
- Department for Planning and Infrastructure
- Environment Protection Authority
- Western Australian Local Government Association
- Department of Environment and Conservation
- Shire of Busselton