The Buayanyup River is located in the central-west of the Geographe Catchment and flows directly to Geographe Bay. The catchment of the Buayanyup River has been farmed since 1934. High quality native vegetation occurs in the upper catchment and supports a number of threatened flora and fauna. A survey of the freshwater fish and crayfish by Murdoch University in 2008 found a diversity of native species including the Western minnow, Western pygmy perch , Nighfish, Gilgie, Smooth marron, South-west shrimp and Koonac.
The waterway is of cultural heritage significance, valued as a place for food, camping, ceremony and spiritual significance. Three sites of Aboriginal heritage significance are found in the catchment. A River Action Plan developed by GeoCatch in 2010 outlines the values, condition and management priorities of the River system.
The Buayanyup River catchment supports a diversity of land uses. Beef and dairy grazing are the dominant uses. The catchment supports seven dairies, vineyards, horticulture and horses. In the very south-east corner of the catchment land-use consists of native vegetation and timber plantations. Residential land-use is growing in the lower catchment with the expansion of Vasse-Newtown.
Image: The catchment supports a diversity of land-uses but is dominated by beef and dairy grazing.
The headwaters of the Buayanyup River occur in state forest where four tributaries flow through native vegetation before flowing through agricultural land in the central catchment. The lower reaches of the river are heavily modified with drainage channels directing water away from agricultural land.
The waterway has been artificially straightened into a drain (Buayanyup Drain) for several kilometres before the river meets Geographe Bay at Abbey Beach. A number of on-stream dams occur on the river. Since 2000, the mean annual flow for the Buayanup River is 28GL/yr of a total of 203GL/yr for the waterways of the Geographe catchment.
The nutrient loads in theBuayanyup River are primarily driven by dairy grazing. Beef grazing, horticulture and point sources (dairy sheds) also contribute significant proportions of the load.
Image: Nutrients are primarily sourced from fertiliser used for dairy grazing, with smaller quantities from beef grazing, point sources (such as dairy sheds) and horticulture.
Nutrient concentrations and targets of the Buayanyup River
The Department of Water and Environmental Regulation has been monitoring the water quality of the Buayanyup River fortnightly since 2006. Data from 2008-2016 is presented in the table below (as data from 2008 represents data from 2006-2008). The data shows total nitrogen concentrations to be consistently above water quality targets. Total phosphorus concentrations have remained below the water quality target of 0.1mg/L. The export of phosphorus is likely to be reduced by the heavy soils in the catchment.
The Buayanyup River catchment is categorised as an ‘intervention’ catchment as waterways are currently meeting the phosphorus target but not the nitrogen target established in the Water Quality Improvement Plan.
Image: Trends in nutrient concentrations of the Buayanyup River
No statistically significant trend in nutrient concentration was observed in the data.
Since 2009 programs led by GeoCatch and partners have focussed on reducing nitrogen and phosphorus entering the waterway. These programs included working with farmers to reduce fertiliser use, managing dairy effluent and undertaking fencing and re -vegetation in the riparian zone. Key achievements between 2009 and 2015 include:
Nine Landholders undertook soil testing and nutrient mapping to inform fertiliser decisions, assisting farmers to use only the phosphorous needed for the pasture growth required.
One dairy effluent management plan was developed to support the re-use of dairy effluent, reducing nutrients entering the waterways.
Fifteen landholders undertook 16.2 km of riparian fencing and 7.2 ha of re -vegetation with the aim to restore and protect the riparian zone, prevent stock access, increase the absorption of nutrients and to reduce sedimentation and pollution.
For the next three years management programs will continue to focus on reducing nutrients entering the Buayanyup River under the Revitalising Geographe Waterways program. Implementation of best practice agricultural dairy effluent management and riparian management are key goals for this ‘intervention’ catchment. As residential urban areas expand in the lower catchment managing nutrient loads from new urban developments and the incorporation of water sensitive urban design are also a priority for this catchment.
At least one effluent upgrade is proposed in the catchment at a farm in Jindong. GeoCatch will work with at least two landholders to undertake fencing and re – vegetation in the riparian zone.
Monitoring the water quality of the Buayanyup River will continue in the Catchment Water Quality Monitoring Program and the Water Quality Improvement Plan will be reviewed and updated.